Two Things You Didn’t Know About Dietary Protein

T-Rains-headshotAfter years of standing in the shadows of carbohydrate and fat research, there’s been an influx of publications in recent years on the benefits of dietary protein. Much of this new science has focused on satiety and preservation of lean mass and how these characteristics facilitate weight loss. Protein, particularly at the expense of carbohydrate, has also been consistently shown to reduce risk for high blood pressure.1 But researchers have now begun exploring the impact of protein on endpoints beyond body composition, weight management, and vascular health, revealing some new and interesting benefits of dietary protein.

Researchers at the University of Missouri recently published results from a randomized, controlled crossover study which compared appetite, satiety, and evening snacking in adolescent girls who consumed either a normal-protein breakfast (13 g), high-protein breakfast (35g), or no breakfast.  Results of the primary outcomes were published last year, and showed that the high-protein breakfast elicited greater feelings of fullness than the normal-protein breakfast.  Further, only the high protein breakfast reduced evening snacking of high-fat foods, a finding that had not been previously explored.2

In late August, Hoertel and collaborators published additional findings from this main study, evaluating food cravings and homovanillic acid (HVA), a metabolite of dopamine.3 [Dopamine is a neurotransmitter associated with motivation, reward, and well-being.  Because dopamine is unable to leave the brain, HVA is typically measured as a surrogate since it correlates with dopamine activity in the brain.]

Results showed that while both the normal- and high-protein breakfasts reduced cravings for savory foods compared to no breakfast, the response was much greater for the high protein breakfast.  In addition, levels of HVA were higher for the high-protein breakfast, suggesting that participants found the higher protein breakfast more rewarding.  How it produces this effect remains to be determined.  One hypothesis presented by the investigators is that increased protein leads to higher concentrations of the amino acid, tyrosine, a precursor to dopamine.  Additional research is needed to better understand the mechanisms involved.

The bottom line is that the benefits of a protein-rich meal for breakfast may extend beyond fullness, impacting food cravings later in the day and substances in the brain that promote feelings of well-being.  Only time will tell what other benefits of protein remain to be discovered.


  1. Buendia JR, Bradlee ML, Singer MR, Moore LL. Diets Higher in Protein Predict Lower High Blood Pressure Risk in Framingham Offspring Study Adults. Am J Hypertens. 2014 Sep 6. [Epub ahead of print]
  2. Leidy HJ, Ortinau LC, Douglas SM, Hoertel HA. Beneficial effects of a higher-protein breakfast on the appetitive, hormonal, and neural signals controlling energy intake regulation in overweight/obese, “breakfast-skipping,” late-adolescent girls. Am J Clin Nutr. 2013 Apr;97(4):677-88.
  3. Hoertel HA, Will MJ, Leidy HJ. A randomized crossover, pilot study examining the effects of a normal protein vs. high protein breakfast on food cravings and reward signals in overweight/obese “breakfast skipping”, late-adolescent girls. Nutr J. 2014 Aug 6;13:80.