Protein is slowly becoming better recognized for its uses besides basic muscle repair and maintenance. Academic research and the mass media together are starting to spread the word. Hopefully consumers will take notice and urge the food industry to invest their R&D efforts towards food that will maximize protein's multiple beneficial effects, including satiety (the feeling of being full), blood sugar control, and relatively high thermal effect (energy used to process and integrate the dietary proteins into the body). I've chosen two recently published peer-reviewed journal articles and one mass media story to share with you highlighting some up-to-date information on related to protein and the human diet.
The first journal article (reference #1) was performed by an international team of researchers and was published in the New England Journal of Medicine at the end of November. This study investigated the utility of four different kinds of diets in keeping off lost weight. The four types of diets used in this study were: low protein content and low glycemic index, low protein content and high glycemic index, high protein content and low glycemic index, and high protein content and high glycemic index. 548 individuals completed the study, giving credence to the results of the work due to the large sample size. If the sample size of a study is low, conclusions drawn from its data are less likely to apply generally to the rest of the population. However, in this case, they had plenty of subjects.
The researchers found that the best diet for maintenance of lost weight was one that had a relatively high protein content and a relatively low glycemic index. If you've been reading this blog regularly, these results should come as no surprise. As we know, a low glycemic index diet helps to maintain satiety, stable energy levels, and low insulin levels, keeping the fat production machinery in low gear. A high protein content is beneficial on all levels, complementing the generally low glycemic index of the entire diet.
The second study (reference #2) was executed by a team of US researchers and was published in the journal Obesity in September. They aimed to evaluate the effects of protein consumption and meal frequency on hunger and satiety in overweight and obese males. They included only 13 subjects in this study, but it still serves as a good base for further research. The study participants were assigned to eat either 14% or 25% of their calories as protein. In addition, they were divided again into groups eating either three or six times per day.
The researchers concluded that a higher protein diet significantly increased satiety and that eating fewer meals may also help you feel fuller longer. While the first conclusion is not surprising, the idea that eating fewer meals may actually help satiety is unexpected. Generally, a greater meal frequency is suggested to help curb hunger, an effect I have found in my own counseling experience. However, the data on this issue was somewhat conflicting, possibly due to the quite small sample size of 13 individuals used in the study. I would suggest that a similar study be performed using far more subjects to clarify the results of this trial. In addition, I would also like to see a third group included that consumes around 40% of their calories from protein. I would hypothesize that the increased satiety seen in the 25% protein group vs. the 14% protein group in this initial study would be even more exaggerated with 40% of calories consumed as protein.
Finally, we have an example of the same theme presented by the mass media for consumption by the generally public (reference #3). Unlike the journal articles, which present pretty hard core statistical evidence at lengthy descriptions of their methods and reasoning, this MSNBC release lays out some simple principles and suggestions for everyday incorporation of protein into an everyday diet. They also back up their claims with evidence gleaned from recent scientific articles, which is nice to see. They touch on the thermal effect of protein, as well as its satiety-inducing properties. The article also mentions the current push to raise the FDA guidelines on suggested protein intake, which is a fantastic idea, in my opinion. We need more articles like this published by large, popular media outlets. The public needs to get information in simple, bite-sized packages and I'm glad to see MSNBC doing their part.
Both scientific journal articles and mass media stories can be good sources of nutrition-related information. However, before you believe either source, it's always prudent to critically analyze how their conclusions were formulated and the reliability of their data. In addition, try to double check for further evidence supporting any new claim you run across. Even journal articles can be wrong from time to time, which is why replication is so important in the scientific process. Do your part to support the truth and rely only on strong, repeatable, data and well-founded, rational conclusions.
References:
1. Larsen, Thomas M., et al. (2010). Diets with High or Low Protein Content and Glycemic Index for Weight-Loss Maintenance. The New England Journal of Medicine, 363(22), 2102-2113.
2. Leidy, Heather J. et al. (2010). The Influence of Higher Protein Intake and Greater Eating Frequency on Appetite Control in Overweight and Obese Men. Obesity, 18, 1725-1732.
3. Yeager, Selene. "Protein really is a prescription for weight loss." MSNBC.com 12 Dec. 2010.