Tomatoes found to protect against sun damage at a molecular level
Researchers have discovered that tomatoes could offer another line of defence in our efforts to protect our skin from the sun, according to a study published in the British Journal of Dermatology.
The study, conducted by researchers from Germany, found that a lycopene-rich tomato nutrient complex and a lutein-containing nutritional supplement both helped to protect the skin from sunburn and photo-ageing (skin ageing in response to sunlight). Lycopene and lutein are two pigments that are produced by vegetables, lycopene is found in high concentration in tomatoes, whereas lutein is commonly found in kale and spinach.
The researchers compared the skin of 65 people who were divided into two treatment groups, one for lycopene and one for lutein. Within these treatment groups the subjects were again divided between the actual treatment and a placebo. Two weeks before the first 12-week treatment phase began, the different groups were subject to a “wash-out” phase, where no treatment occurred to allow the researchers to get an accurate base-line to compare their future results against. After the first treatment phase the different treatment arms underwent another wash-out phase before transitioning from the lycopene or lutein to the placebo, or vice-versa.
At the beginning and at the end of each treatment phase, skin was exposed to two types of ultraviolet (UV) light, UVA1 and UVA/B, in a process known as irradiation. 24 hours later biopsies were taken to see if biomarkers for certain “indicator genes” were present. These genes are suggestive of photo-ageing and inflammation, two common side effects of sun damage.
When the skin of volunteers who were either untreated (received no lycopene or lutein), or who had been treated with a placebo, was analysed it was revealed that UVB/A as well as UVA1 radiation increased expression of indicator genes, including heme oxygenase-1 (HO-1), intercellular adhesion molecule-1 (ICAM-1) and matrix metalloproteinase-1 (MMP-1), all of which are thought to be a sign of UV damage.
In contrast, lycopene as well as lutein treatment significantly reduced the expression of these genes.
Matthew Gass of the British Association of Dermatologists said:
“Eating tomatoes and kale isn’t a substitute for sunscreen or other forms of sun protection such as protective clothing and shade. However, this study shows that these lycopene and lutein supplements could be an extra tool to protect against sun damage.”
Professor Jean Krutmann, one of the researchers from the Leibniz Research Institute for Environmental Medicine, said:
“Our study further supports the concept that dietary strategies are beneficial for human skin in general and that nutritional supplements of the exact kind used in this study are very effective in providing protection against UVA radiation-induced skin damage in particular. It also demonstrates that assessment of molecular markers is a very powerful approach to study efficacy of oral photo-protective strategies and that measurement of erythema responses only poses the risk of underestimating these benefits.”
Previous studies into lycopene have generally assessed its ability to reduce UV-induced erythema, which is the skin reddening that is a sign of sun damage. One such study found that people taking a lycopene mixture had 33 per cent more protection against sunburn, equivalent to a sunscreen with a sun protection factor (SPF) of 1.3. This latest study looks at gene expression as a method of demonstrating sun damage to human skin.
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Study details: Molecular evidence that oral supplementation with lycopene or lutein protects human skin against ultraviolet radiation: Results from a double-blinded, placebo-controlled, cross-over study
Grether-Beck, S.1, Marini, A.1, Jaenicke, T.1, Stahl, W.2 and Krutmann, J.1 (2016).
1IUF – Leibniz Research Institute for Environmental Medicine, Dusseldorf, Germany;
2Institute of Biochemistry and Molecular Biology I, Faculty of Medicine, Heinrich Heine University, Dusseldorf, Germany
Background: Increasing evidence suggests photo-protection by oral supplementation with ß-carotene and lycopene.
Objectives: We examined the capacity of lycopene rich tomato nutrient complex (TNC) and lutein, to protect against UVA/B- and UVA1 radiation at a molecular level.
Methods: In a placebo-controlled, double blinded, randomized cross over study two actives containing either TNC or lutein were assessed for their capacity to decrease the expression of UVA1 radiation-inducible genes including heme oxygenase-1 (HO-1), intercellular adhesion molecule-1 (ICAM-1) and matrix metalloproteinase-1 (MMP-1). 65 healthy volunteers were allocated to 4 treatment groups and subjected to a 2-weeks wash-out phase, followed by two 12-weeks treatment phases separated by another 2-weeks wash-out. Volunteers started either with active and switched then to placebo or vice versa. At the beginning and at the end of each treatment phase skin was irradiated and 24 hours later biopsies were taken from untreated, UVB/A- and UVA1 irradiated skin for subsequent RT-PCR analysis of gene expression. Moreover, blood samples were taken after the wash out and the treatment phases for assessment of carotenoids.
Results: TNC completely inhibited UVA1 as well as UVA/B induced upregulation of HO-1, ICAM-1 and MMP1 mRNA no matter of sequence (ANOVA, p<0.05). In contrast, lutein provided complete protection if it was taken in the first period, but showed significantly smaller effects in the second sequence compared to TNC.
Conclusion: Assuming the role of these genes as indicators of oxidative stress, photo-dermatoses and photo-aging these results might indicate that TNC and lutein could protect against solar radiation-induced health damage.
The British Association of Dermatologists is the central association of practising UK dermatologists. Our aim is to continually improve the treatment and understanding of skin disease. For further information about the charity, visit www.bad.org.uk