Health Canada has issued a warning to consumers about the Trophic brand natural health product labelled "Kelp and Glutamic Acid HCI" because of high levels of iodine.

It warns that pregnant or breastfeeding women, or people with thyroid conditions such as Graves' disease, are most vulnerable.

Too much iodine can lead to the enlargement of the thyroid, the butterfly-shaped gland at the front of the neck that regulates metabolism, and can cause it to become underactive or overactive. While hypothyroidism (underactive thyroid) can lead to infertility and heart disease, hyperthyroidism (overactive thyroid) can cause sudden weight loss, rapid or irregular heart beat, increased sensitivity to heat or irritability.

Babies exposed to excessive levels of iodine while in the womb can be born with an enlarged thyroid. Such a condition can also cause the baby to have difficulty breathing.

In Graves' disease patients, high levels of iodine can reduce the effectiveness of antithyroid medications.

People considering taking this product are advised to consult their doctors before doing so, according to Health Canada.

Kelp and Glutamic Acid HCI is not approved by Health Canada though it is sold in pharmacies and over the Internet.

The company that manufactures the product, Trophic Canada Ltd., has initiated its recall, and Health Canada says it will monitor the situation.

Should Bill C-51 pass, natural health products sold in Canada will require them to be licensed by Health Canada and labelled with a drug identification number before they can be sold in stores.