More than one billion people globally have reduced vitamin D concentrations, which has led to this problem being called the "pandemic" of hypovitaminosis D, with serious consequences for public health.
More than one billion people globally have reduced vitamin D concentrations, which has led to this problem being called the “pandemic” of hypovitaminosis D, with serious consequences for public health. Studies indicate that 40-50% of the population in our area has a vitamin D deficiency, with the lowest levels occurring during the winter months.
Vitamin D is an essential nutrient that plays a key role in maintaining the health of bones and muscles, the function of the immune system, and the functioning of numerous other organ systems. This vitamin is naturally produced in the skin when it is exposed to sunlight, but it can also be obtained through food and supplements. Given its importance and the frequent occurrence of deficiency, in the rest of this blog we will tell you how to recognize vitamin D deficiency and what to do about it.
The recommended daily dose at the level of the EU and the Republic of Croatia is 5 µg per day, which is 100% of the recommended daily intake (%PU). An intake of up to 100 µg per day is considered safe. Vitamin D occurs in only a few food sources, such as cod liver oils and other fatty fish, fish (tuna, sardines, mackerel, cod, herring, salmon), crustaceans and seafood, some types of mushrooms, yeast, beef liver and egg yolk, but also in foods that are additionally enriched with vitamin D, such as some milk and margarine spreads.
Considering that vitamin D is found in only a few food sources (and most of these foods do not contain vitamin D in large quantities), for most people vitamin D is primarily obtained through its production in the body due to exposure of the skin to the sun. However, many factors, such as time of day, season, latitude, altitude, clothing, sunscreen use, skin pigmentation, and age, affect the amount of UVB radiation from sunlight that reaches the skin and the efficiency of vitamin D production. Therefore, vitamin D deficiency is very common, especially in the elderly, those who are rarely exposed to the sun, but also during the winter when the sun’s rays are weaker and the possibility of vitamin D synthesis is lower.
The level of vitamin D in the body can be measured by drawing blood. The adequate concentration of vitamin D in the blood is 75-125 nmol/L.
If your vitamin D level is:
Even if they are regularly exposed to the sun, older people produce 75% less vitamin D3 through the skin than young people.
The use of sunscreens with a protection factor of 30 reduces the synthesis of vitamin D in the skin by more than 95%. Furthermore, dark-skinned people need to be exposed to the sun 3-5x longer to produce the same amount of vitamin D as fair-skinned people.
Symptoms of vitamin D deficiency include:
Vitamin D is necessary for the absorption of calcium and phosphorus from the intestines, which is essential for building and maintaining strong bones and teeth. Inadequate intake of vitamin D over a long period of time can lead to bone demineralization. A lack of vitamin D leads to reduced absorption of calcium and ultimately to the release of calcium from the bones to maintain its concentration in the circulation. Bone density may decrease and the risk of fractures increases, which ultimately leads to the development of osteomalacia and osteoporosis.
Vitamin D stimulates the creation of muscle proteins and prevents their breakdown. It supports the growth and repair of muscle fibers, which is essential for muscle growth and recovery after exercise. Studies have shown that adequate vitamin D levels are associated with improved muscle strength and physical performance. A lack of vitamin D can lead to muscle weakness and an increased risk of falls, especially in the elderly.
Clinical studies have come to the conclusion that vitamin D deficiency affects the occurrence of fatigue in adults as well as in children.
A 2019 study conducted on 480 older adults linked vitamin D deficiency with symptoms of fatigue.
Furthermore, the 2020 study conducted in 39 children linked low levels of vitamin D with poor sleep quality, shorter sleep duration and delayed bedtime, which can lead to increased fatigue.
In vitro studies have shown that 1,25-dihydroxyvitamin D, the active form of vitamin D, has an anti-inflammatory effect. Recent epidemiological evidence indicates a significant association between vitamin D deficiency and increased incidence or exacerbation of infectious diseases and inflammatory autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis. In addition, vitamin D deficiency is associated with an increased risk of SARS-CoV2 and other respiratory infections. Clinical trials generally show that correcting vitamin D deficiency reduces the risk of hospitalization, intensive care unit admission, and death caused by SARS-CoV2 infection.
Vitamin D plays a key role in skin functions that go beyond its role in synthesis and metabolism. Vitamin D affects the differentiation and proliferation of skin cells, has antimicrobial effects and significantly contributes to the immune function of the skin. Also, vitamin D plays an important role in the hair growth cycle, skin protection from photodamage, as well as in the wound healing process. Its role in the prevention and treatment of various skin diseases, including psoriasis, acne and vitiligo, makes it a key factor in dermatology. However, further research is needed to fully elucidate all the mechanisms of its action.
Vitamin D is complexly involved in various signaling pathways of hair follicle growth and differentiation. Review paper from 2021. concluded that most studies showed that lower serum vitamin D levels were associated with the incidence of non-scarring alopecias (types of alopecia that are mostly reversible), such as telogen effluvium, androgenetic alopecia, alopecia areata, and trichotillomania. Vitamin D deficiency is also associated with scarring alopecia.
As we wrote earlier, vitamin D is a very important factor in bone health and is associated with the prevention of osteoporosis. Given that women after entering menopause have an increased risk of developing osteoporosis, a sufficient intake of vitamin D is particularly important for them.
Study: Correlation of vitamin D status with bone mineral density in postmenopausal Croatian women
The research results indicate a connection between bone mineral density and vitamin D concentration, especially at the hip. In women with osteoporosis, the prevalence of severe vitamin D deficiency can be expected to be three times higher than in women with normal bone mineral density.
Furthermore, vitamin D intake is particularly important during pregnancy. One meta-analysis that took into account the results of 22 studies found that women with vitamin D deficiency have a higher risk of preeclampsia (preeclampsia is a serious condition in pregnancy characterized by high blood pressure and damage to organs, most often the liver and kidneys, and can threaten both mother and fetus). In addition, it is believed that vitamin D deficiency during pregnancy increases the risk of gestational diabetes (diabetes during pregnancy) and low birth weight of the child. Therefore, during pregnancy, it is especially important to pay attention to the levels of vitamin D in the body and prevent its deficiency.
Vitamin D can support male reproductive health. One study from 2021. came to the conclusion that supplementation with vitamin D can lead to an increase in testosterone levels in men (they took 83 µg of vitamin D per day for a year). In addition, one study linked the status of vitamin D in the body and the incidence and degree of erectile dysfunction in men. Therefore, to maintain men’s health, it is important to check vitamin D levels and keep them in the optimal range.
Severe vitamin D deficiency most often occurs in the elderly, people with darker skin, and those who live in areas with less sunlight, especially during the winter months. It is more common in women, especially in the postmenopausal age, due to the reduced ability to synthesize vitamin D in the skin and the increased need for calcium. Severe vitamin D deficiency is extremely dangerous because it can lead to serious health problems such as osteoporosis (a condition in which bones become brittle and break easily), increased risk of bone fractures, muscle weakness, and immune disorders. In children, it can cause rickets (a childhood bone disease caused by bone mineralization disorders), while in adults it increases the risk of chronic diseases such as cardiovascular diseases and diabetes.
In case of vitamin D deficiency, it is recommended to take the following steps:
Increase your intake of foods that are rich in vitamin D. These include fatty fish (such as salmon, mackerel, and tuna), fish oil, eggs (especially egg yolks), and fortified dairy products or plant-based beverages.
Spend time in the sun regularly, especially in the morning, when sunlight helps the body naturally produce vitamin D. It is recommended to be in the sun for at least 10-30 minutes several times a week.
If the intake of vitamin D through diet and sun exposure is not sufficient, it is necessary to consider the introduction of dietary supplements with vitamin D into the daily routine. Dietary supplements are especially useful during the winter months when there is less sunlight.
In case of severe vitamin D deficiency, it is necessary to react immediately and consult a general practitioner. The doctor will most likely recommend supplementation with a higher dose of vitamin D in order to quickly compensate for the deficit. Vitamin D should be taken with the largest meal of the day, as this improves its absorption. It is also recommended to take vitamin D with a drop of olive oil or another source of fat, since vitamin D is fat-soluble, which further increases its absorption and effectiveness.
Master of Nutrition from Zagreb, graduated from the Faculty of Food Technology and Biotechnology in Zagreb. In her work, her aim is to bring the idea of flexible, yet healthy and proper nutrition closer to people and to engage in scientific and research work. She has developed a particular interest in dietary supplements as extensions to proper nutrition and their additional contribution to health. Besides proper nutrition, Amanda also enjoys other aspects of a healthy lifestyle, particularly recreational volleyball and running!
Author's ArticlesAl-Shawwa, B., Ehsan, Z., Ingram, D.G. (2020). Vitamin D and sleep in children. Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine. 16(7). 1119–1123. Ao, T., Kikuta, J., Ishii, M. (2021). The Effects of Vitamin D on Immune System and Inflammatory Diseases. Biomolecules. 11(11). 1624. Bikle D.D. (2022). Vitamin D Regulation of Immune Function. Current osteoporosis reports. 20(3). 186–193. Crafa, A., Cannarella, R., Condorelli, R.A., La Vignera, S., Calogero, A. E. (2020). Is There an Association Between Vitamin D Deficiency and Erectile Dysfunction? A Systematic Review and Meta-Analysis. Nutrients. 12(5). 1411. Holick M.F. (2007). Vitamin D deficiency. The New England journal of medicine. 357(3). 266–281. Hu, K.L., Zhang, C.X., Chen, P., Zhang, D., Hunt, S. (2022). Vitamin D Levels in Early and Middle Pregnancy and Preeclampsia, a Systematic Review and Meta-Analysis. Nutrients. 14(5). 999. Kennel, K.A., Drake, M.T., Hurley, D.L. (2010). Vitamin D deficiency in adults: when to test and how to treat. Mayo Clinic proceedings. 85(8). 752–758.
Laktašić-Žerjavić, N., Rukavina, K., Babić-Naglić, D., Curković, B., Anić, B., Soldo-Juresa, D. (2013) Povezanost statusa vitamina D s mineralnom gustoćom kosti u hrvatskih žena u postmenopauzi. Reumatizam. 60(1). 8-13.
Mostafa, W.Z., Hegazy, R.A. (2015). Vitamin D and the skin: Focus on a complex relationship: A review. Journal of advanced research. 6(6). 793–804.
Pennisi, M., Malaguarnera, G., Di Bartolo, G., Lanza, G., Bella, R., Chisari, E. M., Cauli, O., Vicari, E., & Malaguarnera, M. (2019). Decrease in Serum Vitamin D Level of Older Patients with Fatigue. Nutrients. 11(10). 2531.
Pilz, S., Frisch, S., Koertke, H., Kuhn, J., Dreier, J., Obermayer-Pietsch, B., Wehr, E., Zittermann, A. (2011). Effect of vitamin D supplementation on testosterone levels in men. Hormone and metabolic research. 43(3). 223–225.
Płudowski, P., Kos-Kudła, B., Walczak, M., Fal, A., Zozulińska-Ziółkiewicz, D., Sieroszewski, P., Peregud-Pogorzelski, J., Lauterbach, R., Targowski, T., Lewiński, A., Spaczyński, R., Wielgoś, M., Pinkas, J., Jackowska, T., Helwich, E., Mazur, A., Ruchała, M., Zygmunt, A., Szalecki, M., Bossowski, A., … Misiorowski, W. (2023). Guidelines for Preventing and Treating Vitamin D Deficiency: A 2023 Update in Poland. Nutrients. 15(3). 695.
Sato, Y., Iwamoto, J., Kanoko, T., Satoh, K. (2005). Low-dose vitamin D prevents muscular atrophy and reduces falls and hip fractures in women after stroke: a randomized controlled trial. Cerebrovascular diseases (Basel, Switzerland). 20(3). 187–192
Rejnmark L. (2011). Effects of vitamin d on muscle function and performance: a review of evidence from randomized controlled trials. Therapeutic advances in chronic disease. 2(1). 25–37.
Saini, K., Mysore, V. (2021). Role of vitamin D in hair loss: A short review. Journal of cosmetic dermatology. 20(11). 3407–3414
Wei, S.Q., Qi, H.P., Luo, Z.C., Fraser, W.D. (2013). Maternal vitamin D status and adverse pregnancy outcomes: a systematic review and meta-analysis. The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians. 26(9). 889–899.
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