The Best and Worst Foods for Your Thyroid
Is there a thyroid diet?
Your thyroid is your body's silent workhorse—most of the time, it functions so smoothly that we forget it's there. But this little, butterfly-shaped gland that sits at the base of your neck helps regulate your metabolism, temperature, heartbeat, and more, and if it starts to go haywire, you'll notice. An underactive thyroid—when the gland fails to produce enough thyroid hormone (TH)—can bring on weight gain, sluggishness, depression, and increased sensitivity to cold. An overactive thyroid, on the other hand, happens when your body produces too much TH, and can cause sudden weight loss, irregular heartbeat, sweating, nervousness, and irritability.
Genetics, an autoimmune condition, stress, and environmental toxins can all mess with your thyroid—and so can your diet, one factor you can completely control. Here are the foods that may help keep your thyroid humming along, as well as some that won't.
Your thyroid needs iodine to work properly and produce enough TH for your body's needs. Don't get enough iodine, and you run the risk of hypothyroidism or a goiter (a thyroid gland that becomes enlarged to make up for the shortage of thyroid hormone). Most Americans have no problem getting enough iodine, since table salt is iodized—but if you're on a low-sodium diet (as an increasing number of Americans are for their heart health) or follow a vegan diet (more on that later), then you may need to up your intake from other sources.
Many types of seaweed are chockfull of iodine, but the amount can vary wildly, says Mira Ilic, RD, a registered dietician at the Cleveland Clinic. According to the National Institutes of Health, a 1-gram portion can contain anywhere from 11% to a whopping 1,989% of your percent daily value. But since seaweed is especially high in iodine, you shouldn't start eating sushi every day of the week. Too much iodine can be just as harmful to your thyroid as too little by triggering (or worsening) hypothyroidism. To get seaweed's big benefits without going overboard, Cynthia Sass, MPH, RD, and Health's contributing nutrition editor advises sticking to one fresh seaweed salad per week (in addition to sushi), and steering clear of seaweed teas and supplements.
Short of eating a few kelp salads, you probably don't have to worry about getting too much iodine from any other foods. In particular, dairy products are full of this nutrient (and in more manageable amounts), according to a 2012 research in the journal Nutrition Reviews. Part of the reason is because livestock are given iodine supplements and the milking process involves iodine-based cleaners. Plain, low-fat yogurt, or Greek yogurt is a good source—it can make up about 50% of your daily intake of iodine.
Best: Brazil nuts
Just one kernel contains 96 micrograms, which is almost double the daily recommended intake of 55 micrograms. And remember, the max upper limit of selenium is 400 micrograms a day, so don't go overboard. Too much selenium can cause "garlic breath," hair loss, discolored nails, and even heart failure, says Ilic.
By drinking 1 cup of low-fat milk, you'll consume about one-third of your daily iodine needs. Another good idea: Opt for a glass that's been fortified with vitamin D. One 2013 study found that people with an underactive thyroid (hypothyroidism) were more likely to be deficient in D than their healthier counterparts. (Another honorable dairy mention is cheese, especially cheddar: just one slice is good for 12 micrograms of iodine and 7 IU of vitamin D.)
Best: Chicken and beef
Zinc is another key nutrient for your thyroid—your body needs it to churn out TH. Take in too little zinc, and it can lead to hypothyroidism. But get this: If you develop hypothyroidism, you can also become deficient in zinc, since your thyroid hormones help absorb the mineral, explains Ilic. And when that happens, you may also experience side effects like severe alopecia, an autoimmune condition that attacks hair follicles and makes it fall out in clumps, according to one 2013 report.
You probably get enough zinc already (most people in the U.S. do), but if you have a poor diet or a GI disorder that interferes with your ability to absorb zinc, you might be at risk for a deficiency, says Ilic. Meats are a good source: One 3-ounce serving of beef chuck roast contains 7 milligrams; a 3-ounce beef patty contains 3 milligrams; and a 3-ounce serving of dark chicken meat contains 2.4 milligrams.
One 3-ounce serving of baked cod contains about 99 micrograms of iodine or 66% of your daily recommended intake. Canned tuna is another good option: a 3-ounce serving runs about 17 micrograms, or 11% of your daily iodine quota. (Bonus: One 3-ounce serving of canned yellowfin tuna also contains 92 micrograms of selenium.)
One large egg contains about 16% of the iodine and 20% of the selenium you need for the day, making them a thyroid superfood. If you haven't been instructed otherwise by your doctor, eat the whole egg (try our foolproof trick for cooking eggs over easy)—much of that iodine and selenium is located in the yolk, says Ilic.
Berries are chockfull of antioxidants, according to a 2010 study in Nutrition Journal. The researchers examined more than 3,000 foods and found that wild strawberries, blackberries, goji berries, and cranberries ranked especially high.
Good: Cauliflower, kale, broccoli, bok choy
Do a little Googling, and you might turn up a page or two claiming that cruciferous vegetables can cause thyroid troubles. The truth is a little murkier. While it's true that these veggies contain compounds called glucosinolates, which might interfere with your body's production of thyroid hormones in high amounts, it's pretty unlikely that they'll harm your thyroid if you're eating normal-size servings. One case report in the New England Journal of Medicine highlighted the story of an 88-year-old woman who showed up to the ER with hypothyroidism after eating about 2 or 3 pounds of bok choy a day—but, as Ilic points out, "that's not a normal amount."
Bottom line: "Cruciferous vegetables like cauliflower and kale are important for a healthy diet and a healthy thyroid," says Ilic. (And besides, if you cook down the foods, you'll release enzymes that are related to glucosinolates. See? Problem solved.)
Worst: Gluten (if you have celiac disease)
People with celiac disease—the autoimmune disease that's characterized by an intolerance to the gluten in wheat, barley, and rye—are also more likely to have higher rates of thyroid problems, according to a 2007 report by researchers in the United Kingdom. "Eating a gluten-free diet helps control the symptoms, which may also help protect the thyroid gland," says Ilic. But unless you have celiac disease—and we're not talking an L.A.-aversion to gluten, here — you might not want to avoid breads after all. In fact, thanks to some of the baking processes, bread can actually contain some iodine.