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Potential Health Benefits of Dietary Antioxidants from Supplements vs. Foods

In recent years, there has been a great interest in the potential anti-inflammatory effects of specific dietary patterns and foods, especially antioxidant-rich foods. Observational studies have supported the hypothesis that dietary intake of antioxidants (vitamin C, carotenoids, and vitamin E) and diet patterns high in antioxidant-rich foods, such as the Mediterranean diet, to be inversely related to inflammation. However, clinical trials of foods or dietary supplements have yielded inconsistent results. In spite of the lack of evidence, antioxidant supplements are very popular in the U.S. The aim of this study was to compare the efficacy of foods naturally rich in antioxidants with that of antioxidants in a pill form on markers of inflammation in healthy adults at risk of cardiovascular disease.

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Eligible Participants

  • Generally healthy adults, 18 years of age or older
  • Having at least one elevated risk factor for CVD: BMI equal to or higher than 27, pre-hypertension, moderately elevated LDL-cholesterol, or low HDL cholesterol.
  • Not already consuming a diet high in fruits and vegetables (equal to or more than 5 servings per day).

Study Design

Eighty-eight adults were randomized to one of three treatments for 8 weeks: their usual diet and placebo pills (Usual/Plac); their usual diet and antioxidant supplement pills (Usual/Suppl); or to increase their daily intake of certain dietary antioxidants and take a placebo pill (Antiox-Food/Plac). The goal of the intervention was to double their antioxidant intake. Participants in the Antiox-Food/Plac group were instructed to eat more vegetables, fruits, nuts/seeds/oils, and whole grains to achieve their daily antioxidant intake goal by the study’s registered dietitian during a group class and a 1-hour individual session. All participants completed three clinic visits – at the beginning of the study, and 4 and 8 weeks after randomization – to provide blood samples, blood pressure and anthropometric measurements to assess three inflammatory markers (IL-6, sICAM-1 and MCP-1), and other markers of cardiovascular health. They also completed a to complete a 24-hour diet recall at the same time points to assess dietary adherence.

Conclusions

The results of this study showed no beneficial effects on the inflammatory markers investigated in response to antioxidants from foods or supplements. The participants enrolled in this study were not selected based on baseline inflammatory markers concentrations, and they had little room for improvement. It is possible that antioxidants may have a significant anti-inflammatory effect in populations with higher baseline levels of inflammation, or that higher doses may be required in order to observe any effect.

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