New perspective on tomatoes and cardiovascular health
The Nutrition Society Paper of the Month for July is from Proceedings of the Nutrition Society and is entitled ‘Cardiovascular benefits of lycopene: fantasy or reality?‘. Authors: Frank Thies, Lynsey M. Mills, Susan Moir and Lindsey F. Masson.
High consumption of fruits and vegetables reduces the risk of chronic diseases such as cardiovascular disease (CVD) and cancer. However, the actual components of these foods that confer the protective effect and the mechanisms by which they act have yet to be firmly identified.
Epidemiological evidence indicates that a high consumption of tomatoes and tomato-based products reduces the risk of prostate cancer and CVD. These beneficial effects have been mainly ascribed to lycopene, a red carotenoid particularly concentrated in tomato and tomato-based products. Tomatoes and tomato-based products are the main dietary source of lycopene and account for over 80% of lycopene intake in western countries.
Based on results mainly obtained from in vitro studies and animal models, potential biological mechanisms by which lycopene could protect against heart disease and cancer have been proposed. These include cholesterol reduction, inhibition of oxidation processes, modulation of inflammatory markers, enhanced intercellular communication, inhibition of tumorigenesis and induction of apoptosis, metabolism to retinoids and antiangiogenic effects.
With regards to CVD risk, results from intervention studies have given mixed results. Over 50 human intervention trials with lycopene supplements or tomato-based products have been conducted to date. Many showed some beneficial effects but mostly on non-established cardiovascular risk markers such as lipid peroxidation, DNA oxidative damage, platelet activation and inflammatory markers. Only a few studies, mostly underpowered, showed improvement in lipid profiles, C reactive protein and blood pressure.
However, novel mechanisms of action by which lycopene could confer cardiovascular protection have recently been proposed. Findings suggest that increased lycopene intake to a level easily achievable by dietary means can lower inflammatory markers associated with high density lipoprotein (HDL), and can modulate HDL functionality towards an antiatherogenic phenotype. These effects could potentially reduce atherogenesis and consequently the risk of myocardial infarction. Furthermore, in vitro studies indicate that lycopene could modulate T lymphocyte activity which would also inhibit atherogenic processes and confer cardiovascular protection.
Identifying early markers for CVD risk is paramount for disease prevention, and these recent findings suggest that HDL functionality deserves further consideration as a potential early marker for CVD risk, modifiable by dietary factors such as lycopene.
Photo with thanks to Liz West, Flickr, reproduced under a CC license.