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More Support for Protein-rich, Salmon-centric Diets
11/28/2005
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Dr. Perricone’s “eat your protein first” advice gets a boost from new animal study
by Craig Weatherby


Noted anti-aging and diet pioneer Nicholas Perricone. M.D. advises his readers to start every meal with a dose of protein. Here’s how he put it in his latest New York Times bestseller, The Perricone Weight Losst Diet:  “Always eat your protein first.… Why? Because by eating your protein first… you are helping to suppress your appetite. Proteins are digested much more slowly than carbohydrates—even carbohydrates that are high fiber. Also, protein is neutral in terms of its effects on blood sugar.”


Key Points
  • Rats fed a high-protein diet responded by producing glucose in their gut.
  • As a result, the rodents ate less and gained less weight.
  • This finding suggests that eating protein first at a meal may curb appetite.
  • This finding may help explain why high-protein diets often produce more weight loss than high-carb diets in the short term.
While these reasons are sufficient themselves, the results of a new animal study suggest another reason to favor protein foods and put them first at every meal.

Intriguing new findings from France
Scientists at the National Institute of Health and Medical Research (INSERM) in Lyon, France found that when they fed rats a high-protein diet, it significantly increased the activity of genes involved in glucose production in the animals’ small intestines.  Unsurprisingly, this led to increased synthesis of glucose: an effect signaled to the brain from the liver that led the rodents to eat less.

The researchers fed one group of rats a 50-percent-protein diet enriched with soy and milk protein (casein).  Rates in a second group were fed a high-starch/low-protein diet that contained only 17 percent protein.  Both diets contained foods highly appealing to rodents, so taste preference was not considered a significant factor.

By the end of just one week, rats on the protein-rich regimen had consumed 15 percent less food than those in the high-starch group and had gained significantly less weight.

Why would protein stimulate glucose production?
Blood tests showed that two genes involved in intestinal glucose production were much more active in the protein-diet group.  Even after the food in a meal was fully absorbed, the small intestines of the protein-diet rats continued to deliver high levels of glucose into a vessel (the portal vein) that carries blood from the digestive system to the liver.

Lead researcher Dr. Gilles Mithieux hypothesized that protein may prompt the release of a chemical called cyclic AMP, which would stimulate the genes responsible for synthesizing glucose.

Encouraging results; unanswered questions
Asia, where fish constitute the highest proportion of protein intake, also suffers the least obesity and heart disease.

LIFDCs are "low-income/food-deficit countries" as defined by the World Health Organization.

Commenting on the French results, nutrition researcher Dr. Simon Langley-Evans of Nottingham University said, "Diets like Atkins do appear to promote weight loss because they stop hunger.

"It appears to be nothing to do with the metabolic processing of protein, but because people following these diets simply eat less.  It makes sense that if proteins do somehow increase the production of glucose in the small intestine that this would act on neuropeptides that would send signals to the brain that the stomach is full."

We should note that foods very high in fiber, such as bran and non-starchy vegetables, also help suppress appetite.  The difference may lie in the mechanisms of action, with protein exerting its appetite-suppressing effects through a unique effect on brain chemistry.

Further studies are needed to confirm that this protein-driven genetic switching effect also occurs in humans.  However, the preliminary French findings offer encouragement to those attempting weight control via Dr. Perricone’s protein-centered, salmon-heavy approach: especially since the long-chain marine omega-3s in cold water fish also exert several unique weight-control-enhancing physiological effects (To access two articles about these rare metabolic properties, click here and here).


Sources
  • Mithieux G, Misery P, Magnan C, Pillot B, Gautier-Stein A, Bernard C, Rajas F, Zitoun C. Portal sensing of intestinal gluconeogenesis is a mechanistic link in the diminution of food intake induced by diet protein. Cell Metab. 2005 Nov;2(5):321-9.
  • Gevrey JC, Malapel M, Philippe J, Mithieux G, Chayvialle JA, Abello J, Cordier-Bussat M. Protein hydrolysates stimulate proglucagon gene transcription in intestinal endocrine cells via two elements related to cyclic AMP response element. Diabetologia. 2004 May;47(5):926-36. Epub 2004 Apr 14.
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