Data used were from The Swedish Mammography Cohort (from 1987 and 1990), and polled more than 32,500 women aged 49 to 83 residing in the Uppsala and Västmanland counties in central Sweden about their educational level, weight and height, reproductive factors, diet and questions on all major lifestyle factors, history of diseases, and use of some medications.
Researcher Susanne Rautiainen Lagerström, PhD, of the Division of Nutritional Epidemiology, Institute of Environmental Medicine, at the Karolinska Institutet in Stockholm, Sweden, told Nutraceuticals World that she and her colleagues were intrigued by the relationship of dietary antioxidants to incidences of myocardial infarction. “Previous studies have mainly focused on individual antioxidants however, in diet a wide-range of phytochemicals with antioxidant properties are present,” she said.
Dr. Lagerström made it clear that the effect was observable only through the consumption of whole foods, not supplements. “In this study we investigated antioxidants from foods and not from dietary supplements in relation to myocardial infarction, therefore our results can only be generalized to foods and not supplements,” she said. “By looking at the study results we cannot say which source is more effective since we did not study the effect from dietary supplements.”
In their report, the researchers acknowledged that previous randomized controlled trials testing high doses of antioxidant supplements containing one to three compounds failed to see any benefit on coronary heart disease. “One randomized controlled trial that studied the effect of a low-dose mixture of five antioxidant supplements (including 120 mg ascorbic acid, 30 mg vitamin E, 6 mg beta-carotene, 100 μg selenium and 20 mg zinc) did not observe any association with ischemic cardiovascular diseases,” they said. “Notably, in a meta-analysis of high doses and very high doses of single supplements of vitamin A, beta-carotene, or vitamin E tested in several randomized controlled trials, higher all-cause mortality was reported.”
The researchers nodded to the synergistic effect of the food nutrients, in conjunction with the naturally-present antioxidants. “In contrast to supplements of single antioxidants, the dietary total antioxidant capacity reflects all present antioxidants, including thousands of compounds, all of them in doses present in our usual diet, and even takes into account their synergistic effects,” they wrote. “In addition to antioxidant effects, flavonoids also may inhibit the atherosclerotic process through other pathways. Flavonoids have been shown to improve endothelial function, to decrease blood pressure, and to have antiplatelet and anti-inflammatory effects.”
Several foods were deemed to be major contributors to antioxidant intake among respondents in the study population. “In particular, high intake of fruit and vegetables, which contributed 44% of the dietary total antioxidant capacity in our study, have been inversely related to coronary heart disease in many studies,” the researchers wrote. “Whole grains (18% of total antioxidant capacity) also are suggested to lower coronary heart disease risk. Coffee consumption (14% of total antioxidant capacity) has been inversely related to coronary heart disease in some but not in all studies. Chocolate consumption (4% of total antioxidant capacity) has been shown to have favorable effects on cardiovascular risk biomarkers such as flow-mediated dilation and diastolic blood pressure, as shown by a meta-analysis of randomized controlled trials.”
The study’s lead researcher, Dr. Alicja Wolk from the Karolinska Institute in Stockholm, told The Telegraph that her team’s research “contrasted with tests of single antioxidant supplements, which have largely failed to find evidence that they cut heart attacks or mortality rates.”
Worth consideration was the fact that women who ate a lot of fruit and vegetables also tended to eat less saturated fat. As reported by The Telegraph, when the researchers adjusted for intake of fats, the difference in heart attack rates rose to 29%. The study did not examine overall mortality, however, all women were followed until the date of myocardial infarction, death or the end of follow-up, whichever came first.
“Regarding dietary characteristics, women in the highest quintile of total antioxidant capacity of diet, as compared with the lowest quintile, had higher consumption of fruit and vegetables (three-fold), whole grains (15%), coffee (34%), and chocolate (38%), as well as 27% lower intake of saturated fatty acids and 19% lower intake of monounsaturated fatty acids,” the researchers found.
Dr. Lagerström said she and her team plan additional investigations into the role of antioxidants in the diet and they are currently studying the association between total dietary antioxidant content and the relationship to other diseases.