Fruits, legumes, vegetables, nuts, and whole grains, are extremely beneficial to human health. The World Health Organization recommends the consumption of at least five portions of fruits or vegetables daily for a healthy life. An increase in dietary fiber intake and limiting the intake of saturated fats, free sugar, and salt decrease the risk of some types of cancer and cardiovascular diseases. A balanced diet helps promote good health and prevent contracting diseases.
Understanding the benefits of a single dietary component on health is extremely important. Considering this, a recent Antioxidants study evaluated the effect of grape consumption on reducing UV-induced skin erythema. Grape is a very popular fruit with a high global consumption rate. The United States alone produces 6 million tons per year.
Grapes contain hundreds of potential phytochemicals that possess many health benefits. For instance, it contains a small amount of resveratrol, a cancer chemopreventive agent. Additionally, it positively affects the central nervous system (CNS), gastrointestinal health, atherosclerosis, inflammation, vision, urinary bladder function, and osteoarthritis.
UV absorption by the skin promotes the synthesis of various chemicals, hormones, and neural signals that induces stimulatory effects on the brain, regulating homeostasis. Nevertheless, UV exposure also adversely affects an individual’s skin.
Every year more than 3 million US citizens are affected by non-melanoma skin cancer (NMSC), including squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), which might have been induced by UV exposure. Although the incidence of melanoma is multifactorial, the majority of cases are attributed to UV exposure. Early diagnosis and treatment are extremely important for favorable outcomes since the survival rate of individuals with malignant metastatic melanoma is low.
Skin cancer can be prevented by blocking or reducing UV exposure. Interestingly, UV-irradiated hairless mice subjected to oral administration of grape powder showed significantly reduced edema. This data provided preliminary evidence about the effectiveness of grape consumption in preventing severe skin damage. Although animal model-based studies have shown that many potential phytoconstituents can prevent skin cancer, mechanistic insights are limited.
About the study
The current study focused on the potential of grapes to restore skin damage caused by exposure to UV irradiation. A total of 30 White/Caucasian participants, including 15 males and 15 females, were included in this study. The mean age of the candidates was 41.6 years. Five participants were Fitzpatrick skin type II, and the remaining were Type III.
To ensure consistency and continuity of the experiments, a freeze-dried grape powder was developed. This powder contained both fresh seeded and seedless (red, green, and black) grapes. Each participant received 28 packets of grape powder and was recommended to consume two packets daily. Every packet contained 36 grams of freeze-dried grape powder.
The effectiveness of grapes in protecting against UV irradiation of the skin was determined based on the minimal erythema dose (MED). As stated above, the participants were subjected to freeze-dried grape powder equivalent to three daily servings of fresh grapes for two weeks.
A total of 29 candidates completed the study, among which 31% demonstrated significantly greater resistance to UV irradiation. This finding is in line with a previous study that reported grape consumption increased resistance to UV irradiation. It was observed that candidates with lower Fitzpatrick skin types exhibited greater resistance to UV irradiation than those with higher Fitzpatrick skin types.
Both males and females were responsive in promoting UV resistance to the skin after grape intake. Previous studies have shown that consumption of grapes is related to reduced proliferation, enhanced DNA damage repair, increased apoptosis, and decreased mast cell infiltration, serum IgE and Eotaxin, which are highly related to individuals’ response to erythema.
The Commission Internationale de l’Eclairage (CIE) L*a*b* color scale report confirmed that results were not biased due to skin attributes. Interestingly, only nine candidates showed greater resistance compared to others, which might be due to differences in gut microbiome composition.
Two groups were formed, one containing nine participants with high resistance to UV irradiation after grape consumption and another containing the rest of the candidates. The microbial composition and abundance of both groups were compared. Interestingly, on the 15th day of the study, significant differences in taxonomic, enzymic, and pathway analyses were observed between the groups.
Furthermore, on day 30, a considerable reduction in 3-hydroxyphenyl acetic, 2′-deoxyribonic acid, and scyllo-inositol were observed in the UV-resistant group. The difference in skin reaction to UV irradiation was due to polymorphisms in glutathione S-transferase activity.
The consumption of grapes was found to enhance UV resistance to the skin in the majority of the participants. The extent of responsiveness was found to be dependent on Fitzpatrick skin types, i.e., greater resistance was observed in individuals with lower Fitzpatrick skin types. There is a high possibility that the microbiome could directly or indirectly influence the enhancement of UV resistance in volunteers; however, more research is required to test this hypothesis.