Full transcript
0:00Doesn't it seem like when it comes to
0:02nutrition, there are more opinions than
0:04facts to go around?
0:06Every day we hear new [music] theories
0:08about diets and supplements and best
0:10foods to eat. Well, my role is to take
0:13the mystery out of good nutrition and
0:15look at the science. Welcome to the
0:18NutritionFacts podcast. I'm your host,
0:20Dr. [music] Michael Greger. One of the
0:22most common questions I'm asked is about
0:24a natural treatment for Hashimoto's
0:26disease, also known as autoimmune
0:28thyroiditis,
0:30the leading cause of hypothyroidism.
0:33So,
0:34I did a webinar about it. Here's the
0:35whole thing on the best diet for thyroid
0:39health, as well as the healthiest
0:40natural source of iodine.
0:43Adequate dietary iodine is required for
0:46normal thyroid function. In fact, the
0:49two thyroid hormones are named after how
0:51many iodine atoms they contain, T3 and
0:53T4. Now, given that iodine is
0:56extensively stored in the thyroid gland
0:58itself,
0:59it's not something you have to get every
1:01day, but your overall diet needs to have
1:03some good source.
1:05Unfortunately, the common sources aren't
1:07particularly health-promoting. Iodized
1:09salt and dairy foods are because
1:11iodine-based cleansers like Betadine are
1:14used to sanitize the udders, which
1:17results in some iodine leaching into the
1:19milk. They also add iodine to cattle
1:21feed.
1:23And some commercial breads have
1:25iodine-containing food additives.
1:27So, if you put people on a paleo-type
1:29diet and cut out dairy and table salt,
1:31they can develop an iodine deficiency,
1:33even though they doubled their seafood
1:36intake, which can also be a source.
1:38What about those switching to diets
1:39centered around whole plant foods? I
1:41mean, they're also cutting down on ice
1:43cream and Wonder Bread. And if they're
1:45not eating anything from the sea,
1:46seaweed, sea vegetables, they can run
1:49into the same problem.
1:51Her parents reported striving to feed
1:53her only the healthiest foods. The
1:563-year-old only got plant-based,
1:58unsalted, unprocessed foods with no
2:00vitamin supplementation.
2:02Now, that could have been deadly. I
2:03mean, with no vitamin B12, those on
2:05strictly plant-based diets can develop
2:07irreversible nerve damage. But in this
2:09case, a goiter arose first due to
2:12inadequate iodine intake.
2:15Here's another case of veganism as a
2:17cause of iodine-deficient hypothyroidism
2:20in a toddler after weaning. Now, before
2:22weaning, he was fine because his mother
2:24kept taking her prenatal vitamins, which
2:26luckily contained iodine.
2:29Most vegetarians and vegans are
2:30apparently unaware of the importance of
2:32iodine in pregnancy, just as clueless as
2:35their omnivorous counterparts.
2:38The American Thyroid Association and
2:39American Academy of Pediatrics have
2:41recommended that women even just
2:43planning on getting pregnant should
2:45ingest a daily supplement that contains
2:47150 micrograms of iodine. Yet, only 60%
2:50of prenatal vitamins marketed in the US
2:53contain this essential mineral.
2:56So, in spite of the recommendations,
2:58about 40% lack it. Therefore, it's
3:00extremely important that pregnant and
3:02breastfeeding women read the labels to
3:04ensure they're receiving an adequate
3:07amount. Women of reproductive age have
3:08an average iodine level 110, which is
3:11fine for non-pregnant individuals, but
3:14we'd really like to see at least 150 in
3:17pregnancy. It's basically a 24-hour
3:19urine test in which iodine sufficiency
3:21is defined as 100 micrograms per liter
3:23of pee in non-pregnant adults,
3:25which your average vegan fails to reach
3:29in the largest study done to date out of
3:30Boston.
3:32The recommended average daily intake is
3:34150 micrograms a day for most people,
3:36which you can get in like a, you know,
3:37cup and a half of cow's milk. Sadly,
3:40plant-based milks are typically not
3:42fortified with iodine, averaging only
3:44about 3 micrograms per cup. In the
3:47largest systematic study to date,
3:49although many plant-based milks are
3:51fortified with calcium, they only found
3:53just three of 47 fortified with iodine.
3:57Of those that were had as much as cow's
3:59milk, but those that weren't fell short.
4:03Plant-based milk companies brag about
4:05enriching their milks with calcium and
4:08often vitamin B12, D, vitamin A, but
4:10only rarely are attempts made to match
4:12the iodine content. I mean, the only
4:14reason cow's milk has as much as it does
4:16because they they enrich the feed or it
4:18comes dripping off their udders, right?
4:20So, why don't plant milk companies add
4:23iodine, too, right? I was told by a food
4:26scientist at Silk that my carrageenan
4:28video played a role in them switching to
4:30another thickener. Hopefully, they'll
4:32see this video and consider adding
4:34iodine, too, or some company will snatch
4:37at the market advantage opportunity.
4:40The researchers conclude that
4:42individuals who consume plant-based
4:43milks not fortified with iodine may be
4:46at risk for iodine deficiency unless
4:49they consume alternative dietary iodine
4:51sources, the healthiest of which is sea
4:55vegetables.
4:57Okay, so to reiterate, one cause of
5:01hypothyroidism, an underactive thyroid
5:04gland, is inadequate iodine intake. This
5:07is especially important for pregnant
5:09women and women even considering
5:12pregnancy, but that largest study of
5:15vegan iodine status in Boston found most
5:18vegans have insufficient intake. So,
5:22what's the best way to get it? What's
5:23the healthiest natural source of iodine?
5:26That's the name of the next video.
5:31Dairy milk supplies between a quarter
5:33and a half of the daily iodine
5:35requirement in the United States. So,
5:37milk itself has little native iodine.
5:40The milk iodine content is mainly
5:42determined by factors like the
5:44application of iodine-containing teat
5:46disinfectants. The iodine residues in
5:49milk appear to originate mainly from the
5:50contamination of the teat surface. The
5:53teats are are sprayed or dipped with
5:56like a Betadine-type disinfectants, and
5:58the iodine just kind of leaches into the
6:00milk.
6:01Too bad most of the plant-based milks on
6:04the market aren't enriched with iodine,
6:05too. Fortified soy milk is probably the
6:08healthiest of the plant milks, but even
6:10if it was enriched with iodine, what
6:12about the effects of soy on thyroid
6:15function? It's funny, when I searched
6:18the medical literature on soy and
6:19thyroid, this study popped up. A
6:22cost-effective way to train residents to
6:24do thyroid biopsies. Just stick the
6:28ultrasound probe right on top and go to
6:30town. Turns out, on ultrasound, your
6:33thyroid gland looks a lot like tofu.
6:36Anyways, the
6:37the idea that soy may influence thyroid
6:40function originated over eight decades
6:41ago, when marked thyroid enlargement was
6:44seen in rats fed raw soybeans.
6:47Though the observation that people
6:49living in Asian countries have consumed
6:51soy foods for centuries with no
6:53perceptible thyrotoxic effects has
6:54certainly suggests their safety. Bottom
6:57line, there does not seem to be a
6:58problem with people who have normal
7:00thyroid function. However, soy foods may
7:03inhibit the oral absorption of
7:04Synthroid, thyroid hormone replacement
7:06drugs,
7:07but so do all foods, right? That's why
7:10we tell patients to take it on empty
7:12stomach.
7:13But you also have to be getting enough
7:16iodine. So, it may be particularly
7:17important for soy food consumers to make
7:19sure their intake of iodine is adequate.
7:22What's the best way to get iodine? For
7:24those who use table salt, make sure it's
7:26iodized. Currently, only half of table
7:29salt sold contains iodine, and the salt
7:31used in processed foods is typically not
7:33iodized. Of course, ideally, we
7:35shouldn't add salt at all. Dietary salt
7:38is a public health hazard. I think this
7:42title is a little over the top. Dietary
7:45salt is the number one dietary risk
7:47factor for death on the planet Earth.
7:50Why? Beyond more than 3 million people a
7:52year. Twice as bad as not eating your
7:55vegetables. What's the best source of
7:58iodine, then? Sea vegetables, right? You
8:01can get a little iodine here and there
8:02from a whole variety of foods, but the
8:04most concentrated source by far, with up
8:06to nearly 2,000% of your daily allowance
8:09in just a single gram, which is like the
8:10weight of a paper clip, seaweed. Given
8:14that iodine is extensively stored in the
8:16thyroid, it can be safely consumed
8:17intermittently, meaning you don't have
8:19to get get it every day, which makes
8:21seaweed use in a range of foods
8:23attractive, and occasional seaweed
8:24intake enough to ensure iodine
8:27sufficiency. However, some seaweed
8:29should be used with caution due to its
8:32overly high iodine content, like kelp.
8:36Too much iodine can cause
8:37hyperthyroidism, a hyperactive thyroid
8:40gland. A woman presented with a racing
8:42heartbeat, insomnia, anxiety, and weight
8:44loss, thanks to taking just two tablets
8:47a day containing kelp.
8:50In my last video, I noted how the
8:52average urinary iodine level of vegans
8:54was less than the ideal levels, but
8:57there was one kelp-eating vegan with a
9:00urinary concentration over 9,000, right?
9:03Adequate intake is when you're peeing
9:04out 100 to 199. Excessive iodine intake
9:07is when you break 300. 9,437,
9:11way too much.
9:14The recommended average daily intake is
9:16150 micrograms a day for non-pregnant,
9:18non-breastfeeding adults. You may want
9:20to stay below 600 on a day-to-day basis,
9:23whereas a, you know, tablespoon of kelp
9:25may contain 2,000, right? I'd stay away
9:28from kelp because there's too much, and
9:30stay away from hijiki because it
9:32contains too much arsenic.
9:35Here's how much of common seaweed
9:37preparation should give you an
9:38approximate daily allowance. Two nori
9:41sheets, you can literally just nibble on
9:43them as snacks, like I do. One teaspoon
9:46of dulse flakes, which you can just
9:48sprinkle on anything. One teaspoon of
9:50dried arame, which is great for like
9:52adding to soups, or one tablespoon of
9:55seaweed salad.
9:57If iodine is concentrated in marine
10:00foods, this raises the question of how
10:02early hominins living in continental
10:04areas could have met their iodine
10:07requirements?
10:08Well, here's what bonobos do, perhaps
10:10our closest relatives. During swamp
10:13visits, they all forage aquatic herbs.
10:17You can munch on aquatic plants yourself
10:22by incorporating seaweed into your diet,
10:24the healthiest natural source of iodine.
10:27Okay. So, we covered thyroid issues
10:29caused by either too little
10:31or too much iodine intake. But, what
10:34about hypothyroidism or hyperthyroidism
10:37caused by autoimmune diseases like
10:40Hashimoto's thyroiditis?
10:43That's what we'll turn to next in my
10:45video the best diet for hypothyroidism
10:48and hyperthyroidism.
10:51And then I can finish eating my seaweed.
10:53There are several autoimmune diseases
10:55that affect the thyroid gland, the most
10:57common being Graves disease and
11:00Hashimoto's thyroiditis. Graves disease
11:03results in hyperthyroidism, an
11:05overactive thyroid gland. Though
11:08slaughterhouses are supposed to remove
11:09thyroid glands, should some neck meat
11:12slip in, you can suffer a similar
11:14syndrome called hamburger
11:16thyrotoxicosis,
11:18but that's not from your body making too
11:20much thyroid hormone, that's from your
11:21body eating too much thyroid hormone.
11:24Graves disease is much more common, and
11:26meat-free diets may be able to help with
11:29both as plant-based diets may be
11:30associated with a low prevalence of
11:33autoimmune disease in general, as
11:35observed for example in rural
11:36sub-Saharan Africa. Maybe it's because
11:39plants are packed with antioxidants,
11:41which are possible protective factors
11:43against autoimmune diseases. Maybe it's
11:45because plants are packed with
11:46anti-inflammatory compounds. After all,
11:48a whole food plant-based diet is
11:50basically synonymous
11:52with an anti-inflammatory diet. But, you
11:55don't know until you put it to the test.
11:59Turns out
12:00the exclusion of all animal foods was
12:02associated with half the prevalence of
12:04hyperthyroidism compared with omnivorous
12:06diets. Lacto-ovo vegetarian and
12:08fish-only diets were associated with
12:10intermediate protection, but a 52% lower
12:14odds of hyperthyroidism among those
12:16eating strictly plant-based diets.
12:19This apparent protection may be due to
12:20the exclusion of animal foods, the
12:22benefits of plant foods, or or both.
12:25Animal foods like meat, eggs, and dairy
12:27products may contain high estrogen
12:29concentrations for example, which have
12:31been linked to autoimmunity in
12:32preclinical studies. Or the decrease in
12:34animal protein may downregulate IGF-1,
12:37which is not just a cancer-promoting
12:39growth hormone, but may play a role in
12:41autoimmune diseases as well. Or it could
12:44be the good stuff in plants that may
12:46protect cells like the polyphenol
12:48phytochemicals such as flavonoids found
12:50in plant foods. Maybe it's the
12:52environmental toxins that build up the
12:53food chain, for example. Fish
12:55contaminated with industrial pollutants
12:57like PCBs are associated with increased
12:59frequency of thyroid disorders.
13:03Okay, what about the other autoimmune
13:05thyroid disease, Hashimoto's
13:07thyroiditis, which, assuming you're
13:09getting enough iodine, is the primary
13:11cause of hypothyroidism,
13:13an underactive thyroid gland.
13:16Graves disease wasn't the only
13:18autoimmune disorder that was rare or
13:20virtually unknown among those living in
13:23rural sub-Saharan Africa eating near
13:25vegan diets. They also
13:27appear to have less Hashimoto's.
13:30There's evidence that those with
13:31Hashimoto's have compromised antioxidant
13:34status, but we don't know if it's cause
13:36or effect. But, if you look at the
13:37dietary factors associated with blood
13:40levels of autoimmune antithyroid
13:42antibodies, animal fats seem to be
13:44associated with higher levels, whereas
13:46vegetables and other plant foods are
13:47associated with lower levels. So again,
13:50anti-inflammatory diets may be useful.
13:53No surprise as Hashimoto's is an
13:55inflammatory disease. That's what
13:57thyroiditis means, inflammation of the
14:00thyroid gland.
14:01Another possibility is the reduction in
14:03methionine intake, an amino acid
14:05concentrated in animal protein. Thought
14:07to be one reason why the consumption of
14:09whole plant foods is likely to have a
14:11favorable influence on longevity through
14:14decreasing the risk of cancer, heart
14:16disease, and diabetes. And methionine
14:18restriction improves thyroid function in
14:20mice, but has yet to be put to the test
14:23for Hashimoto's in humans.
14:26If you compare the
14:27poop of patients with Hashimoto's to
14:30controls, the condition appears to be
14:31related to a clear reduction in the
14:34concentration of Prevotella species.
14:37Prevotella are good fiber-eating bugs
14:39known to enhance anti-inflammatory
14:41activities. Decreased Prevotella levels
14:44are also something you see in other
14:46autoimmune conditions such as multiple
14:47sclerosis and type 1 diabetes.
14:50How do you get more Prevotella? Eat more
14:54plants. But, put a vegetarian on a diet
14:57of meat, eggs, and dairy, and within as
14:59few as 4 days, you can drive down
15:01levels. So, one would expect those
15:04eating plant-based diets to have less
15:06Hashimoto's. But, in a previous video, I
15:08expressed concern about insufficient
15:10iodine intake, which could also lead to
15:12hypothyroidism. So, which is it? Let's
15:16find out.
15:17Vegan diets tended to be associated with
15:20lower, not higher, risk of hypothyroid
15:22disease. Why the word tended? Because
15:26the associated protection against
15:27hypothyroid incidence and prevalence
15:29studies did not reach statistical
15:31significance.
15:33It wasn't just because they were
15:34slimmer, the lower risk existed even
15:37after controlling for body weight. So,
15:39they think maybe it's because animal
15:41products may induce inflammation. The
15:44question I have though is, if someone
15:46who already has Hashimoto's, I mean,
15:48what happens if you change their diet?
15:50That's exactly what I'll explore next.
15:55Okay, so that was about preventing
15:58hyperthyroidism or hypothyroidism,
16:01preventing Graves disease and
16:03Hashimoto's. But, what about a dietary
16:06intervention to treat Hashimoto's, treat
16:10hypothyroidism? That's what we'll close
16:13out with, a natural treatment for
16:16Hashimoto's disease.
16:18Autoimmune thyroiditis, also known as
16:20Hashimoto's disease, is an
16:22organ-specific autoimmune disorder where
16:25your body attacks your own thyroid
16:27gland, often leading to hypothyroidism
16:30due to destruction and scarring of the
16:32gland itself.
16:33We know there's a genetic component
16:35since identical twins are more likely to
16:37share the disease than fraternal twins.
16:40However, even with identical twins, the
16:42concordance rate was only about 50%,
16:44meaning
16:45even if your identical twin with
16:48basically the exact same DNA as you has
16:50the disease, there's only like a flip of
16:52a coin's chance you'll get it.
16:55Emphasizing that other factors other
16:57than your genes play a role in the
17:00development of the disease. Genes load
17:02the gun, but environment may pull the
17:05trigger.
17:06More than 90 chemicals have been noted
17:08disrupting hormonal balance or thyroid
17:11function. However, only a few such
17:13pollutants show evidence that they
17:14contribute to autoimmune thyroid
17:16disease. These include polyaromatic
17:18hydrocarbons, which smokers get a lot
17:21from their cigarettes. But, in
17:22nonsmokers, exposure comes almost
17:24entirely from food. Polycyclic aromatic
17:28hydrocarbons are primarily formed when
17:29muscle meats such as beef, and pork,
17:31fish, or chicken are cooked by
17:33high-temperature methods such as
17:34grilling.
17:36PBBs
17:37are a type of flame-retardant chemical
17:39no longer manufactured in the US, but
17:41still found in the aquatic food chain.
17:43And PCBs are used in a number of
17:46industrial processes and end up in
17:48people's bodies largely through the
17:50consumption of fish as well, but also
17:52other meats and eggs. So, one might
17:55suspect those eating plant-based diets
17:57would have lower rates of
17:58hypothyroidism. And indeed, despite
18:00their lower iodine intake, vegan diets
18:02tended to be protective. But, they've
18:04never been put to the test in an
18:06interventional trial. A modification of
18:08the Paleolithic diet has been tried in
18:11Hashimoto's patients,
18:13but didn't appear to improve thyroid
18:15function. What did though
18:18was Nigella sativa. That name should
18:21sound familiar to anyone who's read my
18:23latest book How Not to Diet or watched
18:25my latest live presentation
18:27Evidence-Based Weight Loss. Nigella
18:29sativa is the science name for black
18:33cumin, which is just a simple spice, but
18:36it's also used for a variety of
18:38medicinal purposes. In this study, a
18:41randomized double-blind
18:42placebo-controlled trial, 8 weeks of a
18:44half teaspoon of powdered black cumin a
18:46day in Hashimoto's patients, not only
18:49was there a significant reduction in
18:51body weight, which is why I profiled it
18:53in the book, it also significantly
18:56reduced thyroid-stimulating hormone, a
18:58sign that thyroid function was
19:00improving, and even lowered the level of
19:02autoimmune antithyroid antibodies, as
19:05well as increasing blood levels of
19:06thyroid hormone T3 in these Hashimoto's
19:09patients. In addition, there was a
19:11significant drop in interleukin-23, a
19:13pro-inflammatory cell signal thought to
19:15help
19:16promote the autoimmune inflammation of
19:18the thyroid. So, further confirming the
19:20anti-inflammatory nature of the plant.
19:23And what were the side effects? A 17%
19:26drop in LDL bad cholesterol. And given
19:29the fact that patients with Hashimoto's
19:30may be at particularly high risk of
19:32developing heart disease,
19:34this is exactly the kind of side effect
19:36we'd want. Considering these
19:38health-promoting effects of black cumin,
19:39it can be considered as a therapeutic
19:41approach in the management of
19:42Hashimoto's-related metabolic
19:45abnormalities.
19:46A similar trial failed to find a
19:48benefit, though same dose, same time
19:50frame, but no significant changes in
19:53thyroid function.
19:54In contrast with the last study though,
19:56they were not all Hashimoto's patients,
19:58but rather hypothyroid for any reason,
20:01and that may have diluted the results.
20:03And it's possible that telling patients
20:05to take the black cumin doses with their
20:07thyroid hormone replacement therapy may
20:09have interfered with its absorption.
20:11It's similar to other foods and drugs,
20:13which is why patients are normally told
20:15to take it on an empty stomach.
20:17Since there are no downsides, I mean
20:19it's just a simple spice, I figure,
20:21"Hey, why not give it a try?" I mean the
20:22worst that can happen is you'll have
20:25tastier food.
20:27So, a half teaspoon of powdered black
20:31cumin seeds once a day on an empty
20:34stomach for Hashimoto's sufferers.
20:37For those of you who have this disease,
20:39try it out. Let me know how it works.
20:43Visit nutritionfacts.org/audio
20:45to see all the podcast episodes with
20:47descriptions that include links to the
20:49associated videos.
20:51Sources cited and other details are
20:53available on each video's page.
20:55Information about my books, How Not to
20:57Die, How Not to Diet, and [music] How
20:58Not to Age, is at
20:59nutritionfacts.org/books.
21:02All proceeds, which I get, are donated
21:05directly to charity. And I've got a new
21:07book in the publication pipeline, the
21:09manuscript for How Not to Hurt, uh diet
21:13and lifestyle approaches to pain
21:14management, has been handed in and will
21:16be published December 15th. I'm going to
21:19be doing a series of webinars to feature
21:21some of the new research I discovered.
21:23Sign up for our free newsletter at
21:26nutritionfacts.org/subscribe
21:28to stay updated on when those will be.
21:32Nutritionfacts.org is a science-based
21:34nonprofit, and everything on the website
21:36is free. There are no ads, no corporate
21:38sponsorships, no kickbacks. We're
21:40strictly non-commercial, not selling
21:42anything, just put it up as a public
21:43service, as a labor of love, as a
21:45tribute to my grandmother,
21:47whose own life was saved with
21:49evidence-based nutrition. We just have
21:51like a a Wikipedia-type nonprofit model
21:54where everything's free, and we just
21:56hope maybe, you know, one in a thousand
21:57people will find it so valuable that
21:59they'll kick in a few bucks so we can
22:01continue to churn out new content to
22:03help you and your family be healthier.
22:06Thanks for listening.