Abstract
BACKGROUND: Muscle strength is a predictor of mortality in older adults and some dietary components are associated with this variable; however, little is known about the association between omega-3 fatty acids (ω-3) intake and strength in older adults. OBJECTIVE: To assess whether ω-3 intake is associated with muscle strength in individuals over 50 years. We also aimed to evaluate whether an isocaloric substitution of dietary fatty acids types by ω-3 intake could be associated with muscle strength. METHODS: This study included older adults aged from 50 to 85 y, from National Health and Nutrition Examination Survey (NHANES) 1999-2000 and 2001-2002. A total of 2141 individuals (1119 men and 1022 women) were evaluated and provided complete and reliable dietary intake and isokinetic strength of the knee extensors (peak force) data. Linear regression analysis was conducted without (Model 1) and with adjustments (Model 2). Isocaloric substitution analysis was performed to evaluate whether the substitution of polyunsaturated (excluding ω-3), monounsaturated, saturated fats and ω-6 by consumption of ω-3 is associated with strength. RESULTS: Total ω-3, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and alpha-linolenic acid (ALA) intakes were positively associated with peak force in men (Model 1). However, after the adjustments for confounders (Model 2), only total ω-3 intake remained significant. Ω-3 intake was not associated with strength in women. The isocaloric substitution of saturated, polyunsaturated, monounsaturated fats and ω-6 by ω-3 was not associated with peak force. CONCLUSION: The intake of total ω-3 was positively associated with muscle strength in older men, but not in older women. In addition, the substitution of other fatty acids by ω-3 intake was not associated with strength.
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Key Points
Aging leads to a decrease in muscle strength which may occur 2 to 5 times faster than the muscle mass loss. Low muscle strength is associated with higher risk of falls, lower ability to perform activities of daily living and higher risk of death. Few studies have evaluated the association between omega-3 fatty acids (o-3) intake and muscle strength in older adults. A possible explanation for muscle strength losses during aging can be the increase of pro-inflammatory markers, such as interleukin-6 and C-reactive protein. Thus, considering that o-3 presents anti-inflammatory properties, while other fatty acids, such as saturated fat and o-6 may increase the inflammation, it is possible that an isocaloric substitution of saturated fat and o-6 by o-3 intake could decrease the inflammation and increase the chance to present higher muscle strength.
The aim of this study was to investigate whether o-3 intake is associated with muscle strength in individuals over 50 years derived from National Health and Nutrition Examination Survey (NHANES) 1999 to 2002. A second aim was to evaluate whether an isocaloric substitution of dietary fatty acids types by o-3 intake could be associated with muscle strength. The main result of the present study was that the intake of total o-3 was positively associated with peak force in older men, but not in older women. The substitution of saturated, monounsaturated and polyunsaturated (excluding o-3) fats, and o-6 by o-3 was not associated with higher muscle strength. These results show that the association observed between o-3 and muscle strength seems to be related to an increase of o-3 intake per se, and not due to the substitution of other types of fat by o-3. Here it was observed that total o-3, DHA, EPA and ALA intakes were positively associated with peak force (all individuals and men) in crude model.
The sex-dependent association observed in the present study can be probably explained due to sex-differences in o-3 metabolism. Older men evaluated in the present study may have more ALA in the plasma derived from ALA intake, when compared to women. The present study showed that an increased intake of ~2.7 g of o-3 (last vs. first quartile in men) was associated with an increase of 21.0 N, which is equivalent to approximately 2.1 kg of strength. These results seem to be physiologically relevant since an increase of 1 kg of strength can decrease the risk of multiple falls by 17%. In conclusion, the intake of o-3 was positively associated with peak force in older men, but not in older women. Therefore, these findings suggest that the association between o-3 and muscle strength seems to be sex-dependent. In addition, the substitution of other fatty acids by o-3 intake was not associated with strength. These results show that the association between o-3 and muscle strength seems to be related to an increase of o-3 intake per se, and not due to the substitution of other types of fat by o-3.