Full Transcript NutritionFacts Introduction and Hashimoto's Overview 0:00 Doesn't it seem like when it comes to nutrition, there are more opinions than 0:04 facts to go around? Every day we hear new [music] theories 0:08 about diets and supplements and best foods to eat. Well, my role is to take 0:13 the mystery out of good nutrition and look at the science. Welcome to the 0:18 NutritionFacts podcast. I'm your host, Dr. [music] Michael Greger. One of the 0:22 most common questions I'm asked is about a natural treatment for Hashimoto's 0:26 disease, also known as autoimmune thyroiditis, 0:30 the leading cause of hypothyroidism. So, 0:34 I did a webinar about it. Here's the whole thing on the best diet for thyroid 0:39 health, as well as the healthiest natural source of iodine. 0:43 Adequate dietary iodine is required for normal thyroid function. In fact, the 0:49 two thyroid hormones are named after how many iodine atoms they contain, T3 and 0:53 T4. Now, given that iodine is extensively stored in the thyroid gland 0:58 itself, it's not something you have to get every 1:01 day, but your overall diet needs to have some good source. 1:05 Unfortunately, the common sources aren't particularly health-promoting. Iodized 1:09 salt and dairy foods are because iodine-based cleansers like Betadine are 1:14 used to sanitize the udders, which results in some iodine leaching into the 1:19 milk. They also add iodine to cattle feed. 1:23 And some commercial breads have iodine-containing food additives. 1:27 So, if you put people on a paleo-type diet and cut out dairy and table salt, 1:31 they can develop an iodine deficiency, even though they doubled their seafood 1:36 intake, which can also be a source. What about those switching to diets 1:39 centered around whole plant foods? I mean, they're also cutting down on ice 1:43 cream and Wonder Bread. And if they're not eating anything from the sea, 1:46 seaweed, sea vegetables, they can run into the same problem.
Iodine Basics and Deficiency Risks 1:51 Her parents reported striving to feed her only the healthiest foods. The 1:56 3-year-old only got plant-based, unsalted, unprocessed foods with no 2:00 vitamin supplementation. Now, that could have been deadly. I 2:03 mean, with no vitamin B12, those on strictly plant-based diets can develop 2:07 irreversible nerve damage. But in this case, a goiter arose first due to 2:12 inadequate iodine intake. Here's another case of veganism as a 2:17 cause of iodine-deficient hypothyroidism in a toddler after weaning. Now, before 2:22 weaning, he was fine because his mother kept taking her prenatal vitamins, which 2:26 luckily contained iodine. Most vegetarians and vegans are 2:30 apparently unaware of the importance of iodine in pregnancy, just as clueless as 2:35 their omnivorous counterparts. The American Thyroid Association and 2:39 American Academy of Pediatrics have recommended that women even just 2:43 planning on getting pregnant should ingest a daily supplement that contains 2:47 150 micrograms of iodine. Yet, only 60% of prenatal vitamins marketed in the US 2:53 contain this essential mineral. So, in spite of the recommendations, 2:58 about 40% lack it. Therefore, it's extremely important that pregnant and 3:02 breastfeeding women read the labels to ensure they're receiving an adequate 3:07 amount. Women of reproductive age have an average iodine level 110, which is 3:11 fine for non-pregnant individuals, but we'd really like to see at least 150 in 3:17 pregnancy. It's basically a 24-hour urine test in which iodine sufficiency 3:21 is defined as 100 micrograms per liter of pee in non-pregnant adults, 3:25 which your average vegan fails to reach in the largest study done to date out of 3:30 Boston. The recommended average daily intake is 3:34 150 micrograms a day for most people, which you can get in like a, you know, 3:37 cup and a half of cow's milk. Sadly, plant-based milks are typically not 3:42 fortified with iodine, averaging only about 3 micrograms per cup. In the 3:47 largest systematic study to date, although many plant-based milks are 3:51 fortified with calcium, they only found just three of 47 fortified with iodine. 3:57 Of those that were had as much as cow's milk, but those that weren't fell short. 4:03 Plant-based milk companies brag about enriching their milks with calcium and 4:08 often vitamin B12, D, vitamin A, but only rarely are attempts made to match 4:12 the iodine content. I mean, the only reason cow's milk has as much as it does 4:16 because they they enrich the feed or it comes dripping off their udders, right? 4:20 So, why don't plant milk companies add iodine, too, right? I was told by a food 4:26 scientist at Silk that my carrageenan video played a role in them switching to 4:30 another thickener. Hopefully, they'll see this video and consider adding 4:34 iodine, too, or some company will snatch at the market advantage opportunity. 4:40 The researchers conclude that individuals who consume plant-based
Pregnancy, Vegan Diets, and Iodine Status 4:43 milks not fortified with iodine may be at risk for iodine deficiency unless 4:49 they consume alternative dietary iodine sources, the healthiest of which is sea 4:55 vegetables. Okay, so to reiterate, one cause of 5:01 hypothyroidism, an underactive thyroid gland, is inadequate iodine intake. This 5:07 is especially important for pregnant women and women even considering 5:12 pregnancy, but that largest study of vegan iodine status in Boston found most 5:18 vegans have insufficient intake. So, what's the best way to get it? What's 5:23 the healthiest natural source of iodine? That's the name of the next video. 5:31 Dairy milk supplies between a quarter and a half of the daily iodine 5:35 requirement in the United States. So, milk itself has little native iodine. 5:40 The milk iodine content is mainly determined by factors like the 5:44 application of iodine-containing teat disinfectants. The iodine residues in 5:49 milk appear to originate mainly from the contamination of the teat surface. The 5:53 teats are are sprayed or dipped with like a Betadine-type disinfectants, and 5:58 the iodine just kind of leaches into the milk. 6:01 Too bad most of the plant-based milks on the market aren't enriched with iodine, 6:05 too. Fortified soy milk is probably the healthiest of the plant milks, but even 6:10 if it was enriched with iodine, what about the effects of soy on thyroid 6:15 function? It's funny, when I searched the medical literature on soy and 6:19 thyroid, this study popped up. A cost-effective way to train residents to 6:24 do thyroid biopsies. Just stick the ultrasound probe right on top and go to 6:30 town. Turns out, on ultrasound, your thyroid gland looks a lot like tofu. 6:36 Anyways, the the idea that soy may influence thyroid 6:40 function originated over eight decades ago, when marked thyroid enlargement was 6:44 seen in rats fed raw soybeans. Though the observation that people 6:49 living in Asian countries have consumed soy foods for centuries with no 6:53 perceptible thyrotoxic effects has certainly suggests their safety. Bottom 6:57 line, there does not seem to be a problem with people who have normal 7:00 thyroid function. However, soy foods may inhibit the oral absorption of 7:04 Synthroid, thyroid hormone replacement drugs, 7:07 but so do all foods, right? That's why we tell patients to take it on empty 7:12 stomach. But you also have to be getting enough 7:16 iodine. So, it may be particularly important for soy food consumers to make 7:19 sure their intake of iodine is adequate. What's the best way to get iodine? For 7:24 those who use table salt, make sure it's iodized. Currently, only half of table 7:29 salt sold contains iodine, and the salt used in processed foods is typically not
Plant Milks, Iodine Fortification, and Soy 7:33 iodized. Of course, ideally, we shouldn't add salt at all. Dietary salt 7:38 is a public health hazard. I think this title is a little over the top. Dietary 7:45 salt is the number one dietary risk factor for death on the planet Earth. 7:50 Why? Beyond more than 3 million people a year. Twice as bad as not eating your 7:55 vegetables. What's the best source of iodine, then? Sea vegetables, right? You 8:01 can get a little iodine here and there from a whole variety of foods, but the 8:04 most concentrated source by far, with up to nearly 2,000% of your daily allowance 8:09 in just a single gram, which is like the weight of a paper clip, seaweed. Given 8:14 that iodine is extensively stored in the thyroid, it can be safely consumed 8:17 intermittently, meaning you don't have to get get it every day, which makes 8:21 seaweed use in a range of foods attractive, and occasional seaweed 8:24 intake enough to ensure iodine sufficiency. However, some seaweed 8:29 should be used with caution due to its overly high iodine content, like kelp. 8:36 Too much iodine can cause hyperthyroidism, a hyperactive thyroid 8:40 gland. A woman presented with a racing heartbeat, insomnia, anxiety, and weight 8:44 loss, thanks to taking just two tablets a day containing kelp. 8:50 In my last video, I noted how the average urinary iodine level of vegans 8:54 was less than the ideal levels, but there was one kelp-eating vegan with a 9:00 urinary concentration over 9,000, right? Adequate intake is when you're peeing 9:04 out 100 to 199. Excessive iodine intake is when you break 300. 9,437, 9:11 way too much. The recommended average daily intake is 9:16 150 micrograms a day for non-pregnant, non-breastfeeding adults. You may want 9:20 to stay below 600 on a day-to-day basis, whereas a, you know, tablespoon of kelp 9:25 may contain 2,000, right? I'd stay away from kelp because there's too much, and 9:30 stay away from hijiki because it contains too much arsenic. 9:35 Here's how much of common seaweed preparation should give you an 9:38 approximate daily allowance. Two nori sheets, you can literally just nibble on 9:43 them as snacks, like I do. One teaspoon of dulse flakes, which you can just 9:48 sprinkle on anything. One teaspoon of dried arame, which is great for like 9:52 adding to soups, or one tablespoon of seaweed salad. 9:57 If iodine is concentrated in marine foods, this raises the question of how 10:02 early hominins living in continental areas could have met their iodine 10:07 requirements? Well, here's what bonobos do, perhaps 10:10 our closest relatives. During swamp visits, they all forage aquatic herbs.
Seaweed as the Best Natural Iodine Source 10:17 You can munch on aquatic plants yourself by incorporating seaweed into your diet, 10:24 the healthiest natural source of iodine. Okay. So, we covered thyroid issues 10:29 caused by either too little or too much iodine intake. But, what 10:34 about hypothyroidism or hyperthyroidism caused by autoimmune diseases like 10:40 Hashimoto's thyroiditis? That's what we'll turn to next in my 10:45 video the best diet for hypothyroidism and hyperthyroidism. 10:51 And then I can finish eating my seaweed. There are several autoimmune diseases 10:55 that affect the thyroid gland, the most common being Graves disease and 11:00 Hashimoto's thyroiditis. Graves disease results in hyperthyroidism, an 11:05 overactive thyroid gland. Though slaughterhouses are supposed to remove 11:09 thyroid glands, should some neck meat slip in, you can suffer a similar 11:14 syndrome called hamburger thyrotoxicosis, 11:18 but that's not from your body making too much thyroid hormone, that's from your 11:21 body eating too much thyroid hormone. Graves disease is much more common, and 11:26 meat-free diets may be able to help with both as plant-based diets may be 11:30 associated with a low prevalence of autoimmune disease in general, as 11:35 observed for example in rural sub-Saharan Africa. Maybe it's because 11:39 plants are packed with antioxidants, which are possible protective factors 11:43 against autoimmune diseases. Maybe it's because plants are packed with 11:46 anti-inflammatory compounds. After all, a whole food plant-based diet is 11:50 basically synonymous with an anti-inflammatory diet. But, you 11:55 don't know until you put it to the test. Turns out 12:00 the exclusion of all animal foods was associated with half the prevalence of 12:04 hyperthyroidism compared with omnivorous diets. Lacto-ovo vegetarian and 12:08 fish-only diets were associated with intermediate protection, but a 52% lower 12:14 odds of hyperthyroidism among those eating strictly plant-based diets. 12:19 This apparent protection may be due to the exclusion of animal foods, the 12:22 benefits of plant foods, or or both. Animal foods like meat, eggs, and dairy 12:27 products may contain high estrogen concentrations for example, which have 12:31 been linked to autoimmunity in preclinical studies. Or the decrease in 12:34 animal protein may downregulate IGF-1, which is not just a cancer-promoting 12:39 growth hormone, but may play a role in autoimmune diseases as well. Or it could 12:44 be the good stuff in plants that may protect cells like the polyphenol 12:48 phytochemicals such as flavonoids found in plant foods. Maybe it's the 12:52 environmental toxins that build up the food chain, for example. Fish 12:55 contaminated with industrial pollutants like PCBs are associated with increased 12:59 frequency of thyroid disorders. Okay, what about the other autoimmune 13:05 thyroid disease, Hashimoto's thyroiditis, which, assuming you're 13:09 getting enough iodine, is the primary cause of hypothyroidism, 13:13 an underactive thyroid gland. Graves disease wasn't the only 13:18 autoimmune disorder that was rare or virtually unknown among those living in 13:23 rural sub-Saharan Africa eating near vegan diets. They also 13:27 appear to have less Hashimoto's. There's evidence that those with 13:31 Hashimoto's have compromised antioxidant status, but we don't know if it's cause 13:36 or effect. But, if you look at the dietary factors associated with blood 13:40 levels of autoimmune antithyroid antibodies, animal fats seem to be 13:44 associated with higher levels, whereas vegetables and other plant foods are 13:47 associated with lower levels. So again, anti-inflammatory diets may be useful.
Autoimmune Thyroid Disease and Diet 13:53 No surprise as Hashimoto's is an inflammatory disease. That's what 13:57 thyroiditis means, inflammation of the thyroid gland. 14:01 Another possibility is the reduction in methionine intake, an amino acid 14:05 concentrated in animal protein. Thought to be one reason why the consumption of 14:09 whole plant foods is likely to have a favorable influence on longevity through 14:14 decreasing the risk of cancer, heart disease, and diabetes. And methionine 14:18 restriction improves thyroid function in mice, but has yet to be put to the test 14:23 for Hashimoto's in humans. If you compare the 14:27 poop of patients with Hashimoto's to controls, the condition appears to be 14:31 related to a clear reduction in the concentration of Prevotella species. 14:37 Prevotella are good fiber-eating bugs known to enhance anti-inflammatory 14:41 activities. Decreased Prevotella levels are also something you see in other 14:46 autoimmune conditions such as multiple sclerosis and type 1 diabetes. 14:50 How do you get more Prevotella? Eat more plants. But, put a vegetarian on a diet 14:57 of meat, eggs, and dairy, and within as few as 4 days, you can drive down 15:01 levels. So, one would expect those eating plant-based diets to have less 15:06 Hashimoto's. But, in a previous video, I expressed concern about insufficient 15:10 iodine intake, which could also lead to hypothyroidism. So, which is it? Let's 15:16 find out. Vegan diets tended to be associated with 15:20 lower, not higher, risk of hypothyroid disease. Why the word tended? Because 15:26 the associated protection against hypothyroid incidence and prevalence 15:29 studies did not reach statistical significance. 15:33 It wasn't just because they were slimmer, the lower risk existed even 15:37 after controlling for body weight. So, they think maybe it's because animal 15:41 products may induce inflammation. The question I have though is, if someone 15:46 who already has Hashimoto's, I mean, what happens if you change their diet? 15:50 That's exactly what I'll explore next. Okay, so that was about preventing 15:58 hyperthyroidism or hypothyroidism, preventing Graves disease and 16:03 Hashimoto's. But, what about a dietary intervention to treat Hashimoto's, treat 16:10 hypothyroidism? That's what we'll close out with, a natural treatment for 16:16 Hashimoto's disease. Autoimmune thyroiditis, also known as 16:20 Hashimoto's disease, is an organ-specific autoimmune disorder where 16:25 your body attacks your own thyroid gland, often leading to hypothyroidism 16:30 due to destruction and scarring of the gland itself. 16:33 We know there's a genetic component since identical twins are more likely to 16:37 share the disease than fraternal twins. However, even with identical twins, the 16:42 concordance rate was only about 50%, meaning 16:45 even if your identical twin with basically the exact same DNA as you has 16:50 the disease, there's only like a flip of a coin's chance you'll get it. 16:55 Emphasizing that other factors other than your genes play a role in the
Black Cumin for Hashimoto's Treatment 17:00 development of the disease. Genes load the gun, but environment may pull the 17:05 trigger. More than 90 chemicals have been noted 17:08 disrupting hormonal balance or thyroid function. However, only a few such 17:13 pollutants show evidence that they contribute to autoimmune thyroid 17:16 disease. These include polyaromatic hydrocarbons, which smokers get a lot 17:21 from their cigarettes. But, in nonsmokers, exposure comes almost 17:24 entirely from food. Polycyclic aromatic hydrocarbons are primarily formed when 17:29 muscle meats such as beef, and pork, fish, or chicken are cooked by 17:33 high-temperature methods such as grilling. 17:36 PBBs are a type of flame-retardant chemical 17:39 no longer manufactured in the US, but still found in the aquatic food chain. 17:43 And PCBs are used in a number of industrial processes and end up in 17:48 people's bodies largely through the consumption of fish as well, but also 17:52 other meats and eggs. So, one might suspect those eating plant-based diets 17:57 would have lower rates of hypothyroidism. And indeed, despite 18:00 their lower iodine intake, vegan diets tended to be protective. But, they've 18:04 never been put to the test in an interventional trial. A modification of 18:08 the Paleolithic diet has been tried in Hashimoto's patients, 18:13 but didn't appear to improve thyroid function. What did though 18:18 was Nigella sativa. That name should sound familiar to anyone who's read my 18:23 latest book How Not to Diet or watched my latest live presentation 18:27 Evidence-Based Weight Loss. Nigella sativa is the science name for black 18:33 cumin, which is just a simple spice, but it's also used for a variety of 18:38 medicinal purposes. In this study, a randomized double-blind 18:42 placebo-controlled trial, 8 weeks of a half teaspoon of powdered black cumin a 18:46 day in Hashimoto's patients, not only was there a significant reduction in 18:51 body weight, which is why I profiled it in the book, it also significantly 18:56 reduced thyroid-stimulating hormone, a sign that thyroid function was 19:00 improving, and even lowered the level of autoimmune antithyroid antibodies, as 19:05 well as increasing blood levels of thyroid hormone T3 in these Hashimoto's 19:09 patients. In addition, there was a significant drop in interleukin-23, a 19:13 pro-inflammatory cell signal thought to help 19:16 promote the autoimmune inflammation of the thyroid. So, further confirming the 19:20 anti-inflammatory nature of the plant. And what were the side effects? A 17% 19:26 drop in LDL bad cholesterol. And given the fact that patients with Hashimoto's 19:30 may be at particularly high risk of developing heart disease, 19:34 this is exactly the kind of side effect we'd want. Considering these 19:38 health-promoting effects of black cumin, it can be considered as a therapeutic 19:41 approach in the management of Hashimoto's-related metabolic 19:45 abnormalities. A similar trial failed to find a 19:48 benefit, though same dose, same time frame, but no significant changes in 19:53 thyroid function. In contrast with the last study though, 19:56 they were not all Hashimoto's patients, but rather hypothyroid for any reason, 20:01 and that may have diluted the results. And it's possible that telling patients 20:05 to take the black cumin doses with their thyroid hormone replacement therapy may
NutritionFacts Resources and Closing 20:09 have interfered with its absorption. It's similar to other foods and drugs, 20:13 which is why patients are normally told to take it on an empty stomach. 20:17 Since there are no downsides, I mean it's just a simple spice, I figure, 20:21 "Hey, why not give it a try?" I mean the worst that can happen is you'll have 20:25 tastier food. So, a half teaspoon of powdered black 20:31 cumin seeds once a day on an empty stomach for Hashimoto's sufferers. 20:37 For those of you who have this disease, try it out. Let me know how it works. 20:43 Visit nutritionfacts.org/audio to see all the podcast episodes with 20:47 descriptions that include links to the associated videos. 20:51 Sources cited and other details are available on each video's page. 20:55 Information about my books, How Not to Die, How Not to Diet, and [music] How 20:58 Not to Age, is at nutritionfacts.org/books. 21:02 All proceeds, which I get, are donated directly to charity. And I've got a new 21:07 book in the publication pipeline, the manuscript for How Not to Hurt, uh diet 21:13 and lifestyle approaches to pain management, has been handed in and will 21:16 be published December 15th. I'm going to be doing a series of webinars to feature 21:21 some of the new research I discovered. Sign up for our free newsletter at 21:26 nutritionfacts.org/subscribe to stay updated on when those will be. 21:32 Nutritionfacts.org is a science-based nonprofit, and everything on the website 21:36 is free. There are no ads, no corporate sponsorships, no kickbacks. We're 21:40 strictly non-commercial, not selling anything, just put it up as a public 21:43 service, as a labor of love, as a tribute to my grandmother, 21:47 whose own life was saved with evidence-based nutrition. We just have 21:51 like a a Wikipedia-type nonprofit model where everything's free, and we just 21:56 hope maybe, you know, one in a thousand people will find it so valuable that 21:59 they'll kick in a few bucks so we can continue to churn out new content to 22:03 help you and your family be healthier. Thanks for listening.
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