Is White Rice a Yellow-Light or Red-Light Food?

Arsenic is not just considered to be a carcinogen; it’s also designated as a “nonthreshold carcinogen, meaning that any dose, no matter how small, carries some cancer risk”—so there really isn’t a “safe” level of exposure. Given that, it may be reasonable to “use the conservative ALARA” approach, reducing exposure As Low As Reasonably Achievable.

I have a low bar for recommending people avoid foods that aren’t particularly health-promoting in the first place. Remember when that acrylamide story broke, about the chemical found concentrated in french fries and potato chips? (See my video Acrylamide in French Fries for more.) My take was pretty simple: Look, we’re not sure how bad this acrylamide stuff is, but we’re talking about french fries and potato chips, which are not healthy anyway. So, I had no problem provisionally bumping them from my list of yellow-light foods into my red-light list, from “minimize consumption” to “ideally avoid on a day-to-day basis.”

One could apply the same logic here. Junk foods made out of brown rice syrup, rice milk, and white rice are not just processed foods, but also arsenic-contaminated processed foods, so they may belong in the red zone as red-light foods we should avoid. What about something like whole brown rice? That is more difficult, because there are pros to help outweigh the cons. I discuss this in my video Is White Rice a Yellow-Light or Red-Light Food?, where you can see a graphical depiction of my traffic light food system at 0:49.

The rice industry argues that the “many health benefits of rice consumption outweigh any potential risk,” which is the same sentiment you hear coming out of Japan about the arsenic-contaminated seaweed hijiki: Yes, “the cancer risk posed by hijiki consumption exceeds this acceptable [cancer risk] level by a factor of 10,” an order of magnitude, but the Japanese Ministry of Health stresses the “possible health benefits,” such as lots of fiber and minerals, as if hijiki was the only weed in the sea. Why not choose any of the other seaweeds and get all the benefits without the arsenic? So, when the rice industry says the “many health benefits of rice consumption outweigh any potential risk,” it’s as if brown rice was the only whole grain on the planet. Can’t you get the whole grain benefits without the risks by eating oatmeal, barley, or quinoa instead? Or, is there some unique benefit to rice, such that we really should try to keep brown rice in our diet?

Consumer Reports recommended moving rice to the yellow-light zone—in other words, don’t necessarily avoid it completely, but moderate your intake. The rice industry, in a fact sheet entitled “The Consumer Reports Article is Flawed,” criticized Consumer Reports for warning people about the arsenic levels in rice, saying “[t]here is a body of scientific evidence that establishes…the nutritional benefits of rice consumption; any assessment of the arsenic levels in rice that fails to take this information into account is inherently flawed and very misleading.” The rice industry cites two pieces of evidence. First, it asserts that rice-consuming cultures tend to be healthier, but is that because of, or despite, their white rice consumption? And what about the fact that rice-eating Americans tend to be healthier? Perhaps, but they also tend to eat significantly less saturated fat. So, once again, how do we know whether it’s because of—or despite—the white rice?

The rice industry could have cited the study I discuss at 3:12 in my video that showed that brown rice intake of two or more servings a week was associated with a lower risk of diabetes, but presumably, the reason it didn’t is because intake of white rice is associated with an increased risk of diabetes, and white rice represents 95 percent of the U.S. rice industry. Switching out a third of a serving of white rice a day for brown rice might lower diabetes risk by 16 percent, but switching out that same white rice for whole grains in general, like oats or barley, might work even better! So, other grains have about ten times less arsenic and are associated with even lower disease risk. No wonder the rice industry doesn’t cite this study.

It does cite the Adventist studies, though, and some in vitro data. For example, in a petri dish, as you can see at 4:05 in my video, there are rice phytonutrients that, at greater and greater doses, can inhibit the growth of colon cancer cells while apparently leaving normal colon cells alone, which is exciting. And, indeed, those who happened to eat those phytonutrients in the form of brown rice once or more a week between colonoscopies had a 40 percent lower risk of developing polyps. (The consumption of green leafy vegetables, dried fruit, and beans were also associated with lower polyp incidence.) But, the only reason we care about the development of polyps is that polyps can turn into cancer. But, there had never been studies on brown rice consumption and cancer…until now, which I discuss in my video Do the Pros of Brown Rice Outweigh the Cons of Arsenic?.


For those unfamiliar with my traffic light system, I talk about it in my book trailer. Check out How Not to Die: An Animated Summary.

Almost there! This is the corresponding article to the 12th in my 13-video series on arsenic in the food supply. If you missed any of the first 11 videos, see:

Ready for the finale? See Do the Pros of Brown Rice Outweigh the Cons of Arsenic?.

And you may be interested in Benefits of Turmeric for Arsenic Exposure.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Cancer Risk from Arsenic in Rice and Seaweed

A daily half-cup of cooked rice may carry a hundred times the acceptable cancer risk of arsenic. What about seaweed from the coast of Maine?

“At one point during the reign of King Cotton, farmers in the south central United States controlled boll weevils with arsenic-based pesticides, and residual arsenic still contaminates the soil.” Different plants have different reactions to arsenic exposure. Tomatoes, for example, don’t seem to accumulate much arsenic, but rice plants are really good at sucking it out of the ground—so much so that rice can be used for “arsenic phytoremediation,” meaning you can plant rice on contaminated land as a way to clear arsenic from the soil. Of course, you’re then supposed to throw the rice—and the arsenic—away. But in the South, where 80 percent of U.S. rice is grown, we instead feed it to people.

As you can see at 0:52 in my video Cancer Risk from Arsenic in Rice and Seaweed, national surveys have shown that most arsenic exposure has been measured coming from the meat in our diet, rather than from grains, with most from fish and other seafood. Well, given that seafood is contributing 90 percent of our arsenic exposure from food, why are we even talking about the 4 percent from rice?

The arsenic compounds in seafood are mainly organic—used here as a chemistry term having nothing to do with pesticides. Because of the way our body can deal with organic arsenic compounds, “they have historically been viewed as harmless.” Recently, there have been some questions about that assumption, but there’s no question about the toxicity of inorganic arsenic, which you get more of from rice.

As you can see at 1:43 in my video, rice contains more of the toxic inorganic arsenic than does seafood, with one exception: Hijiki, an edible seaweed, is a hundred times more contaminated than rice, leading some researchers to refer to it as the “so-called edible hijiki seaweed.” Governments have started to agree. In 2001, the Canadian government advised the public not to eat hijiki, followed by the United Kingdom, the European Commission, Australia, and New Zealand. The Hong Kong Centre for Food Safety advised the public not to eat hijiki and banned imports and sales of it. Japan, where there is actually a hijiki industry, just advised moderation.

What about seaweed from the coast of Maine—domestic, commercially harvested seaweed from New England? Thankfully, only one type, a type of kelp, had significant levels of arsenic. But, it would take more than a teaspoon to exceed the provisional daily limit for arsenic, and, at that point, you’d be exceeding the upper daily limit for iodine by about 3,000 percent, which is ten times more than reported in a life-threatening case report attributed to a kelp supplement.

I recommend avoiding hijiki due to its excess arsenic content and avoiding kelp due to its excess iodine content, but all other seaweeds should be fine, as long as you don’t eat them with too much rice.

In the report mentioned earlier where we learned that rice has more of the toxic inorganic arsenic than fish, we can see that there are 88.7 micrograms of inorganic arsenic per kilogram of raw white rice. What does that mean? That’s only 88.7 parts per billion, which is like 88.7 drops of arsenic in an Olympic-size swimming pool of rice. How much cancer risk are we talking about? To put it into context, the “usual level of acceptable risk for carcinogens” is one extra cancer case per million. That’s how we typically regulate cancer-causing substances. If a chemical company wants to release a new chemical, we want them to show that it doesn’t cause more than one in a million excess cancer cases.

The problem with arsenic in rice is that the excess cancer risk associated with eating just about a half cup of cooked rice a day could be closer to one in ten thousand, not one in a million, as you can see at 4:07 in my video. That’s a hundred times the acceptable cancer risk. The FDA has calculated that one serving a day of the most common rice, long grain white, would cause not 1 in a million extra cancer cases, but 136 in a million.

And that’s just the cancer effects of arsenic. What about all the non-cancer effects? The FDA acknowledges that, in addition to cancer, the toxic arsenic found in rice “has been associated with many non-cancer effects, including ischemic heart disease, diabetes, skin lesions, renal [kidney] disease, hypertension, and stroke.” Why, then, did the FDA only calculate the cancer risks of arsenic? “Assessing all the risks associated with inorganic arsenic would take considerable time and resources and would delay taking any needed action to protect public health” from the risks of rice.

“Although physicians can help patients reduce their dietary arsenic exposure, regulatory agencies, food producers, and legislative bodies have the most important roles” in terms of public health-scale changes. “Arsenic content in U.S.-grown rice has been relatively constant throughout the last 30 years,” which is a bad thing.

“Where grain arsenic concentration is elevated due to ongoing contamination, the ideal scenario is to stop the contamination at the source.” Some toxic arsenic in foods is from natural contamination of the land, but soil contamination has also come from the dumping of arsenic-containing pesticides, as well as the use of arsenic-based drugs in poultry production and then the spreading of arsenic-laced chicken manure on the land. Regardless of why south central U.S. rice paddies are so contaminated, we shouldn’t be growing rice in arsenic-contaminated soil.

What does the rice industry have to say for itself? Well, it started a website called ArsenicFacts. Its main argument appears to be that arsenic is everywhere, we’re all exposed to it every day, and it’s in most foods. But shouldn’t we try to cut down on the most concentrated sources? Isn’t that like saying look, diesel exhaust is everywhere, so why not suck on a tailpipe? The industry website quotes a nutrition professor saying, “All foods contain arsenic. So, if you eliminate arsenic from your diet, you will decrease your risk…and you’ll die of starvation.” That’s like Philip Morris saying that the only way to completely avoid secondhand smoke is to never breathe—but then you’ll asphyxiate, so you might as well just start smoking yourself. If you can’t avoid it, you might as well consume the most toxic source you can find?!

That’s the same tack the poultry industry took. Arsenic and chicken? “No need to worry” because there’s a little arsenic everywhere. That’s why it’s okay the industry fed chickens arsenic-based drugs for 70 years. If you can’t beat ’em, join ’em.

How can the rice industry get away with selling a product containing a hundred times the acceptable cancer risk? I cover that and so much more in my other videos on arsenic and rice, which also include concrete recommendations on how to mediate your risk.


Check out:

Pesticides were not the only source of arsenic. Poultry poop, too, if you can believe it! I cover that story in Where Does the Arsenic in Chicken Come From? and Where Does the Arsenic in Rice, Mushrooms, and Wine Come From?.

Chronic low-dose arsenic exposure is associated with more than just cancer. See The Effects of Too Much Arsenic in the Diet.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Updating Our Microbiome Software and Hardware

Good bacteria, those living in symbiosis with us, are nourished by fruits, vegetables, grains, and beans, whereas bad bacteria, those in dysbiosis with us and possibly contributing to disease, are fed by meat, junk food and fast food, seafood, dairy, and eggs, as you can see at 0:12 in my video Microbiome: We Are What They Eat. Typical Western diets can “decimate” our good gut flora.

We live with trillions of symbionts, good bacteria that live in symbiosis with us. We help them, and they help us. A month on a plant-based diet results in an increase in the population of the good guys and a decrease in the bad, the so-called pathobionts, the disease-causing bugs. “Given the disappearance of pathobionts from the intestine, one would expect to observe a reduction in intestinal inflammation in subjects.” So, researchers measured stool concentrations of lipocalin-2, “which is a sensitive biomarker of intestinal inflammation.” As you can see at 1:13 in my video, within a month of eating healthfully, it had “declined significantly…suggesting that promotion of microbial homeostasis”—or balance—“by an SVD [strict vegetarian diet] resulted in reduced intestinal inflammation.” What’s more, this rebalancing may have played a role “in improved metabolic and immunological parameters,” that is, in immune system parameters.

In contrast, on an “animal-based diet,” you get growth of disease-associated species like Bilophila wadsworthia, associated with inflammatory bowel disease, and Alistipes putredinis, found in abscesses and appendicitis, and a decrease in fiber-eating bacteria. When we eat fiber, the fiber-munching bacteria multiply, and we get more anti-inflammatory, anti-cancer short-chain fatty acids. When we eat less fiber, our fiber-eating bacteria starve away.

They are what we eat.

Eat a lot of phytates, and our gut flora get really good at breaking down phytates. We assumed this was just because we were naturally selecting for those populations of bacteria able to do that, but it turns out our diet can teach old bugs new tricks. There’s one type of fiber in nori seaweed that our gut bacteria can’t normally breakdown, but the bacteria in the ocean that eat seaweed have the enzyme to do so. When it was discovered that that enzyme was present in the guts of Japanese people, it presented a mystery. Sure, sushi is eaten raw, so some seaweed bacteria may have made it to their colons, but how could some marine bacteria thrive in the human gut? It didn’t need to. It transferred the nori-eating enzyme to our own gut bacteria.

“Consequently, the consumption of food with associated environmental bacteria is the most likely mechanism that promoted this CAZyme [enzyme] update into the human gut microbe”—almost like a software update. We have the same hardware, the same gut bacteria, but the bacteria just updated their software to enable them to chew on something new.

Hardware can change, too. A study titled “The way to a man’s heart is through his gut microbiota” was so named because the researchers were talking about TMAO, trimethylamine N-oxide. As you can see at 3:33 in my video, certain gut flora can take carnitine from the red meat we eat or the choline concentrated in dairy, seafood, and eggs, and convert it into a toxic compound, which may lead to an increase in our risk of heart attack, stroke, and death.

This explains why those eating more plant-based diets have lower blood concentrations of TMAO. However, they also produce less of the toxin even if you feed them a steak. You don’t see the same “conversion of dietary L-carnitine to TMAO…suggesting an adoptive response of the gut microbiota in omnivores.” They are what we feed them.

As you can see at 4:17 in my video, if you give people cyclamate, a synthetic artificial sweetener, most of their bacteria don’t know what to do with it. But, if you feed it to people for ten days and select for the few bacteria that were hip to the new synthetic chemical, eventually three quarters of the cyclamate consumed is metabolized by the bacteria into another new compound called cyclohexylamine. Stop eating it, however, and those bacteria die back. Unfortunately, cyclohexylamine may be toxic and so was banned by the FDA in 1969. In a vintage Kool-Aid ad from 1969, Pre-Sweetened Kool-Aid was taken “off your grocer’s shelves,” but Regular Kool-Aid “has no cyclamates” and “is completely safe for your entire family.”

But, if you just ate cyclamate once in a while, it wouldn’t turn into cyclohexylamine because you wouldn’t have fed and fostered the gut flora specialized to do so. The same thing happens with TMAO. Those who just eat red meat, eggs, or seafood once in a while would presumably make very little of the toxin because they hadn’t been cultivating the bacteria that produce it.


Here’s the link to my video on TMAO: Carnitine, Choline, Cancer, and Cholesterol: The TMAO Connection. For an update on TMAO, see How Our Gut Bacteria Can Use Eggs to Accelerate Cancer, Egg Industry Response to Choline and TMAO, and How to Reduce Your TMAO Levels.

Interested in more on keeping our gut bugs happy? See:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Garlic Powder to Lower Lead Levels

There are so-called chelation drugs that can be taken for acute, life-threatening lead poisoning—for instance if your two-year-old swallowed one of the little lead weights her grandma was using while sewing curtains and the doctor happened to miss it on x-ray, so it stayed lodged inside her until she died with a blood lead level of 283 mcg/dcl, a case I discuss in my video Best Foods for Lead Poisoning: Chlorella, Cilantro, Tomatoes, Moringa?.

However, for lower grade, chronic lead poisoning, such as at levels under 45 μg/dL, there were no clear guidance as to whether these chelation drugs were effective. When they were put to the test, the drugs failed to bring down lead levels long term. Even when they worked initially, in dose after dose, the lead apparently continued to seep from the patients’ bones, and, by the end of the year, they ended up with the same lead levels as the sugar pill placebo group, as you can see at 0:50 in my video. It was no surprise, then, that even though blood lead levels dipped at the beginning, researchers found no improvements in cognitive function or development.

Since much of lead poisoning is preventable and the drugs don’t seem to work in most cases, that just underscores the need “to protect children from exposure to lead in the first place.” Despite the medical profession’s “best intentions to do something to help these kids…drug therapy is not the answer.” Yes, we need to redouble efforts to prevent lead poisoning in the first place, but what can we do for the kids who’ve already been exposed?

The currently approved method, these chelating drugs that bind and remove lead from our tissues, “lack[s]…safety and efficacy when conventional chelating agents are used.” So, what about dietary approaches? Plants produce phytochelatins. All higher plants possess the capacity to synthesize compounds that bind up heavy metals to protect themselves from the harmful effects, so what if we ate the plants? “Unlike other forms of treatment (e.g., pharmacotherapy with drugs), nutritional strategies carry the promise of a natural form of therapy that would presumably be cheap and with few to no side effects.” Yes, but would it work when the drugs didn’t?

We had learned that a meal could considerably cut down on lead absorption, but “the particular components of food intake that so dramatically reduce lead absorption” were uncertain at the time. Although the calcium content of the meal appeared to be part of it, milk didn’t seem to help and even made things worse. What about calcium supplements? Some assert that calcium supplements may help in reducing lead absorption in children, but “recommendations…must be based on evidence rather than conviction.” What’s more, those assertions are based in part on studies on rodents, and differences in calcium absorption and balance between rats and humans make extrapolation tricky. What you have to do is put it to the test. Researchers found that even an extra whopping 1,800 mg of calcium per day had no effect on blood lead levels. Therefore, the evidence doesn’t support conclusions that calcium supplements help.

What about whole foods? Reviews of dietary strategies to treat lead toxicity say to eat lots of tomatoes, berries, onions, garlic, and grapes, as they are natural antagonists to lead toxicity and therefore should be consumed on a regular basis. Remember those phytochelatins? Perhaps eating plants might help detoxify the lead in our own bodies or the bodies of those we eat.

These natural phytochelatin compounds work so well that we can use them to clean up pollution. For example, the green algae chlorella can suck up lead and hold onto it, so what if we ate it? If it can clean up polluted bodies of water, might it clean up our own polluted bodies? We don’t know, because we only have studies on mice, not men and women.

So, when you hear how chlorella detoxifies, they’re talking about the detoxification of rat testicles. Yes, a little sprinkle of chlorella might help your pet rat, or perhaps you could give them some black cumin seeds or give them a sprig of cilantro, but when you hear how cilantro detoxifies against heavy metals, I presume you don’t expect the researchers to be talking about studies in rodents. If we’re interested in science protecting our children, not just their pets, we’re out of luck.

The same is true with moringa, tomatoes, flaxseed oil, and sesame seed oil, as well as black grapes, and black, white, green, and red tea. There are simply no human studies to guide us.

Dietary strategies for the treatment of lead toxicity are often based on rodent studies, but, for tofu, at least, there was a population study of people that showed lower lead levels in men and women who ate more tofu. The researchers controlled for a whole bunch of factors, so it’s not as if tofu lovers were protected just because they smoked less or ate less meat, but you can’t control for everything.

Ideally, we’d have a randomized, placebo-controlled study. Researchers would take a group of people exposed to lead, split them into two groups, with half given food and the other half given some kind of identical placebo food, and see what happens. It’s easy to do this with drugs because you just use look-alike sugar pills as placebos so people don’t know which group they’re in, but how do you make placebo food? One way to do disguised food interventions is to use foods that are so potent they can be stuffed into a pill—like garlic. There had been various studies measuring the effects of garlic in rats and looking at garlic as a potential antidote for lead intoxication distributed among different mouse organs, but who eats mouse organs? One animal study did have some direct human relevance, though, looking at the effect of garlic on lead content in chicken tissues. The purpose was to “explore the possible use of garlic to clean up lead contents in chickens which”—like all of us on planet Earth—“had been exposed to lead pollution and consequently help to minimize the hazard” of lead-polluted chicken meat.

And…it worked! As you can see at 1:59 in my video Best Food for Lead Poisoning: Garlic, feeding garlic to chickens reduced lead levels in the “edible mass of chicken” by up to 75 percent or more. Because we live in a polluted world, even if you don’t give the chickens lead and raise them on distilled water, they still end up with some lead in their meat and giblets. But, if you actively feed them lead for a week, the levels get really high. When you give them the same amount of lead with a little garlic added, however, much less lead accumulates in their bodies.

What’s even more astonishing is that when researchers gave them the same amount of lead—but this time waited a week before giving them the garlic—it worked even better. “The value of garlic in reducing lead concentrations…was more pronounced when garlic was given as a post-treatment following the cessation of lead administration”—that is, after the lead was stopped and had already built up in their tissues. We used to think that “the beneficial effect of garlic against lead toxicity was primarily due to a reaction between lead and sulfur compounds in garlic” that would glom on to lead in the intestinal tract and flush it out of the body. But, what the study showed is that garlic appears to contain compounds that can actually pull lead not only out of the intestinal contents, but also out of the tissues of the body. So, the “results indicate that garlic contain chelating compounds capable of enhancing elimination of lead,” and “garlic feeding can be exploited to safeguard human consumers by minimizing lead concentrations in meat….”

If garlic is so effective at pulling lead out of chickens’ bodies, why not more directly exploit “garlic feeding” by eating it ourselves? Well, there had never been a study on the ability of garlic to help lead-exposed humans until…2012? (Actually, I’m embarrassed to say I missed it when the study was first published. That was back when I was just getting NutritionFacts.org up and running. Now that we have staff and a whole research team, hopefully important studies like this won’t slip through the cracks in the future.)

The study was a head-to-head comparison of the therapeutic effects of garlic versus a chelation therapy drug called D-penicillamine. One hundred and seventeen workers exposed to lead in the car battery industry were randomly assigned into one of two groups and, three times a day for one month, either got the drug or an eighth of a teaspoon of garlic powder compressed into a tablet, which is about the equivalent of two cloves of fresh garlic a day. As expected, the chelation drug reduced blood lead levels by about 20 percent—but so did the garlic. The garlic worked just as well as the drug and, of course, had fewer side effects. “Thus, garlic seems safer clinically and as effective,” but saying something is as effective as chelation therapy isn’t saying much. Remember how chelation drugs can lower blood levels in chronic lead poisoning, but they don’t actually improve neurological function?

Well, after treatment with garlic, significant clinical improvements were seen, including less irritability, fewer headaches, and improvements in reflexes and blood pressure, but these improvements were not seen in the drug group. They weren’t seen after treatment with the chelation therapy drug. So, garlic was safer and more effective. “Therefore, garlic can be recommended for the treatment of mild-to-moderate lead poisoning.


 There are also some human studieson vitamin C. Check out Can Vitamin C Help with Lead Poisoning?.

For even more lead videos, see:

To learn more about chlorella, see:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Eating Seaweed Salad May Boost Immune Function

Eating seaweed salad may boost the efficacy of vaccinations and help treat cold sores, herpes, Epstein-Barr virus, and shingles.

Billions of pounds of seaweed are harvested each year, the consumption of which “has been linked to a lower incidence of chronic diseases,” both physical and mental. For example, women who eat more seaweed during pregnancy appear to be less depressed and experience fewer seasonal allergy symptoms. There’s a problem with these cross-sectional, correlational studies, however, in that they can’t prove cause and effect. Maybe seaweed consumption is just an indicator that people generally are following “traditional Japanese dietary customs,” which have lots of different aspects that could protect against disease. To know for certain whether seaweed can modulate immune function, you have to put it to the test.

As I discuss in my video How to Boost Your Immune System with Wakame Seaweed, typically, researchers start out with in vitro studies, meaning in a test tube or a petri dish, which make for quicker, cheaper, and easier experiments. One study, for example, took eight different types of seaweed and essentially made seaweed teas to drip onto human immune system cells in a petri dish. Studies like these showed that the seaweed wakame, which is the kind you find in seaweed salad, can quadruple the replication potential of T cells, which are an important part of our immune defense against viruses like herpes simplex virus.

No one actually gave seaweed to people with herpes until a study published in 2002. Researchers gave people suffering from various herpes infections about two grams a day of pure powdered wakame, which is equivalent to about a quarter cup of seaweed salad. “All fifteen patients with active Herpetic viral infections”—including herpes virus 1, the cause of oral herpes, which causes cold sores; herpes virus 2, which causes genital herpes; herpes virus 3, which causes shingles and chicken pox; and herpes virus 4, also known as Epstein-Barr virus, which causes mono—“experienced significant lessening or disappearance of symptoms,” as you can see at 2:06 in my video. There was no control group in the study, but with no downsides to eating seaweed, why not give it a try?

Researchers also found that wakame boosted antibody production, so could it be useful to boost the efficacy of vaccines? The elderly are particularly vulnerable to suffering and dying from influenza. While the flu vaccine can help, ironically, the elderly are less likely to benefit from it because immune function tends to decline as we get older. So, researchers took 70 volunteers over the age 60. As you can see at 2:50 in my video, their baseline level of antibodies against a flu virus was about 10 GMT. What you’re looking for in a vaccination is to get a two-and-a-half-fold response, so we’d like to see that antibody level get up to at least 25 GMT to consider it an effective response. The vaccine only boosted levels to 15 to 20 GMT, though. What happened after the subjects were given some wakame extract every day for a month before the vaccination? Their levels jumped up to 30 to 35 GMT. The researchers used an extract in a pill rather than the real thing, though, so they could perform this randomized placebo-controlled study. After all, it’s kind of hard to make a convincing placebo seaweed salad.

“It is hoped that the popular seaweeds eaten daily in Japan, though almost unknown around the world outside of Japanese restaurants, will be consumed…for possible immunopotentiation”—that is, immune-boosting potential—“and for attenuating the burden of infectious diseases in the elderly.”

What else can seaweed salad do (other than taste delicious)? See my video Wakame Seaweed Salad May Lower Blood Pressure.

In general, sea vegetables are good sources of iodine, as I discuss in Iodine Supplements Before, During, and After Pregnancy, and may also be one reason Japanese women have historically had such low rates of breast cancer, which I cover in Which Seaweed Is Most Protective Against Breast Cancer?.


What else can we do to boost our immunity? Check out my videos:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

How to Treat Endometriosis with Diet

“Endometriosis is a major cause of disability and compromised quality of life in women and teenage girls.” It “is a chronic disease which is under-diagnosed, under-reported, and under-researched…[and for patients, it] can be a nightmare of misinformation, myths, taboos, lack of diagnosis, and problematic hit-and-miss treatments overlaid by a painful, chronic, stubborn disease.”

Pain is what best characterizes the disease: pain, painful intercourse, heavy irregular periods, and infertility. About one in a dozen young women suffer from endometriosis, and it accounts for about half the cases of pelvic pain and infertility. It’s caused by what’s called “retrograde menstruation”—blood, instead of going down, goes up into the abdominal cavity, where tissue of the uterine lining can implant onto other organs. The lesions can be removed surgically, but the recurrence rate within five years is as high as 50 percent.

Endometriosis is an estrogen-dependent disease, so might the anti-estrogenic effects of the phytoestrogens in flaxseeds and soy foods help, as they appear to do in breast cancer? I couldn’t find studies on flax and endometriosis, but soy food consumption may indeed reduce the risk of that disease. What about treating endometriosis with soy? While I couldn’t find any studies on that, there is another food associated with decreased breast cancer risk: seaweed.

Seaweeds have special types of fiber and phytonutrients not found in land plants, so in order to get these unique components, we would need to incorporate sea vegetables into our diet. Seaweeds, may have anti-cancer properties, including anti-estrogen effects. Japanese women have among the lowest rates of breast, endometrial, and ovarian cancers, as well as longer menstrual cycles and lower estrogen levels circulating in their blood, which may help account for their low risk of estrogen-dependent cancers. We assumed this was due to their soy-rich diets, but their high intake of seaweed might also be helping.

When seaweed broth was dripped on human ovary cells that make estrogen, estrogen levels dropped. Why? It either inhibits production or facilitates breakdown of estrogen. It may even block estrogen receptors, lowering the activity of the estrogen that is produced. This is in a petri dish, though. Does it happen in women, too? Yes.

Researchers estimated that an effective estrogen-lowering dose of seaweed for an average American woman might be around five grams a day, but, apparently, no one has tried testing it on cancer patients yet. However, it has been tried on endometriosis, as I discuss in my video How to Treat Endometriosis with Seaweed.

Three women with abnormal menstrual cycles, including two with endometriosis, volunteered to add a tiny amount of dried, powdered bladderwrack, a common seaweed, to their daily diet. This effectively lengthened their cycles and reduced the duration of their periods—and not just by a little. As you can see at 3:14 in my video, subject 1 had a 30-year history of irregular periods, averaging every 16 days. Taking just a quarter-teaspoon of this seaweed powder a day added 10 days onto her cycle, up to 26 days, and adding a daily half-teaspoon increased her cycle to 31 days, nearly doubling its length. Furthermore, as you can see at 3:38 in my video, all three women experienced marked reductions in blood flow and a decreased duration of menstruation. For 30 years, subject 1 had been having her period every 16 days, and it typically lasted 9 days. Can you imagine? Then, by just taking a daily half-teaspoon of seaweed, her period came just once a month and only lasted about four days. Most importantly, in the two women suffering from endometriosis, they reported “substantial alleviation” of their pain. How is that possible? There was a 75 percent drop in estrogen levels after just a quarter-teaspoon of seaweed powder a day and an 85 percent drop after a half-teaspoon. 

Of course, with just a few women and no control group in that study, we need bigger, better studies. But, that study was published more than a decade ago and not a single such study has been published since. Millions of women are suffering with these conditions. Does the research world just not care about women? The more pointed question is: who’s going to fund the work? Less than a teaspoon of seaweed costs less than five cents, so a larger study may never be done. But, without any downsides, I suggest endometriosis sufferers give it a try.


For more on endometriosis, see my video What Diet Best Lowers Phthalate Exposure?, and, to learn about the anti-estrogenic effects of the phytoestrogens in flaxseeds on breast cancer, see Flaxseeds and Breast Cancer Survival: Clinical Evidence.

Interested in more on sea vegetables? See:

I recommend staying away from kelp and hijiki, though. Why? See Too Much Iodine Can Be as Bad as Too Little.

Learn more about other natural remedies for menstrual problems:

In health,
Michael Greger, M.D.

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