Ask the Doctor Immune Boosters
"Should people with Hashimoto's thyroiditis avoid immune-system boosters such as echinacea and garlic? Are there any foods that should be avoided? I am curious about some of the claims made by herbalists and nutritionists." -- LC, Scarsdale, N.Y.
Both echinacea and garlic contain substances that have been shown in a handful of experimental studies to increase the ability of lymphocytes to attack cancer cells. The full significance of these findings remains uncertain and controversial. Nonetheless, "alternative medicine" practitioners have recommended them to "boost" the immune system.
Hashimoto's thyroiditis is an autoimmune disorder in which one's own lymphocytes enter and destroy thyroid tissue. A Medline search failed to find any information regarding the effects of echinacea or garlic extracts on autoimmune processes. So it is unknown whether patients with autoimmune disorders should avoid these substances. Nonetheless, since the mechanism by which the lymphocytes cause injury to tumor cells or thyroid cells is similar, there is a possibility that these substances might augment autoimmune problems.
Other chemicals which "boost" the immune system have been shown to increase autoimmune thyroid disease. Interferon, which has been used to help the immune system clear hepatitis B virus in patients with chronic infections, does increase the chance of developing autoimmune thyroid disease, including Hashimoto's thyroiditis.
Many "alternative medicine" practitioners suggest kelp tablets, thyroid extracts, or other sources of iodine for patients with thyroid disease. Worldwide, the most common cause of hypothyroidism and goiter is iodine deficiency, and iodine-containing substances are the mainstay of treatment. However, there is no iodine deficiency in the United States, and such treatment may actually be harmful to patients with Hashimoto's thyroiditis. Primarily in patients who are not yet taking levothyroxine (patients with small goiters and normal or slightly reduced thyroid function), iodine may result in worsening hypothyroidism and increased goiter size. Iodine-containing douches, topical antiseptics, iodine-containing expectorants, and seaweeds in salads, Japanese foods, or Portuguese stews may also cause problems in patients with untreated Hashimoto's thyroiditis.