Get the Lead Out

You know the feeling you get – when you learn something new about a health problem you’ve been trying to reverse – maybe high blood pressure, diabetes, or heart disease. Well – there’s nothing I like better than bringing you the information that will help you do just that. Welcome to the NutritionFacts podcast. I’m your host – Dr. Michael Greger.

Today, we explore what dietary change can simultaneously help detoxify mercury, lead, and cadmium from the body.

We’ve previously explored the issue of lead contamination in calcium supplements like bonemeal, but it wasn’t just bonemeal. Substantial quantities of lead were found in other, more common, over-the-counter supplements. Still, testing revealed continued public health concern over bonemeal, but thankfully it’s not as popular these days. So, most of us are not likely to get directly exposed to the lead in bonemeal any more, but we may get indirectly exposed through the animals we eat.

In the U.S., five billion pounds of meat and bonemeal are produced as slaughterhouse by-products every year. What do we do with these millions of tons every year? We feed it back to farm animals, particularly chickens. Now, most of the lead in the bonemeal passes right through the animals into their waste, but then we take that waste (cow, pig, and chicken feces) and feed it back to the animals again. You guessed it! So, you can see how the levels of contaminants might build up in their bodies.

I’ve talked previously about what that might mean for making something like chicken soup, but the original concern about these kinds of feeding practices, feeding cows to cows, and pigs and chickens, was the spread of prion diseases, like Mad Cow Disease. But it’s not just prions that this kind of recycling can magnify, but other toxic substances, including lead. So, a more plant-based diet may be able to lower lead exposure, and an even more plant-based diet could theoretically lower exposure even more. But you’ve got to put it to the test.

But should we expect to find a benefit? Yes, lead is one of the toxins found in meat, but half of our dietary exposure probably comes from plant foods. Dietary modeling studies in Europe suggest that vegetarians would be exposed to about the same amount of lead compared to the general population, with the exception of those who eat a lot of wild game, which can end up with a thousand times more lead than most other foods.

In fact, a vegetarian diet may even be higher in lead. But, it’s not what you eat; it’s what you absorb. As we learned from the cadmium story, the uptake of toxic heavy metals from animal food sources into human intestinal lining cells may be higher than that from vegetable sources. That’s how you have a vegetarian with some of the lowest concentrations of lead and cadmium in their blood, despite higher concentrations in their diet. But you don’t know, until you…put it to the test.

There seemed to be a tendency towards higher fecal elimination of lead following a change to a vegetarian diet, with nine subjects on average tripling their elimination of lead, three unaffected, and four dropping by about half. But the study only lasted a few months, and the difference wasn’t statistically significant. So, let’s try a year. A shift towards a diet characterized by large amounts of raw vegetables, fruits, and unrefined foods, whole grains, with the exclusion of meat, poultry, fish, and eggs (though it did include fermented dairy, like a type of soured milk), as well as cutting back on processed food and junk. They took clippings of hair before and after the shift, and got significant reductions in heavy metals, including cutting their lead level nearly in half. Within three months, their toxic heavy metal levels went down, and stayed down. How do we know it wasn’t just a coincidence? Because they went back up a few years later after the study was over, after they went back to more of their regular diet, and their mercury, cadmium, and lead levels shot back up to where they were before.

Same thing with a different group after two years. The drop in mercury is easy to explain, presumably due to the drastic drop in fish consumption, and the drop in alcoholic beverages may have contributed to the drop in lead, but it also could have been a cadmium-like effect, where the decrease in hair lead content could be due to the dietary shift resulting in less absorption of lead into the body in the first place.

In our next story, we look at one of the most concentrated sources of the toxic metal cadmium.

“Cadmium is known as a highly toxic metal that represents a major hazard” to human health. It sticks around in our body for decades, because our body has no efficient way to get rid of it, and may contribute to a variety of illnesses, including “heart disease, cancer, and diabetes.” Most recently, data suggest that cadmium exposure may impair cognitive performance even at levels once thought to be safe.

Recent studies suggest “cadmium exposure may produce adverse health effects at lower exposure levels than previously predicted,” including increased risk of hormonal cancers. For example, researchers on Long Island estimated that about 40% of breast cancer in the U.S. may be associated with elevated cadmium levels.

“Inhalation of cigarette smoke is one of the major routes for human [exposure to cadmium].” Seafood consumption is another “dominant route” of human exposure—even more so than from cigarette smoke. The highest levels, though, are found in organ meats. But, how many horse kidneys can you eat? Because people eat so few organs, grains and vegetables actually end up contributing the largest amount.

But, wait a second. “…[w]hole grains and vegetable[s]…are among the major dietary sources of fiber, phytoestrogens, [and] antioxidants” that may protect against breast cancer. And, indeed, even though the risk of breast cancer goes up as women consume more and more cadmium, even though on paper, most cadmium comes from grains and vegetables, breast cancer risk goes down, the more and more whole grains and vegetables women eat.

So, maybe the animal-sourced cadmium is somehow worse? Or, the benefits of plant foods just overwhelm any adverse effects of the cadmium? This study may have helped solve the mystery. It’s not what we eat; it’s what we absorb.

“[Cadmium] bioavailability from animal-based foods [may be] higher than…from vegetable-based foods.” There appears to be something in plants that inhibits cadmium absorption. In fact, if you add kale to your boiled pig kidneys, you can cut down on the toxic exposure. Just one tablespoon of pig kidney, and we may exceed the daily safety limit—unless we eat kale, in which case we could eat a whole quarter-cup. “[T]he pronounced effects of the inhibitory factors in kale…point[s] out the importance of vegetable foods in terms of prevention of health hazard[s] from [cadmium] ingested as mixed diets in a real situation.”

“Even if a vegetarian diet contains more lead and cadmium than a mixed diet, it is not certain that it will give rise to higher uptake of the metals…because the absorption of lead and cadmium is inhibited by [plant compounds such as] fibre and phytate.” And, it’s not just in lab animals. Having whole grains in our stomach up to three hours before we swallow lead can eliminate 90% of absorption—thought to be due to phytates in whole grains, beans, and nuts grabbing onto it.

So, vegetarians may have lower levels, even though they have higher intakes. “In fact, a significant decrease in the hair concentrations of lead and cadmium [was seen] after the change from [an omnivorous] to [a] vegetarian diet…, indicating a lower [absorption] of the metals.”

Here’s that study. They took folks eating a standard Swedish diet, and put them on a vegetarian diet. Lots of whole unrefined plant foods: no meat, poultry, fish, eggs, and junk food, that was discouraged.

Within three months on a vegetarian diet, their levels significantly dropped, and stayed down for the rest of the year-long experiment. But then, they came back three years later—three years after they stopped eating vegetarian. And, what did they find? Their levels of mercury, cadmium, and lead shot back up.

Since the cadmium in plants is based on the cadmium in soil, plant-eaters that live in a really polluted area, like Slovakia, which has some of the highest levels, the so-called “black triangle” of pollution, thanks to the chemical and smelting industries. Those who eat lots of plants there can indeed build up higher cadmium levels, especially if you eat lots of plants. It’s interesting. “In spite of the significantly higher blood cadmium concentrations as a consequence of a greater cadmium intake from [polluted plants], all the antioxidants in those same plants were found to help “inhibit [the] harmful effects of higher free radical production” caused by [the] cadmium exposure.

Still, though, in highly polluted areas, it might be an especially good idea not to smoke, or eat too much seafood or organ meats. But, even if we live in the Slovak Republic’s black triangle of pollution, the benefits of whole plant foods would outweigh the risks. In highly polluted areas, zinc supplements may decrease cadmium absorption. But, I’d recommend against multi-mineral supplements, as they have been found to be contaminated with cadmium itself.

Finally today – did you know that the toxic heavy metal contamination of Ayurvedic dietary supplements is, in most cases, intentional?

How do toxic heavy metals get into Ayurvedic medicines in the first place? In most cases, high levels of metals in Ayurvedic traditional herbal preparations result from intentional incorporation of certain metallic preparations like lead oxide, mercury sulfide, arsenic trioxide. Not to worry, though. The heavy metals are claimed to be detoxified by, for example, heating and cooling the herbal mixtures in cow’s urine.

This is not just an India issue. Traditional medicines from around the world incorporate these poisons. In the Middle East, saoott is used as a teething powder for infants. It’s 51% lead; one of a number of black lead-containing substances used as teething powder.

Bokhoor is a Middle Eastern practice of burning lead sulfides to produce pleasant fumes to calm infants. They’ll be calm, all right.

Traditional Latin American medicines include azarcon and greta—almost pure lead, used to treat constipation.

In traditional Chinese herbal medicine, mercury is considered to have a tranquilizing and (if you can believe it) detoxifying effect.

But wait a second. Haven’t these remedies been used for centuries? Sure, but that doesn’t mean they’re safe. In the West, let’s not forget that bloodletting was among the most common medical practices performed by doctors for almost 2,000 years.

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My last two books are “How to Survive a Pandemic” and the “How Not to Diet Cookbook.” Stay tuned for Dec 5, 2023 for the launch of my one “How Not to Age.” And – of course – all the proceeds I receive from the sales of all my books go to charity. 

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