The Role of Circulating Lycopene in Low-Grade Chronic Inflammation: A Systematic Review of the Literature

Background and aims: In recent years, it has become clear that low-grade chronic inflammation is involved in the onset and progression of many non-communicable diseases. Many studies have investigated the association between inflammation and lycopene, however, results have been inconsistent. This systematic review aims to determine the impact of circulating lycopene on inflammation and to investigate the effect of consuming tomato products and/or lycopene supplements on markers of inflammation. Methods: Eligible studies, published before March 2020, were identified from PubMed, EBSCOhost and ScienceDirect. Human studies published in English, that evaluated the effect of circulating lycopene in relation to inflammation biomarkers were screened and included. Studies assessing lycopene intake or general intake of carotenoids/antioxidants without measuring circulating lycopene, as well as those not reporting inflammation biomarkers as outcomes, were excluded. Results: Out of 80 publications identified and screened, 35 met the inclusion criteria. Results from 18 cross-sectional studies suggest that lycopene levels are adversely affected during inflammation and homeostatic imbalance. Most of the 17 included intervention studies reported increased circulating lycopene levels after tomato/lycopene supplementation, but almost no changes in inflammation biomarkers were observed. Conclusions: There is little evidence that increasing tomato intake or lycopene supplementation diminuates this inflammation. However, depletion of lycopene may be one of the first signs of low-grade inflammation. The available data thereby imply that it is beneficial to consume lycopene-rich foods occasionally to stay healthy and keep circulating lycopene at a basal level