A Healthy Thyroid

Hello and welcome to the Nutrition Facts podcast, I’m your host Dr. Michael Greger. 

Now, I know I’ve made a name for myself in explaining how not to do certain things – just look at my books – How NOT to Die – and my upcoming book, How NOT to Diet.  But what I want to share with you is actually quite positive: what’s the best way to live a healthy life? Here are some answers.

Today we focus on that butterfly-shaped gland found low on the front of the neck –the thyroid.  The thyroid gland is part of the endocrine system, which is made up of glands that produce, store, and release hormones into the bloodstream. So what’s the best way to keep your thyroid healthy?  We begin with the use of artificial food coloring Red Dye No. 3.  It has yet to be banned despite its purported role in causing thousands of cases of thyroid cancer.

Fifteen million pounds of food dyes are sold every year in the U.S. Why? “Foods are artificially colored to make unattractive mixtures of basic ingredients and food additives acceptable to consumers.” See, food colorings are added to countless processed food products to “conceal the absence of fruits, vegetables, or other ingredients, and make the food ‘appear better or of greater value than it actually is.’” Otherwise, cherry popsicles might actually look like they have no cherries in them!

I’ve talked about the role of food dyes in causing ADH symptoms in kids. But, what about their role in cancer?

Due to cancer concerns, Red dye #1 was banned in 1961. Red #2 was banned in 1976, and then Red #4 was banned. What about Red #3, used today in everything from sausage to maraschino cherries? It was recently found to cause DNA damage in human liver cells in vitro, comparable to the damage caused by a chemotherapy drug whose whole purpose is to break down DNA.

But, Red #3 was found to influence children’s behavior more than thirty years ago, and interfere with thyroid function over forty years ago. Why is it still legal?

An article from the New York Times about Red #3 published way back in 1985. Already by then, the FDA had postponed action on banning the dye 26 times, even with the Acting Commissioner of the FDA saying Red #3 was “of greatest public health concern,” imploring his agency to “not knowingly allow continued exposure” (at high levels in the case of Red #3) of the public to color additives that have clearly been shown to induce cancer. The credibility of the Department of Health and Human Services would suffer if decisions are not made soon on each of these color additives.” That was written thirty years ago.

At the end of the day, industry pressure won out. “FDA scientists and FDA commissioners have recommended that the additives be banned. But there has been tremendous pressure to delay the recommendations from being implemented.”

In 1990, concerned about cancer risk, the FDA banned the use of Red #3 in anything going on our skin, but it remained legal to continue to put it in anything going into our mouths. Now, the FDA said at the time that they were planning on stopping that too, and ending all “remaining uses” of Red #3, lamenting that “The cherries in 21st-century fruit cocktail could well be light brown.” That was 1990.

Over 20 years later, it’s still in our food supply. After all, the agency estimated that “the lifetime risk of thyroid tumors in humans from Red #3 in food was at most 1 in 100,000.”

“Based on today’s population, that would indicate that Red #3 is causing cancer in about 3000 people.”

In our next story we learn about a study that finds the majority of retail pork tested is contaminated with antibiotic-resistant strains of the foodborne bacteria that can hurt our thyroid.

Every year, the federal government tests thousands of retail meat samples for the presence of four types of antibiotic-resistant bacteria. But, Yersinia enterocolitica is not among them. This, despite the fact that nearly 100,000 Americans are sickened by foodborne Yersinia every year. This is yet another public health breach, filled this week by Consumers Union.

Pigs are assumed to be the main reservoir for the pathogen, and pork and pork products, the main source of human infection. Most foodborne pathogens tend to come from a variety of sources, but 100% of the attributable Yersinia outbreaks reported in the United States over the last decade or so were caused by pork.

So, how contaminated is the U.S. pork supply? Consumers Union tested nearly 200 pork samples from cities across the country, and found more than two-thirds contaminated with Yersinia—90% of which were resistant to one or more antibiotics.

In most cases, Yersinia food poisoning just causes acute gastroenteritis— characterized by fever; abdominal pain; often bloody diarrhea. Sometimes cases can be confused with appendicitis though, leading to unnecessary emergency surgery. Long-term consequences of infection include chronic inflammation of the eyes, kidneys, heart, and joints. Within a year of a bout of Yersinia food poisoning, victims are at 47 times the risk of coming down with autoimmune arthritis. And, the bacteria may also play a role in triggering an autoimmune thyroid condition, known as Graves’ disease.

How widespread is Yersinia in U.S. pigs? A national USDA survey of fecal samples found half of American herds tested were infected. The emergence of human infection over the last century may in part be due to changes in the meat industry, such as slaughter plant consolidation, and an increase in farm size and intensification of production. Higher stocking densities of pigs on factory farms is one of the factors that’s been associated with increased prevalence among herds. Inside some swine confinement buildings, researchers have been able to culture the bacteria right out of the air.

The pork industry crowds pigs because overcrowding pigs may pay, according to the trade publication National Hog Farmer. You can, evidently, maximize profits by dropping the space per pig to six square feet—that’s like a 200-pound pig in the equivalent of two feet by three feet. They acknowledge this presents some problems—inadequate ventilation, increased health risks—but, sometimes, “crowding pigs a little tighter will make you more money.”

The equation for pork producers is even simpler when it comes to Yersinia, since the bacteria does not cause clinical disease in pigs. Thus, it does not present a production problem. The fact that the industry bottom line isn’t directly affected, no matter how high infection rates climb, may explain why there’s no industry-wide Yersinia monitoring and control programs in place in the United States. The costs of crowded confinement can simply be passed on to the tens of thousands of Americans who continue to be sickened every year, at an annual cost estimated at a quarter billion dollars.

Research from Europe suggests pigs raised using organic methods may have 50 times lower odds of harboring infection, compared to pigs raised conventionally. Unfortunately, you can’t really extrapolate that to the U.S., since organic production here is really more about what animals are fed, rather than how they are treated. The researchers attribute the lowered infection rates to factors like lower stocking densities, and lower levels of stress among the animals.

If stress is indeed a contributing factor, things may be looking up in Europe. On January 1, 2013, just about a month away, gestation crates for pregnant pigs are going to be banned across all 27 nations of the European Union—whereas in the U.S., where crating continues to be a predominant practice, pregnant sows have been shown to have among the highest prevalence of Yersinia infection. Though consumers don’t directly eat as many of the moms, the sows can be a source of infection for piglets, who can then carry the infection through to slaughter.

“Practices that restrict natural motion, such as these sow gestation crates, induce high levels of stress in the animals and threaten their health, which in turn may threaten our health too.”

Crated sows have been shown to have impaired immunity—thought to be as a result of elevated stress hormone levels, related to the frustration of normal maternal behaviors, like nest building.

Yersinia is one of the reasons why the disease resistance of mother pigs matters when it comes to public health. Thankfully, major retailers, restaurant chains, and leaders in the pork industry have started phasing out gestation crates, which may end up improving the welfare of both animals and humans.

Another proposal to break the Yersinia cycle from farm to fork is to pay producers an incentive bonus if they keep Yersinia-free flocks. That’s the carrot. And the stick is that fresh meat would only be allowed from infection-free herds, diverting pork from infected herds to just making pre-cooked products.

“Although such a two-way splitting of pig-meat production would pose a logistic problem,” it could be actually possible if “enough emphasis were to be placed on cost/benefit for public health.”

There are also measures effective at reducing Yersinia contamination of the meat in the slaughter plant. “By sealing off the excised rectum with a plastic bag” during evisceration, you may get a ten-fold drop in carcass contamination. According to data from the Norwegian National Institute of Public Health, human Yersinia infection rates dropped about 25% after the introduction of the plastic bag technique across pig slaughterhouses in Norway.

Let me end by putting the new Consumer Reports finding in perspective. Yersinia in pork ranks only sixteenth in terms of the greatest foodborne disease burdens in the United States.

The worst, in terms of societal cost and quality-adjusted years of life lost, is poultry-borne Campylobacter bacteria—found contaminating 38% of chicken breasts in the latest retail meat survey released this year.

Then comes the Toxoplasma brain parasite in pork; Listeria in deli meat; and Salmonella in, again, poultry.

So, as concerning as this new report may be, the greatest food safety concern may be the original white meat.

In our final story, we hear about a study that advises pregnant women to take a daily iodine supplement.

Although severe iodine deficiency was eliminated in the United States nearly a century ago, after the introduction of iodized salt, iodine intake has declined in recent decades. Public health efforts to limit salt intake to decrease cardiovascular risk, in conjunction with increasing use of non-iodized salt, may in part be to blame.

Now, not adding salt to foods is a good thing, as sodium is considered the second leading dietary killer in the world—second only to not eating enough fruit. But if you do add table salt, make sure it’s iodized, as it is a myth, and often also false advertising, that so-called “natural” sea salt contains significant amounts of iodine.

Fruits and vegetables provide iodine, but the amounts can vary depending on where it’s grown; how much iodine is in the soil. Because iodine is particularly important for fetal brain development, there’s a recommendation that all U.S. women who are pregnant, lactating, or even planning a pregnancy should ingest dietary supplements containing 150 mcg of potassium iodide per day.

Is there evidence that they’re not getting enough now? Well, we’d like to see urine levels in pregnant women over 150. But in the U.S., pregnant women only average about 125. For example, a recent survey in New York City showed only about half of pregnant women were making the cut. Don’t most women take prenatal vitamins, though?

Only about half of prenatal multivitamins contain any iodine at all. And so, only about one in five pregnant women in the U.S. are following the recommendations of the American Thyroid Association to take a daily iodine supplement—specifically in the form of potassium iodide rather than seaweed, as the levels in seaweed are subject to natural variability. Though the iodine content was as much as 90% off in some of the potassium iodide prenatal supplements, the kelp supplements varied even wider, off by as much as 170%.

Now, the American Thyroid Association admits they don’t have evidence that the current borderline insufficiency levels are leading to undesirable outcomes, and so, their rational that all pregnant women take iodine supplements is a bit tenuous. But until such data are available, they figure better safe than sorry.

A randomized, placebo-controlled interventional trial would answer the question once and for all, but the existing evidence for iodine supplementation during pregnancy is so convincing that it would be considered unethical to randomize pregnant women to a placebo. And so, when it comes to sufficient iodine intake during pregnancy, I’d recommend, just do it.

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