Evaluating associations between Mediterranean diet adherence indexes and biomarkers of diet and disease

Objective

We examined associations between two Mediterranean diet (MD) adherence indexes (the MD index, MDI, and the MD score, MDS) and several blood biomarkers of diet and disease.

Subjects

We studied 328 individuals from Catalonia (Northeastern Spain), ages 18–75, who provided fasting blood samples, a subset of the 2346 individuals as part of a larger representative and random sample from the 1992–1993 Catalan Nutritional Survey.

Design and method

Diet was measured using 24-h recalls. Biomarkers studied were plasma levels of β-carotene, α-tocopherol, retinol, vitamins B12, C and folates as well as serum total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides. Multivariate linear regression was used to analyse associations of the nutrient biomarkers with the dietary pattern indexes, adjusting for potential confounders.

Results and conclusions

Subjects with higher MD adherence, as measured by the two dietary indexes, had significantly higher plasma concentrations of β-carotene, folates, vitamin C, α-tocopherol and HDL cholesterol. The most highly significant relationship was that between folates and the adherence to the MD Pattern, as determined by both indexes.

These research findings suggest the potential usefulness of biomarkers as complementary tools for assessing adherence to a dietary pattern. This type of data not only informs the development of robust dietary adherence indexes, but it also provides specific clues about the potential physiological mechanisms that explain the beneficial effects of the MD pattern on chronic disease risk.

High-fiber cereal reduces postprandial insulin responses in hyperinsulinemic but not normoinsulinemic subjects

OBJECTIVE

The objective of this study was to compare the plasma glucose and insulin responses elicited by two ready-to-eat breakfast cereals (one being high and the other being low in cereal fiber) and to see if the differences in response depended on subjects' fasting plasma insulin.

RESEARCH DESIGN AND METHODS

Nondiabetic men (n = 77) were studied on two occasions after 10- to 14-h overnight fasts. They consumed 25 g of available carbohydrate from high- or low-fiber breakfast cereals in random order with blood taken at intervals for 2 h. Data from the 42 men with high fasting plasma insulin (FPI) on screening (>40 pmol/l) were compared with those from the 35 men with normal FPI (< or =40 pmol/l).

RESULTS

Hyperinsulinemic men had significantly higher waist circumference and BMI, lower HDL cholesterol, and a trend toward higher triglycerides (P = 0.07) than control subjects. In all 77 subjects, the incremental area under the glucose response curve (AUC) after high-fiber cereal was 11.8 +/- 5.5% (P = 0.036) less than after low-fiber cereal with the reductions being equivalent in the hyperinsulinemic (12.6 +/- 8.3%) and control (10.9 +/- 9.1%) groups. However, insulin peak rise was reduced by the high-fiber cereal only in hyperinsulinemic men (351 +/- 29 vs. 485 +/- 55 pmol/l) but not in control subjects (211 +/- 20 vs. 220 +/- 20 pmol/l; cereal x group interaction P = 0.044). Insulin AUC after the high-fiber cereal, expressed as a percentage of that after low-fiber cereal, was negatively related to FPI (P = 0.009) but not to age, BMI, or waist circumference.

CONCLUSIONS

The high-fiber cereal reduced glucose responses to the same extent in normal and hyperinsulinemic men, but reduced insulin responses only in hyperinsulinemic subjects.

A solubilized cellulose fiber decreases peak postprandial cholecystokinin concentrations after a liquid mixed meal in hypercholesterolemic men and women

Viscous dietary fibers can modify the alimentary responses to a meal and improve glucose tolerance. There may be a relationship between the effect of these fibers in the gut and the ability of the hormone cholecystokinin (CCK) to slow gastric emptying and affect glucose homeostasis. We investigated the acute and long-term (adaptive) glucose and CCK responses to liquid mixed test meals, with or without 5 g of solubilized cellulose (SC), a novel viscous fiber, in 33 hypercholesterolemic men and women. In the acute study, there was a lower peak CCK concentration (P = 0.01) after a SC-containing test meal compared with a fiber-free test meal. The CCK area under the curve responses also tended to be lower after the fiber-containing meal (P = 0.08). After a 6-wk intervention with 2.5 g of SC or placebo twice daily, fasting plasma glucose concentration tended to decrease in the SC group, whereas it increased in the control group (for between-group difference in change, P = 0.13). There were no differences between the groups in the changes from baseline to the end of the study in any other variable. There were significant gender differences in several variables at baseline. These findings support the hypothesis that CCK may mediate the effect of viscous fibers on glucose metabolism. The gender differences in glucose and CCK may explain some of the discrepancies in the results of similar experiments reported to date.

Do whole-grain oat cereals reduce the need for antihypertensive medications and improve blood pressure control?

OBJECTIVES

Our study compared 2 whole grain oat-based cereals with 2 refined grain wheat-based cereals to determine their effects on the need for antihypertensive medications in people with high blood pressure (BP).

STUDY DESIGN

This 12-week, randomized controlled parallel-group trial with = 6 weeks of voluntary follow-up was designed to investigate the antihypertensive effects of oats. After 4 weeks of baseline feeding, medication dose was maintained or reduced by half or completely throughout the middle 4 weeks of the study. In the final 4 weeks, participants continued cereal consumption; medication was adjusted according to the protocol.

POPULATION

Men and women (n = 88) being treated for hypertension with a mean baseline BP below 160/100.

OUTCOMES MEASURED

Primary study outcomes included change in SBP and DBP as well as antihypertensive medication reduction. Secondary measures included blood lipid, fasting glucose, and insulin levels and side effects related to elevated BP and increased dietary fiber intake.

RESULTS

Seventy-three percent of participants in the oats group versus 42% in the control group were able to stop or reduce their medication by half. Treatment group participants whose medication was not reduced had substantial decreases in BP. The oats group experienced a 24.2-mg/dL reduction in total cholesterol levels, a 16.2-mg/dL decrease in low-density lipoprotein cholesterol levels, and a 15.03-mg/dL drop in plasma glucose levels vs controls.

CONCLUSIONS

Results suggest that a diet containing soluble fiber-rich whole oats can significantly reduce the need for antihypertensive medication and improve BP control. Considering the lipid and glucose improvements as well, increased consumption of whole oats may significantly reduce cardiovascular disease risk.