Cardiovascular risk: tea, vitamin C supplements and vegetables best antioxidants for the heart

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

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

Oxidative stress and antioxidants

Oxidative stress, along with inflammation, is implicated in the onset of cardiovascular disease, as reactive oxygen species, very damaging free radicals, can oxidize low-density lipoproteins, giving rise to a series of reactions that lead to the formation of the plaques responsible for atherosclerosis. High consumption of fruits and vegetables is associated with a reduced risk of cardiovascular disease, and the beneficial effects of these foods appear to be due to the antioxidant properties of the phytochemicals and vitamins in which they are rich. Among the most commonly consumed foods, those that contain a high percentage of substances with antioxidant action are:

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

Being able to accurately measure the amount of antioxidants consumed from food is not easy because of the combined and synergistic action of all the antioxidants in the diet. Total antioxidant capacity (TAC) is a cumulative measure that takes into account all the antioxidant molecules consumed, and in addition to being an index of their intake, it is also an indicator of the quality of the diet followed. Several research groups have reported an inverse association between CT value and the risk of stroke and heart failure, and have demonstrated the many positive effects of a diet high in CT on reducing inflammation and improving endothelial function. Regarding the action of antioxidant supplements, studies investigating their beneficial effects on cardiovascular risk are scarce, but they show that they play a key role in inhibiting lipid oxidation and other harmful reactions by reactive oxygen species.

Antioxidants from foods and supplements protect cardiovascular health

Considering the large extent to which antioxidant supplements contribute to CT and the increase in recent years in consumption of the supplements, the study authors also assessed their role in the association between CT and cardiovascular risk. The researchers analyzed data from 4,039 male and female subjects who had participated in a large study, the 2007-2012 National Health and Nutrition Examination Survey. 

Of each, the total amount of antioxidants consumed was calculated from information obtained from food diaries and the cardiovascular risk from specific analyses, The results showed that, in the following order, tea, antioxidant supplements, vegetables, orange juice, fruit, and red wine were the products that had contributed the most to the total antioxidant capacity. Supplements were thus found to be the second highest source of antioxidants, contributing 31 percent to the daily TAC. As for foods, strong associations were found between high TAC value and consumption of citrus fruits, fruit juices, berries, apple and vegetable composites. Other fruit drinks and coffee did not appear to contribute significantly to TAC. Thirty-five percent of the study participants had reported using antioxidant supplements. This group of people showed 1.6 times higher CT than the others. The most commonly consumed supplements were found to be vitamin C supplements, which accounted for 28 percent of total TAC, vitamin E supplements 2.1 percent, and flavonoid supplements, which contributed 1.2 percent. 

In addition, those who had taken the supplements consumed more foods high in antioxidants than those who did not take them. In the first group of people, in fact, the foods that contributed most to CT were mixed vegetables, berries, and red wine. In the subjects who did not use supplements, products such as fruit juices, potatoes and beer contributed to CT. The most interesting result emerged from the blood tests of each subject: those who had a very high TAC value from both foods and supplements showed lower triglycerides and a higher concentration of HDL cholesterol, the so-called good cholesterol, than those who took few antioxidants. 

Higher TAC was also associated with lower levels of insulin, and lower HOMA-IR, an index quantifying insulin resistance, and C-reactive protein, a molecule indicating the presence of inflammation. In addition, when the elevated CT value was due to supplement consumption alone it was associated with a lower body mass index. In contrast, there was no significant association between TAC, calculated from food and supplements, and waist circumference, blood pressure, body mass index, the amount of low-density lipoprotein (so-called bad cholesterol), total cholesterol, and fasting glucose value.

Vitamin C supplements protect health

Taken together, these results support the hypothesis that a diet rich in antioxidants along with the use of supplements is able to reduce the risk of cardiovascular disease. In fact, supplements have been identified as the second largest source of antioxidants contributing to CT. As Kijoon Kim, who directed the research, pointed out, the results obtained with the CT scan calculated considering diet and supplements were different from the results obtained with the one due to food alone. In the former case, the CT scan showed an inverse association with insulin levels and insulin resistance and an improvement in the triglyceride and cholesterol profile, confirming the very important role of supplements in maintaining cardiovascular health. Vitamin C supplements were found to be the most widely used by the subjects involved in the study, contributing strongly to the TAC value. This finding is supported by the fact that, as shown in other studies, vitamin C supplementation has beneficial effects on reducing fasting insulin levels and improves 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: January 4, 2016