• Laura Chaparro, science journalist

    Vitamin D: should we take supplements?

    3 Mar

    The sun is the source of life. The ultraviolet rays that reach our skin, for example, help the body synthesize vitamin D. However, many people, probably because they do not spend enough time in the sun, have low levels of this substance and so consider taking vitamin supplements. Scientists are divided regarding supplements: yes or no? The debate goes on.


    Vitamin D affects the health of our skin without us even noticing. For example, when vitamin D levels are correct our immune system is strengthened and we run a lower risk of having acne. But this is not all; the sunlight that facilitates vitamin D production can reduce the symptoms of certain kinds of skin rash. This is also the case with eczema and psoriasis. A lack of vitamin D, on the other hand, is associated with a greater risk of cancer of the colon, breast and prostate and also with osteoporosis, diabetes and certain heart disorders.

    Sunlight, therefore, is the best way to increase vitamin D levels, although scientists recommend moderate exposure. It is considered healthy to sunbathe for 15 minutes three to four times a week. Higher doses could increase the risk of skin cancer.


    The sun is not the same for everyone
    Sunbathing is sometimes not enough, as where we live influences vitamin D synthesis. Many people in the Scandinavian countries, with few hours of weak sunshine annually, have vitamin D deficiencies. They are not the only ones, however, as 70% of Europeans also have low levels of this substance.

    What’s more, for people with very pale skin or freckles, not even sunlight will increase the vitamin D levels, as confirmed by researchers at the University of Leeds (UK).


    Generous servings of fish and dairy products

    Is vitamin D only synthesized by the sun? No, about 90% of this substance is produced with the help of the sunlight that falls on our skin, but the remaining 10% is obtained from our intake of certain foods.

    These include fatty fish like salmon, tuna and mackerel. Beef liver, cheese and egg yolk also contain vitamin D – although in smaller amounts – and also some fungi.


    Contradictory positions

    When neither sunlight nor diet ensure optimum levels of vitamin D, we take vitamin supplements. They are particularly recommended for vulnerable population groups such as children, pregnant or menopausal women and older people. However, there is no scientific consensus regarding the issue.

    The European Menopause and Andropause Society recommends that post-menopausal women take vitamin D supplements to improve their bone mineral density. The UK Department of Health also recommends these supplements for vulnerable groups.

    These recommendations are not shared, however, by the US Institute of Medicine. In a 2010 report, its experts claimed that vitamin D levels did not have to be as high as previously recommended because high doses could be harmful, especially for the heart and kidneys. In addition, vitamin D is liposoluble (that is, soluble in fatty substances) and so is stored in the body and not easily eliminated.

    Vitamin D is found in supplements in two forms: as D2 (ergocalciferol) and D3 (cholecalciferol). Both increase blood concentrations of vitamin D. Taking supplements in excessive quantities or over lengthy periods of time can cause nausea, vomiting and weight loss.


    Best practices

    Although the debate remains open and there is no consensus on the use of supplements, experts do agree on the importance of everybody checking their levels of vitamin D with their doctor.

    A balanced diet consisting of fatty fish (salmon, sardines), dairy products (milk, yoghurt) and eggs, in combination with sunbathing for 15 minutes three or four times a week, will help synthesize the vitamin D necessary for the body to function optimally and the skin to stay in good condition.



    Agencia SINC


    Office of Dietary Supplements (ODS-NIH)