The potential health benefits of vitamin D, from muscle development to bone health, from potential anti-cancer activity to reduced risks of heart disease, have been making headlines and occupying column inches for several years.
As the science has developed, leading researchers in the field have called for significant increases in national recommendations. Only recently, the U.S. Institute of Medicine (IOM) recently announced updated Dietary Reference Intakes (DRIs) for vitamin D that tripled the recommended daily allowance across all groups, except those over 50 years of age, for whom the updated allowance increased by 200 IU. Upper intake levels were also raised for all groups.
However, according to an Analyst Insight by Monica Feldman, available here, the “conflicting information on the benefits of vitamin D has led to confusion among the medical community and consumers, who found it difficult to know how much vitamin D they should be taking”.
As such, Feldman asks the question, is the market for vitamin D supplements at risk of decline?
“A number of recent studies on vitamin D deficiency published in the last decade fueled significant sales of vitamin D supplements,” states Feldman. “[However], vitamin D supplements see rising competition from fortified foods and other supplements such as fish oils and multivitamins.”
Renowned vitamin D researcher, Michael Holick PhD, MD, Professor of Medicine at Boston University Medical Center, recently told NutraIngredients-USA.com that the most realistic approach to boosting the nation’s intake of vitamin D is for food manufacturers to increase the dose of vitamin D per serving.
Dr Holick noted that milk is already fortified with vitamin D, as are some yogurt. Dr Holick himself led a recent study funded by the US National Institutes of Health (NIH) and the Beverage Institute for Health & Wellness, a division of Coca-Cola North America, into the efficacy of fortified orange juice to raise vitamin D levels (American Journal of Clinical Nutrition, 2010, Vol. 91, pp. 1621-1626).
Lallemand/American Yeast has also been building the science to support the use of its vitamin D2-rich yeast for the production of fortified bread. Indeed, a recent study found that vitamin D-deficient rats fed bread made with vitamin D2-rich yeast experienced the same improvements in bone mineral content and bone mineral density as rats fed bread formulated with vitamin D3 (Journal of Agricultural and Food Chemistry, 2011, Vol. 59, pp 2341-2346).
Dr Holick is looking for more of the same: “The issue is can we expand the number of foods that are fortified with vitamin D,” he added.
Back to Feldman, who says that the rise of functional foods will not eradicate the single vitamin D supplement market: “Moving forward, the recent reports on vitamin D intake will not make single vitamin D supplements disappear from the shelves. People with a medical deficiency and those faithful to the vitamin craze will support future sales.”
Data on D
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former is produced in the skin on exposure to UVB radiation (290 to 320 nm). The latter is derived from plants and only enters the body via the diet.
Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
In adults, vitamin D deficiency may precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.