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Women Need to Bone Up on Vitamin D
10/31/2005
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Studies suggest mature women need much more than most actually consume

by Craig Weatherby



A series of studies released since May of this year combine to paint a picture of fractured bone health among women in their mature years… and the finger of blame points toward a shortage of bodily vitamin D.


According to Professor Michael F. Holick, Ph.D., M.D. of Boston University—a leading vitamin D researcher—many Americans have inadequate blood levels of vitamin D: a nutrient critical to bone health and cancer prevention.


Vitamin D currently only makes up four per cent of all vitamin sales and lags well behind calcium in terms of bone health supplements. But a fast-growing body of evidence underlines its importance in protecting against fractures.


Vitamin D missing in mature women

Earlier this month, a joint Canadian/American team led by Dr. Holick confirmed that post-menopausal women who have osteoporosis or at risk of developing it do not have enough vitamin D in their bodies.


They measured the vitamin D blood levels in 1,536 women taking medication to prevent or treat osteoporosis. All had been post-menopausal for at least two years and were 55 years of age or older. Nearly 60 percent of the women reported taking 400 IU—the U.S. recommended daily allowance (RDA)—or more of supplemental vitamin D every day.


Normal adult vitamin D blood levels range from 50 to 140 nano moles per liter (20-56 nano grams per milliliter) but Dr. Holick and others say that the “normal” level is itself inadequate for bone health.  He says that the optimal blood level starts at 115 nmol/liter (45 ng/ml), or more than double the low end of the normal range, which most older women don't even reach.


Almost one in five of the post-menopausal women in the study had suffered a fracture caused by falling within the past five years. Their mean vitamin D blood level was below normal, and even the mean vitamin D levels of those in the top 25 percent were well below normal and far short of optimal.


Dr. Holick’s team found that vitamin D inadequacy was significantly greater in women who reported taking less than 400 IU of vitamin D daily, and that the deficiency was substantial even for those who came close to consuming that amount.


He and colleagues concluded that the prevalence of vitamin D inadequacy in post-menopausal women is “unacceptably high”.  As they said, “Both physicians and the public need to be better educated about how to optimize vitamin D supplementation in these women.”


International study supports U.S./Canadian findings

Dr. Holick’s results were supported by those obtained at the Vrije Universiteit Medical Center in Amsterdam, which conducted a study similar to his.

During the summer and winter, the Dutch team measured vitamin D levels in 2,589 postmenopausal women with osteoporosis living in 18 countries across Europe, the Middle East, Latin America, and the Asia Pacific region.


They found that the prevalence of vitamin D inadequacy is high regardless of latitude or season. Almost two-thirds of the women (64 percent) suffered from vitamin D inadequacy. As expected, the portion of women with vitamin D deficiencies was lower (59 percent) during summer months and higher (68 percent) during winter months.


Fractures tied to vitamin D deficiency

The authors of two studies published this year—one conducted in Scotland and one in Minnesota—examined women with bone fractures to determine whether any dietary deficiencies might explain their condition.


Glasgow hospital study

The Scottish study involved 548 women over 60 admitted to South Glasgow University Hospital during a four-year period.  Researchers found that 97.8 percent of them had vitamin D levels below normal, while about one in four had vitamin D levels so low they were difficult to detect.


In a second phase of the study, the researchers measured vitamin D levels among the first 50 patients admitted to the hospital with an osteoporosis fracture after November 2004.


More than 80 percent of the fracture patients had vitamin D levels well below the optimal concentrations recommended by Dr. Holick and other experts.


As the authors concluded, "…the mean vitamin D level in the 13 patients with hip fracture was lower than in the 37 with non-hip fractures.… It may be that vitamin D represents a correctable risk factor for fragility fracture in the elderly, possibly specifically for the hip."


Minnesota osteoporosis clinic study

Researchers studied 82 adults aged 52 to 97 who were hospitalized with hip fractures between August 2001 and January 2002.  On admission, half reported taking at least 400 IU of vitamin D per day via supplements (including multivitamins) and 13 percent were taking osteoporosis medication. Their mean vitamin D blood levels ranged well below still-inadequate "normal" levels and very far below optimal levels.


While the patients who reported taking vitamin D supplements had significantly greater vitamin D levels, the researchers still considered these levels suboptimal.


As the Minnesota team said, “Nearly all patients in this study hospitalized for fracture had vitamin D inadequacy. Significant opportunity exists to ensure adequate and persistent vitamin D intake in a high risk fracture patient population.”


What’s a woman (or man) to do?

Vitamin D can be obtained from foods and supplements, and it’s manufactured in the skin when sunlight hits it.


The recommended solution to the epidemic shortage of vitamin D is to spend at least a half-hour in the sun every day (15 minutes if you have fair skin)—without sunscreen—take 400 IU of vitamin D in supplemental form, and eat foods rich in vitamin D.

Vital Choice fish fit the last part of this prescription in bountiful fashion.

We had an independent lab measure the amounts of vitamin D in single 3.5 ounce servings of our fish, with the results shown in the chart below. The tests ranked sockeye salmon first (687 IU), followed by albacore tuna (544 IU), silver salmon (430 IU), king salmon (236 IU), sardines (222 IU), halibut and sablefish.

This means that a single serving of Vital Choice sockeye salmon, albacore tuna, or silver salmon averages more vitamin D than the US RDA of 400 IU.  It is interesting that our lab's results differ from official USDA tables, which rank the vitamin D content of sardines just above salmon's. These discrepancies may result from natural variations in the genetics and diet of regionally distinct sardines and salmon. Regardless of the reason, we're happy to report that our salmon and tuna test so very high in this vitally important nutrient.


Sources

  • Holick MF, Siris ES, Binkley N, Beard MK, Khan A, Katzer JT, Petruschke RA, Chen E, de Papp AE. Prevalence of Vitamin D Inadequacy Among Postmenopausal North American Women Receiving Osteoporosis Therapy. Obstet Gynecol Surv. 2005 Oct;60(10):658-659.
  • Gallacher SJ, McQuillian C, Harkness M, Finlay F, Gallagher AP, Dixon T. Prevalence of vitamin D inadequacy in Scottish adults with non-vertebral fragility fractures. Curr Med Res Opin. 2005 Sep;21(9):1355-61.
  • Simonelli C, Weiss TW, Morancey J, Swanson L, Chen YT. Prevalence of vitamin D inadequacy in a minimal trauma fracture population. Curr Med Res Opin. 2005 Jul;21(7):1069-74.
  • Holick MF. Calcium and Vitamin D. Diagnostics and Therapeutics. Clin Lab Med. 2000 Sep;20(3):569-90)
  • Lips P, Chandler J, Lippuner K, et al. High Prevalence of Vitamin D Inadequacy among Community Dwelling Post-Menopausal Women with Osteoporosis (M275). Poster Session 118. Osteoporosis Epidemiology: Diet and Environmental Factors. Abstracts of the 27th Annual Meeting of the American Society for Bone and Mineral Research, September 26, 2005, Nashville TN. Accessed online October 28, 2005 at http://www.asbmr.org/meeting/abstracts.cfm

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