9 Foods to Avoid With Hypothyroidism
What you eat can affect your thyroid gland as well as your body's ability to use thyroid hormone. Learn which foods to avoid when managing hypothyroidism.

Hypothyroidism can be a tricky condition to manage, and what you eat can interfere with your treatment. Some nutrients heavily influence the function of the thyroid gland, and certain foods can inhibit your body's ability to absorb the replacement hormones you may take as part of your thyroid treatment. There's no such thing as a "hypothyroidism diet" that will make you well, but eating smart can help you feel better despite the condition. Here are nine foods to limit or avoid as you manage hypothyroidism:

Soy
The hormone estrogen can interfere with your body's ability to use thyroid hormone, says Stephanie Lee, MD, PhD associate chief of endocrinology, nutrition, and diabetes at Boston Medical Center and an associate professor at the Boston University School of Medicine. Soy is loaded with plant-based phytoestrogen, and some researchers believe too much soy may increase a person's risk for hypothyroidism. People with hypothyroidism should moderate their intake of soy. However, because soy hasn't been definitively linked to hypothyroidism, there are no specific dietary guidelines.

Cruciferous Vegetables
Cruciferous vegetables, such as broccoli and cabbage, can interfere with the production of thyroid hormone, particularly people who have an iodine deficiency. Digesting these vegetables can block the thyroid's ability to absorb iodine, which is essential for normal thyroid function. People with hypothyroidism may want to limit their intake of broccoli, Brussels sprouts, cabbage, cauliflower, kale, turnips, and bok choy. Cooking the vegetables can reduce the effect that cruciferous vegetables have on the thyroid gland. Limiting your intake to 5 ounces a day appears to have no adverse effect on thyroid function.

Gluten
People with hypothyroidism should consider minimizing their intake of gluten, a protein found in foods processed from wheat, barley, rye, and other grains, says Ruth Frechman, RDN, a dietitian and nutritionist in the Los Angeles area and a spokesperson for the Academy of Nutrition and Dietetics. Gluten can irritate the small intestine and may hamper absorption of thyroid hormone replacement medication.

Fatty Foods
Fats have been found to disrupt the body's ability to absorb thyroid hormone replacement medicines, Dr. Lee says. Fats may also interfere with the thyroid's ability to produce hormone as well. Some health care professionals recommend that you cut out all fried foods and reduce your intake of fats from sources such as butter, mayonnaise, margarine, and fatty cuts of meat.

Sugary Foods
Hypothyroidism can cause the body's metabolism to slow down, Frechman says. That means it's easy to put on pounds if you aren't careful. "You want to avoid the foods with excess amounts of sugar because it's a lot of calories with no nutrients," she says. It's best to reduce the amount of sugar you eat or try to eliminate it completely from your diet.

Processed Foods
"Processed foods tend to have a lot of sodium, and people with hypothyroidism should avoid sodium," Frechman says. Having an underactive thyroid increases a person's risk for high blood pressure, and too much sodium further increases this risk. Read the Nutrition Facts label on the packaging of processed foods to find options lowest in sodium. People with an increased risk for high blood pressure should restrict their sodium intake to 1,500 milligrams a day, according to the U.S. Centers for Disease Control and Prevention.

Excess Fiber
Getting enough fiber is good for you, but too much can complicate your hypothyroidism treatment. Guidelines currently recommend that older adults take in 20 to 35 grams of fiber a day. Amounts of dietary fiber from whole grains, vegetables, fruits, beans, and legumes that go above that level affect your digestive system and can interfere with absorption of thyroid hormone replacement drugs. If you're on a high-fiber diet, ask your doctor if you need a higher dose of thyroid medication. Your maintenance dose may need to be increased if you aren't absorbing enough medication.

Coffee
Caffeine has been found to block absorption of thyroid hormone replacement, Lee says. "People who were taking their thyroid medication with their morning coffee had uncontrollable thyroid levels, and we couldn't figure it out," she says. "I now have to be very careful to tell people, 'Only take your medication with water.'" You should wait at least 30 minutes after taking your medication before having a cup of joe.

Alcohol
Alcohol consumption can wreak havoc on both thyroid hormone levels in the body and the ability of the thyroid to produce hormone. Alcohol appears to have a toxic effect on the thyroid gland and suppresses the ability of the body to use thyroid hormone. Ideally, people with hypothyroidism should cut out alcohol completely or drink in careful moderation.