Vitamin D deficiency
Vitamin D deficiency has been a favorite topic of debate among researchers, as 1 billion people worldwide appear to be deficient in vitamin D, making it one of the most common nutritional deficiencies worldwide2. It is defined with levels < 25(OH)D<12ng/ml, while inadequacy is defined as 12 and 20ng/ml (30 - 50 nmol/L), with desirable levels being 25(OH)D > 20ng/ml (50 nmol/L)7. Although Greece is a country with more than 250 days of sunshine per year, the latest scientific data also look ominous for the Greek population. A recent study by Dimakopoulos et al. reported that 65% of Greeks are either deficient or insufficient in vitamin D2, data which are aligned with similar studies in other Mediterranean countries. But what is happening and the rates are so high? Many factors play a role, some of which are discussed below:
- The dark skin color. The presence of melanin in the skin is an inhibitor of vitamin D synthesis.
- The latitude of Greece.
- Working indoors.
- Environmental pollution.
- The limited time outdoors and the time we go out.
- The need to use sunscreen with an SPF > 30.
- The type of clothing.
- Limited dietary sources of vitamin D.
In addition, factors that have been associated with low vitamin D levels include excess body weight, age, sedentary lifestyle and smoking2,7.
For the reasons discussed above, vitamin D deficiency has become a global public health issue and supplementation by a doctor and/or dietician - nutritionist is becoming one of the most effective solutions for correcting low vitamin D levels. The dosage of the supplement depends on many factors, the most important being the index of stored vitamin D through blood testing, medical history and lifestyle factors. Although vitamin D is one of the vitamins stored in the body, adverse effects from overdosing appear to be extremely rare with dosages of up to 10000IU per day have been shown to be safe for the general population so far7.
Although, vitamin D supplementation is a health issue that concerns almost everyone, there are specific population groups, who are more prone to deficiency and these include:
- Elderly people
- People with a history of fractures and/or osteoporosis
- Postmenopausal women
- People with excess body weight
- People with malabsorption
Refers to people with Inflammatory Bowel Disease (IBD), chronic gastritis, bowel perforation and other clinical conditions of the gastrointestinal tract.
- People with kidney and liver disease
- People with dark skin
- People who are frequently ill
At last, we should not forget that spending 20-30 minutes a day in the sun - especially in the early morning or late afternoon - a balanced diet, the inclusion of physical activity and avoiding tobacco use are the foundations for maintaining and/or increasing vitamin D levels. This is a vitamin which is of paramount importance for our physical and mental health and regular monitoring of vitamin D levels enables us to work on any bad habits and to choose the right supplement for us with the helpful guidance of a health professional.
1Chiang, C. M., Ismaeel, A., Griffis, R. B., & Weems, S. (2017). Effects of vitamin D supplementation on muscle strength in athletes: a systematic review. The Journal of Strength & Conditioning Research, 31(2), 566-574.
2Dimakopoulos, I., Magriplis, E., Mitsopoulou, A. V., Karageorgou, D., Bakogianni, I., Micha, R., ... & Roma, E. (2019). Association of serum vitamin D status with dietary intake and sun exposure in adults. Clinical nutrition ESPEN, 34, 23-31.
3Gorter, E. A., Hamdy, N. A., Appelman-Dijkstra, N. M., & Schipper, I. B. (2014). The role of vitamin D in human fracture healing: a systematic review of the literature. Bone, 64, 288-297.
4Martineau, A. R., Jolliffe, D. A., Hooper, R. L., Greenberg, L., Aloia, J. F., Bergman, P., ... & Camargo, C. A. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. bmj, 356.
5Menon, V., Kar, S. K., Suthar, N., & Nebhinani, N. (2020). Vitamin D and depression: a critical appraisal of the evidence and future directions. Indian journal of psychological medicine, 42(1), 11-21.
6Pereira, M., Dantas Damascena, A., Galvão Azevedo, L. M., de Almeida Oliveira, T., & da Mota Santana, J. (2022). Vitamin D deficiency aggravates COVID-19: systematic review and meta-analysis. Critical reviews in food science and nutrition, 62(5), 1308-1316.
7Pludowski, P., Holick, M. F., Grant, W. B., Konstantynowicz, J., Mascarenhas, M. R., Haq, A., ... & Wimalawansa, S. J. (2018). Vitamin D supplementation guidelines. The Journal of steroid biochemistry and molecular biology, 175, 125-135.
Maria Kirmanidou, Dietitian & Sport Nutritionist
MSc in Sport Nutrition
Holland & Barrett Product Trainer