How much vitamin D do you need and what affects vitamin D level in the body?

Do you know what is the right dose of vitamin D for you? Recommendations for vitamin D supplementation can vary depending on several factors, including genetics, age, skin color, overall health, medication or area where you live. In this article, we'll take a closer look at some of the variables that affect the concentration of vitamin D in the body, so you can get an idea of how much vitamin D you need.

Article at a glanc:

1. A vitamin D deficiency pandemic?
2. The "sunshine vitamin" and its effect on our health
3. Which factors can affect the vitamin D level?
4. How to find out if you are vitamin D deficient?
5. What is the ideal vitamin D status?
6. How much vitamin D should you supplement?
7. Závěr

A vitamin D deficiency pandemic?

Vitamin D deficiency is widespread worldwide and also the European population is deficient to an alarming extent. A large analysis of 14 European population studies in 2016 revealed that more than 40% of Europeans are vitamin D deficient (serum 25(OH) vitamin D levels below 50 nmol/l) and 13% of Europeans are severely deficient (25(OH) vitamin D levels below 30 nmol/l) [1].

In 2018, the Czech National Institute of Health published an analysis including 398 blood serum samples, which examined not only the body's supply of vitamin D (through measurement of the 25(OH)D metabolite in blood serum). The results of this analysis showed that 68% of the czech population had insufficient levels (25(OH)D levels below 75 nmol/l), while only 32% of people had normal vitamin D levels (values above 75 nmol/l). Logically, the lowest levels were measured in winter, specifically in March. [2]

The "sunshine vitamin" and its effect on our health

Vitamin D plays a key role in maintaining our health. This so-called "sunshine vitamin" influences cell proliferation and differentiation, thereby promoting optimal cell function throughout the body, supporting the immune system and, last but not least, maintaining healthy bones and teeth by regulating calcium metabolism. 

On the other hand, vitamin D deficiency is associated with an increased risk of a number of diseases, including respiratory infections, cardiovascular disease, osteoporosis, neuro-psychiatric disorders and autoimmune diseases (such as multiple sclerosis, type 1 diabetes, rheumatoid arthritis, psoriasis and others) [3] [4].

Which factors can affect the vitamin D level?

As already mentioned, a number of factors affect the level of vitamin D in the body. Recommendations for vitamin D supplementation may vary depending on these variables.

• Genetics

Genes involved in vitamin D metabolism also affect the serum vitamin D levels. Genetic variants affect how much vitamin D we need. Thus, the same dose of vitamin D will lead to a different response in each individual. 

• Age 

Older people have a reduced capacity of the skin to synthesize vitamin D. A recent study in 2020 [5] calculated that vitamin D production in the skin decreases by 13% for every decade of life after age 25. Older people also spend more time indoors and have less exposure to sunlight, which is the most important source of vitamin D.

• Skin color

People with darker skin are more likely to be vitamin D deficient due to the higher amount of melanin in their skin. Melanin is the pigment that determines skin color and protects the skin from the sun's UV radiation. For these individuals, a longer period of exposure to sunlight is then needed for sufficient vitamin D synthesis.

• Body weight

Body weight is another factor affecting vitamin D requirements. In general, higher body fat is associated with lower vitamin D levels. Thus, obese people may need a higher intake of vitamin D to achieve similar 25(OH)D levels compared to people with normal weight. [6]

Overweight and obese people are generally at higher risk for common diseases, so vitamin D dosing should also be dependent on BMI to ensure that these individuals get the necessary amount of vitamin D to promote health. [7] The Endocrine Society recommends increasing the dose of vitamin D supplements by 2 to 3 times in obese patients.

• Latitude of residence

Countries near the equator have enough sunlight throughout the year. Conversely, people living further from the equator have less sunlight, which also contributes to lower vitamin D levels in the body. In our geographical conditions, it is important to ensure adequate vitamin D intake through high quality supplementation, especially during the winter.

• Certain health issues

Vitamin D is a fat-soluble vitamin and the ability of the intestines to absorb fats from the diet is important for its absorption. Malabsorption of fats is associated with health problems, including some forms of liver disease, cystic fibrosis, celiac disease, Crohn's disease and ulcerative colitis. Inflammatory bowel disease also contributes to vitamin D deficiency.

• Pregnancy, breastfeeding & infants

The vitamin D content in breast milk is closely related to the vitamin D status of the mother. Thus, breast milk consumption alone may not be sufficient to meet the vitamin D needs of breastfed children. A study investigating maternal vitamin D status and its effect on breast milk vitamin D content concluded that vitamin D deficiency is widespread during pregnancy and breastfeeding and may increase the likelihood of vitamin D deficiency in breastfed infants who are not sufficiently exposed to sunlight and do not receive vitamin D supplements. [8] Studies also suggest that breast milk from mothers who take daily supplements containing at least 2,000 IU of vitamin D3 has higher levels of this vitamin. 

Vitamin D supplementation in pregnancy has been shown to help reduce the risk of pre-eclampsia by 60%, the incidence of gestational diabetes by 50% and preterm birth by 40%. Prenatal screening of 25(OH)D levels to detect women with vitamin D deficiency and follow-up may thus be an effective way to reduce these pregnancy risks. [9]

• Magnesium

Various steps in the vitamin D metabolism pathway depend, for example, on magnesium as a cofactor. In the case of magnesium deficiency, vitamin D activation is reduced. The combined effects of magnesium and vitamin D deficiency can lead to increased health risks such as bone fractures.

In conclusion, there are certain groups of people who need more vitamin D than others. These include, for example, the elderly, people with dark skin, obese individuals, people who avoid the sun in the summer, people living further from the equator and, last but not least, those who suffer from certain health conditions such as liver or kidney disease, malabsorption syndromes or inflammatory bowel disease.

How to find out if you are vitamin D deficient?

Testing for 25-hydroxyvitamin D or 25(OH)D from the blood is generally considered the best indicator for assessing vitamin D status in the body. In Czech laboratories, the normal range for 25(OH)D is 75 nmol/l - 250 nmol/l. Levels below 75 nmol/l are considered insufficient and levels below 50 nmol/l indicate a severe vitamin D deficiency. 

At Trime, we now offer the opportunity to take a simple quiz. Answering a few questions will help you identify if you are vitamin D deficient.

What is the ideal vitamin D status?

International guidelines vary in their recommendations for adequate vitamin D status and unfortunately there is currently no consensus on what are the optimal concentrations of circulating 25(OH)D. In an extensive research study focusing on the immunological effects of vitamin D, the authors concluded that although the optimal level of vitamin D remains unclear, it is advisable from a health perspective to maintain serum 25(OH)D levels between 100 and 150 nmol/l. [10]

Jakub Pribyl, author of Trime recipes and a long-time consultant for personalized nutrition, agrees. 

"The reference limits for 25-hydroxyvitamin D vary from one laboratory to another, so many people with a mild 25(OH)D deficiency can be classified as compliant by a doctor and yet already be in a deficiency state according to the latest criteria. Similarly, recommendations from different professional societies and health organizations regarding vitamin D supplementation vary. The range for reference intake of vitamin D from diet or supplementation is between 400 - 5 000 IU/day. 

From my own experience, I consider optimal values of 25(OH)D measured in serum to be between 100 nmol/l - 150 nmol/l, which few people achieve in domestic conditions without supplementation. Therefore, I find it useful to measure the 25(OH)D level at least 2 times a year. E.g. at the beginning of the "sun" season at the end of April/May and then sometime during November, when the "summer" vitamin D reserves are already depleted. This gives everyone a better idea of where they really stand with their vitamin D metabolism and whether or not they are getting enough from diet and sun." says Jakub Pribyl.

How much vitamin D should you supplement?

Current recommendations from the European Food Safety Authority (EFSA) state 600 IU per day as a preventive daily dose of vitamin D for adults. [11] This recommended dose may be sufficient to prevent rickets. However, vitamin D is also important in other areas of health and immunity, so many experts agree that this dose is insufficient and it would be advisable to re-evaluate the current recommendation.

There is no consensus among different organizations on the tolerable upper intake level (UL) for vitamin D supplementation. While the Endocrine Society states UL for adults of 10 000 IU, EFSA recommends not to exceed 4000 IU/day. [12] [13]

The table below shows the recommended dosage for vitamin D intake for Individuals at risk for vitamin D deficiency by the Endocrine Society Guidelines

Conclusion

Vitamin D sufficiency is crucial for maintaining our overall health, yet the majority of our population is deficient. Appropriate recommendations for vitamin D intake depend on individual health status, body weight, latitude of residence, or dietary and cultural practices. In our geographic conditions, sun exposure and dietary intake of vitamin D alone are insufficient to maintain optimal vitamin D concentrations throughout the year. Therefore, supplementation is often necessary to achieve optimal vitamin D status. Adverse effects associated with vitamin D supplementation, such as hypercalcemia, are rare and usually result from long-term use of extremely high doses, exceeding tens of thousands of IU per day.

Sources:

[1] Cashman KD, Dowling KG, Škrabáková Z, Gonzalez-Gross M, Valtueña J, De Henauw S, Moreno L, Damsgaard CT, Michaelsen KF, Mølgaard C, Jorde R, Grimnes G, Moschonis G, Mavrogianni C, Manios Y, Thamm M, Mensink GB, Rabenberg M, Busch MA, Cox L, Meadows S, Goldberg G, Prentice A, Dekker JM, Nijpels G, Pilz S, Swart KM, van Schoor NM, Lips P, Eiriksdottir G, Gudnason V, Cotch MF, Koskinen S, Lamberg-Allardt C, Durazo-Arvizu RA, Sempos CT, Kiely M. Vitamin D deficiency in Europe: pandemic? Am J Clin Nutr. 2016 Apr;103(4):1033-44. doi: 10.3945/ajcn.115.120873. Epub 2016 Feb 10. PMID: 26864360; PMCID: PMC5527850.

[2] https://szu.cz/wp-content/uploads/2022/12/Odborna_HBM_2018.pdf

[3] Wang H, Chen W, Li D, Yin X, Zhang X, Olsen N, Zheng SG. Vitamin D and Chronic Diseases. Aging Dis. 2017 May 2;8(3):346-353. doi: 10.14336/AD.2016.1021. PMID: 28580189; PMCID: PMC5440113.

[4] Charoenngam N, Holick MF. Immunologic Effects of Vitamin D on Human Health and Disease. Nutrients. 2020 Jul 15;12(7):2097. doi: 10.3390/nu12072097. PMID: 32679784; PMCID: PMC7400911.

[5] Chalcraft JR, Cardinal LM, Wechsler PJ, Hollis BW, Gerow KG, Alexander BM, Keith JF, Larson-Meyer DE. Vitamin D Synthesis Following a Single Bout of Sun Exposure in Older and Younger Men and Women. Nutrients. 2020 Jul 27;12(8):2237. doi: 10.3390/nu12082237. PMID: 32727044; PMCID: PMC7468901.

[6] Žmitek K, Hribar M, Hristov H, Pravst I. Efficiency of Vitamin D Supplementation in Healthy Adults is Associated with Body Mass Index and Baseline Serum 25-Hydroxyvitamin D Level. Nutrients. 2020 Apr 29;12(5):1268. doi: 10.3390/nu12051268. PMID: 32365732; PMCID: PMC7284348.

[7] Sadat-Ali M, AlTabash KW, Al-Turki HA, AlMousa SA, AlSayed HN. Time out: should vitamin D dosing be based on patient's body mass index (BMI): a prospective controlled study. J Nutr Sci. 2021 Dec 13;10:e106. doi: 10.1017/jns.2021.100. PMID: 35059187; PMCID: PMC8727721.

[8] Dawodu A, Tsang RC. Maternal vitamin D status: effect on milk vitamin D content and vitamin D status of breastfeeding infants. Adv Nutr. 2012 May 1;3(3):353-61. doi: 10.3945/an.111.000950. PMID: 22585912; PMCID: PMC3649470.

[9] Maryam Rostami and others, Effectiveness of Prenatal Vitamin D Deficiency Screening and Treatment Program: A Stratified Randomized Field Trial, The Journal of Clinical Endocrinology & Metabolism, Volume 103, Issue 8, August 2018, Pages 2936–2948,

[10] Charoenngam N, Holick MF. Immunologic Effects of Vitamin D on Human Health and Disease. Nutrients. 2020 Jul 15;12(7):2097. doi: 10.3390/nu12072097. PMID: 32679784; PMCID: PMC7400911.

[11] https://www.efsa.europa.eu/en/press/news/161028

[12] Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2011;96:1911–30.

[13] Amrein, K., Scherkl, M., Hoffmann, M. et al. Vitamin D deficiency 2.0: an update on the current status worldwide. Eur J Clin Nutr 74, 1498–1513 (2020).