Life Extension Magazine

Life Extension Magazine February 2012


Postprandial Glucose

Berries modify the postprandial plasma glucose response to sucrose in healthy subjects.

Sucrose increases postprandial blood glucose concentrations, and diets with a high glycaemic response may be associated with increased risk of obesity, type 2 diabetes and CVD. Previous studies have suggested that polyphenols may influence carbohydrate digestion and absorption and thereby postprandial glycaemia. Berries are rich sources of various polyphenols and berry products are typically consumed with sucrose. We investigated the glycaemic effect of a berry purée made of bilberries, blackcurrants, cranberries and strawberries, and sweetened with sucrose, in comparison to sucrose with adjustment of available carbohydrates. A total of twelve healthy subjects (eleven women and one man, aged 25-69 years) with normal fasting plasma glucose ingested 150 g of the berry purée with 35 g sucrose or a control sucrose load in a randomised, controlled cross-over design. After consumption of the berry meal, the plasma glucose concentrations were significantly lower at 15 and 30 min (P < 0.05, P < 0.01, respectively) and significantly higher at 150 min (P < 0.05) compared with the control meal. The peak glucose concentration was reached at 45 min after the berry meal and at 30 min after the control meal. The peak increase from the baseline was 1.0 mmol/l smaller (P = 0.002) after ingestion of the berry meal. There was no statistically significant difference in the 3 h area under the glucose response curve. These results show that berries rich in polyphenols decrease the postprandial glucose response of sucrose in healthy subjects. The delayed and attenuated glycaemic response indicates reduced digestion and/or absorption of sucrose from the berry meal.

Br J Nutr. 2010 Apr;103(8):1094-7

A MUFA-rich diet improves posprandial glucose, lipid and GLP-1 responses in insulin-resistant subjects.

OBJECTIVE: To study the effects of three weight-maintenance diets with different macronutrient composition on carbohydrate, lipid metabolism, insulin and incretin levels in insulin-resistant subjects. METHODS: A prospective study was performed in eleven (7 W, 4 M) offspring of obese and type 2 diabetes patients. Subjects had a BMI > 25 Kg/m2, waist circumference (men/women) > 102/88, HBA1c < 6.5% and were regarded as insulin-resistant after an OGTT (Matsuda ISIm <4). They were randomly divided into three groups and underwent three dietary periods each of 28 days in a crossover design: a) diet high in saturated fat (SAT), b) diet rich in monounsaturated fat (MUFA; Mediterranean diet) and c) diet rich in carbohydrate (CHO). RESULTS: Body weight and resting energy expenditure did not changed during the three dietary periods. Fasting serum glucose concentrations fell during MUFA-rich and CHO-rich diets compared with high-SAT diets (5.02 +/- 0.1, 5.03 +/- 0.1, 5.50 +/- 0.2 mmol/L, respectively. Anova < 0.05). The MUFA-rich diet improved insulin sensitivity, as indicated by lower homeostasis model analysis-insulin resistance (HOMA-ir), compared with CHO-rich and high-SAT diets (2.32 +/- 0.3, 2.52 +/- 0.4, 2.72 +/- 0.4, respectively, Anova < 0.01). After a MUFA-rich and high-SAT breakfasts (443 kcal) the postprandial integrated area under curve (AUC) of glucose and insulin were lowered compared with isocaloric CHO-rich breakfast (7.8 +/- 1.3, 5.84 +/- 1.2, 11.9 +/- 2.7 mmol . 180 min/L, Anova < 0.05; and 1004 +/- 147, 1253 +/- 140, 2667 +/- 329 pmol . 180 min/L, Anova <0.01, respectively); while the integrated glucagon-like peptide-1 response increased with MUFA and SAT breakfasts compared with isocaloric CHO-rich meals (4.22 +/- 0.7, 4.34 +/- 1.1, 1.85 +/- 1.1, respectively, Anova < 0.05). Fasting and postprandial HDL cholesterol concentrations rose with MUFA-rich diets, and the AUCs of triacylglycerol fell with the CHO-rich diet. Similarly fasting proinsulin (PI) concentration fell, while stimulated ratio PI/I was not changed by MUFA-rich diet. CONCLUSIONS: Weight maintenance with a MUFA-rich diet improves HOMA-ir and fasting proinsulin levels in insulin-resistant subjects. Ingestion of a virgin olive oil-based breakfast decreased postprandial glucose and insulin concentrations, and increased HDL-C and GLP-1 concentrations as compared with CHO-rich diet.

J Am Coll Nutr. 2007 Oct;26(5):434-44

Mediterranean diet and insulin sensitivity, lipid profile and blood pressure levels, in overweight and obese people; the Attica study.

BACKGROUND: We aimed to investigate if overweight and obese adults “close” to Mediterranean diet present better insulin, lipids profile and better pressure levels, compared to individuals close to a more Westernized diet. METHODS: The ATTICA study is a population-based cohort that has randomly enrolled 3042 adult men and women, stratified by age - gender, from the greater area of Athens, during 2001-2002. Of them, in this work were have studied 1762 participants with excess body weight, meaning overweight (BMI: 25-29.9 kg/m2) and obese (BMI>30 kg/m2). 1064 were men and 698 women (20-89 years old). Adherence to Mediterranean diet was assessed through a diet-score that was based on a validated food-frequency questionnaire. Blood pressure was measured and also fasting glucose, insulin and blood lipids. Insulin sensitivity was also assessed by the homeostasis model assessment (HOMA) approach (glucose x insulin/22.5). RESULTS: Individuals with excess bodyweight in the highest tertile of diet score, were more insulin sensitive than those in the lowest tertile (11.4% lower HOMA, p = 0.06), had 13% lower levels of total cholesterol (p = 0.001) and 3 mmHg decrease of systolic blood pressure levels (p < 0.001), when adjusted for age, sex and BMI. Multivariate analysis after taking into account several confounders demonstrated that insulin sensitivity, total cholesterol and systolic blood pressure were independently but only modestly correlated with Mediterranean diet in people with excess bodyweight. CONCLUSION: Adherence to Mediterranean diet is modestly associated with a better insulin sensitivity, lower levels of total cholesterol and lower levels of systolic blood pressure in overweight and obese subjects. This may suggest that compared to general population, the beneficial effect of this diet in cardiovascular system of excess body weight people is limited.

Lipids Health Dis. 2007 Sep 19;6:22

Adherence to the Mediterranean diet attenuates inflammation and coagulation process in healthy adults: The ATTICA Study.

OBJECTIVES: We studied the effect of the Mediterranean diet on plasma levels of C-reactive protein (CRP), white blood cell counts, interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, amyloid A, fibrinogen, and homocysteine. BACKGROUND: To the best of our knowledge, the mechanism(s) by which the Mediterranean diet reduces cardiovascular risk are not well understood. METHODS: During the 2001 to 2002 period, we randomly enrolled 1,514 men (18 to 87 years old) and 1,528 women (18 to 89 years old) from the Attica area of Greece (of these, 5% of men and 3% of women were excluded because of a history of cardiovascular disease). Among several factors, adherence to the Mediterranean diet was assessed by a diet score that incorporated the inherent characteristics of this diet. Higher values of the score meant closer adherence to the Mediterranean diet. RESULTS: Participants who were in the highest tertile of the diet score had, on average, 20% lower CRP levels (p = 0.015), 17% lower IL-6 levels (p = 0.025), 15% lower homocysteine levels (p = 0.031), 14% lower white blood cell counts (p = 0.001), and 6% lower fibrinogen levels (p = 0.025), as compared with those in the lowest tertile. The findings remained significant even after various adjustments were made. Borderline associations were found regarding TNF-alpha (p = 0.076), amyloid A levels (p = 0.19), and diet score. CONCLUSIONS: Adherence to the traditional Mediterranean diet was associated with a reduction in the concentrations of inflammation and coagulation markers. This may partly explain the beneficial actions of this diet on the cardiovascular system.

J Am Coll Cardiol. 2004 Jul 7;44(1):152-8

Adverse effects of dietary fructose.

The consumption of fructose, primarily from high-fructose corn syrup (HFCS), has increased considerably in the United States during the past several decades. Intake of HFCS may now exceed that of the other major caloric sweetener, sucrose. Some nutritionists believe fructose is a safer form of sugar than sucrose, particularly for people with diabetes mellitus, because it does not adversely affect blood-glucose regulation, at least in the short-term. However, fructose has potentially harmful effects on other aspects of metabolism. In particular, fructose is a potent reducing sugar that promotes the formation of toxic advanced glycation end-products, which appear to play a role in the aging process; in the pathogenesis of the vascular, renal, and ocular complications of diabetes; and in the development of atherosclerosis. Fructose has also been implicated as the main cause of symptoms in some patients with chronic diarrhea or other functional bowel disturbances. In addition, excessive fructose consumption may be responsible in part for the increasing prevalence of obesity, diabetes mellitus, and non-alcoholic fatty liver disease. Although the long-term effects of fructose consumption have not been adequately studied in humans, the available evidence suggests it may be more harmful than is generally recognized. The extent to which a person might be adversely affected by dietary fructose depends both on the amount consumed and on individual tolerance. With a few exceptions, the relatively small amounts of fructose that occur naturally in fruits and vegetables are unlikely to have deleterious effects, and this review is not meant to discourage the consumption of these healthful foods.

Altern Med Rev. 2005 Dec;10(4):294-306