Editor's note: Part one of this article appeared in the Oct. 7, 2004 issue.
In part one of "The Whey to Weight Loss", I emphasized whey protein's particular ability to increase serum tryptophan levels so as to lessen appetite via the neurotransmitter serotonin.I also noted that, interestingly enough, dieters are at risk of being relatively low in tryptophan as a result of their dieting.
In part two, I will briefly review another reason whey protein is to be strongly considered as an integral part of weight-loss diets, namely by providing an interesting subfraction of whey protein called glycomacropeptides (GMPs).
Glycomacropeptides are unique peptides composed of a chain of 64 amino acids with a low molecular weight of 6,700 Daltons, bonded to carbohydrate molecules. This protein fraction is one of the most easily absorbed proteins known to nature.
Glycomacropeptides are cleaved from kappa-casein, a component of milk, the proteins of which are composed of both casein and whey. GMPs are found in the "natural" whey that is a byproduct of the cheese-making process. These multibeneficial peptides are present in manufactured whey protein powders and supplements in greater or lesser quantity, depending upon the type of processing utilized. Some whey powders may contain 15 percent or more of its proteins as GMPs, while others may contain only a few percent.
GMPs have been shown in research to exert numerous possible health benefits.1 These studies suggest that GMPs:
- are rich in "muscle feeding" branched chain amino acids (BCAAs);
- improve intestinal health by suppressing gastric disorders related to bacteria and viruses;.
- prevent heartburn by reducing gastric acid secretion by as much as 53 percent;
- reduce inflammation in the newborn's stomach by regulating immune responses;
- lower the risk of heart attack and stroke by inhibiting platelet aggregation and binding of I-fibrinogen to platelets;
- prevent influenza through their antimicrobial and antibacterial qualities;
- prevent cavities by inhibiting the adhesion of tartar to teeth; and
- suppress appetite by stimulating the release of cholecystokinin (CCK), a hormone that signals the brain of fullness.
Let's focus briefly on the last benefit listed. Glycomacropeptides are indeed well-known to create feelings of satiety and fullness and decrease food intake.2-4 As everyone has experienced, after eating a large meal, especially one high in fat, you feel full and satisfied. This feeling of fullness or satiety is created in part by a protein called cholecystokinin (CCK), which is released in the small intestine in response to food entering the small intestine from the stomach.
CCK signals us to stop eating in three ways:
- It triggers nerves in the lining of our alimentary system, signaling our brains that our stomachs are full.
- It slows stomach emptying so we feel full longer.
- It works directly on the appetite control centers in the brain to lessen hunger.
After eating, CCK levels rise, signaling the brain to stop eating. However, it may be that as many as 20 percent of humans have suboptimal CCK function, perhaps related to zinc metabolism, although frank deficiency is rare.5-7 Perhaps it remnant of pre-agrarian societies, when constant hunger may have assisted survival, such "dysfunction" was an advantage! In any case, as many as one in five people in this day and age have a CCK response that either does not rise to optimal hunger-ending levels, or they suffer from receptor insensitivity that blunts the appetite-suppressing effects of normal CCK levels. Nonetheless, even with normal CCK levels and sensitivity, spiking CCK levels without a large, high-fat meal has obvious advantages that should be consistent with most rational weight-loss approaches.
Of interest, lecithin, which is often used to "instantize" whey protein drink powder mixes, affects CCK in a similar way, as does phenylalanine, one of the many amino acids found in complete, balanced whey protein formulas.
In conclusion, whey protein powders formulated with whey protein concentrates and isolates are 80 to 90 percent easily digested, balanced, complete proteins, and low in fat and sugars. As such, they are in themselves perfect for inclusion in low- and moderate-carbohydrate dietary weight-loss strategies. Whey protein's additional potential to decrease appetite by safely and naturally increasing the neurotransmitter serotonin and the hormone CCK may certainly qualify properly prepared whey-protein-based meal replacement formulas and plans as a dieter's best nutritional friend.
- Gibbs J, Young RC, Smith GP, et al. Cholecystokinin decreases food intake in rats. Physiol Psychol Sept. 1973;84(3):488-95.
- Della-Fera MA, Baile CA, Schneider BS, Grinker JA. Cholecystokinin antibody injected in cerebral ventricles stimulates feeding in sheep. Science, May 8, 1981;212(4495):687-9.
- Della-Fera MA, Baile CA. Peptides with CCK-like activity administration intracranially elicit satiety in sheep. Physiol Behav June 1981;26(6):979-83.
- Cholecystokinin. http://arbl.cvmbs.colostate.edu/hbooks/pathphys/
- Ahima RS, Flier JS. LEPTIN. Annual Review of Physiology March 2000;62:413-437.
- Christos S, Mantzoros MD, et al. Zinc may regulate serum leptin concentrations in humans. Journal of the American College of Nutrition 1998;17(3):270-275.
John Maher, DC, ABAAHP
Del Mar, California
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