A randomised study on the effects of fish protein supplement on glucose tolerance, lipids and body composition in overweight adults

Abstract

The popularity of high-protein diets for weight reduction is immense. However, the potential benefits from altering the source of dietary protein rather than the amount is scarcely investigated. In the present study, we examined the effects of fish protein supplement on glucose and lipid metabolism in overweight adults. A total of thirty-four overweight adults were randomised to 8 weeks' supplementation with fish protein or placebo tablets (controls). The intake of fish protein supplement was 3 g/d for the first 4 weeks and 6 g/d for the last 4 weeks. In this study, 8 weeks of fish protein supplementation resulted in lower values of fasting glucose (P,0·05), 2 h postprandial glucose (P, 0·05) and glucose-area under the curve (AUC) (five measurements over 2 h, P, 0·05) after fish protein supplementation compared to controls. Glucose-AUC was decreased after 8 weeks with fish protein supplement compared to baseline (P, 0·05), concomitant with increased 30 min and decreased 90 min and 2 h insulin C-peptide level (P,0·05), and reduced LDL-cholesterol (P,0·05). Body muscle % was increased (P,0·05) and body fat % was reduced (P, 0·05) after 4 weeks' supplementation. Physical activity and energy and macronutrients intake did not change during the course of the study. In conclusion, short-term daily supplementation with a low dose of fish protein may have beneficial effects on blood levels of glucose and LDL-cholesterol as well as glucose tolerance and body composition in overweight adults. The long-term effects of fish protein supplementation is of interest in the context of using more fish as a protein source in the diet, and the effects of inclusion of fish in the diet of individuals with low glucose tolerance should be evaluated.

High intake of fatty fish, but not of lean fish, affects serum concentrations of TAG and HDL-cholesterol in healthy, normal-weight adults: a randomised trial

“…This is supported by results from animal studies showing that fish proteins may have a lowering effect on TAG and cholesterol as well as improve glucose tolerance (19)(20)(21)(22)(23)(24)(25)(26) . In line with this, we have recently shown that supplementation with cod protein as tablets reduced fasting glucose and LDL-cholesterol as well as postprandial glucose concentrations in healthy, overweight adults (17) . The present study was designed to investigate the impacts of high intake of lean or fatty fish (cod and salmon, respectively) compared with lean meat (chicken) on indicators of CVD and type 2 diabetes risk factors, including lipid and glucose regulation.…”

“…It should be noted that as all participants had serum lipid concentrations within the normal reference ranges the clinical significance of the effects of fatty fish intake on TAG and HDL-cholesterol concentrations in serum is uncertain. We have recently shown that cod protein supplementation reduced serum LDL-cholesterol concentration in overweight adults, with no effect on serum concentrations of TAG, total cholesterol and HDL-cholesterol (17) . Reduced serum TAG has been reported in overweight subjects when lean fish was part of …”

“…Numerous studies in overweight, dyslipidaemic, hypertensive, insulin-resistant and/or diabetic subjects have been conducted to investigate the effects of fish intake on serum lipids and glucose regulation (12,13,17,18,(29)(30)(31)(32)(33)(34)(35)47) ; however, no studies on the effect of high fish intake in a group of young, healthy, nonsmoking, normal-weight adults have been published to date. In the present study, we investigated the effects of high intake of lean or fatty fish compared with lean meat for 4 weeks on serum lipids and glucose regulation in healthy, normal-weight adults.…”

“…The health benefits of fish consumption have traditionally been attributed mainly to the effect of n-3 fatty acids, and, although the TAG-lowering effect of fish oil and long-chain n-3 fatty acids is well documented, there is controversy regarding the cholesterol-regulating as well as glucose-regulating effects of marine n-3 fatty acids (6)(7)(8)(9)(10)(11)(12)(13)(14) . Studies suggests that there are other components in fish such as fish proteins that may be beneficial to human health and affect risk factors leading to CVD, beyond n-3 fatty acids (15)(16)(17)(18) . This is supported by results from animal studies showing that fish proteins may have a lowering effect on TAG and cholesterol as well as improve glucose tolerance (19)(20)(21)(22)(23)(24)(25)(26) .…”

“…Serum fructosamine concentration as a measure of the mean glucose concentration over the last 1-3 weeks (27) was examined. In addition, methylglyoxal (MG) and N ε -(carboxymethyl) lysine (CML) were analysed, as changes in lipid and glucose regulation may affect the production of MG from the glycation process by degradation of glucose, Schiff's bases or from Amadori products such as fructosamine, and the production of CML insulin-resistant and/or diabetic subjects (12)(13)(17)(18)(29)(30)(31)(32)(33)(34)(35)(36)(37) ; however, as no studies on the effect of high fish intake in a group of young, healthy, non-smoking, normal-weight adults have been published, little is known about how fish intake may affect lipid and glucose metabolism in this population. As the choice of preparation methods of fish and meat as well as the choices of side dishes and accessories may explain some of the different health effects from fish consumption compared with meat (38)(39)(40)(41) , participants in the present study were instructed to follow a recipe booklet to prepare fish and lean meat dinners, respectively, with comparable preparation methods and side dishes.…”