Vitamin D. Everyone’s talking about it, but you may not know very much about this important vitamin. If so, you are in luck! In this bulletin, we unearth the many uses for vitamin D and the latest news about it. According to the Linus Pauling Institute, this fat-soluble vitamin is vital for maintaining regular calcium metabolism and can be either consumed through food or supplements, or synthesized internally through sun exposure (1). Research says vitamin D can lend a helping hand in bone health, immune health, diabetes support, heart health and more (1). Yet, much debate has arisen over these applications and the new vitamin D recommendations from the Institute of Medicine (IOM).
The Controversy
IOM stated in November 2010 that its new recommended dietary allowance (RDA) for vitamin D is 600 IUs for those ages one through 70 and 800 IUs for those over 71. Previous adequate intakes (AIs) were 200 IUs for those one through 50, 400 IUs for those 51–70 and 600 IUs for those 71 and older (2).
Not everyone agrees with the RDA change. In the January issue of WholeFoods Magazine, Dallas Clouatre, Ph.D., of Jarrow Formula, stated that a “reasonable intake to prevent seasonal fluctuations is approximately 1,600 IUs/day” (3).
University of Maryland Associate Professor of Medicine, Elizabeth Streeten, M.D., also feels larger doses of vitamin D could be helpful for certain individuals. In a June 2010 University of Maryland Health Today podcast, Streeten said, “It is a fat-soluble vitamin, so when you take in vitamin D, it has to diffuse or go to all of the different places of the body including the fats. The more fat there is, the more vitamin D it takes to tank up the stores. So, anywhere from 1,000 to 4,000 units a day is what most adults need, and up to 10,000 units a day has been shown to be safe” (4). The IOM upped the safer tolerable limit from 2,000 to 4,000 IUs, however. Consult with your healthcare provider before taking larger doses.
Another bone of contention is that the new recommendations are for healthy individuals who don’t have a history of vitamin D deficiency. Some feel that those with deficiencies (due to poor diet, lack of sun exposure or a health issue) may benefit from doses over 4,000 IUs. But again, the IOM has not recommended these larger doses. If you feel you could benefit from getting upwards of 4,000 IUs of vitamin D per day, talk to your doctor before doing so.
Last, as previously mentioned, some research supports the use of vitamin D for reasons outside bone health. But, the IOM feels further investigation into these applications is warranted before they can recommend the vitamin for areas like immune health. Many in the nutrition industry feel the evidence is strong. According to the Linus Pauling Institute, vitamin D may have “a variety of effects on immune system function, which may enhance innate immunity and inhibit the development of autoimmunity.” But again, talk with a healthcare professional before taking vitamin D for reasons other than bone and overall wellness (1).
Vitamin D and Bone Health
The IOM supports the use of vitamin D for bone health, since it is essential for the efficient use of calcium by the body. The skeletal system needs an ample amount of calcium to reach its full potential bone mass. Many factors such as exercise, smoking and vitamin D affect bone mass. Vitamin D helps in the absorption of calcium and thus directly affects the skeletal system.
Thus, much research supports the use of vitamin D for healthy bones. An 18-year study conducted in the United States with 72,000 postmenopausal women as participants found those who consumed at least 600 IUs per day of vitamin D from diet and supplements had a 37% lower risk of osteoporotic hip fracture than women who consumed less than 140 IUs per day of vitamin D (1). Evidence suggests vitamin D3 supplements of at least 800 IU/day may be helpful in reducing bone loss and fracture rates in elderly.
There Are Different Types of Vitamin D?
Yes, there are two types: vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) (1). Vitamin D3 is synthesized by humans through exposure to ultraviolet-B (UVB) from sunlight or can be acquired through diet and supplementation. Plants synthesize ergosterol, which is converted to vitamin D2 by ultraviolet light. Some feel that the body makes better use of D3 while others support the use of vitamin D2 for vegans/vegetarians.
Food for Thought
Types of food containing vitamin D vary. The Office of Dietary Supplements, a National Institute of Health, states fatty fish, salmon and mackerel can provide us with vitamin D as well as beef liver, cheese, egg yolks and mushrooms (in smaller amounts). Also, almost all milk in the United States is fortified with vitamin D. Nonetheless, be sure you’re getting enough from all sources. Streeten explains that one cup of milk may only contain 100 IUs of vitamin D, which is not sufficient for our recommended daily vitamin D intake (4). Read labels carefully and visit your local health food store for supplements if your diet is deficient in vitamin D. WF
References
1. J. Higdon, Linus Pauling Institute Micronutrient Information Center, “Vitamin D,” Dec. 8, 2010, http://lpi.oregonstate.edu/infocenter/vitamins/vitaminD, accessed Dec. 23 2010,
2. Office of Dietary Supplements, Health Information, “Dietary Supplemental Fact Sheet: Vitamin D, Quick Facts,” Nov. 30, 2010,http://ods.od.nih.gov/factsheets/VitaminD-QuickFacts, accessed Dec. 23, 2010.
3. “IOM Recommends New Levels for Vitamin D and Calcium,” WholeFoods Magazine, 34 (1), 8 (2011).
4. University of Maryland Medical Center, Video Podcasts: Maryland Health Today, “Video Transcript: Vitamin D and Bone Health,” June 4, 2010, www.umm.edu/videos/transcripts/mht_vitamind_bonehealth_streeten.htm., accessed Dec. 23 2010.
Published in WholeFoods Magazine, February 2011
