Hello and welcome to Nutrition Facts. I’m your host, Dr. Michael Greger. Today, we’re going to explore smart nutrition choices based, naturally, on facts. Whenever there is a new drug or surgical procedure, you can be assured that you and your doctor will probably hear about it because there’s a corporate budget driving its promotion. But what about advances in the field of nutrition? That’s what this podcast is all about.
Today’s episode is something of a puzzler. How can the rice industry get away with selling a product containing 100 times the acceptable cancer risk? That is not a rhetorical question – it’s a real one. Even at low-level exposure, arsenic is not just a known human carcinogen, but it may impair our immune function and increase our risk of cardiovascular disease and diabetes. Here’s the story about the effects of too much arsenic in the diet.
When people hear arsenic, they think of it as an acute poison, and indeed, a tiny amount, a hundred milligrams, could kill you in an hour. That’s like the weight of a tenth of a paper clip. But, there’s also chronic arsenic poisoning, where even a dose 10,000 times as small can be harmful if you’re exposed day after day, for years at a time. Chief among the concerns is cancer.
Arsenic is “classified…as a class I carcinogen”—that’s the highest level, things known to cause cancer in humans, alongside stuff like asbestos, cigarette smoke, formaldehyde, plutonium, processed meat (consumption of bacon, ham, hot dogs, and lunch meat). So, arsenic is pretty bad stuff, implicated in tens of thousands, or even hundreds of thousands, of cancer cases worldwide every year.
Of course, cancer is just our #2 killer; what about heart disease? “Long-term exposure to low to moderate arsenic levels was [also found] associated with cardiovascular disease incidence and mortality,” meaning heart attacks and strokes.
Arsenic is also considered “an immunotoxicant,” meaning toxic to our immune system. How do we know that? Well, there’s a virus called varicella, which is what causes chickenpox—the first time we get it. Our immune system is able to stamp it down, but not stamp it out. The virus retreats into our nerve cells, where it lies in wait for our immune function to dip. And, when it does, the virus re-emerges, and causes a disease called shingles. We’ve all been exposed to the virus, but only about one in three of us will get shingles, because our immune system is able to keep it at bay. But as we get older or immunosuppressed, the virus can slip its muzzle, like if you’re given arsenic chemotherapy. Shingles is a common side effect, because the arsenic drugs not only kill the cancer, but also some of your immune cells, too. But, that’s at high doses.
Might even low doses of arsenic, like the kind we’re exposed to in our daily diet, impact our immune function?
And, if you’re pregnant, arsenic can pass to your baby, and may not just increase the risk of miscarriage and infant mortality, but “may [also] affect an infant’s immune development, and susceptibility to infections early in life.” But, you don’t know, until you put it to the test.
Infant infections in relation to prenatal arsenic exposure in a study out of New Hampshire; and indeed, the more arsenic the mom was exposed to during pregnancy, the higher risk of infection during infancy—though “[i[t’s unknown whether arsenic-induced” changes in gene expression can impact the health of not only your children, but your grandchildren as well. Regardless, arsenic exposure isn’t good for mom’s own health—associated with increasing blood pressure.
If arsenic suppresses immune system function, though, then at least, maybe, as a silver lining, you get fewer allergies or something, which is kind of an overreaction of the immune system? Apparently not. Those with higher arsenic levels tend to have higher rates of food allergies, tend to not sleep as well, tend to not feel as well. If you ask people how they would rate their health, those reporting “excellent” or “very good” tended to have lower levels of arsenic, compared to those who just reported “good, fair, or poor.” They tended to have higher levels.
What about diabetes? Here’s two dozen population studies on arsenic exposure and confirmed diabetes. Any result over one suggests increased risk for diabetes. Anything below one suggests lower risk. But, population studies can’t prove cause and effect. While it would be nice to demonstrate a cause-and-effect relationship, is it necessary? Look, we know it’s a carcinogen; we know it causes cancer. What more do we need to take steps to decrease our exposure?
A half-cup of cooked rice a day may carry a hundred times the acceptable cancer risk. But what about Maine coast seaweed? Here’s the research.
“At [some] point during the reign of King Cotton, farmers in the south central [U.S.] controlled boll weevils with arsenic-based pesticides, and residual arsenic still contaminates the soil.” Now, different plants have different reactions to arsenic exposure. For example, tomatoes don’t seem to accumulate much, 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 it from the soil, Of course, then, you’re supposed throw it and the arsenic away, but in the South, where 80% of U.S. rice is grown, we instead feed it to people.
But, national surveys have shown that most arsenic exposure has been measured coming from meat, poultry, and fish in our diet, rather than grains, but most of that is from the fish. So, if seafood is contributing 90% of our arsenic exposure from food, then why are we even talking about the 4% from rice? Because the arsenic compounds in seafood are “mainly organic”—used here as a chemistry term, nothing to do with pesticides—and organic arsenic compounds, because of the way our body can more easily deal with them, “have historically been viewed as [relatively] harmless.” Now, recently, there’ve been some questions about that assumption, but there’s no question about the toxicity of inorganic arsenic, which you can get more of from rice.
As you can see, rice contains more of the toxic inorganic arsenic than seafood, with one exception. Hijiki, an edible seaweed—a hundred times more contaminated than rice, leading some researchers to refer to it as the “so-called edible…seaweed.” Governments have started to agree. “In 2001, the Canadian [government] advised the public not to eat hijiki.” Then, the UK, the rest of Europe, Australia, New Zealand, then China “advised the public not to eat hijiki, and banned imports and sales” of the stuff. Japan, where they actually have a hijiki industry, just advised moderation.
What about Maine coast seaweed—domestic, commercially-harvested seaweed from New England? We didn’t know, until now. Thankfully, only one type had significant levels of arsenic, a type of kelp. But, it would take over 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 like 3,000%, ten times more than reported in this life-threatening case report attributed to a kelp supplement. So, I’d recommend to avoid hijiki due to its excess arsenic content, and avoid 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.
What does a number like this mean, though: 88.7 micrograms of inorganic arsenic per kilogram of raw white rice? I mean, that’s only 88.7 parts per billion. That’s like 88.7 drops of arsenic in an Olympic-size swimming pool of rice. So, how much cancer risk are we talking about? Well, just to put it in context, “[t]he usual level of acceptable risk for carcinogens is” one extra cancer case per million. That’s how we typically regulate cancer-causing substances. Whenever some industry wants to release some new chemical, we want them to show that it doesn’t cause more than one in a million excess cancer cases. Now, we have 300 million people in this country; so, that doesn’t make the 300 extra people who get cancer feel any better, but you have to cut it off somewhere. Okay.
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 10,000. 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 one 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…heart disease, diabetes, skin lesions, [kidney] disease, hypertension, and stroke.” The only reason they just stuck to calculating the cancer risks is that assessing all the other risks would take a lot of time, and that “would delay taking any needed action to protect [the public’s] health” from the risks of rice.
Yes, “physicians can help patients reduce their dietary arsenic exposure, [but] regulatory agencies, food producers, legislative bodies have the most important roles” in terms of public health scale changes. “[A]rsenic content in US-grown rice has been relatively constant throughout the last 30 years,” which is a bad thing.
“Where[ver]…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 dumping arsenic-containing pesticides, “and the use of arsenic-based drugs in poultry production,” and then spreading the arsenic-laced chicken manure on the land. Regardless of why Southern rice paddies are so contaminated, maybe we shouldn’t be growing rice in arsenic-contaminated soil.
What does the rice industry have to say for itself? Well, they started a website, called ArsenicFacts, no less. Always got to be skeptical of any group that claims “facts” in their title; *ahem*. Their main argument appears to be, look, arsenic is everywhere; we’re all exposed to it every day. It’s in most foods. So, what, we shouldn’t try to cut down on the most concentrated sources? Isn’t that saying like, look, diesel exhaust is everywhere; so, why not suck on a tailpipe? They quote some nutrition professor saying, look, all foods have a little bit. So, eliminating arsenic would decrease your risk, but you’d die of starvation. That’s like Philip Morris saying look, the only way you’re going to completely avoid secondhand smoke in your life is to never breathe—and then you’d asphyxiate; so, might as well just start smoking yourself. If you can’t avoid it, might as well consume the most toxic source you can find.
That’s the same tact the poultry industry took. Arsenic & chicken? No need to worry, because there’s a little arsenic everywhere. See? So, that’s why it’s okay that we fed our chickens arsenic-based drugs for 70 years. If you can’t beat ‘em, join ‘em.
Arsenic levels were tested in 5,800 rice samples from 25 countries. Here’s what they found out.
The arsenic found in five servings of rice a week poses a hundred times acceptable cancer risk. What does the rice industry have to say about that? When the story first broke that U.S. rice had some of the highest arsenic levels in the world, and all the headlines started, the USA Rice Federation said, “Enough Nonsense about Arsenic Already!” The study, in their minds, was “not only inaccurate in the highest degree, but also maliciously untrue.” To which one of the researchers replied, look, you’re the one who’s been ignoring the arsenic problem for decades. Had the problem of planting rice in arsenic pesticide-soaked former cotton fields been addressed, then safe soil could have been identified, low-arsenic rice varieties developed—instead of just developing arsenic-resistant varieties, so the plants can build up excessive levels of arsenic without dying themselves.
Not all rice producers have been so head-in-the-sand dismissive, though. After a subsequent Consumer Reports exposé, one rice company detailed how it was taking matters into its own hands. Lundberg Farms started testing hundreds of samples of its rice to share the results with the FDA. “We’re committed to providing safe food,” said the CEO, “and dealing with this problem very openly.” They’re not just sharing their results with the FDA, but with everyone. If you go to their website, you can see they apparently followed through on their testing promise. This is for their brown rice. Now, they use parts per million to make it look better than it is, but compared to the average U.S. brown rice level of 154, Lundberg does do better. In fact, their aromatic brown rice, presumably their brown basmati and brown jasmine, average less than national white rice levels. And so, apparently, does their red and black rice. In fact, none of those samples even reached the average U.S. brown rice level.
Most other brands were pretty comparable—Uncle Ben’s, for example, and Walmart, though Whole Foods scored the worst—about a third higher than these others, and exceeding the national average.
In the largest review to date, based on 5,800 rice samples from 25 countries, the highest total arsenic average came from the United States, with U.S. studies averaging overall about double that of rice out of Asia, with the high levels in the U.S. blamed on the heavy historic use of arsenic-based pesticides. But, not all of the U.S. Yes, U.S. rice averages twice the arsenic of Asian rice. For example, nearly all rice samples tested in upstate New York, imported from India or Pakistan, had arsenic levels lower than 95% of domestically-produced rice. There’s significantly more arsenic in rice from Texas and Arkansas than rice from California. If you just look at California rice, then it’s actually comparable to rice produced around the rest of the world. This is presumably some of the data that led Consumer Reports to suggest brown basmati from California, India, or Pakistan might be among the safer rice choices.
If the arsenic is from pesticides, would organic rice have less than conventionally-grown rice? No, which makes sense, because arsenic pesticides were banned like 30 years ago. It’s just that 30,000 tons of arsenic chemicals already got dumped onto cotton fields in the southern states. So, it’s understandable why there’s still lingering arsenic residues, even if you don’t add an ounce of any new pesticides. That’s why they specifically select for arsenic-resistant varieties of rice plants in the South. If only there were arsenic-resistant humans.
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Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.
This is an approximation of the audio content, contributed by Allyson Burnett.