Does Increased Protein Intake Lead to Better Physical Performance in Post-Menopausal Women?

Sarcopenia is the medical term for “muscle loss”. As we age, a complex series of events transpires to lead to a greater loss of muscle mass. This loss of muscle mass can have very serious consequences to our health, physical performance, osteoporosis and risk of ongoing injury and falls. The muscle mass we lose tends to be Type 2 fibers (Nilwikk et al, 2013). Type 2 muscle fibers are the muscles that help us produce power – whether that power is in the form of performing a heavy squat or picking up a heavy grocery bag. A key principle however, is that results of multiple large observational studies suggest that we can slow or reverse loss of Type 2 muscle fibers as we age by implementing specific variables, chiefly resistance training and appropriate nutritional intake. (Frontera, 1985)

In regard to nutritional intake, specifically protein, current RDA recommendation for adults is 0.8 gm/kg/day of body weight. However, with the current rave of high protein diets, some have suggested that this is far below what is really needed for optimal performance. For better understanding, we can look to an article published in 2014 by the Journal of Nutrition, Health and aging: Adequate Dietary Protein is Associated with Better Physical Performance Among Post-Menopausal Women 60-90 years. (Gregorio, 2014)

The purpose of this study was to examine the relationship of dietary protein to body composition and physical performance among older, community-dwelling, independent post-menopausal women. They hypothesized that physical function would be greater in those that consumed a higher protein diet.

Methods

The authors compiled data from 3 trials over a period 3 years, encompassing a total of 387 healthy women aged 60-90 years. The first 2 studies evaluated the effects of DHEA with gentle aerobic or yoga exercises, and the third trial evaluated fish oil vs placebo. In the first 2 studies, participants were included if they found some level of frailty. The participants were gathered from the 3rd trial if they reported levels of low protein. The reason for evaluating three separate trials was to broaden search number and participant variability.

Once the participants were selected, body composition (lean mass vs fat mass) was assessed. Physical function was measured using standardized measures. Questionnaires were administered to assess physical activity, quality of life and recent health issues such as falls. The participants then met with a dietician to learn about macronutrient tracking.

Results

The participants were divided into two groups: those that consume less than 0.8 mg/kg/day (low group) and those that consumed more than 0.8 mg/kg/day (high group).

Those in the low group noted the following:

·         Higher rates of HTN, Osteoarthritis and Falls associated with Fracture

·         Decreased time of a single leg stance

·         Slower walking speed

·         Decreased perceived physical function via self-report

Those in the high group noted the following:

·         Lower weight and BMI

·         Lower fat and higher lean muscle mass

·         Increased overall intake of Fats, Carbs, Proteins -> suggesting more balanced nutrition

·         Increased physical performance (walking speed and time of single leg stance)

·         Less fracture risk associated with falls

Discussion

This evaluation does tend to show an association between improved lean muscle mass, improved physical function and overall, wellbeing among those that consumed a diet high in protein. We do need to be careful, attributing these findings strictly to the consumption of protein. As noted, those with higher protein intake were also noted to consume on average higher levels of all macronutrients. The study did not decipher the source of the protein consumed as animal vs plant based – these two types do have different properties. This study only looked at an association, not causation. It may have been that those in whom an overall decline was already in process did not move as much nor eat as much as their counterparts. The study only collected protein intake from self-reports thus we need to consider overall accuracy.

What this study does show, however, is that we can have an impact on our aging outcomes. Eating a well-balanced, nutrient dense diet (ideally with at least 0.8mg/kg/day protein/day) coupled with a physical activity program rich with resistance training principles can improve our strength, physical function, fracture risk, perceived strength and overall quality of life.

References

Nilwik R, Snijders T, Leenders M, et al. The decline in skeletal muscle mass with aging is mainly attributed to a reduction in Type 2 muscle fiber size. Exp Gerontology 2013; 48:492

Fontera WR, Meredith CN, O’reilly KP, et al. Strength conditioning in older men: skeletal muscle hypertrophy and improved function. J Appl Physiol (1985) 1988; 64: 1038

Gregorio L, Berindis A, Kleppinger A, Sullivan R, Mangano K, Bihuniak J, Kenny A, Kerstetter J, Insogna K. Adequate Dietary Protein is Associated with Better Physical Performance Among Post-Menopausal Women 60-90 years. Journal of Nutrition, Health and Aging. 2014; 18(2): 155-160