Cardiovascular Risk: Tea, Vitamin C Supplements and Vegetables Are the Best Antioxidants for the Heart

A diet rich in foods and supplements with antioxidant properties is associated with a reduced cardiovascular risk. In particular, tea, vitamin C supplements, vegetables, orange juice, berries, and red wine contribute the most to increasing total antioxidant capacity (TAC), a measure of antioxidants consumed through the diet. The higher the TAC, the lower the levels of triglycerides, cholesterol, and inflammatory substances in the blood, all factors predisposing to cardiovascular disorders.

These are the most important data emerging from research published in the journal Nutrients, conducted by researchers from the University of Connecticut (USA).

Oxidative Stress and Antioxidants

Oxidative stress, together with inflammation, is involved in the onset of cardiovascular diseases, as reactive oxygen species, very damaging free radicals, can oxidize low-density lipoproteins, leading to a series of reactions that result in the formation of plaques responsible for atherosclerosis. A high consumption of fruits and vegetables is associated with a reduced risk of cardiovascular diseases, and the beneficial effects of these foods seem to be due to the antioxidant properties of phytochemicals and vitamins they are rich in. Among the most commonly consumed foods, those containing a high percentage of antioxidant substances are:

• red fruits
• pomegranate
• citrus fruits
• carrots
• peppers
• tomatoes
• broccoli
• tea
• chocolate
• red wine

Measuring precisely the amount of antioxidants consumed with foods is not easy due to the combined and synergistic action of all antioxidants present in the diet. Total antioxidant capacity (TAC) is a cumulative measure that takes into account all antioxidant molecules ingested and, besides being an index of their intake, also represents an indicator of the quality of the diet followed. Several research groups have reported an inverse association between TAC values and the risk of stroke and heart failure, and have demonstrated numerous positive effects of a high-TAC diet on reducing inflammation and improving endothelial function. Regarding the effects of antioxidant supplements, studies investigating their beneficial effects on cardiovascular risk are scarce but show that they play a key role in inhibiting lipid oxidation and other harmful reactions caused by reactive oxygen species.

Antioxidants from Foods and Supplements Protect Cardiovascular Health

Considering the large extent to which antioxidant supplements contribute to TAC and the increase in supplement consumption in recent years, the study authors also evaluated their role in the association between TAC and cardiovascular risk. Researchers analyzed data from 4,039 subjects, men and women, who had participated in a large study, the National Health and Nutrition Examination Survey 2007-2012. 

For each participant, the total amount of antioxidants consumed was calculated based on information obtained from food diaries, and cardiovascular risk was assessed through specific analyses. Results showed that, in the following order, tea, antioxidant supplements, vegetables, orange juice, fruit, and red wine were the products that contributed the most to total antioxidant capacity. Supplements were thus the second highest source of antioxidants, contributing 31% to daily TAC. Regarding foods, strong associations were found between high TAC values and the consumption of citrus fruits, fruit juices, berries, apples, and vegetable compounds. Other fruit-based beverages and coffee did not seem to contribute significantly to TAC. Thirty-five percent of study participants reported using antioxidant supplements. This group showed a TAC 1.6 times higher than others. The most consumed supplements were vitamin C, representing 28% of total TAC, vitamin E 2.1%, and flavonoid-based supplements contributing 1.2%. 

Moreover, those who took supplements consumed more antioxidant-rich foods compared to those who did not take them. In the first group, foods contributing most to TAC were mixed vegetables, berries, and red wine. In subjects not using supplements, products like fruit juices, potatoes, and beer contributed to TAC. Blood analyses of each subject revealed the most interesting result: those with very high TAC values, coming from both foods and supplements, showed lower triglyceride levels and higher HDL cholesterol concentration, the so-called good cholesterol, compared to those consuming few antioxidants. 

High TAC was also associated with lower insulin levels, lower HOMA-IR, an index quantifying insulin resistance, and C-reactive protein, a molecule indicating the presence of inflammation. Furthermore, when high TAC values were due to supplement consumption alone, they were associated with a lower body mass index. No significant association was found between TAC, calculated from foods and supplements, and waist circumference, blood pressure, body mass index, low-density lipoprotein (so-called bad cholesterol), total cholesterol, and fasting glucose levels.

Vitamin C Supplements Protect Health

Overall, these results support the hypothesis that a diet rich in antioxidants combined with supplement use can reduce the risk of cardiovascular diseases. Supplements were identified as the second source of antioxidants contributing to TAC. As highlighted by Kijoon Kim, who led the research, the results obtained with TAC calculated considering diet and supplements differed from those obtained with TAC from foods alone. In the first case, TAC showed an inverse association with insulin levels and insulin resistance and an improvement in triglyceride and cholesterol profiles, confirming the very important role of supplements in maintaining cardiovascular health. Vitamin C supplements were the most used by the study subjects, strongly contributing to TAC values. This finding is supported by other studies demonstrating that vitamin C supplementation has beneficial effects on reducing fasting insulin levels and improving vasodilation in patients with non-insulin-dependent diabetes mellitus. 

Source: Kijoon Kim, Terrence M. Vance and Ock K. Chun, “Greater Total Antioxidant Capacity from Diet and Supplements Is Associated with a Less Atherogenic Blood Profile in U.S. Adults” Nutrients, Published: 4 January 2016