Too much sun exposure can cause skin cancers, but getting small amounts of sunlight on your skin for short periods may have some benefits beyond providing vitamin D. It appears that sunlight may help to reduce risk for heart attacks by:
• reducing blood cholesterol levels
• increasing tissue levels of nitric oxide to lower high blood pressure
• increasing ghrelin levels to help reduce inflammation
The problem is that nobody really knows how much sun exposure an individual can tolerate without increasing skin cancer risk.
Ultraviolet Rays from Sunlight May Lower Cholesterol
Cholesterol and vitamin D are made from the same chemical in the skin, called 7-dehydrocholesterol. Ultraviolet rays convert this precursor to vitamin D, leaving less to be converted to cholesterol, so cholesterol levels go down with sunlight exposure. That is why blood cholesterol levels are higher in the winter and lower in the summer, when there is more exposure to the sun’s rays (QJM, 2001 Mar;94(3):173-4). People being treated for a heart attack have lower levels of vitamin D than are found in people admitted to the hospital for other medical conditions (Int J Vitam Nutr Res, 2015;85(1-2):23-30).
• Low levels of vitamin D are associated with higher blood cholesterol levels in Iranian children and adults (J Health Popul Nutr, 2017, M10.1186/s41043-017-0096-y).
• Lack of sunlight exposure can cause vitamin D deficiency, an independent predictor of heart attack risk in older patients (QJM, 1996 Aug;89(8):579-89). Sunlight lowered both the good HDL cholesterol and bad LDL cholesterol (Arch Razi Inst, 2021 Oct 31;76(4):1069-1076).
• Vitamin D pills (cholecarciferol) increased total cholesterol and HDL cholesterol, while sunlight exposure significantly reduced total cholesterol, the bad LDL cholesterol and the good HDL cholesterol (Indian J Endocrinol Metab, 2017 May-Jun; 21(3): 393–398).
• Sunlight lowers total cholesterol and both the bad LDL and the good HDL cholesterol, while vitamin D pills raised total cholesterol, HDL and LDL (Photochem Photobiol Sci, 2017 Mar 16;16(3):374-380).
• People with high blood vitamin D levels are at reduced risk for high blood pressure, heart disease, and diabetes (Dis Markers, Oct 20, 2015;2015:580474).
• Skin contains significant stores of nitrogen oxides, which can be converted to nitric oxide by ultraviolet radiation. Human studies show that this can dilate arteries to lower high blood pressure and may also lower high blood sugar levels (Blood Purif (2016) 41 (1-3):130–134; Sci Rep, 2017; 7: 11105).
• People who had low exposure to sunlight had a much higher incidence of high blood pressure than those exposed to sunlight. High blood pressure is a major risk factor for heart attacks (Photobiol Sci, Feb 2021;20:285–292).
Lack of Sunlight Associated with Inflammation
• An overactive immune system (inflammation) is associated with increased risk for heart attacks and certain cancers. Vitamin D deficiency is strongly associated with higher C-reactive protein, a marker of inflammation (International Journal of Epidemiology, Feb 2023;52(1):260–271).
• Sunlight can cause your stomach and intestines to make more ghrelin, a hormone that helps to decrease inflammation and high blood pressure (Int J Endocrinol, May 25, 2020;2020:1385138), so it may help to reduce heart attack risk. However, ghrelin also can make you hungry so that you eat more and can gain excess weight (Nat Metab, Apr 2022;4:883–900), which would increase your risk for a heart attack.
• Ultraviolet ray exposure has been shown to help lower high blood pressure (J of the Amer Heart Assoc, Mar 3, 2020;9(5).
• Even though sunlight is a major risk factor for skin cancers, research has failed to show an increased all-cause death rate in skin cancer patients. Increased sun exposure, as recorded by the number of weeks spent on sun-bathing holidays, is associated with reduced death rate from all causes 25 years later (Cancer Epidemiol Biomarkers Prev 2011;20:683-690), even at the expense of increased melanoma (Cancer Epidemiol Biomarkers Prev 2010;19:111-120).
• Skin cancers can be used as an indicator of lifetime sun exposure. A case-control study of 4.4 million Danish patients over the age of 40 showed that non-melanoma skin cancer patients had the same all-cause death rate as age- and sex-matched healthy people (Int J Epidemiol 2013;42:1486-1496; Int J Epidemiol 2014;43:1991).
My Recommendations
A little sun exposure may have health benefits, but we do know that too much sun exposure can cause skin cancers. Never expose your skin to so much sunlight that it damages the DNA to increase cancer risk. All of the symptoms of sunburn — redness, burning, itching, or pain — are evidence that DNA may have been been damaged. Also, trying to get a dark tan from sun exposure may be asking for trouble. Read my report on protecting yourself from skin cancer.
