Recently the Institute of Medicine (IOM) called for a 300% increase to its recommended daily intake of vitamin D. The IOM now suggests 600 daily i.u., up from 200 daily i.u. and suggests an upper limit of 4,000 i.u. daily. The US-Canadian IOM panel considered over 1,000 published studies and scientist testimonials and focused on the role of vitamin D and calcium in maintaining strong bones. Several studies have shown Vitamin D to be essential for bone health, immune function preventing cardiovascular disease and the focus in recent years has been on its ability to dramatically reduce the risk of certain cancers – most notably, breast, colon, and pancreatic cancers.
Vitamin D can be obtained from the sun, dietary sources and from supplements. However dietary sources are limited to salmon, mackerel, tuna, sardines, and cod liver oil and in modern life we are faced with limited sun exposure, particularly in northern latitudes. Supplements are a more consistent way to ensure adequate intake and carry less risk than unprotected sun exposure. There is now serious discussion about how much vitamin D it takes to raise the body’s stores of it to healthy levels.
How much do you need?
Blood tests can measure your body’s vitamin D stores and according to the American Cancer Society, many people have unexpectedly low levels. The IOM’s increase in recommended intake to 600 i.u. is a vote of confidence for supplementation but these levels may be found to be inadequate . If more concrete evidence continues to rise about the role of vitamin D in the prevention of disease, the recommended daily intake by the IOM could sky rocket again. The Canadian Cancer Society recommends supplementing with 1,000 i.u. per day. Osteoporosis Canada recommends 1,000 i.u. and up to 2,000 i.u. daily for those over 50. The pediatric society calls for up to 2,000 i.u. for pregnant and lactating women. Health Canada’s upper limit suggestion is 2,000 – 3,000 i.u. varying by age.
Dosing and Toxicity
For daily maintenance, we like D3 5,000 by Metagenics. According to research by Robert P. Heaney, M.D., healthy humans utilize about 4,000 i.u. of vitamin D per day from all sources.
4,000 i.u. is also the IOM’s upper limit. If you are concerned about exceeding this upper limit, you can take 5,000 i.u. only 3-5 times per week instead of daily. However humans make at least 10,000 units of vitamin D within 30 minutes of full body sun exposure. This range of dose – the level found in nature – is widely recommended by doctors and other healthcare practitioners to maintain adequate stores and correct deficiency.
Sun exposure has never been reported to produce toxic levels of vitamin D. Too many glasses of water can kill you so use common sense when choosing your supplement dose. Keep it under 10,000 i.u. unless instructed by your doctor. To correct deficiency, doctors may order up to 50,000 i.u. weekly but in these cases the exact dose will be highly individualized according to a patient’s specific level. We have read that vitamin D toxicity can result from chronic daily consumption of 40,000 – 50,000 i.u. and high doses of vitamin D is known to cause kidney damage. Even normal levels of vitamin D can cause health problems such as hypercalcemia in those with vitamin D hypersensitivity syndrome. Do not take vitamin D if you have any of the following causes of vitamin D sensitivity:
- primary hyperparathyroidism
- sarcoidosis and other granulomatous diseases
- oat cell carcinoma of the lung
- non-Hodgkin lymphoma
Always consult your doctor before taking any supplements or medication.
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