LYCOPENE AND HUMAN HEALTH
Wednesday, December 13th 2017

Lycopene and Cardiovascular Diseases

Böhm, V.
Institute of Nutrition, Friedrich Schiller University Jena
Dornburger Str. 25-29, 07743 Jena, Germany
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The risk factors that predispose one to cardiovascular diseases have been identified by means of several studies in well-defined population groups [1, 2]. Among the most important “cardiovascular risk factors” are cigarette smoking and serum cholesterol levels. Smoking has been reported to increase atherosclerotic diseases by about 50% and at least doubles the incidence of coronary artery disease. Moreover, considerable evidence supports the direct relation between cardiovascular diseases and increased levels of serum low-density lipoprotein (LDL) cholesterol. There is now a scientific consensus that atherosclerosis represents a state of increased oxidative stress characterized by lipid and protein oxidation in the vascular wall. One initial step leading to the development of atherosclerosis might be the oxidation of unsaturated lipids in the LDL particles [3, 4]. Human LDL particles are heterogeneous in nature, and the smaller and denser particles are more prone to oxidation. There is much debate about the antioxidant content of these particles, and carotenoids – mainly lycopene – may play a key role in protecting LDL particles. In addition to LDL oxidation, other oxidative events are involved in vascular diseases. These include the production of reactive oxygen and nitrogen species by vascular cells, as well as oxidative modifications contributing to important clinical manifestations of coronary artery disease, such as endothelial dysfunction and plaque disruption. The contribution of antioxidants to cardiovascular diseases has been investigated to some degree; however, only scarce data are available about the specific effects of lycopene or tomato products [5-10].

Diet is believed to play a major role in the development of cardiovascular diseases. The gastric digestion of food containing oxidisable lipids and iron catalysts for peroxide decomposition (such as (met)myoglobin from muscle meat) can be accompanied by an extensive formation of potentially toxic lipid hydroperoxides which are implicated in the process of atherosclerosis. Much interest and research are focused on identifying ways to prevent cardiovascular diseases through dietary changes. Primarily, epidemiological studies as well as some in vitro and limited in vivo experiments support the hypothesis that carotenoids, including β-carotene and lycopene, may protect lipoproteins and vascular cells from oxidation. In particular, lycopene is known to be an efficient scavenger of reactive oxygen species, including singlet oxygen (1O2) and other excited species [11, 12]. Lycopene also reduces the amount of oxidative DNA damage in cell culture and in rats in vivo [13, 14]. In addition, clinical studies demonstrated that a lycopene-rich diet protects against oxidative DNA damage in human leukocytes in vitro [15] and prostate tissue in vivo [16]. Several findings suggest that the redox properties of carotenoid molecules can deeply influence cell growth, by affecting molecular pathways involved in cell proliferation and apoptosis. A variety of animal and cell-culture studies also supports a role for lycopene in cell growth. All together, these findings suggest that lycopene can modify cell growth of smooth muscle cells present in the atheroma.

Besides cardiovascular diseases, recent evidence points to carotenoids as effective antioxidants for inhibiting the development of degenerative diseases such as cancer, cataracts, etc. Intake of β-carotene has been inversely linked to incidence of lung cancer, as well as similar correlations between lutein and macular disease and between lycopene or tomato-based products and prostate cancer [17-19]. However, lycopene, being the strongest singlet oxygen quencher as well as a potent antioxidant compared to other carotenoids, has rarely been tested in studies for its role in cardiovascular disease prevention. Although some papers [20-22] reported inverse correlation between incidence for degenerative diseases and the consumption of fruit and vegetable instead of correlations to single ingredients of these foods, there is only scarce scientific knowledge on the interactions between different food components regarding their protective potential. Important points of bioavailability of lycopene as well as molecular mechanisms of its protective effects are not yet completely investigated.

Lycopene is mainly contained in tomatoes, the second-most important vegetable in Europe (after potatoes) and in higher concentrations in processed tomato products like ketchup, tomato sauce/juice, as well as in red coloured fruits like water melon and guava. Accordingly, the main dietary source of lycopene in Europe and the US is mainly processed tomato products. Tomatoes and tomato products have been under investigation for their protective effects on health for many years. However, the scientific reasons for their positive effects are not yet completely clear. Besides lycopene, which has been studied now for more than a decade, tomatoes contain other positive ingredients, including other carotenoids, ascorbic acid, tocopherols, folate, polyphenols, etc., whose interactions with lycopene have not yet been investigated in detail. Tomatoes have not been considered as an important source of folate in the diet, but due to their great consumption, the contribution of tomatoes to the total intake of folate might be relevant. A poor intake of folates in the diet has been associated with an increase of homocysteine level in human plasma, which is considered a risk factor in cardiovascular diseases.

This brief review has shown that there is a wealth of information about development of cardiovascular diseases as well as good evidence that certain foods – such as tomatoes – are healthy. However, these two aspects are not sufficiently linked because research has lacked a “total food chain” approach. The missing link in the chain is the development of healthy new foods and nutritional guidelines that bring these two ends of the food chain together.

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References

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