Enkele recente gerandomiseerde studies tonen aan dat aanvullend vitamine D (of door veel zonlicht, of door extra tabletje vitamine D of door veel vis te eten) voor vrouwen die bisfosfonaten gebruiken dit de resultaten gunstig beïnvloed. Daarnaast toont een dubbelblinde gerandomiseerde studie aan dat wanneer jonge meisjes extra vitamine D krijgen dit hun botdichtheid gunstig beïnvloed. Hieronder uitstekende en uitgebreid verklarende artikelen in het Engels van de website Vital Choices over deze recente studies. Eerst het artikel over vitamine D bij vrouwen die bisfosfonaten gebruiken, daarna het artikel over de teenagers en effect van vitamine D.
Vitamin D Boosts Bone-Drugs' Benefits; Vitamin D & Magnesium Bolster Teen Girls’ Bones New clinical studies support the value of key bone-building nutrients and show that vitamin D increases benefits of leading anti-osteoporosis drugs by Craig Weatherby
The results of recent studies offer encouragement that two key nutrients can help women in their battle to build and maintain strong bones. The good news is twofold:
1) Vitamin D -- the “sunshine-and-seafood” nutrient -- may enhance the effects of drugs used to combat osteoporosis in women.
2) Vitamin D and magnesium may benefit the bones of teenage girls.
Here's the scoop on both developments.
Vitamin D adds to benefits of bone-boosting drugs
Bisphosphonate-class drugs such as Fosamax® are the ones most commonly prescribed to post-menopausal women to treat osteoporosis and prevent fractures.
Some experts question the diagnoses used to justify prescribing these drugs to women. This is what we reported in a July, 2005 article titled “Diseased by Definition: Drug Profits Distort Medical Decisions” (excerpt in blue):
By succeeding in their attempts to get expert panels to turn “low bone density”—itself a subjective description—into a “disease” called osteopenia, Merck and its fellow drug makers automatically expanded the target market for their drugs and devices.
This radical change happened despite little evidence of a link between bone density and bone fractures, or the kind of fractures that Fosamax® has some small ability to help prevent, which is not even associated with the degree of bone-density picked up in tests.
The Seattle Times series quoted Dr. Steven Cummings of the University of California, a recognized expert on osteoporosis:
“The word 'prevention,' which has become so popular, has also created problems. Drug therapy for women with osteopenia does do some good because it reduces the risk of spine fractures, but women with osteopenia have a low risk of those fractures. So taking a drug for osteopenia probably does not improve the quality of life for women with osteopenia. It does generate huge sales.”
And, unsurprisingly, the available evidence suggests that bisphosphonates such as Fosamax® do not work as well when women’s vitamin D blood levels are too low, either because they do not consume enough dietary vitamin D (from supplements or seafood) or get enough sun exposure to ensure that their bodies make adequate amounts of vitamin D.
Researchers at Kings College in London set out to see whether calcium/vitamin D supplements would enhance the likely strength of hip bones in either of two groups (Deane A et al 2007):
Group A: Post-menopausal women taking bisphosphonates.
Group B: Post-menopausal women who’d stopped taking bisphosphonates but had continued to take calcium (one gram) and vitamin D (800 IU) supplements.
The vulnerability of their hip bones was estimated by measuring the two main indicators: bone mineral density (BMD) and blood levels of parathyroid hormone (PTH). As blood levels of PTH rise, bone mineral density falls, so high PTH levels are undesirable.
They recruited 112 women taking bisphosphonates and 35 women who had been on bisphosphonates for more than five years but had discontinued the drug.
The authors measured the women’s bone mineral density (BMD) at the beginning of the 15-month study and again at the end.
The women taking bisphosphonates (Group A) who had the highest blood vitamin D levels also showed the lowest PTH levels and the highest BMD in their hips.
The women in Group B – who were no longer taking bisphosphonates but were taking a daily vitamin D/calcium supplement -- showed no significant bone loss in their lower backs (lumbar spine) or hips.
These women did display a gradual decline in BMD just below the hip joint, in a region called the femoral neck.
As the authors wrote, “Strategies should be adopted to increase physicians’ awareness of the rationale for ensuring adequate vitamin D status in women receiving bisphosphonates … discontinuation of bisphosphonates (Alendronate or Etidronate) for a short period after long-term treatment, whilst continuing with calcium/vitamin D supplements, does not adversely affect BMD at the lumbar spine and hip.” (Deane A et al 2007)
Vitamin D and magnesium bolster teen girls’ bones Two separate studies combine to verify the independent value of vitamin D and magnesium for building the strength of adolescent girls’ bones. Vitamin D found good for teen girls’ bones Last June, researchers at the University of Helsinki in Finland published the results of a well-designed (randomized, double-blind, placebo-controlled) clinical trial conducted in 212 teenage girls (Viljakainen HT et al 2006). The main goal of the study was to discover whether dietary vitamin D increases the bone mineral content (BMC) of teenaged girls’ thighs and lower backs. Another was to see whether vitamin D increases BMC by increasing uptake of minerals into bone, or by decreasing loss of minerals: an effect called bone resorption. It has been presumed that dietary vitamin D increases bone mineral content (BMC), given the nutrient’s demonstrated anti-osteoporosis, anti-fracture benefits, but never conclusively proven. (See “Vitamin D Builds Bone in Pre-Menstrual Girls”, “Vitamin D Called Key to Babies’ Birth Weight and Bone Health”, “Vitamin D Called More Critical for Bones than High-Dose Calcium”, “Women Need to Bone Up on Vitamin D”, and “Vitamin D for Bone Health”. The researchers recruited girls whose calcium intake was considered adequate for this one-year trial, and divided them into three groups: Group A took 5 mcg (200 IU) of vitamin D per day. Group B took 10 mcg (400 IU) of vitamin D per day. Group C took inactive placebo pills. Note: 400 IU per day is the US RDA, which most experts believe should be raised to 1,000 or 2,000 IU. The form given was vitamin D3: the optimally effective form, which is created in skin by sunlight and found in seafood. (Many supplements contain a weaker, cheaper form called D2.) At the end of the one-year study period, the girls’ bone mineral content (BMC) – a good guide to bone strength – was measured in their thigh bones (femurs) and lower backs (lumbar spines). The girls in Group A (200 IU of vitamin D per day) showed a 14.3 percent increase in the BMC of their thigh bones. The girls in Group B (400 IU of vitamin D per day) showed a 17.2 percent increase in the BMC of their thigh bones. The placebo group showed no increase in the BMC of their thigh bones. Only the girls in Group B (400 IU of vitamin D per day) showed a significant increase in BMC levels in the lower back. The results of tests for relevant biochemical markers showed that the vitamin D supplements increased femoral BMC by decreasing bone loss (resorption), rather than by increasing mineral uptake into bones. Magnesium found good for teen girls’ bones Higher magnesium intake is associated with better bone health among adults, but it is often overshadowed by an excessive concentration on calcium, despite the lack of any convincing connection between calcium intake and bone health. Many Asian and African countries where calcium intake is much lower than in the US have lower rates of osteoporosis: probably because they have higher blood levels of vitamin D – from diet or sun exposure – and possibly because of higher magnesium intake. And the importance of magnesium to adolescents has not been studied. To redress this lack of data, researchers at the Yale University School of Medicine conducted a well-designed (placebo-controlled, double-blind, randomized), one-year trial to test the effects of giving girls magnesium supplements (Carpenter TO et al 2007). The Yale team recruited healthy 8- to 14-year-old Caucasian girls and had them record their diets. The 120 girls with dietary magnesium intake of less than 220 mg per day were invited to participate.
The girls took 300 mg of magnesium per day (in two 150 mg doses) or a placebo, for 12 months.
The researchers measured changes in bone mineral content (BMC) of the girls’ hips, upper femur (femoral neck and Ward’s area), and lower back (lumbar spine).
After one year, the magnesium group showed significant greater bone mineral content in the hip, compared with the placebo group. This effect was evident in girls ranging in development from pre- and early puberty to mid-late puberty.
Lumbar spinal BMC was slightly (but not significantly) greater in the magnesium group.
As the Yale group concluded, “A positive effect of Mg supplementation on integrated hip BMC was evident in this small cohort.” (Carpenter TO et al 2007)
Viljakainen HT, Natri AM, Karkkainen M, Huttunen MM, Palssa A, Jakobsen J, Cashman KD, Molgaard C, Lamberg-Allardt C. A positive dose-response effect of vitamin D supplementation on site-specific bone mineral augmentation in adolescent girls: a double-blinded randomized placebo-controlled 1-year intervention. J Bone Miner Res. 2006 Jun;21(6):836-44.
Carpenter TO, DeLucia MC, Zhang JH, Bejnerowicz G, Tartamella L, Dziura J, Petersen KF, Befroy D, Cohen D. A randomized controlled study of effects of dietary magnesium oxide supplementation on bone mineral content in healthy girls. J Clin Endocrinol Metab. 2006 Dec;91(12):4866-72. Epub 2006 Oct 3.
Deane A, Constancio L, Fogelman I, Hampson G. The impact of vitamin D status on changes in bone mineral density during treatment with bisphosphonates and after discontinuation following long-term use in post-menopausal osteoporosis. BMC Musculoskelet Disord. 2007 Jan 10;8:3.
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