Low vitamin D linked to reduced muscle power in girls.
Article Type: Report
Subject: Teenage girls (Health aspects)
Alfacalcidol (Health aspects)
Calcifediol (Health aspects)
Vitamin D (Health aspects)
Muscles (Research)
Muscles (Physiological aspects)
Author: Hunter, Kim
Pub Date: 03/22/2009
Publication: Name: Australian Journal of Medical Herbalism Publisher: National Herbalists Association of Australia Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 National Herbalists Association of Australia ISSN: 1033-8330
Issue: Date: Spring, 2009 Source Volume: 21 Source Issue: 1
Topic: Event Code: 310 Science & research
Geographic: Geographic Scope: England Geographic Code: 4EUUE England
Accession Number: 200253723
Full Text: Ward KA et al. 2009. Vitamin D Status and Muscle Function in Post-Menarchal Adolescent Girls. J Clinical Endocrinol & Metabol 94:2;559-63.

Researchers in this study discovered that in the adolescent girls they tested, vitamin D levels were positively associated with muscle power and force. The authors recruited 99 adolescent girls between the ages of 12 and 14 at an inner city, multi-ethnic school in Manchester, England. Blood samples showed that the average vitamin D levels were 21.3 nmol/L, ranging from 2.5 to 88.5 nmol/L. While none of the girls had any physical symptoms of vitamin D deficiency, the researchers report that 75% of the screened population had low 25(OH)D levels. Muscle strength and force were measured using technique called jumping mechanography, which derives power and force measurements from a subject's performance in a series of jumping activities. In these tests girls without vitamin D deficiency performed significantly better.

It is known that vitamin D deficiency can weaken the muscular and skeletal systems, but until now, little was known about the relationship of vitamin D with muscle power and force. The study found that vitamin D is positively related to muscle power, force, velocity and jump height in adolescent girls. The researchers further wrote that sub-optimal force might have implications for long-term bone development.

Vitamin D refers to two biologically inactive precursors--D3, also known as cholecalciferol, and D2, also known as ergocalciferol. 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. Recent studies have indicated that even in countries with high sun levels such as Australia, large sections of the population (including seemingly healthy adolescents) may be vitamin D insufficient or deficient.

Kim Hunter

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