Iodine's Effect on Calcium Absorption

Iodine is a trace mineral naturally present in seaweed, dairy products, seafood and some fruits and vegetables. This essential nutrient can be added to foods in the form of iodized salts and is available as a dietary supplement. All the body’s cells need iodine to work properly. Glands such as the thyroid gland and adrenal glands need iodine to produce and release hormones. However, certain minerals – including calcium – can affect iodine levels in the body.

Calcium Metabolism

One of the many functions of a healthy thyroid gland is to produce a hormone known as calcitonin, which works to lower blood calcium levels. The hormone aids in calcium metabolism by maintaining proper calcium levels in the body preventing the development of either hypocalcemia or hypercalcemia – low or elevated calcium levels in the blood. If left untreated, hypercalcemia can have serious health consequences including abnormal heart rhythm, kidney damage or osteoporosis. Although the body needs calcium for strong bones, this dietary mineral also plays a role in helping the heart, muscles and nervous system to work.

The recommended dietary allowance for iodine for healthy adults ages 19 and older is 150 mcg daily. Pregnant women need 220 mcg daily – lactating women 290 mcg, according to standards developed by the Institute of Medicine’s Food and Nutrition Board. The calcium requirement for adult men and women between the ages of 19 and 50 is 1,000 mg daily. Women age 51 and older need 1,200 mg. Men older than age 70 need increased calcium intake as well. Talk to your doctor first before taking calcium or iodine supplements 12. Some nutrients interact with each other or with certain types of medications.


Goitrogens are substances that suppress thyroid function by blocking iodine uptake. This action can lead to hypothyroidism or enlargement of the thyroid gland. Calcium, magnesium, fluoride and manganese are minerals that can interfere with the body’s absorption of iodine. Raw vegetables such as:

  • cabbage
  • broccoli
  • kale
  • cauliflower
  • brussels sprouts
  • mustard
  • lima beans are some foods in which goitrogens are present

In the case of plant foods, goitrogens usually become inactive when you cook the vegetables.

Thyroid Medications

Calcium can interfere with the body’s ability to absorb synthetic thyroid hormones that doctors prescribe to treat hypothyroidism – under active or low thyroid. Take calcium supplements or calcium-fortified juices three or four hours before or after taking thyroid medications 2. Avoid taking thyroid drugs with foods that bind the iodine impairing thyroid function.