Vitamin D Deficiency is Common but Preventable

Vitamin D is a fat soluble vitamin which plays a key role in bone growth and maintenance, immunity against infection and protection against cancer, heart disease and auto-immune diseases like type 1 diabetes.

Vitamin D is found in only a few foods such as fatty fish and fish oils, eggs and fortified milk.  Milk is fortified with about 400 international units of vitamin D per quart, while cod liver oil contains about 1,300 international units of vitamin D per tablespoon and fatty fish like salmon, herring, mackerel or sardines contain about 300 international units of D per 4 ounce serving (Stechschulte, 2009).  Vitamin D can also be made from cholesterol in body if the skin is exposed to sunlight.  In recent years, use of sunscreen to reduce skin cancer risk has also increased risk of vitamin D deficiency (Stechshulte, 2009).   

Vitamin D deficiency is extremely common. Vitamin D deficiency is more common in older persons, dark skinned people and people who live far from the equator as compared to younger persons, light skin people or people who live near the equator.  One huge study of 15,242 US adults reported that vitamin D deficiency was found in 70% of whites, 96% of blacks and 91% of Mexican Americans (Ginde, 2009)!

Various studies have reported that sufficient vitamin D consumption of 800 international units a day can significantly reduce risk of many cancers. It is estimated that if every US adult consumed sufficient vitamin D, colon cancer rates would drop by 50% and breast cancer rates would drop about 30%. Vitamin D supplementation is also associated with significantly lower heart disease rates and incidence of auto-immune diseases like lupus and type 1 diabetes. In the elderly, vitamin D supplementation significantly reduces risk of memory loss (dementia), bone loss (osteoporosis) and falls (Stechschulte, 2009).

The UA recommended daily allowance for vitamin D is only 400 international units per day. Many researchers suggest that this limit should be raised to at least 800 international units daily (Stechschulte, 2009). I urge that all adults who do not get heavy sun exposure to consume 800 to 2,000 international units of vitamin D daily in foods such as vitamin D fortified milk, cod liver oil and vitamin D supplements.  A review of 20 studies reported that high dose vitamin D supplements (700 international units a day or more) reduced bone breaks in the elderly by 23%, but lower dose vitamin D (400 international units a day) did not reduce rates of bone fractures in elders. 

Vitamin D supplements are quite safe in reasonable doses. Numerous studies have given patients 5,000 to 18,000 international units of vitamin D daily for years with no reported health problems or changes in calcium metabolism (Hathcock, 2007). Vitamin D can be toxic if taken in huge quantities. Some studies have reported that supplemental Vitamin D levels of 100,000 or more international units a day for periods of months to years can interfere with calcium metabolism (Hatchcock, 2007).

References consulted for this blog include:

Ginde AA, Liu MC, Carlos CA, et al.  Demographic differences and trends of vitamin D insufficiency in the US population.  Archives of Internal Medicine 2009;169(9):626-32.

Hathcock JN, Shao A, Vieth R, Heaney R.  Risk assessment for vitamin D.  American Journal of Clinical Nutrition 2007;85:6-18.

Stechschulte BA, Kirsner RS, Federman DG.  Vitamin D: bone and beyond, rationale and recommendation for supplementation.  American Journal of Medicine 2009;122:793-802.