Gender-specific association between dietary acid load and total lean body mass and its dependency on protein intake in seniors

Authors: FAURE, AUDRY - University Of Zurich; FISCHER, KARINA - University Hospital Zurich; DAWSON-HUGHES, BESS - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; BISCHOFF-FERRARI, HEIKE - University Of Zurich

Submitted to: Osteoporosis International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2017
Publication Date: 10/2/2017
Citation: Faure, A., Fischer, K., Dawson-Hughes, B., Bischoff-Ferrari, H.A. 2017. Gender-specific association between dietary acid load and total lean body mass and its dependency on protein intake in seniors. Osteoporosis International. https://doi.org/10.1007/s00198-017-4220-z.

Interpretive Summary: The decline of muscle mass that occurs with aging leads to a decrease in muscle strength, which is one of the major factors contributing to falls and the loss of physical function in seniors. Muscle wasting can occur in the presence of a mild metabolic acidosis. The diets of people in industrialized countries are often acidogenic due to a greater consumption of acid-forming foods compared to alkaline-forming foods. Meat and cereal grains are acid-forming foods because they contribute to the formation of sulfuric acid, whereas fruits and vegetables are alkaline-forming foods because they are metabolized to bicarbonate. A widely used measure of the overall acid-base balance of the diet is the potential renal acid load (PRAL.) The aim of this study was to investigate the association between the PRAL and total body lean mass in 247 male and female seniors age 60 years and older. PRAL was calculated from dietary intake data, and lean mass was determined by dual-energy x-ray absorptiometry (DXA.) We found that total lean mass was lower in women consuming acid-producing diets, whereas there was no such association seen in men. This study suggests that acid-producing diets may contribute to loss of muscle mass in women, raising the possibility that increasing fruit and vegetable intake may have a positive effect on their muscle mass.

Technical Abstract: Background: Sarcopenia, the age-related decline of muscle mass, is one of the most important causes of loss of physical function and falls in seniors. Causes of sarcopenia are multiple, but there is evidence that diet-related mild metabolic acidosis may play a role in the development of skeletal muscle mass loss. Objective: We investigated if dietary acid load is associated with total lean body mass in male and female seniors age 60 years and older. Methods: We investigated 243 seniors (mean age 70.3 +/- 6.3; 53% women) age 60 years and older who participated in the baseline assessment of a clinical trial on vitamin D treatment and rehabilitation after unilateral knee replacement due to severe knee OA. Potential renal acid load (PRAL) was assessed based on individual nutrient intakes derived from a food frequency questionnaire. Body composition including percentage of total lean body mass (%TLM) was determined using dual-energy X-ray absorptiometry. Cross-sectional analyses were performed for men and women separately using multivariable regression models controlling for age, physical activity, smoking status, protein intake (g/kg BW per day), energy intake (kcal), and serum 25-hydroxyvitamin D concentration. We included a pre-defined subgroup analysis by protein intake (<1g/kg BW day, >1g/kg BW day) and by age group (<70 years, >/=70 years). Results: Adjusted %TLM decrease significantly across PRAL quartiles only among women (Ptrend = 0.004). Moreover, in subgroup analysis, the negative association between the PRAL and %TLM was most pronounced among women with low protein intake (<1 g/kg BW per day) and age below 70 years (P = 0.002). Among men, there was no association between PRAL and %TLM. Conclusion: Our results suggest that the effect of the dietary acid load on %TLM is gender-specific, with a negative effect on total lean mass only in senior women. Therefore, an alkaline diet, including high consumption of fruits and vegetables, may be beneficial for persevering total lean mass in senior women, especially in those with low protein intake.