Close to 20 million Americans have some form of thyroid disease, according to the Cleveland Clinic. Caffeine, a known stimulant, may make thyroid symptoms worse, which is why some doctors recommend their patients avoid it. However, since the research results are mixed and caffeine may actually have positive benefits in some cases, check with your doctor about whether caffeine consumption is right for you.
Thyroid and Hormones
The thyroid is a small, butterfly-shaped gland resting in the middle of your lower neck. Its main role is to control your metabolism by producing thyroid-stimulating hormone, or TSH, which in turn creates hormones known as T4 and T3 that tell your cells how much energy to use. If your thyroid makes too much hormone, it leads to a condition called hyperthyroidism; if the opposite is true, it's called hypothyroidism. Other thyroid disorders include Hashimoto's thyroiditis, in which your immune system attacks your thyroid gland, and thyroid cancer.
Caffeine's Effect on Thyroid Hormones in Rodents
A study published in the "Journal of Pharmacology and Experimental Therapeutics" in July 1980 found that caffeine doses of 30 to 50 mg per kilogram of body weight -- the equivalent of 16 to 26 oz. for a 150-lb. person -- significantly decreased TSH in rats. However, research reported in "Food and Chemical Toxicology" in February 1996 found no signs of thyroid toxicity or effects from caffeine given over a period of 90 days to hamsters.
Thyroid Cancer
Thyroid cancer is among the top 12 most common forms of cancer, with 44,670 new cases estimated for 2010, according to the National Cancer Institute. In a case-controlled study, researchers in Greece interviewed patients with thyroid cancer, benign thyroid disease and controls regarding their diet and lifestyle. The results, published in the June-July 1989 issue of "Acta Chirurgica Scandinavica," found that people who drank the most caffeinated coffee had the lowest risk for thyroid disease. However, a study published in the April 2003 "Cancer Science" found that a combination of low iodine levels and excess caffeine consumption promoted thyroid cancer in rats.
Considerations
Caffeine is a stimulant that can cause restlessness, anxiety, insomnia and a rapid heartbeat, symptoms similar to those of thyroid disease. This could make it more difficult to tell if your thyroid medications are working. It could also make you attribute your symptoms to caffeine and not realize you may have a thyroid condition instead. Excess caffeine can cause other health problems, like stomach upset, depression, fibrocystic breast disease and blood pressure problems. If you decide to consume caffeine, stick with a moderate level -- about three 8-oz. cups of coffee per day.
References
- Cleveland Clinic: Thyroid Disease
- "Journal of Pharmacology and Experimental Therapeutics"; Effects of Caffeine on Anterior Pituitary and Thyroid Function in the Rat; E. Spindel, et al.; July 1980
- "Food and Chemical Toxicology"; Absence of Effect of Caffeine on the Thyroid in the Syrian Golden Hamster: Results of a 90-Day Study; W. Bartsch, et al.; February 1996
- "Acta Chirurgica Scandinavica"; Does Coffee Consumption Protect Against Thyroid Disease?; A. Linos, et al.; June-July 1989
- "Cancer Science"; Synergistic Interaction Between Excess Caffeine and Deficient Iodine on the Promotion of Thyroid Carcinogenesis in Rats Pretreated With N-Bis(2-Hydroxypropyl) Nitrosamine; H.Y. Son, et al.; April 2003
- Drugs.com: Caffeine Side Effects
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