The headline in the March 23, 2009, issue of Scientific American, “Vitamin D deficiency soars in the U.S., study says,” could lead anyone to be alarmed. The study referred to, published in the Archives of Internal Medicine, concluded that less than a quarter of Americans were getting enough of the suddenly popular vitamin. (see the Scientific American article)
Between 1988 and 1994, 45 percent of nearly 19 thousand people examined as part of the National Health and Nutrition Examination Survey had levels of vitamin D below 30 ng/mL, what a growing number of experts consider sufficient for overall health. By 2000, only 23 percent of people met that level. (Only 3 percent of African Americans were considered vitamin D sufficient, a precipitous drop from the 12 percent results in the previous survey.)
What accounts for the alarming decrease? Several suppositions surfaced: First, that concern over skin cancer led many to cover up or slather on sunscreen, preventing natural production of vitamin D from sunlight. Another was the decrease in consumption of vitamin D foods, such as dairy — specifically, a geometric substitution of carbonated beverages for milk. Most dietary vitamin D comes from fortified dairy and other foods and beverages, such as milk substitutes, orange juice and breakfast cereals. Natural sources of vitamin D include fatty fish (salmon, herring, mackerel and tuna) and egg yolks.
However, some researchers believe the vitamin D deficiency epidemic is an illusion. They purport a more standard cutoff point for deficiency as 11 ng/ml or lower, classifying only 10 percent of Americans deficient. Adding to the alarm and confusion is the emerging new face of vitamin D, beyond its bone-building reputation. A flood of research in the past decade reveals possible roles for the fat-soluble, hormone-like compound in protecting against a broad spectrum of diseases, including cancer, multiple sclerosis, cardiovascular diseases, diabetes, mood and cognitive dysfunctions and immune disorders.
In light of this upwelling of interest, the U. S. and Canadian governments tasked the Washington, D.C.-based Institute of Medicine (IOM) with reviewing the data on health outcomes associated with calcium and vitamin D. After exhaustive review, a committee of experts concluded there is no epidemic and the extraskeletal role of vitamin D has been overstated.
The committee “reviewed a range of health outcomes, including but not limited to cancer, cardiovascular disease and hypertension, diabetes and metabolic syndrome, falls, immune response, neuropsychological functioning, physical performance, preeclampsia and reproductive outcomes.” This review suggested information about the health benefits beyond bone health were from studies that were inconclusive and thus could not be considered reliable. The review did uphold “a strong body of evidence from rigorous testing substantiates the importance of vitamin D and calcium in promoting bone growth and maintenance.”
The IOM report (www.iom.edu) was like throwing cold water on a hot vitamin. Then, on January 31 this year, the USDA and the Department of Health and Human Services released the 2010 Dietary Guidelines for Americans. One of the 23 key recommendations: “Choose foods that provide more potassium, dietary fiber, calcium, and vitamin D,” declaring those nutrients at risk due to inadequate consumption of vegetables, fruits, whole grains, milk and milk products, and seafood in the modern American diet.
The new recommendations for vitamin D intake were tripled from those in 1997, from 200 IU to 600 IU with an upper limit of 4000 IU. “The RDAs for vitamin D, which assume minimal sun exposure, are 600 IU (15 mcg) per day for children and most adults and 800 IU (20 mcg) for adults older than 70 years. As intake increases above 4,000 IU (100 mcg) per day, the potential risk of adverse effects increases.”
The experts have spoken, right? Not quite. Writing in the Journal of Bone and Mineral Research last March (“Why the IOM Recommendations for Vitamin D are Deficient,” Vol. 26, No. 3), researchers Robert Heaney and Michael Holick — both participated in the 1997 IOM review — state flatly that conclusions of the 2011 committee “fail on three grounds: logic, science and guidance.”
Heaney and Holick objected that, “By admitting science was inconclusive, the IOM panel was not in a position to make conclusions. Also, since the panel also concluded it didn't know at what blood level any nonskeletal benefits for vitamin D could be ensured, they can't declare people are getting enough of it. Logically, they could only say it is unknown whether more D confers possible nonskeletal benefits.”
According to Heaney and Holick, the IOM's statement that skeletal health can be ensured at blood levels of vitamin D of 20 ng/mL is “simply incorrect … a serum level of 30 ng/mL is closer to the bottom end of the acceptable range for skeletal health.” They also suggest the new DRIs are a welcome increase but inadequate and the safe upper limit of 4000 IU too low, that even 10,000 IU is probably safe.
The Harvard School of Public Health agrees, declaring the IOM recommendations may be underestimating need and overstating concerns for safety. They noted, “Most of the randomized trials … focused on bone health, and there's been a lack of randomized trials on vitamin D and other chronic diseases.” The Harvard report added, “Unfortunately, the IOM committee interpreted this lack of trials as evidence of no benefit — in effect, ignoring the substantial evidence from cohort and other studies that vitamin D plays an important role in lowering the risk of several chronic diseases.”
If this leaves the picture of vitamin D somewhat cloudy, what's the take-away for processors? The dispute over the DRIs is one of “too low” versus “minimal,” and that's the key. The minimum is the amount necessary to avoid disease (specifically, rickets). Vitamin D intake as well as exposure to sunlight has declined.
Meanwhile, as Harvard pointed out, absence of evidence of benefits is not evidence of absence of benefits, and the wealth of cohort and other types of studies should not be frivolously dismissed. Add to this the high levels of vitamin D that are safe, the intense consumer demand for vitamin D products and the wealth of available vitamin D ingredient systems (including water-soluble forms), food and beverage makers can readily err on the side of enhancement while creating safe, healthy, desired and eminently marketable D-enhanced products. In this case, it would seem D does make the grade after all.