| | Thyroid supplements
Here's some info I found in the book "Thyroid Balance" by Glenn Rothfeld, MD.
Minerals, Vitamins and Thyroid Function
Minerals can interfere with the absorption of many nutrients and medications. Calcium and iron both reduce the amount of thyroid hormone supplement that enters your bloodstream from your digestive tract. Many foods that are high in calcium are easy to identify: milk, cheese, and dairy products head the list. Others aren't so obvious, like tofu, canned sardines, molasses, spinach, broccoli, and green beans.
Because calcium has become such an important health concern for maintaining bone health, many food products are fortified with calcium. One of the most common of these is orange juice. Most people take their thyroid hormone supplement in the morning. If you are one of them, and you then have milk and orange juice for breakfast, you might end up canceling out much of the thyroid hormone supplement's effect. Pop your daily multivitamin with iron and calcium, and you've certainly done so!
Take your thyroid hormone at least 2 hours before or after taking multivitamins or eating foods high in calcium. Most doctors and pharmacists recommend that you take thyroid hormone on an empty stomach, and then have nothing ot eat or drink (other than water) for 30 minutes. This allows the thyroid hormone to get into your digestive tract without interference from food.
Other vitamins and minerals aid thyroid function. Beta carotene helps your thyroid gland produce thyroid hormone. In return, T3 is necessary for your body to produce vitamin A from beta carotene. Some people develop a yellowish coloration on their palms and the soles of their feet if they are unable to convert the carotene in their diet to active forms. This can be a subtle sign of thyroid deficiency.
Selenium is necessary for the de-iodinase enzyme that produces T3 from T4. Vitamin E protects thyroid hormone from being broken down. Vitamins B2, B6, C and niacin also improve thyroid function. Zinc plays a key role in immune function and also cell health. And calcium, even though you need to take it separately from thyroid hormone, is particularly important when thyroid imbalance is a factor, because thyroid function affects how your body uses and stores calcium.
These days, many people take nutritional products on the advice of friends, natural medicine doctors, even Internet chatrooms. It's important to know the effects of these products. Nutrients other than vitamins and minerals also influence thyroid function. If taken in high doses, L-carnitine, an amino acid used for energy, can suppress thyroid function by blocking T3 production. Alpha lipoic acid, a potent antioxidant, has a similar effect.