Writing in this month's American Journal of Clinical Nutrition , researchers from the Tuscany Regional Agency, (Italy), Johns Hopkins School of Medicine, Azienda Sanitaria Firenze, (Italy), and the National Institute on Aging, report that people with the lowest blood levels of the mineral were 94 per cent more likely to have poor knee and grip strength, relative to those with the highest selenium blood levels.
However, lead author Fulvio Lauretani notes that more studies are needed before selenium supplementation can be recommended to the elderly.
"To our knowledge, this is the first study to show an association between plasma selenium concentrations and poor muscle strength in older adults," wrote the researchers.
European selenium levels have been falling since the EU imposed levies on wheat imports from the US, where soil selenium levels are high.
As a result, average intake of selenium in the UK has fallen from 60 to 34 micrograms per day, leading to calls from some to enrich soil and fertilizers with selenium to boost public consumption.
The European recommended daily intake (RDI) is 65 micrograms.
The study, a cross-section of the InCHIANTI study from two towns in the Chianti area of Italy, measured plasma selenium levels and the strength of the hip, grip, and knee of 891 elderly men and women above the age of 65. Lauretani and co-workers report that the average plasma selenium levels of all the participants was 0.95 micromoles per litre, below the values considered the minimum level of plasma selenium necessary in the bloodstream for maximum production of selenoproteins (1.25 micromoles per litre).
After adjusting the results for potential confounding factors, such as age, sex, total energy intake, and BMI, the researchers report that people with the lowest plasma concentrations were 69, 94 and 94 per cent more likely to have poor hip, knee, and grip strength, compared to those with the highest selenium levels.
"Low plasma selenium is independently associated with poor skeletal muscle strength in community-dwelling older adults in Tuscany," wrote the authors.
They stated, however, that it is currently unclear if increased intake of selenium could maintain or improve muscle strength, and called for future studies to evaluate if selenium supplements could slow the age-related decline in muscle strength.
The European market for selenium supplements is estimated to be worth around €40m. This suggests that there is potential for food makers if they can improve consumer understanding of the mineral's benefits, with selenium-enriched products largely ignored by companies, unlike the supplements where a significant number of selenium products are available, both in combination with other nutrients and alone.
Source: American Journal of Clinical Nutrition August 2007, Volume 86, Number 2, Pages 347-352 "Association of low plasma selenium concentrations with poor muscle strength in older community-dwelling adults: the InCHIANTI Study" Authors: F. Lauretani, R.D. Semba, S. Bandinelli, A.L. Ray, J.M. Guralnik and L. Ferrucci