Researchers from the Council for Responsible Nutrition (CRN), Mount Sinai Hospital , Toronto , and Creighton University , Omaha , NE , conducted a review of human clinical trials of vitamin D to reassess the current Tolerable Upper Intake Level (UL) for vitamin D. The review applied the risk assessment methodology employed by the Food and Nutrition Board (FNB) to derive the UL, to determine a revised safe UL in light of research conducted since 1997, when the current UL of 2000 I.U. was established.
The study was published in the January 2007 issue of the American Journal of Clinical Nutrition (85, 1:6-18, 2007).
New benefits of vitamin D supplementation, beyond bone health, have continued to be discovered since the current UL was established in 1997. CRN researchers felt that the current UL was outdated and not based on current evidence; they viewed it as too restrictive, curtailing research, commercial development, and optimum nutrition policy.
The review applied FNB risk assessment methodology to relevant, well-designed human clinical trials of vitamin D conducted since 1997. Collectively, the absence of toxicity in the trials reviewed lead researchers to conclude that a supplement of 10,000 IU of vitamin D3 daily is a safe UL.
Vitamin D is unique among vitamins in that it can be obtained from dietary sources as well as being produced when the skin is exposed to sunlight. It is also unique in that it has the characteristics of both a vitamin and a hormone since it is produced in one tissue, affects another, and its production is controlled by an internal feedback loop. Vitamin D is fat-soluble and is stored in the liver and tissues. Individuals with dark skin pigmentation produce vitamin D less efficiently than light-skinned individuals. Vitamin D production tends to diminish, as people grow older. Diseases of the liver, pancreas, intestines, and gall bladder, which interfere with fat absorption, may reduce vitamin D absorption. Certain anti-convulsive drugs may cause vitamin D deficiency.
Vitamin D is essential for proper mineral absorption. It promotes calcium and phosphorus absorption in the intestines, balances their deposition in the bones, and is involved in regulating calcium excretion by the kidneys. Vitamin D deficiency, even in the presence of adequate calcium may result in soft teeth and bones (rickets). Vitamin D is required for maintenance of muscle and nerve tone, including the heart, by regulating cell permeability and blood calcium levels. Insulin secretion and blood sugar regulation may also be effected by vitamin D. Research indicates that vitamin D plays important roles in the normal functioning of the immune system, reproductive system, and thyroid.
Since vitamin D receptors are present in virtually all tissue types in the body, additional actions of vitamin D are expected to continue to be identified.
Vitamin D deficiency may be common among people living in northern latitudes and those who dramatically limit their sun exposure (i.e. due on skin cancer risk). A young, healthy, fair-skinned person with a full day of sun exposure may produce 10,000 I.U. of vitamin D, while the elderly may produce insufficient vitamin D even with significant sun exposure. Vitamin D deficiency is a suspected causative factor in the development of osteoporosis, hip fractures, arthritis, and high blood pressure among the elderly. Recent research indicates that there may be a reduced incidence of cancers of the colon, rectum, breast, ovary, and prostate in individuals who maintain a high-normal blood level of vitamin D.
Vitamin D3 5000 provides Vitamin D3, cholecalciferol, natural vitamin D from fish liver oil. Take Vitamin D3 5000 as a dietary supplement, one or two capsules daily. Consider reducing supplementation during times of abundant sun exposure.
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