Vitamin D plays a vital role the body, promoting healthy bones by regulating the metabolism of calcium and phosphate. Vitamin D deficiency can lead to rickets, osteomalacia and osteoporosis, but levels that are too high can also cause problems.
Vitamin D Supplements in the Elderly
Further evidence that too much vitamin D can be as harmful as a deficiency comes from a new study in the Journal of Clinical Endocrinology and Metabolism. Comparing frailty with vitamin D levels in women over the age of 69 years, the researchers found the risk of frailty to be lowest at a concentration of 20−29 nanograms per millilitre (ng/ml) and highest at both less than 20 ng/ml and more than 30 ng/ml.
These findings may conflict with the increasingly common practice of monitoring vitamin D levels in elderly patients and giving supplements when they drop below a certain point.
“Vitamin D supplementation has grown in popularity, yet the association between vitamin D status and risk of adverse health outcomes in older adults is uncertain,” says Dr Kristine Ensrud, Professor of Medicine and Epidemiology at Minneapolis VA Medical Center and the University of Minnesota and lead author of the study.
Vitamin D and Sperm Quality
Meanwhile, a Danish study has found no links between low vitamin D and sperm quality in 18- to 21-year-old men. Among the 300 men in the study, 92 had below-normal levels of vitamin D in their blood, while 19 were vitamin D deficient. However, measures of semen quality such as sperm swimming ability showed no dfferences between high, normal and low vitamin D groups.
The researchers say more studies are needed definitely to rule out a relationship between vitamin D and sperm quality, but for the moment vitamin D “may not be important” for men with levels in the normal range.
Latest Recommendations for Dietary Vitamin D
Vitamin D is obtained in the diet, particularly from oily fish and eggs, and is made in the body from the action of sunlight on precursor molecules in the skin. To standardize existing recommendations for dietary intake, the US Institute of Medicine published a new Recommended Dietary Allowance for vitamin D in November 2010.
This latest guideline, which is based on more evidence than the old recommendations, assumes little or no exposure to sunlight and includes any supplements taken, is 15 micrograms per day for both males and females aged 1 to 70 years. Any significant deviations below or above this amount may lead to symptoms of vitamin D deficiency or excess.
Take Care with Vitamin D Intake
Having adequate vitamin D is essential for bone growth and maintenance, but as with most aspects of nutrition, it is important to strike a healthy balance between too much intake and too little. Research into the effects of too-high and too-low vitamin D levels continues to suggest that a moderate intake is best.
Sources:
- Are Serum Levels of Vitamin D Associated with Semen Quality? Results from a Cross-sectional Study in Young Healthy Men. Accessed 30-06-11
- Circulating 25-Hydroxyvitamin D Levels and Frailty Status in Older Women. Accessed 30-06-11
- The 2011 Report on Dietary Reference Intakes for Calcium and Vitamin D from the Institute of Medicine: What Clinicians Need to Know. Accessed 30-06-11
Disclaimer
The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
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