Dietary Supplements

The best dietary supplement is cod liver oil, which provides a concentrated form of natural vitamin D. Cod liver oil is the best type of vitamin D because it contains the vitamin D3 (cholecalciferol) form, which is better utilized by the body than the vitamin D2 form obtained from plants, a common source in other dietary supplements. Vegetarians who won’t take animal sources of vitamin D must rely more on the sun. Many supplements of cod liver oil also contain vitamin A, an important nutrient for athletes. However, avoid those that provide you with more than about 5,000 IU of vitamin A a day. High levels of vitamin A can also be toxic (causing such problems as liver stress, loss of bone density, and hair loss), and it can interfere with vitamin D metabolism.

In some individuals who have very low blood levels of vitamin D, even modest amounts of vitamin D supplementation may not normalize blood levels, and much higher doses may be necessary to correct this serious deficiency. In some cases, 50,000 IU a day or more for the first week may be the start of optimal therapy, but this should be done under the guidance of a health-care professional. These doses must be carefully monitored with blood levels to avoid toxicity while assuring levels are returning to normal. These very high doses of vitamin D, both in oral and injectable forms, in doses of 25,000 to 100,000 units, come with a risk of overdose. Vitamin D toxicity can cause significant mineral imbalance, especially of calcium and phosphorus, and fatigue, constipation, forgetfulness, nausea, and vomiting.

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