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Vitamin D levels and physical function in older adults

Posted on: September 16, 2015   by  John Cannell, MD


As a person ages, they lose physical abilities. How much physical ability a person loses with age depends on the individual. More specifically, their activity level, how frequently they exercise, and now, once again it appears to depend on the individual’s vitamin D level.

Researchers in Finland, led by Dr. Marika Salminen, conducted the research.

Salminen M, Saaristo P, Salonoja M, Vaapio S, Vahlberg T, Lamberg-Allardt C, Aarnio P, Kivelä SL. Vitamin D status and physical function in older Finnish people: A one-year follow-up study. Arch Gerontol Geriatr. 2015 Aug 20.

They measured 25(OH)D levels in 518 Finnish seniors and divided those levels into 3 groups: < 20 ng/ml (50nmol/l) (low), between 20 and 30 ng/ml (50 – 75 nmol/l) (intermediate) and above 30 ng/ml (75 nmol/l) (adequate). They also measured different physical functions including leg strength, time to walk a certain distance and time needed to come from a sitting to standing position five times in a row.

Of the 518 subjects, 106 individuals had levels below 20 ng/ml; 261 had intermediate levels and only 151 had “adequate” vitamin D levels. I inferred they did not have enough subjects with levels above 40 ng/ml to conduct an analysis.

During the 12-month follow-up, there were significant differences in changes between the different groups regarding knee extensor strength of right (p = 0.044) and left (p = 0.010), lower extremity and in 10-m walking test (p = .040). Physical exercise did not have an effect on the findings. It seems that exercise is only beneficial if vitamin D levels are above 30 ng/ml (75 nmol/l).

Interestingly, sun exposure did not affect the results either. However, the authors controlled for sun exposure by classifying subjects as “yes” to sun exposure for subjects who had their blood drawn from June 1st to November 30th and “no” to sun exposure for those who received their blood draw between December 1st and May 30th.

It is important to note that May has almost as much sunlight as August, and November has almost as little sunlight as February. It would be more interesting to classify “yes” to those subjects who had their blood drawn from June to August and “no” sunlight to those subjects drawn between November and February.

The authors wrote,

“In conclusion, low 25OHD concentrations predicted deterioration in physical function during 12 months among community-dwelling older Finnish men and women. The results of this study and some earlier studies indicated that 25OHD should be at least 30 ng/ml in order to prevent decline in PF among community-dwelling older people.”

Here is yet another study implying you should either receive adequate, safe, sensible sun exposure or supplement with enough vitamin D to maintain adequate levels as you age.


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