Category: Nutrition

The Link Between Breast Cancer and a Virus in Meat and Dairy

Exposure to the bovine leukemia virus from meat and dairy (or a blood transfusion from those who eat meat or dairy) is a risk factor for cancer.

In 2015, researchers in California found bovine leukemia virus (BLV) stitched into the DNA of human breast cancer tumors from mastectomies. The virus was found at much higher rates than in normal breast tissue obtained from breast reduction surgeries. Based on this difference, they calculated that as many as 37% of breast cancer cases may be attributable to exposure to BLV, likely through consuming milk or meat from infected animals.

In response, the milk and meat industries seemed more concerned about consumer confidence than consumer cancer. But scientifically, the research priority turned to the question: Could the California results be replicated? The answer, it turns out, was yes. They were replicated among women in Iran. Replicated in Brazil. In Australia, the link was even stronger. In Texas, they found the same thing. Women diagnosed with breast cancer were found to be so much more likely to have bovine leukemia virus DNA in their breast tissue compared with women without cancer, that the attributable risk was calculated at 51.82%, indicating that this meat and dairy virus may be responsible for at least half of the breast cancer cases among the women in Texas they studied.

All in all, six of the eight studies performed to date found the virus in human breast tissues, which “suggests strongly that BLV does infect humans, and breasts can be targets of infection.” Four of the five studies that compared infection rates in cancerous versus normal breast tissue found that the odds of detecting the virus in tumors were, on average, four times higher. How does that compare to other breast cancer risk factors? If you go on hormone replacement for five years, you can bump up your breast cancer risk by 30%. If you take birth control pills for more than a dozen years, your risk may go up by 40%. If you’re obese when you’re older, your risk can go up by 60%. Having a first-degree relative with breast cancer may double your risk. But having your breast infected with bovine leukemia virus may quadruple your risk, as you can see below and at 2:16 in my video Breast Cancer and the Bovine Leukemia Virus in Meat and Dairy.The only risk factors more potent than BLV infection were having the BRCA gene mutation, like Angelina Jolie has, or a high dose of ionizing radiation, like being in the wrong place at decidedly the wrong time, like Hiroshima and Nagasaki during World War II.

Beyond confirmation, one study suggested that older patients had a greater likelihood of testing positive for bovine leukemia virus. That makes sense if BLV is from exposure to dairy and meat. The older we get, the more meals we’ve had—and the more opportunities to become infected over time. Researchers also discovered that the virus comes first, before the cancer diagnosis; they found it was present in some breast tissues 3 to 10 years before cancer was found. “This argues against the idea of viral invasion of already malignant cells,” quashing the theory that maybe the virus is somehow just attracted to the cancer after the fact. Could this explain the consistent findings that breast cancer tissue is more likely to harbor infection? Again, the data showed no — the virus appeared to come first. While the review doesn’t provide absolute proof that BLV is a cause of breast cancer, based on the best available balance of evidence, BLV infection does indeed appear to be a risk factor for breast cancer.

The latest revelation is that BLV has now been found in human blood, too. This has a number of potential ramifications. Blood banks, for example, don’t screen for it. So, it’s possible you can get it from consuming meat or dairy, as well as from getting blood from someone who consumed meat or dairy. This could also mean that BLV could cause leukemia in people. It does in chimpanzees. Two infant chimps were fed milk from cows naturally infected with BLV, and both died of leukemia. We didn’t even know chimps could get leukemia. This certainly suggests the possibility of transmission or induction of leukemia through the ingestion of milk from BLV-infected cows, or blood-borne spread could carry the virus to other organs. In cattle, the virus causes blood cancers, but this may be just because dairy cattle are slaughtered and turned into hamburger when they are still so young, so maybe they don’t have time for tumors to grow in other organs.

How concerned should we be about bovine leukemia virus? “It is not clear whether this is a good news story or a bad news story.” If future studies show that BLV does cause breast cancer in people, there will be significant repercussions for the dairy and cattle industries. But that means there is something we can do about it. Perhaps action should be taken now to eradicate the infection from cattle, rather than waiting for a final verdict. Twenty-one nations have already eradicated BLV from their dairy cattle. In contrast, the BLV prevalence in the United States just keeps increasing. If industries are not going to step up and try to eliminate the disease, then the least they could do is eliminate some of the practices that spread the disease between animals.

BLV is spread via blood through contaminated needles, saw or gouge dehorners, ear taggers, hoof knives, tattoo pliers, nose tongs, and other tools of the agribusiness trade. Though “in view of the emerging information about BLV in human breast cancer, it is prudent to encourage the elimination of BLV in cattle, particularly in the dairy industry.” The hope is that, either way, it may help reduce the scourge of breast cancer.

Doctor’s Note

If you missed the previous video, see Bovine Leukemia Virus as a Cause of Breast Cancer.

Avoiding infectious risks like BLV is another advantage of making meat without animals. See my video, The Human Health Effects of Cultivated Meat: Food Safety.

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May 8, 2026
Could Bovine Leukemia Virus be a Cause of Breast Cancer?

As many as 37% of breast cancer cases may be attributable to exposure to the bovine leukemia virus.

The incidence of breast cancer continues to increase worldwide. In the United States, this amounted to a 40% increase in the incidence by the turn of the century. Presently, the main approach to preventing mortality is early detection and treatment. That’s important, but why not focus more on primary prevention—protecting people from risk factors so they don’t develop breast cancer at all?

“Overall, it is estimated that 20% of all human cancers have an infectious origin.” Viruses can trigger cancer by turning on cancer genes or turning off cancer-suppressing genes, but they can also contribute to tumor formation just by causing chronic inflammation. Currently, cancer-causing viruses are considered “the major plausible hypothesis for a direct cause of human breast cancer.” How did we get here?

It all started about 40 years ago when a professor of virology at UC Berkeley learned how the mammary tumor virus was discovered in mice. Scientists switched baby mouse pups from mothers with a high incidence of mammary cancer with the babies from mouse strains with a low incidence and found that the cancer incidence in pups matched their foster mothers’—not their biological ones’—showing it wasn’t genetic. “It occurred to me that humans are foster nursed on the cow,” the professor said.

Bovine leukemia virus (BLV) had just been identified as a cancer-causing cow virus. At the time, only about 10% of U.S. dairy cows were infected, but now it’s closer to half. Initially, 66% of herds were affected. Then, it was more like 80%, based on their milk testing positive for the virus, and 100% of the herds in the larger industrial farms. And now, more than 94% of U.S. herds are affected, continuing the historical trend of BLV persistently proliferating within U.S. dairy herds.

We’ve long known that people in countries that consume the most milk have the highest breast cancer incidence. But, as you can see below and at 2:32 in my video, Bovine Leukemia Virus as a Cause of Breast Cancer, the link between dairy consumption and breast cancer incidence isn’t only on the country level.Individual women who are lactose intolerant and consume less dairy also seem to have decreased risk of breast cancer. Milk contains many things that could be contributing to the cancer risk, such as saturated fat and the presence of cancer-promoting growth hormones like IGF-1.

Yes, we know bovine leukemia virus is present in beef and dairy products. About half of the milk and meat samples turn up positive for the virus. In fact, you can sample the virus straight out of the air on dairy farms, on surfaces, and in the milk itself. Most milk is pasteurized, but many dairy products, like raw, aged cheeses, are not. And who hasn’t eaten a pink-in-the-middle hamburger at some point in their life?

Yes, we have evidence that people are exposed to the virus. Yes, we have evidence that people are actively infected with the virus. But it wasn’t until 2015 that we learned infection rates were highest in cancerous breast tissue, as you can see below and at 3:30 in my video.So much so that as many as 37% of breast cancer cases may be attributable to exposure to the bovine leukemia virus.

That was enough for me to make a whole series of videos on the role the virus plays in breast cancer and how the meat and dairy industries responded to the news. What’s the latest update? That’s what I’ll cover next.

Doctor’s Note

You may remember that I’ve previously discussed The Role of Bovine Leukemia in Breast Cancer and the Industry Response to Bovine Leukemia Virus in Breast Cancer.

Stay tuned for the next video: Breast Cancer and the Bovine Leukemia Virus in Meat and Dairy.

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May 6, 2026
A Cancer-Causing Contaminant in Meds and Meat

Billion-dollar drugs have been pulled from the market for less carcinogenic contamination than is found in a single serving of grilled chicken.

In 2018, one of the bestselling blood pressure drugs, valsartan—sold as Diovan—was found to be contaminated by the “probably carcinogenic” nitrosamine known as N-nitrosodimethylamine (NDMA). It’s believed that about 20 million people worldwide were prescribed the drug tainted with this contaminant, which has a cancer risk shown to exceed that of many known potent carcinogens, such as asbestos, PCBs, and benzo[a]pyrene.

As I discuss in my video Cancer-Causing NDMA in Medications (Zantac, Metformin) and Meat, the U.S. Food and Drug Administration (FDA) estimated that taking the drug for a few years could cause cancer in as many as 1 in 8,000 people, whereas the European equivalent of the FDA estimated the cancer risk could be as high as 1 in 5,000. It is unlikely, researchers wrote in this 2019 paper, that drugs like valsartan are “a unique case.” And indeed, a few months later, the FDA announced it had found NDMA in ranitidine. Ranitidine, the acid reflux drug sold as Zantac, is one of the most prescribed drugs on the planet, in addition to being sold over the counter.

Then in 2020, some formulations of metformin, a popular diabetes drug sold as Glucophage, were found to be contaminated. The finding of NDMA in common medicines led the FDA to call for the immediate withdrawal of all Zantac from store shelves, yanking the drug from the market because its testing showed NDMA levels could, in some circumstances, exceed the acceptable daily intake limit of 96 nanograms per day. It was so bad that the FDA found levels of this carcinogenic contaminant in Zantac are similar to the exposure levels you would experience if you ate grilled or smoked meats!

Wait, what?

NDMA has not only been found in contaminated drugs. It is a known byproduct of tire plants, pesticide manufacturing, and leather tanning, and it is found in food and beverages, including processed meat and beer. Now that we know NDMA can transfer through the placenta, this may explain the relationship between maternal cured meat consumption during pregnancy and the risk of childhood brain tumors. For example, eating hot dogs while pregnant may increase childhood brain tumor risk by 33%, and sausages by 44%. Bacon consumption may increase childhood brain tumor odds by 60 or 70%. But it’s not just processed meat. Researchers have found it in poultry products as well. A single serving of chicken contains more than 100 nanograms of NDMA, as you can see below and at 3:02 in my video.

Remember how the FDA said the acceptable daily intake limit is 96 nanograms? Just half a chicken breast contains 110 nanograms.

Now, raw poultry doesn’t have any NDMA; it comes from the cooking process. In fact, the dry-heat cooking of meat, like broiling or grilling, even creates airborne NDMA, releasing this very potent carcinogenic compound into the air. So, even if you’re getting a salad at a charcoal grill restaurant, just being indoors where meat is being grilled could be a signiﬁcant cancer risk.

Nitrosamines are also found in cigarette smoke, and pressure was put on the tobacco industry to try to remove them, arguing “there is simply no logical reason why a removable carcinogen should be allowed to remain in a consumer product….” That’s the same reason Zantac was yanked from store shelves.

Okay, so let’s get this straight. Zantac—which is one of the best-selling drugs in history, bringing in billions of dollars—was pulled from the market because it contained a probable carcinogen that exceeded the acceptable daily limit, but there may be more of the contaminant in a single serving of chicken?! So, my question is: Why aren’t they pulling poultry off the shelves, too?

Doctor’s Note

NDMA is a nitrosamine, a class of carcinogens also found in processed meat. See, for example, How Much Cancer Does Lunch Meat Cause?.

How can you make meat less cancer-causing? See Carcinogens in Meat.

Is Organic Meat Less Carcinogenic? Check out the video to find out.

Note: The article shown at minute 1:04 of the video I reference has since been retracted due to analytical artifact.

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May 1, 2026
Peeling Back the Onion Claims

What did randomized, controlled human trials find about the ways we may—or may not—benefit from eating onions?

Onions are potentially a good source of antioxidants, which, interestingly, are concentrated in the outer layers just beneath the papery peel. White onions, for example, contain more than ten times the antioxidants in the outer layer compared to the inner core. Unfortunately, most people discard the most nutrient-rich outermost layers, “thus losing a valuable part of the antioxidant-rich material.” In general, yellow onions have more antioxidants than white onions. Red onions beat them both, based on three different antioxidant testing methods, as seen at 0:39 in my video Are Onions Beneficial for Testosterone, Osteoporosis, Allergies, and Cancer?

Though red onions are indeed slightly better, yellow and white onions are no slouches, containing considerable levels of antioxidant activity. We know they’re nutritious, but are there any particular clinical benefits to eating onions? There are all sorts of headlines in the medical literature touting miraculous benefits, but what are these claims based on?

For example, there’s a review purporting to have evidence that testosterone levels in males are enhanced by onion, but the researchers were referring to studies like one on the effects of onion juice after testicular torsion in rats. Who cares what happens after a rat’s testicle is rotated 720 degrees counterclockwise? (Except, of course, the rat.) You don’t know what happens in people until you put human testes to the test. Only then was it discovered that onion extract doesn’t appear to affect men’s testosterone.

What about bone health? Evidently, older white women who ate onions at least once a day had an overall bone density that was 5% greater than women who ate onions no more than once a month. Now, 5% might not sound like a lot, but that improvement in bone density could potentially mean decreasing their hip fracture risk by more than 20% if, indeed, it is cause and effect.

Daily administration of onion for four weeks did cause a big bump in bone density. This could lead to a safe, effective, and low-cost approach to osteoporosis in—you guessed it—rats. Another rodent study!

Great strides have been made in treating osteoporosis with drugs, but they have the potential for serious adverse side effects, so scientists have turned their attention to natural remedies. In one study, researchers randomized people to drink onion juice or placebo onion juice for 8 weeks. Improvement was noted for a marker of bone health; however, they didn’t actually follow participants long enough to compare osteoporosis rates.

Do shallots exhibit anti-allergy activity or offer any therapeutic effects for relieving allergic runny noses? Sixteen patients were randomized equally into an antihistamine group or a group that got antihistamines and capsules containing dried shallot powder. It looked like the shallot group did better after four weeks, but there was no statistically significant difference in total symptoms between the two groups. So, another #onionfail.

What about testing the effects of eating fresh yellow onion to try to decrease the toxic effects of a chemotherapy drug called doxorubicin in breast cancer patients? Unfortunately, no significant benefit was found in decreasing damage to the liver or heart. But eating fresh yellow onion was found to help reduce high blood sugar levels and insulin resistance in breast cancer patients during doxorubicin-based chemotherapy. The drug isn’t just toxic to the liver and heart—it may also contribute to insulin resistance.

So, researchers performed a randomized, triple-blind, controlled clinical trial, randomizing patients to eat a whole onion a day or a third of an onion a day for eight weeks. What happened? The higher-dose onion group experienced a significant decrease in blood sugars and insulin resistance compared to the lower-dose group. Levels rose in the lower-dose group but fell in the higher-dose group, as you can see below and at 4:28 in my video.

So, make onions your friend. What’s the worst that can happen—a little onion breath and body odor?

Doctor’s Note

What else can we do for breast cancer? See related posts below.

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April 29, 2026
How to Boost Your Life Expectancy by 12 to 14 Years
What can physicians do to promote healthy, life-extending lifestyle changes?

A pivotal paper published in Europe more than a decade ago entitled “Healthy Living Is the Best Revenge” found that practicing just four simple, healthy lifestyle factors compared to none could potentially have a strong impact on preventing chronic diseases. We’re talking nearly 80% less chronic disease risk, slashing diabetes risk by 93%, dropping heart attack risk by 81%, and cutting stroke risk in half and cancer risk by 36%. Think about what that means. The potential for preventing disease and death is enormous. In the United States alone every year, there are a half million first heart attacks, a half million first strokes, a million new cases of diabetes, and a million new cancer diagnoses. The message is clear: Practicing a few healthy behaviors can have a huge impact.

What are those four fabled factors?
- never smoking
- not being obese
- averaging about a half hour of exercise a day
- following healthful dietary principles, including a lot of fruits, vegetables, and whole grains, and less meat
Follow those four simple rules and boom! Enjoy nearly 80% reduced risk of major chronic diseases.

What does that mean for mortality risk? As I discuss in my video How to Increase Your Life Expectancy 12 to 14 Years, a similar combination of four healthy behaviors predicted “a 4-fold difference in total mortality in men and women, with an estimated impact equivalent to 14 y[ears] in chronological age,” meaning the individuals were dying at such a reduced rate that it was as if they were 14 years younger. “Finally, a Regimen to Extend Human Life Expectancy,” proclaimed a commentary in reference to a study that had made a similar analysis of the impact of healthy lifestyle behaviors on life expectancies. But this time, it looked directly at the U.S. population, which is particularly important, since Americans have a shorter life expectancy compared to people living in nearly all other higher-income countries. The researchers concluded that a healthy lifestyle could substantially reduce premature mortality and increase life expectancy in U.S. adults. Okay, but by how much? They estimated that adhering to a low-risk lifestyle could extend life expectancy at age 50 by 14 years in women and 12.2 years in men. So, if you’re 50 right now, instead of only living to 79 if you’re a woman and 75½ if you’re a man in the United States, taking even just basic care of yourself could propel you to an average life expectancy of 93 if you’re a woman and 87½ if you’re a man.

The bottom line is it’s never too late to turn back the clock. A midlife switch just to the basics—at least five daily servings of fruits and vegetables, walking 20 minutes a day, not smoking, and maintaining a healthy weight—leads to a substantial reduction in mortality even in the following few years. We’re talking a 40% lower risk of dying in the subsequent four years. Indeed, “making the necessary changes to adhere to a healthy lifestyle is extremely worthwhile, and…middle-age is not too late to act.”

As an aside, when I realized the 12 to 14 years of added life expectancy were based on data from health professionals, I got excited about all the potential ripple effects. If health professionals start getting healthier, they can become role models for more healthful living and potentially save more lives than just their own. But that may have been wishful thinking. Practicing what you preach can sometimes backfire. Evidently, “displays of excellence can paradoxically turn off the very people they are trying to inspire.”

It’s reasonable to assume that not being a hypocrite and trying to walk the walk would lead to positive consequences, inspiring confidence in others. Don’t you want a dance instructor who can dance, a music teacher who can play, and a health professional who’s healthy? But “this simple intuition fails to take into account the concerns about devaluation than an expert’s superior behavior elicits in others”—that is, that may make people feel inadequate. For example, you know how vegetarians often become targets of ridicule and hostility? That’s because they may come off as morally superior and make other people feel like they’re being looked down upon.

There was an elegant demonstration of this phenomenon in a study where “principled deviants who take the high road threaten others’ moral self-worth.” Participants were asked to complete “a racist task,” and those “moral rebels” who refused to do so were cheered on by observers but disparaged by their fellow participants who had done the task. Why? Because the rebels’ stance was “an implied indictment of their spinelessness.” Isn’t that interesting?

So, when doctors portray themselves as “the picture of health,” patients might think they’re being holier-than-thou, which can unintentionally alienate those who need the doctors’ help the most. It’s easy to imagine how someone with a weight issue might feel threatened and judged by a physician triathlete. But what are we supposed to do? We want healthy practitioners. Physicians who smoke are less likely to tell their patients to quit smoking, physicians who are overweight are less likely to advise about weight loss, and physicians who don’t work out are less likely to talk about exercise. What doctors can do to make patients more comfortable is emphasize that their role is to help people meet their own personal health goals, whatever they may be. Studies show that when doctors take this approach, it increases the appeal of “fitness-focused” physicians to overweight patients. So, doctors can then display model behavior without inadvertently alienating those who would most benefit from their counsel.

Doctor’s Note

For more on lifestyle medicine, see related posts below.
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April 24, 2026
Do Vitamin C Supplements Help Reduce Anxiety?

What are the risks and benefits of using vitamin C for depression and anxiety?

“In adults, emerging evidence suggests that higher daily intake of ﬁber-rich fruit and vegetable servings is associated with lower incidences of anxiety, greater happiness, higher life satisfaction, and greater social-emotional well-being,” says a review in the journal Nutrients. So, “persuading people to consume more fruits and vegetables may not only benefit their physical health in the long-run, but also their mental well-being in the short-run,” concluded a study in Social Science & Medicine. Fruit consumption, for example, has a protective association with leading killers like heart disease, stroke, diabetes, and cancer, as well as depression. The question is why?

Several mechanisms have been proposed. For example, one posits it’s the antioxidant and anti-inflammatory properties of produce, which scavenge the free radicals that are involved in some of the inflammation associated with depression. If that’s the case, what about simply taking vitamin C supplements? The brain has some of the highest levels of vitamin C in the body, so it’s thought that if extra vitamin C is consumed, it may have some sort of therapeutic role in brain diseases, especially given that it is not just an antioxidant, but also has other critical functions in the brain, such as helping to build neurotransmitters like dopamine. But you don’t know whether it actually helps until you put it to the test.

One study found a beneficial effect of adding vitamin C as an adjunct treatment to an antidepressant, while another study found no benefit from vitamin C supplementation.

So, there are mixed results for vitamin C and depression. Another study found no benefit when it came to depression, but those randomized to vitamin C instead of placebo pills did show a significant decrease in anxiety level. And this wasn’t only seen in that study.

The effects of oral vitamin C supplementation on anxiety in high school students were studied in a double-blind, randomized, placebo-controlled trial. The teens were given 500 mg a day of vitamin C or a placebo. That daily amount of vitamin C is about what you’d find in five oranges, four yellow kiwifruit or guavas, or one and a half yellow bell peppers. Within just two weeks, the vitamin C reduced anxiety levels compared to placebo, as well as provided a significant drop in heart rate.

Given these data showing that vitamin C may have an anxiety-reducing effect, researchers sought to find out if a single dose could acutely affect emotional states. And indeed, within only two hours of taking some vitamin C, study participants experienced a significant drop in anxiety compared to placebo, though only among those who started out the most anxious in the first place, as you can see below and at 2:42 in my video Do Vitamin C Supplements Help With Anxiety?.

As a bonus, vitamin C supplementation may lower our blood pressure a few points, but whole fruits and vegetables can do the same thing—and may even do it better for those who need it the most, as shown below and at 2:53 in my video.

As I’ve shown previously, simply adding just two servings of fruits and vegetables a day can have psychological well-being benefits within only two weeks—and without the kidney stone risk associated with vitamin C supplements, though that appears to be only a problem in men.

Doctor’s Note

For more on vitamin C and on anxiety, check out related posts below.

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April 22, 2026
Which Potato Is the Most Nutritious?

Are yellow-fleshed potatoes healthier than white? And what about the glycoalkaloid toxins?

The high glycemic impact of potatoes may increase the risk of type 2 diabetes, perhaps by chronically overstimulating the insulin-producing cells in the pancreas. In my last two blogs, I explained how you can decrease the glycemic impact of white potatoes by eating them cold, chilling then reheating them, or adding broccoli, lemon juice, or vinegar. What else can we do?

Well, the pigments in brightly colored berries can act as starch blockers, as you can see below and at 0:38 in my video The Healthiest Type of Potato.

So, if you’re going to eat a high glycemic food, you may be able to moderate its impact by, for example, spreading raspberries on your toast, adding strawberries to your cornflakes, or sprinkling blueberries into your pancake batter. I’m not saying you have to put blackberries in your baked potato, but given that the natural color compounds in fruits can slow down starch digestion, what about pigmented potatoes?

Even regular yellow potatoes like Yukon gold may be preferable to white, but the best may be purple potatoes—not just purple-skinned potatoes but purple-fleshed potatoes. If you’ve never seen purple potatoes, they are remarkable—they have almost a neon-blue glow, which you can see below and at 1:14 in my video.

And not only do they look cool, but purple potatoes cause less of an insulin spike and less of a blood sugar spike compared to even the yellow-fleshed potatoes, suggesting that switching from yellow or white potatoes to purple ones “could have large potential in maintaining public health.”

How do we know the pigments themselves are responsible, rather than other differences between the different potato varieties? Researchers tried using a control made of berries in a potato starch jelly, but that approach would seem to add even more variables. In a test tube, extracts of purple- and red-fleshed potatoes can act as starch blockers. So, if you extract and purify the purple potato pigments, you could remove any other effects of the different potato varieties by adding those purple pigments to yellow potatoes. And lo and behold, compared to plain yellow potatoes, this results in suppressions of blood sugar and insulin spikes. Instead of an overshoot reaction, where blood sugars can actually drop below fasting levels, you get the gentler rise and fall in blood sugars you’d expect from a lower glycemic food, as you can see below and at 2:25 in my video.

The authors suggest purple potato extracts could be produced to make supplements or fancy functional foods, but it might be more cost-effective to get these compounds from consuming purple potatoes themselves.

The purple potato pigments may also affect inflammation. The Potato Association of America likes to paint potatoes as an anti-inflammatory food, but what it doesn’t tell you is that this benefit may be limited to pigmented potatoes. When study participants were randomized to eat a small white potato every day for six weeks versus a yellow- or purple-fleshed potato, those in the purple potato group achieved significantly lower levels of inflammation compared to those in the white potato group, measuring both C-reactive protein and interleukin-6, shown below and at 3:13 in my video.

Pigmented potato consumption also alters oxidative stress. Within hours of eating a large purple potato, you get a nice 60% bump in the antioxidant power of your bloodstream, and this translates into less free radical DNA damage. If you compare the antioxidant activity of white potatoes, yellow potatoes, and purple potatoes, Yukon gold has about twice the antioxidant power as white, but purple has 20 times the antioxidants. That’s comparable to what you might see in berries. Half a purple potato has about the same polyphenol antioxidant content as half a cup of blueberries.

Purple potatoes can increase the antioxidant capacity of our bloodstream, whereas straight white potato starch can act as a pro-oxidant and decrease it. Eat a purple potato, and, over the next eight hours, the antioxidant capacity of your bloodstream goes up. In contrast, if you eat white potato starch devoid of any pigment, you can end up worse off than where you started, as you can see below and at 4:12 in my video.

Okay, but does this translate into different physiological effects? Yes, indeed. When people ate either purple potatoes or white potatoes for two weeks, the purple potatoes improved a measure of arterial stiffness, whereas the white potatoes did not. And this translates into a drop in blood pressure, even in those already taking high blood pressure drugs, suggesting purple potatoes are an effective blood pressure–lowering agent.

But what about the toxic glycoalkaloid compounds found in potatoes? The toxic human dose starts around 2 to 5 mg/kg of body weight, and the lethal dose is not too far behind. But the average amount of total glycoalkaloids found in most potatoes, however, is less than 100 mg/kg; so, at the average American weight of 180 pounds, a toxic dose is like four to nine pounds of potatoes. What happens when you approach that amount? It’s possible you can get nausea, vomiting, or diarrhea that could be easily confused with something like gastroenteritis or food poisoning. Some people can start to get sick at just 1.25 mg/kg of body weight or even experience symptoms at 1 mg/kg. That would only be about two pounds of potatoes at the average American weight. It’s also possible that the glycoalkaloids could start accumulating if you eat potatoes day in and day out. But what about those people who go on a fad potato diet and eat three or four pounds a day? They can do that without risking getting sick if they peel their potatoes, which removes nearly all of the glycoalkaloids.

Doctor’s Note

This is the last in a five-video series on potatoes. If you missed any of the others, see:

You may also be interested in The Best Way to Cook Sweet Potatoes.

The video on berries I mentioned is Getting Starch to Take the Path of Most Resistance.

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April 17, 2026
How to Tame Blood Sugar Spikes after Eating Potatoes

Broccoli, vinegar, and lemon juice are put to the test to blunt the glycemic index of white potatoes.

White potatoes have a high glycemic index, and consumption of high glycemic impact foods may increase the risk of diabetes. Normally, after a meal, we’d like our blood sugars to rise and fall gently and naturally. But with high glycemic foods like potatoes, we get an exaggerated blood sugar spike. This leads our body to over-compensate with insulin, forcing our blood sugars lower than when we started, which results in negative metabolic consequences, such as a rise in triglyceride fats in the blood, as you can see below and at 0:34 in my video How to Reduce the Glycemic Impact of Potatoes.

However, potatoes are a good source of vitamin C, potassium, and polyphenols, which may counterbalance their glycemic impact. This may explain why potatoes appear to have a neutral effect when it comes to lifespan, unlike other whole plant foods that have been associated with actively living longer.

In my last blog, I explained how the act of chilling cooked potatoes can dramatically lower their glycemic index, even if you then reheat them in a microwave. How else might we reduce the glycemic impact of white potatoes? The same way you make anything better in your nutritional life—add broccoli. Eating two servings of cooked broccoli with your mashed potatoes would certainly do it, immediately cutting the insulin demand by nearly 40%. In contrast, adding chicken breast makes things worse, and adding tuna fish makes things even worse still, nearly doubling the amount of insulin your body has to pump out, as shown below and at 1:31 in my video.

Why does plant protein make things better, but animal protein makes things worse? Because decreased consumption of branched-chain amino acids improves metabolic health. I cover this in my book How Not to Diet, as well as in my video on the topic.

Speaking of How Not to Diet, remember the section on vinegar? The graph below illustrates the blood sugar and insulin spikes that someone with prediabetes may experience after eating a bagel. When that same bagel is consumed alongside a tablespoon or so of apple cider vinegar diluted in about a quarter cup of water, though, the spikes are significantly reduced, as you can see below and at 2:10 in my video.

Does it work for potatoes, too? Simply chilling potatoes may cut down on the blood sugar and insulin spikes, but to get significant drops in both, you just have to add about a tablespoon of vinegar to drop levels by 30% to 40%. And that was just plain white distilled vinegar.

Is it the vinegar itself, or would any acidic condiment do? In a test tube, lemon juice appeared to have a remarkable starch-blocking effect, but you can’t know if it works in people until you put it to the test. And indeed, lemon juice reduces the glycemic responses to bread. And not just by a little, but by about 30%, as you can see below and at 2:50 in my video.

Now, the study participants were drinking a half cup of lemon juice, but that makes it even more remarkable that it was helpful because that added an extra half teaspoon of sugar, yet they still had a better blood sugar response. Vinegar is more potent, though. Just one to two tablespoons a day of vinegar diluted in water can significantly improve both short- and long-term blood sugar control in people with diabetes, which is why clinicians may want to include vinegar consumption as part of their dietary recommendations for their patients with diabetes.

Doctor’s Note

This is the fourth video in a five-part series on potatoes. Missed the first three? See:

What about the glycoalkaloid toxins in potatoes? I cover that and discuss the best kind of potato in my upcoming final video in the series: The Healthiest Type of Potato.

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April 15, 2026
Why Cooling Potatoes Lowers Their Glycemic Load

If you eat potatoes when they’re cold, as in potato salad, or chilled and reheated, you can get a nearly 40% lower glycemic impact.

If you systematically pull together all the best studies on potato consumption and chronic disease risk, an association is found for the risk of type 2 diabetes and hypertension—but that’s for French fries. Consumption of boiled, baked, or mashed potatoes was not associated with the risk of high blood pressure, but there was still a pesky link with diabetes. Overall, eating potatoes is not related to risk for many chronic diseases, but boiled potatoes could potentially pose a small increase in risk for diabetes. That’s one of the reasons some question whether they should be counted as vegetables when you’re trying to reach your recommended daily servings of fruits and vegetables.

If you look at other whole plant foods—nuts, vegetables, fruits, and legumes (which are beans, split peas, chickpeas, and lentils)—they’re associated with living a longer life. Significantly less risk of dying from cancer, dying from cardiovascular diseases like heart attacks, and 25% less chance of dying prematurely from all causes put together. But no such protection is gained from potatoes for cancer, heart disease, or overall mortality. So, the fact that potatoes don’t seem to affect mortality can be seen as a downside. Now, it’s not like meat, which may actually actively shorten your life, as you can see below and at 1:28 in my video Glycemic Index of Potatoes: Why You Should Chill and Reheat Them.

But there may be an opportunity cost to eating white potatoes, since every bite of a potato is a lost opportunity to put something even healthier in your mouth—something that may actively make you live longer.

So, potatoes are kind of “a double-edged sword.” The reason that potato consumption may have just a neutral impact on mortality risk is that all the fiber, vitamin C, and potassium in white potatoes might be counterbalanced by the adverse effects of their high glycemic index. Not only are high glycemic impact diets “robustly associated” with developing type 2 diabetes, but current evidence suggests that this relationship is cause and effect.

A front group for the potato industry called the Alliance for Potato Research and Education funded a study that found that intake of non-fried potatoes does not affect blood sugar markers, when compared with the likes of Wonder Bread, that is, so that isn’t really saying very much. Foods with a glycemic index (GI) higher than 70 are classiﬁed as high-GI foods (high glycemic index foods), and those lower than 55 are low-GI foods. Pure sugar water, for example, is often standardized at 100, and white bread and white potatoes are also way up there as high glycemic index foods. But when you compare them to an intact grain, like barley groats (also known as pot barley), which is a super-low GI food, you can see how refined grains and potatoes are simply no match. Check out the numbers below or at 2:47 in my video.

Is there any way we can have our potatoes and eat them too, by somehow lowering their glycemic index? Well, if you boil potatoes and then put them in the fridge to cool, some of the starch crystallizes into a form that can no longer be broken down by the starch-munching enzymes in your gut, as you can see below and at 3:06 in my video.

However, the amounts of this so-called resistant starch that are formed are relatively small, making it hard to recommend cold potatoes as a solution. But when put to the test, you actually see a dramatic drop in glycemic index in cold versus hot potatoes, shown below and at 3:23 in my video.

So, by consuming potatoes as potato salad, for instance, you can get nearly a 40% lower glycemic impact. The chilling effect might, therefore, also slow the rate at which the starch is broken down and absorbed. So, people who want to minimize dietary glycemic index may consider precooking potatoes and having them chilled or reheated. The downside of eating potatoes cold is that they might not be as satiating as eating hot potatoes. But you may get the best of both worlds by first cooling them and then reheating them, which is exactly what was done in that famous study I profiled in my book How Not to Diet. The single most satiating food out of the dozens tested was boiled-then-cooled-then-reheated potatoes, as you can see below and at 4:09 in my video.

There is actually an appetite-suppressing protein in potatoes called potato protease inhibitor II, but the way you prepare your potatoes makes a difference. Both boiled and mashed potatoes are significantly more satiating than French fries, as shown below and at 4:26 in my video.

That was for fried French fries, though. What about baked French fries? Folks had a big drop in appetite after eating boiled mashed potatoes, compared to white rice or white pasta, which is right where fried French fries were stuck, as well as baked French fries. So, though baked fries may be your BFF, they’re not very satiating.

Doctor’s Note

Just to be clear, you don’t have to reheat. Chilling is the crucial step to dramatically lower the glycemic index, so you can certainly enjoy a cold potato salad. If you’re trying to control your weight, though, you may want to avoid even baked fries.

This is the third in a five-video series on potatoes. If you missed the first two, see Do Potatoes Increase the Risk of Diabetes? and Do Potatoes Increase the Risk of High Blood Pressure and Death?.

Chilling isn’t the only trick to blunt the glycemic impact. You can also add vinegar, lemon, or broccoli.

Stay tuned for the final two videos in this series: How to Reduce the Glycemic Impact of Potatoes and The Healthiest Type of Potato.

Join the resistance! Check out related posts below.

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April 10, 2026

Explore NutritionFacts.org Resources

NutritionFacts.org has a wide range of resources to help you on your journey to a healthier life.

Primers

**The How Not to Die Documentary**

In celebration of the 10th anniversary of the publication of How Not to Die, the Greenbaum Foundation commissioned a documentary about Dr. Greger’s life and work. The film also includes interviews with many of the leading luminaries in the evidence-based nutrition movement.

Daily Dozen Meal Planning Guide

The healthiest diet is one that maximizes the intake of foods-as-grown—whole plant-based foods—and minimizes the consumption of processed and animal-based foods. In his New York Times Best Seller, How Not to Die, Dr. Greger covers the whys of eating healthfully, exploring diet’s role in the prevention, treatment, and sometimes even reversal of the fifteen leading causes of death in the United States, before diving into the hows of eating healthfully and sharing his Daily Dozen checklist, grocery shopping tips, and meal planning ideas.

In our Daily Dozen Meal Planning Guide, we walk you through the steps of incorporating the Daily Dozen into your life and give you additional strategies to help you build more healthful eating habits. Download your free copy of the guide today.

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Email Series

We offer three, free, engaging and motivating email series to support you in living healthfully:

Join us for our How to Live Longer series, where we go through some of the most important information Dr. Greger uncovered on the science behind healthy aging. Sign up for this free email series and learn how to live longer, vibrantly.
Our weekly Plant-Based Living email series gives you simple takeaways and actionable tips on healthy eating. Whether you’re new to a whole food, plant-based lifestyle or would benefit from reminders on some of the key aspects of evidence-based nutrition, this free series is for you.
Join us for 11 weeks of Daily Dozen support emails to help you Do the Dozen with ease. Sign up for this free series today.

Dr. Greger’s Live Presentations

From the comfort of your own home, join Dr. Greger as he dives into the content of each of his acclaimed books with these recordings of his live presentations. Be sure to check out his newest presentation on ultra-processed foods.

Optimum Nutrient Recommendations

Check out our Optimum Nutrient Recommendations for more on vitamin B12, calcium, vitamin D, omega-3 fatty acids, iodine, iron, and selenium.

Topic Pages

To view our entire video library organized by subject, explore our topic pages.

Recipes

Each recipe in our collection uses only health-promoting ingredients, based on Dr. Greger’s Daily Dozen and dining by traffic light system. These whole food, plant-based dishes, sauces, condiments, and sides come from The How Not to Age Cookbook, The How Not to Die Cookbook, and The How Not to Diet Cookbook, part of Dr. Greger’s award-winning series, as well as contributions from the NutritionFacts.org team and friends.

VIEW ALL RECIPES

Podcast

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Join Dr. Greger live each month for an exciting Q&A. Sign up for our free newsletter to get the date and link of the upcoming live Q&A directly in your inbox. You can also check out past Q&A sessions recordings.

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Six of our webinars are now available for on-demand CME credits via the LearnWorlds platform. What’s a CME? CME stands for Continuing Medical Education for doctors and other medical professionals. Physicians need to get a certain amount of credits to stay licensed, and we’re honored we can offer accredited classes.

International Content

The entire NutritionFacts.org website has been translated into Spanish, and we also have Spanish Facebook and Instagram pages. On DrGreger.org, you’ll find shirts, stickers, and Evidence-Based Eating Guides in Spanish, too.

Check out our NutritionFacts in China page for links to all our Chinese content, including social media, books, and infographics. On DrGreger.org, we also have shirts and Evidence-Based Eating Guides in Chinese.

Dr. Greger’s books have been translated in many languages. Check out this page for more information.

Want to see all the NutritionFacts videos available in your language? Visit our search page and check out the ‘Subtitle Language’ menu on the right side or press the ‘Filters’ button if you’re on a mobile device. After you make your selection, the results will list all the videos subtitled in that language. For instructions on how to access subtitles and translations in our videos, see Closed Captions and Translations. For more on translations, check out our Information About Our Translated Resources page.

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Host a Screening

Share the latest in evidence-based nutrition with your community by hosting a free screening of Dr. Greger’s How Not to Die, Evidence-Based Weight Loss, or How Not to Age presentation. Each video runs for approximately one hour. Your free Digital Event Kit will include the video, an introduction to NutritionFacts, and tips for hosting. An engaging, fun trivia game for attendees is also included in the How Not to Die and Evidence-Based Weight Loss screening kits. Each screening event is approximately two hours long.

By providing these fun and educational event kits, we hope to make it easier than ever to spread the message about evidence-based eating.

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In the DrGreger.org store, you can find digital downloads of our video collections, shirts, and outreach materials.

The Daily Dozen App

Download the free Daily Dozen app today and start including some of the healthiest foods in your diet. Track your servings, analyze your progress, and learn along the way. The app is available in the App Store and Google Play.

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April 8, 2026