Study Review

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The following is my review of a review article published in the Journal of Applied Physiology in 2009 titled Aging , Exercise, and Muscle Protein Metabolism by Rene Koopman and Luc J. C. van Loon.

Introduction

The elderly population is steadily growing due to greater longevity. As this population continues to grow, even moreso with the aging of the "Baby Boomer" generation, a greater strain is put on the healthcare system as there is a greater need for hospitalization and institutionalization. Of the greatest factors in aging is the decrease in quality of life due to muscle mass loss or sacropenia. This review examined the effects of the interaction between nutrition, exercise and the adaptive response of skeletal muscle. 

Methods

This article reviewed 134 articles to examine the interactions between nutrition, exercise and the adaptive response of skeletal muscle in aging.

Results/Conclusion

This review article concluded that protein ingestion before, during or post- resistance type exercise in both the young and elderly significantly stimulated the net muscle protein growth. Also, prolonged resistance exercise was an effective intervention in the prevention and treatment of muscle mass loss in the elderly.

Commentary 

This was a well written article that highlights the importance of adequate protein intake and resistance exercise in the prevention of age-related muscle mass loss.
  

References

Koopman, R., van Loon, L.J.C. (2009). Aging, exercise, and muscle protein metabolism. J Appl Physiol. 106:20402048. doi: 10.1152/japplphysiol.91551.2008

Study Review

 

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The following is my review of a study published in the Journal of the American Dietetic Association in 2009 titled A Moderate Serving of High-Quality Protein Maximally Stimulates Skeletal Muscles Protein Synthesis in Young and Elderly Subjects by Drs. T. Brock Symons, Melinda Sheffield-Moore, Robert R. Wolfe, and Douglas Paddon-Jones.

Introduction

Sufficient dietary protein is important for the maintanence and function. The elderly are at an increased risk of protein malnutrition leading to sacropenia and decreased quality of life. This study sought to determine if a larger portion of protein could be beneficial.

Methods

This study randomly selected 17 young and 17 elderly subjects from volunteers that responded to an ad in the local paper. Each of the two groups was then randomly divided into either a 113g beef group and a 340g beef group. The study sought to determine whether a moderate or high protein serving elicited a greater muscle protein synthesis. The larger portion was thought to represent the exaggerated portion sizes available in most restaurants.

Results

This study determined that although the larger 340g serving increased protein synthesis by 50%, the moderate 113g serving  was equally effective with less calories.

Commentary 

I liked this study because it focused on real-world food, instead of protein supplements like previous studies have done. The findings make sense to me because your body can only process so much protein before it begins converting the excess to storage fat. Consuming more protein than the USDA recommendation can be beneficial, but excess amounts serve only to increase calorie intake and may inhibit fat loss.
  

References

Symons, T.B., Sheffield-Moore, M., Wolfe, R.R., Paddon-Jones, D. (2009). A Moderate Serving of High-Quality Protein Maximally Stimulates Skeletal Muscles Protein Synthesis in Young and Elderly Subjects. J Am Diet Assoc. 2009;109:1582-1586. doi: 10.1016/j.jada.2009.06.369

Study Review

image source: http://www.webmd.com/osteoporosis/ss/slideshow-osteoporosis-overview

The following is my review of a study published in Osteoporosis International in 2011 titled Does dietary protein reduce hip fracture risk in elders? The Framingham osteoporosis study by D. Misra, S. D. Berry, K. E. Broe, R. R. McLean, L. A. Cupples, K. L. Tucker, D. P. Kiel & M. T. Hannan.

Introduction

This article was part of the Framingham Osteoporosis Study. The Framingham Osteoporosis Study is a large, population-based study of elderly men and women. There have been numerous studies previous conducted on the association between dietary protein and bone mineral density. However, the results have been unclear or conflicting. This study examined the the relationship between dietary protein intake and the incidence of hip fracture in elderly men and women.

Methods

The Framingham Study started in 1948 with the enrollment of two thirds of the households in Framingham, MA between the ages of 28-62. The purpose was to study the risks factors of heart disease over 60 years with biennial examinations. The current study obtained it's test subjects from the 1988-1989 baseline exam attendees that completed the Food Frequency Questionnaire (126 questions). They excluded participants with a previous history of hip fracture. This yielded a sample of 946 study subjects. They obtained protein intakes, and other baseline information (smoking, physical activity, calcium and vit D intakes, etc from the FFQ. Femoral neck BMD was obtained by Lunar dual photon absorptiometry.

Results

Over an 11.6 year follow up of the 946 subjects, 100 suffered hip fractures (80 females, 20 males). Increased protein intake showed a mild protective effect, however it was not statistically significant.

Commentary 

I'm not sure what to make of this study. I'm a little skeptical of studies based on questionnaires due to the inherent errors from subjects not being 100% truthful. I was a little confused by the 1000 year incident rate information. Also, the fact that all the subjects were taken from the same geographical location limits it's ability to represent a larger, worldwide population. 
  

References

Misra D., Berry S. D., Broe K. E., McLean R. R., Cupples L. A., Tucker K. L., Kiel D. P., & Hannan M. T. (2011). Does dietary protein reduce hip fracture risk in elders? The Framingham osteoporosis study. Osteoporos Int . 22:345–349. DOI 10.1007/s00198-010-1179-4

Study Review

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The following is my review of a study published in the June 2002 publication of Obesity Research titled Effect of Protein Intake on Bone Mineralization during Weight Loss: A 6-month Trial by Annebeth R. Skov, Nikolaj Haulrik, Søren Toubro, Christian Mølgaard, and Arne Astrup. According to Wiley Online Library this article was first published online on September 6, 2012.

Introduction

The purpose of this study was to analyze the long-term effects of dietary protein on bone mineralization. Osteoporotic fractures are an increasing problem with serious implications in health. Low protein intake in the elderly is a problem that can lead to an increase in low bone quality. With the prevalence of obesity increasing, despite the fact that a larger body mass tends to increase bone mineralization, weight loss to prevent the ill effects of comorbidities associated with obesity is generally the desired outcome. The often advised dietary recommendations are for a low fat, high complex carbohydrate diet. However, due to the longer satiation effects of protein, a low fat, high protein diet could possibly reduce excess calorie consumption due to frequent bouts of hunger on a lower protein diet. Nonetheless, it has been claimed that protein from animal sources reduces bone mineral content, in addition to the bone mineral losses seen in weight loss. The authors therefore found that it was relevant to study the influences of reduced-fat diets with high and low protein content on bone mineralization in overweight and obese subjects.

Methods

The study involved sixty-five overweight or obese individuals in a 6-month randomized, placebo-controlled dietary-intervention. It compared two controlled diets with isocaloric fat content (30%), one with high protein (25%) and one with low protein content (12%).

Results

The study found that there was no significant difference in BMC loss between the high protein or the low protein groups. However, they noted a more positive correlation between body fat loss and BMC loss than with body weight loss. At the end of 6 months, after adjusting for the differences in fat loss, there was a greater loss of BMC in the low protein group compared of the high protein group. The study found that independent of weight loss, there was less BMC loss with a high protein diet.

Commentary

Overall I agree with the findings of this study. The issues I have are with the diets. In Table 2 the carbohydrate content increased in both diet from baseline to 6 months. Also, the calcium and vitamin D intake for the low protein group decreased while in the high protein group they increased. I am unsure if this is due to the change in macro-nutrients (increased or decreased protein from baseline). That alone could have greatly contributed to the higher rate of BMC loss in the low protein group. It would be beneficial in a future study if not only the fat content were kept the same between groups, but all other micro- and macro-nutrient levels be kept at about the same level as baseline, if possible.

Skov, A. R., Haulrik, N., Toubro, S., Mølgaard, C., &Astrup, A. (2002, June). Effect of Protein Intake on Bone Mineralization duringWeight Loss: A 6-Month Trial. Obesity Research, 10(6), 432-438.doi:10.1038/oby.2002.60