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J Cachexia Sarcopenia Muscle. 2019 Mar 24. doi: 10.1002/jcsm.12413. [Epub ahead of print]

Higher dietary nitrate intake is associated with better muscle function in older women.

Author information

1
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia.
2
Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia.
3
Centre for Kidney Research, Children's Hospital at Westmead, School of Public Health, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia.
4
Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, WA, Australia.
5
Medical School, Sir Charles Gairdner Unit, The University Western Australia, Perth, WA, Australia.
6
School of Human Sciences (Exercise and Sports Science), The University Western Australia, Perth, WA, Australia.
7
Western Australian Institute of Sport, Mt Claremont, WA, Australia.

Abstract

BACKGROUND:

In younger individuals, dietary nitrate supplementation has been shown to improve short-term vascular and muscle function. The role of higher habitual nitrate intake as part of a typical diet on muscle function in ageing has not been investigated. A cross-sectional study of relationships between dietary nitrate and measures of muscle function in older community-dwelling Australian women (n = 1420, ≥70 years) was undertaken.

METHODS:

Participants completed a semi-quantitative food frequency questionnaire assessing dietary intake over the previous year. Total nitrate from vegetables and non-vegetable sources was calculated from a validated instrument that quantified the nitrate content of food recorded within the food frequency questionnaire. Handgrip strength and timed-up-and-go (TUG) were assessed, representing muscle strength and physical function, respectively. Cut-points for weak grip strength (<22 kg) and slow TUG (>10.2 s) were selected due to their association with adverse outcomes. Linear and logistic regressions were used to examine the relationship between total nitrate intake and muscle function measures.

RESULTS:

Mean ± standard deviation (SD) total nitrate intake was 79.5 ± 31.2 mg/day, of which 84.5% came from vegetables. Across the unadjusted tertiles of nitrate intake (<64.2 mg/day; 64.2 to <89.0 mg/day; ≥89.0 mg/day), women in the highest tertile had a 4% stronger grip strength and a 5% faster TUG performance compared with the lowest tertile. In multivariable-adjusted models, each SD higher nitrate intake (31.2 mg/day) was associated with stronger grip strength (per kilogram, β 0.31, P = 0.027) and faster TUG (per second, β -0.27, P = 0.001). The proportion of women with weak grip strength (<22 kg) or slow TUG (>10.2 s) was 61.0% and 36.9%, respectively. Each SD higher nitrate intake (31.2 mg/day) was associated with lower odds for weak grip strength (OR 0.84, 95% CI 0.74-0.95, P = 0.005) and slow TUG (OR 0.86, 95% CI 0.76-0.98, P = 0.021). Compared with women in the lowest tertile of nitrate intake, women in the highest nitrate intake tertile had lower odds for weak grip strength (OR 0.65, 95% CI 0.49-0.87, Ptrend= 0.004) and slow TUG (OR 0.72, 95% CI 0.53-0.97, Ptrend  = 0.044).

CONCLUSIONS:

This investigation highlights potential benefits of nitrate-rich diets on muscle strength and physical function in a large cohort of older women. Considering poor muscle strength and physical function is associated with a range of adverse health outcomes such as falling, fractures, cardiovascular disease, and mortality, increasing dietary nitrate, especially though vegetable consumption may be an effective way to limit age-related declines in muscle function.

KEYWORDS:

Geriatrics; Muscle strength; Nutrition; Physical function; Vegetables

PMID:
30907070
DOI:
10.1002/jcsm.12413
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