Demand for vitamin D. Proper supplementation

Numerous scientific studies have shown that even a balanced and varied diet is not able to provide the total daily dose of vitamin D (up to 20%), because the main source of vitamin D for the body is skin synthesis, which occurs with the participation of UV radiation (290-320 nm ). However, in areas above 33° latitude (all of Europe), due to the angle of incidence of sunlight, this synthesis is most efficient in the spring and summer period from 10:00 to 15:00, and in the winter months it is practically impossible [1]. In addition, many factors, such as cloud cover or air pollution, the use of sunscreens, high degree of skin pigmentation, advanced age, inactivity during the hours of the highest availability of sunlight, additionally inhibit the synthesis of vitamin D. As a result, vitamin D deficiency is common, both in Poland (about 90% of adults, children and adolescents) [2] and around the world [3]. Therefore, appropriate and well-chosen supplementation may become crucial in ensuring the correct level of vitamin D.  

VITAMIN D REQUIREMENT

In 2018, the Polish Team of Experts, in cooperation with the European Society of Vitamin D – EVIDAS, developed current guidelines for supplementation and treatment with vitamin D. The start of supplementation should be preceded by an assessment of the body’s supply of vitamin D, most often by determining the concentration of the liver metabolite – calcifediol, i.e. 25(OH )D3 in blood serum [4]. According to the guidelines for Central Europe, it was assumed that the body’s supply of vitamin D is suboptimal at the concentration of 25(OH)D3 of 20-30 ng/ml (50-75 nmol/l).  

Vitamin D level	Calcidiol concentration
	ng/ml	nmol/l
Severve deficiency
Deficiency	< 20	< 50
Suboptimally	20–30	50–75
Optimal	30–50	75–125
High	50–100	125–250
Toxic	>100	>250

Tabel 1. Vitamin D requirement [2]   To ensure the pleiotropic effect, it was considered to maintain the concentration at the level of 30-50 ng/ml (75-125 nmol/l). Higher concentrations in blood serum (>100 ng/ml, i.e. >250 nmol/l) may indicate improper supplementation and is an indication for absolute discontinuation of the treatment (Table 1) [2].

RECOMMENDATIONS FOR SUPPLEMENTATION WITH VITAMIN D IN THE GENERAL POPULATION

Selection of the dose in individual age groups also depends on body weight, degree of insolation (season of the year), lifestyle and eating habits, which is why it should be determined individually for each patient, and the guidelines only include intervals in which vitamin D should be dosed, and not strictly defined doses (Table 2).  

NEWBORNS AND INFANTS
born <32 weeks of gestation	800 IU/day day from the first days of life, regardless of the method of feeding
born between 33-36 weeks of gestation	400 IU/day from the first days of life regardless of the method of feeding
0–6 months	400 IU/day from the first days of life regardless of the method of feeding
6–12 months	400–600 IU/day depending on the daily amount of vitamin D taken with food
CHILDREN (1–10 YEARS)*	if adequate solar exposure is not met, 600–1000 IU/day**
YOUTH (11–18 YEARS)*	if adequate solar exposure is not met, 800–2000 IU/day**
ADULTS (19–65 YEARS)*	if adequate solar exposure is not met, 800–2000 IU/day**
SENIORS (>65–75 LAT), PEOPLE WITH DARK SKIN	800–2000 IU/day**
SENIORZY (>75 LAT)	2000–4000  IU/day**
WOMEN DURING PREGNANCY AND LACTATING
during the procreation period and planning a pregnancy	if adequate solar exposure is not met, 800–2000 IU/day**
during pregnancy	25(OH)D control and maintenance of the concentration > 30-50 ng/ml, Without 25(OH)D control – 2000 IU/day, throughout pregnancy and lactation

Table 2. Vitamin D supplementation in the general population and in groups at risk of vitamin D deficiency [2]   *in healthy children staying in the sun with uncovered forearms and lower legs for at least 15 minutes from 10.00 to 15.00 without sunblock in the period from May to September, supplementation is not necessary, although it is still recommended and safe **depending on body weight and vitamin D supply in the diet, throughout the year [2]. A special risk group are people with obesity who require a double dose of vitamin D compared to the dose recommended for peers with a normal body weight [2].

WHAT DOSAGE OF VITAMIN D IS SAFE?

The upper acceptable daily doses of vitamin D for a healthy population are:

• neonates and infants: 1000 IU/day
• children aged 1-10 years: 2000 IU/day
• adolescents aged 11-18 years: 4000 IU/day
• adults and seniors: 4000 IU/day.

It should be emphasized that the upper acceptable daily doses should not be confused with the doses recommended in the treatment of vitamin D deficiency and should not be exceeded without medical supervision [2].

DIETARY SUPPLEMENTS AND MEDICINAL PREPARATIONS CONTAINING VITAMIN D AND ITS ANALOGUES

Cholecalciferol (D3) is most often used in the supplementation and treatment of vitamin D deficiency in Poland and Europe, unlike the American market, where ergocalciferol (D2) is also popular. In Poland, vitamin D may be available in:

• dietary supplements in doses of 400-2000 IU (in accordance with Resolution No. 4/2019) [5],
• over-the-counter (OTC) medicinal products – up to 4000 IU,
• medicinal products subject to medical prescription (Rx) – 7,000, 10,000, 2,000, 25,000, 30,000 IU [6].

Preparations containing vitamin D present on the market are available in the form of tablets, capsules, drops, and aerosols or twist-off capsules are convenient for children. In patients with disorders of hepatic metabolism of vitamin D, accompanying chronic liver diseases, cholestasis, chronic treatment with glucocorticoids or anticonvulsants, calcifediol – 25(OH)D3 is used [2, 7]. In the case of vitamin D renal metabolism disorders and diseases with reduced 1α-hydroxylase activity, such as renal failure, nephrotic syndrome, chronic kidney disease, hypophosphatemic rickets and other vitamin D-resistant rickets, and in hypoparathyroidism, active vitamin D metabolites and analogues are used such as alfacalcidol (1αOHD3), calcitriol (1α,25(OH)2D3), paricalcitol (19nor1α,25(OH)2D2) [2].  

VITAMIN D SUPPLEMENTATION IN THE ERA OF COVID-19

More and more scientific data shows that ensuring an adequate level of vitamin D improves the body’s immunity, moreover, by modulating the immune response, vitamin D can mitigate the course of COVID-19 and prevent the occurrence of acute respiratory distress syndrome (ARDS) [8]. Currently, there is no scientific consensus on the optimal dose of vitamin D supplementation in the case of COVID-19, however, it is assumed that the concentration of 25(OH)D3 in the blood should be at least 40-50 ng/ml. In the case of confirmation of vitamin D deficiency, some experts recommend supplementation to obtain the optimal concentration with doses of 2000-4000 IU/day, and in the case of severe deficiencies, consideration of periodic intake under medical supervision in order to quickly eliminate the vitamin D deficit. This is especially important in adults in high-risk groups (people over 70 years of age, patients with diabetes, cardiovascular diseases, obese) [9].    

Piśmiennictwo

1. Hossein-Nezhad A, Holick MF. Mayo Clin. Proc. 2013;88:720–755.
2. Rusińska A, Płudowski P, Walczak M, Boroszewska-Kornacka M, Bossowski A i wsp. Pediatria, nr 4 tom 15, 2018.
3. Palacios C, Gonzalez L. J Steroid Biochem Mol Biol. 2014;144 Pt A:138‐145.
4. Marcinowska-Suchowierska E, Sawicka A. Postępy Nauk Medycznych. 2012;XXV:273-279.
5. Uchwała nr 4/2019 Zespołu do Spraw Suplementów Diety w sprawie wyrażenia opinii dotyczącej maksymalnej dawki witaminy D w zalecanej dziennej porcji w suplementach diety. 22.05.2019
6. https://pub.rejestrymedyczne.csioz.gov.pl/
7. Płudowski P, Karczmarewicz E, Bayer M, Carter G, Chlebna-Sokół D i wsp. Endokrynol Pol 2013;64:319–327
8. Aygun H. Naunyn Schmiedebergs Arch Pharmacol. 2020;393:1157-1160.
9. Grant WB, Lahore H, McDonnell SL, Baggerly CA, French CB i wsp. Nutrients. 2020;2;12:988.

 

Biographical note

Marlena Dudek-Makuch has 20 years of experience in phytochemical and biological research and scientific information (assistant professor at the Department of Pharmacognosy, Poznań University of Medical Sciences). She authored experimental and review papers on isolation and identification of compounds of plant origin and evaluation of their biological activity. Since 2015 she has been teaching postgraduate courses “Herbs in Practice and Therapy”. She currently works at CHC in the Regulatory Affairs Department of the R&D Division. She is responsible, among others, for preparing Expert Reports (clinical report, non-clinical report) for medicinal products, clinical report for changes in the availability category of a medicinal product (switch OTC), clinical assessment for medical devices and conducting activities in the area of safety supervision of medical devices, as well as safety assessment of plant raw materials used in medicinal products, medical devices and dietary supplements. She is a member of the Polish Herbal Committee.