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Scientists have been investigating grapes to see if they can help with UV damage. Carlos Ciudad Photos/Getty Images
  • A new study finds that grapes may reduce the chances of sunburn for some people.
  • The cause of sunburn—UV radiation from the sun—is implicated in the development of skin cancers.
  • The study suggests that microbiome differences may explain why grapes reduce some peoples’ sensitivity to UV exposure and not others.

Some people become less sensitive to the damaging effects of the sun’s ultraviolet (UV) rays after consuming grapes, according to a new study in humans.

A third of the study’s participants became less prone to skin-reddening from UV rays after two weeks of eating three servings of grapes daily in powdered form.

For some individuals, the protective effect lasted a month after the grape consumption ended.

The difference between those who were less likely to get sunburned and others appear to be differences in their microbiomes and metabolomes. This suggests an intriguing connection between the gut and UV resistance.

The study is published in Antioxidants.

It was partly funded by the California Table Grape Commission, which had no other involvement in the research. One of the authors was a member of their scientific advisory committee.

According to the Skin Cancer Foundation, more than 9,500 cases of skin cancer are diagnosed daily in the U.S. More than two people die of skin cancer every hour.

Over-exposure to UV radiation is the cause of about 90% of non-melanoma cancers—including basal cell and squamous cell cancers—and is considered a major factor in melanoma. Non-melanoma cancers can typically be managed.

Burning your skin in the sun five or more times doubles your risk of melanoma. One blistering sunburn in childhood or adolescence can also double your risk.

The American Cancer Society predicts 97,610 new melanoma diagnoses in the U.S. this year, and that 7,990 people will die from the disease. Early detection of melanoma increases the chances of survival.

The latest on UV damage from LED nail dryers

Recent research also suggests that LED UV nail polish dryers may alter skin cells on a molecular level, potentially leading to fingertip skin cancers. Reports of such cancers in people who use gel polishes led to the investigation.

Dermatologist Dr. Beth G. Goldstein, who was not involved in this research, said, however, that it “clearly documents damage to the cell lines that created extensive oxidative damage and results in cellular markers that are seen in skin cancers.”

While Dr. Goldstein said further epidemiological study is necessary to fully understand the risk of nail polish dryers, it might be a good idea to use them less often:

“Rare use a few times a year is likely not as concerning, perhaps, [as] use every two weeks, which is not uncommon.”

“There are alternative nail products, such as dip powder, or options that do not require UV light for curing, and would not cause skin damage as one may consider could happen with these devices,” said Dr. Goldstein.

In 2021, about 6.05 million tons of grapes were produced in the U.S. Grapes have been shown to have a positive role to play in “atherosclerosis, inflammation, cancer, gastrointestinal health, central nervous system effects, osteoarthritis, urinary bladder function, and vision,” according to the new study.

Lead author of the study, Dr. John Pezzuto, a professor and dean at Western New England University in Springfield, Massachusetts, explained his interest in studying grapes to Medical News Today.

“Many years ago, I published a seminal paper describing the potential of resveratrol to mediate anti-inflammatory activity and prevent skin cancer in model systems,” he recalled.

“In addition to relatively low quantities of resveratrol, grapes contain scores of additional phytochemicals, so it is reasonable to explore the health benefits of the grape as a whole food,” he added.

Studies of grapes’ role as a protectant against skin cancer date back a decade or more, with the first human trials conducted in 2021. The new study is an expansion and confirmation of this earlier work.

For the current study, 36 people were enrolled, 7 (19%) of whom dropped out, leaving 29 participants with full data. Thirteen were female, and 16 male — their ages ranged from 24 to 55.7 years.

The group was primarily white (21 people), with the remainder being Hispanic. The authors report that 25 participants had a type III , while the remainder had type II.

The trial began with a two-week restricted diet period. This was followed by a two-week study period during which individuals prepared and for two 36-gram packets of freeze-dried, ground-seeded, and seedless red, green, and black grapes each day. This is the equivalent of three servings of grapes (378gm in total).

The participants supplied researchers with fecal, urine, and blood samples at the end of the restricted diet period, the end of the grape-eating period, and one month afterward. The researchers also administered UV irradiation sensitivity tests at each of these times.

The resulting analysis found that nine participants exhibited reduced sensitivity to UV exposure at the end of the grape-eating period. For three of them, the effect was still present a month later.

The study’s findings were similar, but not the same, as the 2021 study. The authors speculate that differences in Fitzpatrick skin types are to account for and that people with lighter skin types may derive greater UV protection from grapes.

The researchers looked for differences in the samples of the people on whom grapes had no effect, the people who developed brief resistance to UV irradiation, and those who retained resistance longer. They hoped to explain why participants responded differently.

“People who demonstrated greater resistance to UV irradiation showed the most profound differences in their microbiome,” said Dr. Pezzuto.

The study says that the nine people who achieved UV resistance “were clearly distinguished from the remaining 20 volunteers through metabolomic analyses as well as microbiomic analyses.”

Dr. Pezzuto added that there was, for example, a perfect correlation between resistance to UV irradiation and a reduction in a urinary metabolite that indicates UV-induced skin damage.

While he noted that it is impossible to establish a cause-and-effect relationship with this study, “this strong correlation does seem to be more than a coincidence. Additional research would be of interest.”

Dr. Pezzuto cautioned that his study “is not to suggest people should be careless and avoid the use of sunscreens, for example.”

“The broader significance of this work, in my view, is the ability of human grape consumption to augment our cellular systems that defend us against free radicals and reactive oxygen species that can lead to adverse effects.”
— Dr. John Pezzuto