A new study has found that regular consumption of dietary sources of vitamin A can reduce the risk for squamous cell carcinoma, the second most common type of skin cancer. This disease shows up as rough, thickened or wart-like skin, scaly red patches or open sores. It usually is related to past sun exposure but sometimes can arise on skin that hasn’t been exposed to sun. You can see what this type of skin cancer looks like on the website of the Skin Cancer Foundation.
Vitamin A plays a vital role in bone growth, reproduction and immune system health. It also helps the skin and mucous membranes repel bacteria and viruses more effectively. It is essential to healthy vision and may slow the decline of retinal function in people with retinitis pigmentosa.
The news that optimum vitamin A intake lowers the risk of one type of skin cancer comes from two studies involving 123,570 men and women. Researchers from Brown University first asked the participants about their hair color, the number of severe sunburns they had over time and any family history of skin cancer. They then followed the participants for more than 26 years. during which 3,978 of them developed squamous cell carcinoma. Results showed that those with the highest intake of vitamin A had a 17 percent reduced risk of the disease compared to those whose vitamin A intake was lowest.
Those whose vitamin A intake was highest reported eating an amount equivalent to that found in one medium baked sweet potato or two large carrots daily. Those whose daily vitamin A intake was lowest consumed an amount found in one-third cup of sweet potato fries or one small carrot. In both groups most of the vitamin A came from fruits and vegetables, rather than animal-based foods or dietary supplements. In addition to sweet potatoes and carrots, leafy green vegetables as well as apricots and cantaloupe are good sources. The vitamin also is found in milk, some kinds of fish and liver. The researchers further reported that consuming high levels of other plant-based pigments related to vitamin A – such as lycopene, found in tomatoes and watermelon – was associated with a reduced skin cancer risk.
Study leader Eunyoung Cho, an associate professor of dermatology and epidemiology, noted that the new study “provides another reason to eat lots of fruits and vegetables as part of a healthy diet.” She added that too much vitamin A, particularly from supplements and animal sources, can lead to nausea, liver toxicity, increased risk of osteoporosis and hip fracture, while side effects from high levels of plant-based vitamin A are minimal. Dr. Cho says she would next like to conduct a clinical trial to see if vitamin A in the form of supplements can help prevent squamous cell carcinoma.
Andrew Weil, M.D.
Learn more: Screening For Skin Cancer
Eunyoung Cho et al, “Association of Vitamin A Intake With Cutaneous Squamous Cell Carcinoma Risk in the United States,” JAMA Dermatology, July 31, 2019, doi: 10.1001/jamadermatol.2019.1937