Science & Technology: Vitamin D (Vitamin D: How Much Is Enough)

UVR Induced. The amount of vitamin D produced by UVR is directly proportional to the number of vitamin D-effective photons and the exposure dose/time spent in the sun or in a sunbed. As you can see from the table, the claim that five to 10 minutes of sunlight exposure is sufficient is false, deceptive and misleading. For instance:

At noon on a typical Midwestern summer day, it takes a total of 950 minutes—17 56-minute sessions (28 minutes per side)—to reach 120 nmol/L, and a total of 1,400 minutes—25 56-minute sessions (28 minutes per side) to reach 150 nmol/L.

At noon in the tropics, it takes 292 minutes—nine 32-minute sessions (16 minutes per side)—to reach 120 nmol/L, and 416 minutes—13 32-minute sessions (16 minutes per side)—to reach 150 nmol/L.

In the strongest noontime terrestrial sunlight file in our data bank, it takes 132 minutes—six 22-minute sessions (11 minutes per side)—to reach 120 nmol/L, and 198 minutes—nine 22-minute sessions (11 minutes per side)—to reach 150 nmol/L.

In a 360-degree exposure sunbed equipped with 160-watt new-era sunlamps, it takes 108 minutes—12 nine-minute sessions—to reach 120 nmol/L, and 153 minutes—17 nine-minute sessions—to reach 150 nmol/L.

In a 360-degree exposure sunbed equipped with 160-watt traditional sunlamps, it takes 98 minutes—12 8.2-minute sessions—to reach 120 nmol/L, and 139 minutes—17 8.2-minute sessions—to reach 150 nmol/L.

Obviously, sunbeds are a more efficient source of vitamin D-effective photons than all but the strongest sunlight. In addition, it only takes 26 minutes—six 4.4-minute sessions—in a 360-degree booth equipped with FS Series sunlamps to reach 120 nmol/L, and 36 minutes—eight 4.4-minute sessions—to reach 150 nmol/L. This information is important because the studies that provided the baseline values for UVR-induced vitamin D production utilized FS Series sunlamps and it has been overlooked and/or ignored by vitamin D experts that, a) the booth used irradiated the entire surface of the body, while sunlight only strikes one side of the body at a time and that, b) the sunlamps employed had 60-percent UVB—a much higher number of vitamin D-effective photons than does sunlight. It was the failure to recognize and compensate for these two important factors that led to the incorrect belief that five to 10 minutes of sunlight exposure is adequate for vitamin D sufficiency.

The data contained in this article shows that, a) there is a pandemic of vitamin D insufficiency in the United States—more than 50 percent of the population meets the definition of insufficiency when a blood level threshold of 75 nmol/L is used, more than 90 percent are insufficient when 120 nmol/L is used, and more than 98 percent are insufficient when 150 nmol/L is used; b) the most efficient and consistent year-round source of vitamin D-effective photons is the controlled UV exposure found at a professional indoor tanning salon; c) that the current RDA for vitamin D is woefully inadequate; d) that it takes a long time to reach either 120 nmol/L or 150 nmol/L when taking daily vitamin D supplements; e) that the vitamin D from supplements has less biological activity than UVR-induced vitamin D; f) that maintaining a sufficient level of vitamin D is necessary for our optimal health and well being; and, g) that the vested-interest lies told by sunscreen industry and dermatology community are responsible for causing millions of people to avoid UVR exposure and, therefore, are detrimental to the health and well-being of the American public. Do your part to help resolve the pandemic of vitamin D insufficiency in the United States by sending a copy of this article to your local media outlets and to your local and state legislators.

Patricia E. Reykdal owns and operates four tanning salons in Tucson, Ariz. Her husband, Donald L. Smith, is director of research of the Non-Ionizing Radiation Research Institute. Together, they have written more than 250 articles promoting sensible, moderate and responsible exposure to ultraviolet radiation. You can e-mail comments or questions to reyksmith@aol.com.