There are lots of good reasons to try and follow a healthier diet–you lose weight, you feel good, but the main reason–to live a longer, happy, productive life. Sounds good, right? And though it may sound deceptively easy, the devil is in the details. Welcome to the Nutrition Facts podcast. I’m your host, Dr. Michael Greger.
Back by popular demand, it’s the Nutrition Facts Grab Bag with the latest news on a whole variety of topics. First up, a review of the evidence on the effects of coconut oil on weight loss and belly fat.
I was surprised to see, in a popular infographic, that there was promising evidence that coconut oil could help with obesity. Well, if you pump the stomachs of rats with purified medium-chain fatty acids—one component of coconut oil—they end up eating less food. But, you don’t know if there’s any relevance to humans until you put it to the test.
Researchers compared breakfasts with the same amount of dairy fat, coconut-oil fat, or tallow (beef fat), and “no…effect…[on] hunger, fullness, satisfaction,” or how much they then went on to eat at lunchtime. So, where did this whole idea, that coconut fat was somehow different, come from? Well, six years ago, an “open-label pilot study” was published. They asked 20 men and women to eat two tablespoons of coconut oil a day for a month, and the men appeared to lose about an inch off their waist. Now, “open-label” means that the participants knew what they were eating; there wasn’t like some placebo control. In fact, there was no control group at all. So, you don’t know if the effects would have just happened anyway, without the coconut oil. There’s a well-recognized effect in dietary studies, where just being in a dietary study under observation tends to lead to a reduction in caloric intake—because you know they’re going to weigh you, and looking over your shoulder. But, there had never been a controlled study of coconut oil and waistlines in men and women until 2015.
About a hundred men and women were given about a tablespoon of coconut oil a day for three months, and lost nearly an inch off their waist after three months, compared to control. What did the control group get instead? Nothing. There was no placebo. And so, they were comparing doing something with doing nothing. And, when one does that, there’s often a placebo effect, regardless of the true efficacy of the treatment. And, they also suggested the coconut-oil group may want to take their dose with fruit. And, if they did end up eating more fruit, that, in and of itself, may help—as, despite its sugar content, fruit consumption tends to be associated with “anti-obesity effects.”
What we need, to see if coconut oil has some special effect, is to give people a spoonful of coconut oil versus some other oil, and see if there’s any difference. And, when you do that—two tablespoons of coconut oil a day, versus two tablespoons of soybean oil a day—no significant difference in waistlines. But, what did happen was a significant increase in insulin resistance in the coconut-oil group, which is what eventually causes type 2 diabetes—despite being told to increase fruits and vegetables, cut down on sugars and animal fat, and despite an exercise program of walking 50 minutes a day, four days a week.
The only other placebo-controlled study of coconut oil and waistlines was published in 2017, and no significant changes in weight or waist or hip measurements, total fat, belly fat, nor butt fat. No benefit to coconut oil for obesity over placebo shown in any study to date.
So, how can coconut oil proponents get away with saying otherwise? Well, they like to talk about studies like this, showing that Pacific Islanders who ate more traditional coconut-based diets are slimmer than those eating more modern diets with fewer coconut products. But, guess what they were eating instead? “The modern[ized] dietary pattern [was] primarily characterized by high intake[s] of sausage [and] eggs and processed foods.”
Certain gut bacteria can supercharge the benefits of soy foods, resulting in even more bone protection, better control of menopausal symptoms, and lower prostate cancer risk. The question is how can we foster the growth of these good bacteria?
“Menopause is characterized by a decrease in estrogen, which triggers the uncomfortable symptoms of hot flushes, night sweats, sleep disturbances, and vaginal dryness. Among these menopausal symptoms, hot flushes are reported by many women to be the most bothersome.” I already summarized the available evidence on the role of soy phytoestrogens to alleviate those symptoms. Here’s the latest meta-analysis. Although the balance of evidence points to soy benefits, the individual study results are all over the place. Yes, some studies show 20, 30, even 40% better than control, but some showed no effect.
This is something that’s been noted by the professional societies, like the American College of OB/GYNs. Yes, these supplements may work, the evidence is so inconsistent. This may be partly because the supplements used were extracted from different parts of the soybean. Maybe it would be better if they just used soy foods rather than supplements. The dosing would be about “two servings of traditional soy foods” a day—like two cups of soy milk, which is what you see older women in Japan doing, who have some of the lowest reported rates of hot flashes in the world. But, even the studies on soy foods, as opposed to supplements, have had “conflicting results.” Why all the inconsistency? It may have to do with our gut bacteria.
People who eat foods made from soybeans, which have these “health-promoting isoflavones,” tend to have lower rates of a variety of chronic diseases. So, we can garner this protection by eating more soy foods, right? Well, it may be a little “more complicated” than that. There are certain gut bacteria that can convert isoflavones in soy into a potentially even more beneficial compound, called equol. Not all individuals can make this conversion, though, because not all individuals have the specific types of good bacteria in their gut that do it. So, there’s two types of people in the world: “equol producers” and “equol nonproducers”—depending on their gut flora. And so, this may help account for the variations in health benefits we see in clinical studies. It may help explain why some people seem to benefit from soy more than others.
For example, in the study I covered before, about how soy milk appears to prevent bone loss in the spines of postmenopausal women, if you split the women into equol producers and nonproducers, soy did work in non-equol producers, but seemed to work even better in the women whose gut bacteria is able to take the soy to the next level.
The more equol Japanese women make from the soy they eat, the fewer menopausal symptoms they may have. Some studies suggest equol-producing men may get less prostate cancer. If that’s the case, maybe we should look into improving the intestinal environment to enable equol production. Only a minority “of the Western adult population” is able to produce equol, though almost every other animal species appears to produce it; no problem. In fact, that’s how it got its name. It’s named equol because it was first discovered in horses. But, interestingly, horses during the summer, not winter—because that’s when their gut bacteria had access to the phytoestrogens in clover. That was our first clue equol was made from plants. If you’re not Mr. Ed, though, “can [you] take someone who [doesn’t] make equol and convert them [in]to an equol-producer? Certainly, [you can] do the reverse; excessive use of antibiotics” can wipe out your good bugs. But how can you acquire the right good bugs? Suggested strategies include dietary alteration or probiotics.
The standard probiotic regimens don’t seem to help; so, how about dietary alteration? Well, about half of Japanese and Korean individuals can produce equol, but only as low as one in seven Americans. Maybe it’s because more soy is eaten in Asia? I mean, that would make sense—if you eat a lot of soy, you may foster the growth of bacteria in your gut that can digest soy. But, a month of soy isoflavone supplement exposure didn’t seem to convert nonproducers into producers. But, just two weeks of drinking three glasses of soy milk a day was able to convert three of six women into producers. For example, this woman started out not making any at all, or maybe a little bump between hours 50 and 60, but after two weeks of drinking soy milk, when they had her drink some more, she had nice equol spikes.
It didn’t work for all women, though. And, when they tried the same experiment in men, nothing happened. Hmm, back to the drawing board. Is there any group of Westerners that have high equol production rates that may offer a clue? Vegetarians have among the highest equol production rates ever recorded—more than four times as “likely to be…equol producers as their nonvegetarian counterparts.” The question is, why? They don’t think it’s because of the soy, given the conflicting soy data. Maybe it’s because they’re eating more prebiotics, like fiber?
Or, maybe “dietary fat intake decreases the capacity of gut…flora to [make] equol.” Or, maybe it has something to do with cholesterol intake? Analyzing the diets of equol producers, they do seem more likely to be eating more carbs, plant protein, and fiber. But, researchers have tried giving people fiber supplements along with soy, but that didn’t seem to work. Whatever it is about those eating plant-based diets, they may soon be the only remaining majority equol producers, as Asian populations continue to westernize their diets.
Do calcium citrate and calcium carbonate have as much lead as calcium supplements derived from dolomite and animal bone? Here’s what we found out.
I’ve explored the role calcium supplements may play in reducing lead exposure during pregnancy and breastfeeding, but this is assuming that the supplements aren’t themselves contaminated. It all started with an extraordinary case report published in 1977, entitled “Lead-Contaminated Health Food.”
“A doctor prescribed a dietary supplement…for a young woman with [painful periods].” Not just any woman, though: TV and film actress Allison Hayes, famous for such roles as Attack of the 50-Foot Woman. And, not just any physician, but physician to the stars, Dr. Henry Bieler, who told his patients to forget about toxic drugs. “Food is your best medicine”—which, in this case, was a calcium supplement made from horse bone. She took it every day, but got weaker and sicker, and by 1967, her acting career was over, when she was unable to walk without a cane. She saw doctor after doctor after doctor, to no avail. She decided she could give up, commit suicide, or figure it out herself.
So, she had some friends drive her to a medical library. By then, she couldn’t even walk, and “had to be carried in.” She sat on the floor day after day, and finally came across a book on industrial toxicology that described what she soon realized was a classic case of lead poisoning. She paid to have the calcium supplement tested, and indeed, it was full of lead. At first, she was relieved, but “[t]hen the anger set in.” Doctor after doctor had basically dismissed her as hysterical, and she had to depend on herself to end up educating them.
The silver lining was that the FDA, in a letter, actually credited her for being “a ‘key stimulus’” for their plans to look into regulating heavy metals in foods and supplements. Unfortunately, the letter arrived after she had already died, from leukemia, which may have been triggered by the lead poisoning, or the 300 X-ray exams she got from those 22 baffled physicians.
You’d think the supplement industry would clean up its own act, but perhaps “[i[t is unrealistic to expect the ‘health food’…and ‘wellness’ [industry] to dampen their evangelistic promotion of these products” on their own. Where did the lead come from? Well, lead gets stored in your bones; and so, when you eat supplements made out of bones, you can get exposed. So, was that one calcium supplement just “the tip of an iceberg”? At first, we thought it was just from the bone supplements and dolomite, a mineral that can be lead-contaminated. But then, calcium carbonate—oyster shell calcium, chelated calcium─was found to have comparable lead levels to animal bone. And so, this inspired a comprehensive survey of the “Lead content [of] 70 [different] brands of calcium supplements.” And, “lead levels…varied by almost 300-fold,” some of which two, three, or even four times the tolerable daily intake of lead for children—especially the most common: “natural source calcium,” like oyster shell, with more than half exceeding the benchmark for children.
A follow-up study confirmed that most calcium supplements from natural sources exceeded at least some of the most stringent lead standards, but the levels only got up to about eight micrograms, whereas some of the synthetic sources were up to three times that.
A small human study of calcium citrate was performed, in which bone biopsies were taken before and after about five years of supplementation. No change in the control group, as expected, and only a statistically insignificant increase in the calcium citrate group, though “[O]ne [can’t] assume that a given brand is uniformly safe, because some of their products may have high and others low lead levels.” So, name brands, or “recognized pharmaceutical companies” that should know better, are no guarantee.
But, the good news is that after decades of concern, lead levels in calcium supplements have come down—so much so that lead level changes in your blood, taking the average lead-contaminated calcium supplement, would be “minimal” at this point. So, these findings on supplement lead contamination should be a cause for “celebration,” not “alarm”—or at least according to a calcium supplement manufacturer consultant.
To see any graphs, charts, graphics, images or studies mentioned here, please go to the Nutrition Facts podcast landing page. There, you’ll find all the detailed information you need, plus links to all the sources we cite for each of these topics.
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Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.
This is just an approximation of the audio content, contributed by Allyson Burnett.