Sun awareness campaigns have scared people away from sun exposure because of the risk of skin cancer. Still, it is essential to get enough vitamin D from the sun during the summer period, as long as we avoid getting sunburned. Vitamin D is vital for our immune defense, mood, bone health, cancer prevention, and many other things. A Swedish study has revealed that lack of sunshine is every bit as dangerous as smoking, and according to a British study, vitamin D inhibits cellular ageing. A Danish study has even shown that lack of vitamin D increases the risk of early death. The big questions are how much vitamin D do we get from sun exposure during the summer period, when do we need to take vitamin D supplements, and why should old people, dark-skinned individuals, and certain other population groups take vitamin D all year round?
From May to September, the sunlight in the Northern hemisphere is sufficiently powerful to enable us to synthesize vitamin D in our skin. This process involves a precursor of cholesterol and UVB-rays from the sun. The vitamin D that we produce is stored in the liver and converted into its active form in the kidneys and other places when the body needs vitamin D. However, the liver’s vitamin D stores are often depleted in the course of the winter, and some people are better than others to produce and utilize the vitamin. To be on the safe side, the Danish Veterinary and Food Administration has started recommending that all people take a vitamin D supplement during the period from October to April. And those who do not get enough sunshine or cover up their arms, legs, and face should take a supplement all year round.
It is commonly known that people with dark skin produce vitamin D at a slower rate than people with fair skin, which is why they need to take vitamin D all year round, at least if they live at northern latitudes. The same goes for older people who produce less vitamin D due to their thin skin and have trouble with activating the vitamin. Overweight individuals and people with diabetes also have this problem. Pregnant women should take the vitamin all year round due to their increased need for the nutrient. Children up to the age of four years and people with red hair and sensitive skin are generally advised to be careful with sun exposure and should therefore take a vitamin D supplement throughout the year.
Studies suggest that sun factor cream blocks the vitamin D synthesis. A good idea is therefore to get 15-30 minutes of unprotected sun exposure before applying sunscreen.
The official recommendation for vitamin D is 5-20 micrograms per day for the vulnerable groups, but the requirement for vitamin D varies from person to person. Many people may have an increased need for the nutrient. We humans are able to produce comparatively large quantities of vitamin D from sun exposure. Unlike the risk of overdosing with a vitamin D supplement, it is not possible to produce too much vitamin D from sunlight. The daily safe upper intake level for adults is 100 micrograms per day.
Vitamin D synthesis on a summer day
Lack of sun is just as dangerous as smoking
Swedish scientists have studied the sun exposure habits of nearly 30,000 women in the age group 25-64 years for a 20-year period. The comprehensive study showed that women who spent time in the sun had a lower risk of dying of cardiovascular disease and lived 0.6 to 2.1 years longer on average than women who did not spend time in the sun on a regular basis. In addition, the study showed that non-smoking women who avoided the sun had the same life expectancy as women who smoked and spent time in the sun. This indicates that it is every bit as harmful to avoid the sun as it is to smoke. The study is published in Journal of International Medicine.
Did you know that vitamin D is viewed as a hormone, which all cells in the body need?
Vitamin D inhibits ageing processes
Ageing processes are one of the main causes of atherosclerosis, dementia, cancer, and other life-threatening diseases. The length of telomeres in our cells are of huge importance. Telomeres are small protein structures that are placed at the end of cellular DNA strands and prevent fraying of the DNA, sort of like the protective plastic snips at the ends of shoelaces. Each time a cell divides, the telomeres are reduced in length. When there is no more left, the DNA dissolves and the cell dies. In a study where scientists measured concentrations of vitamin D in the blood of 2,160 women aged 18-79 years, they found that higher blood levels of vitamin D were linked to longer telomeres. The scientists therefore assume that vitamin D inhibits the ageing process. The study is published in American Journal of Clinical Nutrition.
Low vitamin D levels in the blood increase the risk of early death
Danish researchers from Herlev Hospital and the University of Copenhagen conducted a study of 96,000 people where they found a relation between low vitamin D levels in the blood and early death caused by cancer, cardiovascular disease, and other things. The study is published in British Medical Journal
Patients with normal skin cancer live longer
According to a Danish research project from Århus Hospital and Ålborg Sygehus, patients with normal skin cancer live longer. The study shows that patients who get normal skin cancer generally tend to stick with a healthy and sensible lifestyle and avoid smoking and being overweight. The healthy lifestyle also includes spending time in the sun, and although these people overdid it (after all, they got skin cancer), they had more vitamin D in their blood.
Vitamin D makes melanoma less aggressive
Too much sun, especially sunburns during the childhood period, may increase your risk of melanoma that can be very dangerous if it is not treated in time. A study from the University of Leeds in England, however, has revealed that vitamin D affects melanoma cells and causes them to be less aggressive. If you avoid the sun, you should make sure to get plenty of vitamin D by taking a supplement.
Blood levels of vitamin D
Your doctor can measure your vitamin D status. Blood levels of vitamin D are normally categorized as “deficiency” (less than 30 nmol/L), “insufficiency” (30-50 nmol/L), and “sufficiency” (above 50 nmol/L). Several leading experts believe that the optimal level lies in the range between 60 and 100 nmol/L. Many people reach optimal levels of vitamin D during the peak of summer and have the lowest levels in early spring.
Other of benefits of sun exposure
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Helene Sandström. Den optimala D-vitamindosen i vinter? Det beror på dina genar. Nordic Nutrition Council. Sep. 3 2020
Steen Ahrenkiel. D-vitamin behov og mangel i Danmark. Biokemisk forskning 2009
Lindquist PG, Epstein E, Nielsen K et al. Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the melanoma in Southern Sweden cohort. Journal of Internal Medicine. 2016
J Brent Richards et al. Higher serum vitamin D concentration are associated with longer leukocyte telomere length in women. American Journal of Clinical Nutrition 2007
Afzal Shoaib et al. Genetically low vitamin D concentration and increased mortality: mendelian randomization analysis in three large cohorts. British Medical Journal. 2014
Københavns Universitet. Det Sundhedsvidenskabelige Fakultet. Lave niveauer af D-vitamin øger dødeligheden. 2014
Peter Aagaard. Patienter med almindelig hudkræft lever længere. Dagens Medicin. 2020
Sathya Muralidhar et al. Vitamin D-VDR signaling inhibits Wnt/beta-catenin-mediated melanoma progression and promotes anti-tumor immunity. Cancer Research 2019
Jerk W langer. Politikens Store Lægebog. Politikens håndbøger.
5 Ways the Sun Impacts Your Mental and Physical Health | Tri-City Medical Center (tricitymed.org)
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