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Side effects of taking kelp supplements

Updated July 19, 2017

Kelp is a type of brown or green seaweed. A popular health supplement, it is generally marketed to help with weight loss, low thyroid function, high blood pressure and arthritis. It contains a high concentration of folic acid and several other vitamins and minerals, including iodine.

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In some developing countries, lack of dietary iodine is linked to birth defects. However, few people in the United States or Western Europe need more iodine in their diets. Also, many kelp supplements contain more than the recommended daily allowance of iodine. And while kelp has been promoted as a cure or at least relief for thyroid problems, which can lead to extreme weight loss or gain, it is more likely that too much iodine can actually cause thyroid imbalance. Furthermore, a few studies have linked iodine overdose with acne.

Contamination or Pollution

Many parts of the ocean are polluted with toxic metals. If kelp is harvested from a polluted area, these toxins may be included in a supplement. According to one study, some kelp supplements may be contaminated with arsenic, which can be fatal in large doses. Symptoms of arsenic poisoning may include memory loss, hair loss, headache, drowsiness and confusion. If you take kelp supplements and experience any unusual symptoms, you should stop taking the supplement and contact your health care professional immediately.

Allergic Reactions

If you are allergic to kelp or any ingredient in a supplement, you may experience shortness of breath; itchiness or hives on any part of your skin; or swelling in the throat, face or other areas of your body. Itchy or watery eyes and excessive sneezing or runny nose are usually symptoms of environmental allergens, but it may also indicate an allergic reaction to a food or supplement. If you suspect you are allergic to any supplement, immediately stop taking it and, if symptoms continue, see your doctor as soon as possible.

Drug Interactions

Kelp is a blood thinner. Do not take it with aspirin or any other drug to reduce blood pressure. It may also cause a decrease in red blood cells or platelets. And while blood thinners are used to decrease blood pressure, kelp may also cause high blood pressure in some people.


Kelp is thought to help with weight loss, arthritis, rheumatism and some thyroid conditions (although it may aggravate others). It is a good source of many essential vitamins and minerals, including potassium, iodine, bromine, protein, and Vitamin C and Vitamin B-2. It also functions as a blood thinner, which may be beneficial to people with high blood pressure.

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About the Author

Rachel Quagliariello is an opera singer and actress living in Virginia. She holds a B.M. in voice from Liberty University and an M.M. in voice from James Madison University. She teaches voice at Mary Baldwin College in Staunton, Va. Several of her articles for Demand Studios have been published on eHow.

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