The thyroid is a popular topic in medicine (hence my second blog post on the gland). Responsible for how quickly our body uses energy, this small organ has a large effect on our overall health. Reduced thyroid function is a common problem that is not always obvious on lab tests. Many foods and everyday chemicals can have negative effects on the health of the thyroid gland, causing symptoms such as weight gain, fatigue, depression, constipation and dry hair and skin.


Although soy products are widely used for osteoporosis, cancer prevention, and menopausal symptoms, laboratory and human studies have shown that soy isoflavones, reduce thyroid hormone production. These compounds inhibit thyroid peroxidase, the enzyme that incorporates iodine to complete the synthesis of thyroid hormones. Soy can also inhibit the conversion of T4 to the active thyroid hormone, T3.


Thiocyanate is a detoxification product of cyanide and it inhibits the transport and uptake of iodine into the thyroid to produce thyroid hormones. Thiocyanate levels increase with consumption of goitrogens, such as brussel sprouts, broccoli, cabbage, and cauliflower, environmental toxins and cigarette smoke. The effect is pronounced in individuals with iodine deficiency and is reversed with iodine supplementation.


Despite being banned in the 1970s, polychlorinated biphenyls are still present in the environment. Long-term exposure to PCBs causes thyroid dysfunction, increased thyroid volume and nodule formation. By increasing the release of TSH, these industrial chemicals can cause an insensitivity or resistance of your body to thyroid hormones.


Pesticides are still ubiquitous in the environment and studies show that exposure increases the risk of developing thyroid problems. Similarly, nearly 60% of the pesticides used today can alter thyroid hormone production and make losing weight more difficult.

Antibacterial Products

Marketed as a tool to keep you healthy, synthetic antibacterial compounds can have negative effects on your health. Triclosan, which is added to soaps, can disrupt normal thyroid functioning.

Heavy Metals

Chronic exposure to heavy metals—mercury, lead and aluminum—alters the immune system, causing the production of antibodies that attack your own cells. These autoantibodies can lead to the autoimmune thyroid conditions, Grave’s Disease and Hashimoto’s thyroiditis.


Plastics are dangerous to the body in a number of ways. In addition to the cancer-promoting properties of BPA in water bottles, storage containers and sports equipment, this chemical decreases the sensitivity of thyroid receptors, causing thyroid hormone resistance.

Although the thyroid gland has numerous effects on your health, its function is easily disrupted with food and chemical exposure. Limiting this exposure while enhancing your body’s detoxification pathways is an important first step to maintaining optimal thyroid function.