Positive Health Online

Abstract

MORCOS and CAMILO, Department of Medicine, Division of Cardiology, University of California, Irvine, California, USA, investigated possible toxic effects of long-term dietary intake of a combination of fish oil (omega-3 fatty acid) and garlic food supplements in rats.

Background

Dietary supplementation with fish oil and/or garlic are now well recognized as having beneficial effects on blood lipid levels. However, formal evaluation of any potential toxic effects of the combination on organ structures and functions have not been performed.

Methodology

The study was a double-blind, placebo-controlled trial carried out on 28 Sprague-Dawley rats . Over a period of 12 months, the rats were fed 1) a 'lab chow' diet supplemented with the equivalent of 3x the maximum recommended human daily (body-weight-adjusted) dosage of fish oil and the usual recommended daily dosage of garlic (the US Food and Drug Administration [FDA] recommends a maximum daily dose of 3 g omega-3 fatty acids and a usual daily dose of 1200 mg of garlic for a 70-kg human); or 2) a placebo -supplemented lab chow diet. The animals were evaluated at baseline and at 2, 6 and 12 months.

Results

As would be expected, the fish oil/garlic-supplemented group exhibited lower blood levels of triglycerides, total cholesterol and low-density lipoprotein (LDL) during the acute phase (early time points) of the study. Over the course of the study, no differences were found between the supplemented and placebo groups with regard to external appearance, activity levels, daily food consumption, blood cell counts, kidney function, thyroid function, prothrombin time (PT) or activated partial prothrombin time (PPT), and no structural changes in organs were detected. At the end of the study, supplemented rats still showed lowered triglyceride and LDL levels, but total cholesterol and high- density lipoprotein (HDL) levels had become elevated .

Conclusion

No toxic effects on organ structure or function were seen due to chronic supplementation with fish oil and garlic, but some altered metabolic activities were apparent. The researchers report that the elevations in total cholesterol and HDL levels during the chronic toxicity period occur simultaneously with elevations in plasma levels of the liver enzymes ALT and AST, which are not involved in cholesterol synthesis. From this, they suggest that levels of liver enzymes that are involved in cholesterol synthesis (such as HMG-CoA reductase) may similarly become elevated ('escape suppression') during chronic toxicity .

References

Morcos NC, Camilo K. Acute and chronic toxicity study of fish oil and garlic combination. International Journal of Vitamin and Nutrition Research 71 (5): 306-12. Sep 2001.