Vitamin D, which is actually a collection of five compounds, is essential for strong immunity, healthy bones and normal cognition. However, due to indoor lifestyles, concerns of skin cancer and dietary factors, vitamin D deficiency is at epidemic proportions in the United States, affecting an estimated 70 percent of individuals, according to the book "Medical Nutrition and Disease: A Case-based Approach" by Lisa Hark. An early sign of vitamin D deficiency is loss of appetite, although heavy mega-dosing with vitamin D supplements can lead to toxicity and reduce appetite also.
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Vitamin D Recommendations
According to the National Institutes of Health, recommended daily levels of vitamin D has been recently increased to reflect the results of a growing body of scientific research. The newer recommendations include 400 international units, or IU, of vitamin D per day for infants, 600 IU for adults up to the age of 70 and 800 IU for those older than 70. These recommendations are meant to avoid deficiency symptoms, and some health authorities argue that higher levels, at least 1,000 IU daily, are needed to promote health. According to "Advanced Nutrition: Macronutrients, Micronutrients and Metabolism," 10,000 IU of supplemental vitamin D2 per day is considered safe, although Caucasian skin exposed to summer sunshine will produce that much vitamin D3 in under 30 minutes. This physiological capacity suggests the body needs and can process high levels of vitamin D.
Symptoms of Vitamin D Deficiency
The main cause of vitamin D deficiency is inadequate sun exposure, mainly due to indoor lifestyles, fear of skin cancer and wrinkles, use of sunblocks and living in climates that don't get enough UV-B radiation from the sun. Early symptoms of vitamin D deficiency include loss of appetite, which may be related to other symptoms, such as nausea, fatigue, weakness, depression and heavy sweating, according to "Vitamins: Fundamental Aspects in Nutrition and Health." The general uncomfortable state of vitamin D deficiency may make food unappetizing, as it has not been shown that vitamin D is related to the hunger reflex.
Symptoms of Vitamin D Toxicity
Vitamin D toxicity is very rare and cannot occur from too much sun exposure, which causes the skin to produce vitamin D3. For this reason, supplementing with vitamin D3 is the obvious choice. However, many manufacturers offer vitamin D2 within supplements, and heavy mega-dosing can lead to toxicity in theory, as it is stored in the body as a fat-soluble vitamin. The site, VitaminDCouncil.org, estimates that perhaps 40,000 IU per day would cause toxicity in an adult, although that figure would be less with kidney and metabolic diseases. The main consequence of vitamin D toxicity is a buildup of calcium in the bloodstream, which can cause nausea, vomiting and loss of appetite.
Vitamin D Food Sources
Dietary sources of vitamin D2 could cause toxicity in theory, but in practice it is exceeding rare. According to the "American Dietetic Association Complete Food and Nutrition Guide," great sources of vitamin D include fish, especially salmon, mackerel, cod and tuna. Other good sources include beef and pig liver, shrimp, egg yolks and fortified products, such as milk, cereals, grains and orange juice.