Effects of Dietary Antioxidants to Prevent Cardiovascular Disease

Study design and measurements This study is a cross-over field trial. Participants were asked to consume a specific variety of red wine "tannat" daily in their diet for one month. After a wash-out period of one month, the same participants were asked to consume a placebo drink daily for another month. Quantitative measurements of blood lipids, vitamin E, and Total Antioxidant Capacity before and after consumption of wine and placebo were measured. The study aimed to investigate whether consumption of red wine is associated with any changes in the levels of blood lipids, vitamin E, and Total Antioxidant Capacity and whether such changes - if any -equally occur in hypercholesterolemic individuals.

Participants were advised to abstain from consuming antioxidant supplements, antioxidant-rich foods (including deep-colored fruits and vegetables such as berries, tomatoes, carrots, broccoli, apples and plums, green tea, caffeine and chocolate), caffeine and alcohol 2 weeks prior to the beginning of initial measurements and during the 3-month experimental period. Participants (occasional alcohol drinkers) included in the study received no monetary compensation. According to the U.S. Department of Agriculture 2010 Dietary Guidelines, moderate drinking corresponds to one drink per day for women and two for men14. Consequently, female subjects were given 5 bottles of red wine for 1 month (1 glass per day), and male subjects were given 10 bottles (2 glasses/per day) and instructed to report any side effects or failure to participate. The single grape variety of Tannat, from a location in Northern Greece, was selected among several varieties of red wine for its content in phenolic compounds and high antioxidant gradient when tested in vitro. Participants were encouraged to not alter their dietary habits or physical activity level during the study. To verify their compliance with the instructions provided, we interviewed them before and after the experiment, and we also measured the quantity of wine used. One day prior to the beginning of the intervention, participants underwent physical and routine biochemical examinations and completed two questionnaires, one related to their health status and the other to their characteristics. To confirm protocol adherence, a team of colleagues contacted the participants by telephone every 2nd day and they visited the clinic to obtain 1 bottle of wine and answered a questionnaire regarding their adherence with the protocol requirements.

For each subject, measurements of serum TAC and vitamin E were performed pre and post 1 month of red wine ingestion and pre and post placebo drink ingestion after a 1 month wash out period. For vitamin E measurements, fasting subjects were requested to abstain from alcohol for 24 hours prior to the blood draw. Serum levels of Total Cholesterol (TC), triglycerides (TG), HDL-cholesterol, and LDL-cholesterol were also measured by enzymatic methods. For serum HDL-cholesterol levels, fasting blood was collected in tubes with a clot activator and was determined enzymatically.

For the assessment of cardiovascular risk, pre and post red wine consumption ratios (LDL/HDL-cholesterol and vitamin E/TC) were calculated. TG/HDL-cholesterol, a marker for insulin resistance, was also proposed as a surrogate marker of cardiovascular risk assessment. TC/HDL and LDL/HDL are also considered to be strong predictors of the degree of clinical benefit from lipid-lowering interventions.