Vitamin D

In my previous post I wrote about vitamins that a healthy person gets sufficiently from food and that the vitamin jars recommended by pharmacies and sales reps are not necessary. In this regard, vitamin D is the only exception and I will explain more below.

Vitamin D is necessary for the calcium and to a lesser extent also for the iron, zinc and magnesium to absorb in the intestine. Vitamin D affects mainly the bone growth, development and strength (taken together with calcium), and reduces the risk of osteoporosis and easily fractured bones in older age. Rachitis used to be the result of vitamin D deficiency but today in modern societies the occurrence of this disease has reduced significantly especially thanks to the use of vitamin D.

Vitamins D3 or cholecalciferol and D2 or ergocalciferol are important for us.

The most important source of vitamin D3 is the UVB radiation from the sun, which in contact with skin initiates a sequence of reactions that result in active vitamin D3, first in the liver and then in the kidneys. By allowing the sun to shine at least on our arms and face at least two times a week for 10–15 minutes (without using sunscreen) we equip our body with sufficient amount of vitamin D3. If you then wish to continue staying in the sun it is recommended to protect your skin from the harmful influence of the UV-rays – wear covering clothing and use sunscreen. The vitamin D3 “reserves” gathered during the sunnier summer months run out a few months later and a weeklong exotic vacation in the middle of winter only provides a 1–1.5 month-long effect. From the aspect of vitamin D3 production, the positive effect of the sun is unavailable on our latitude from September-October to March, which is why in the mean time we can only rely on certain foods or take vitamin D supplements. Foods that provide vitamin D are fatty fish, eggs and dairy products enriched with vitamin D. Vitamin D2 is found in some mushrooms.

Considering the aforementioned it is recommended for the Nordic people, including people living Estonia where there is little sunlight during a 6-month period, to take vitamin D3 supplements. At the moment (April 2016), the recommendations below are valid, but these may change after a while.

It is recommended for the majority of the population (18–74-year-olds) to take 10 micro grams (μg) or 400IU (International Unit) from October to March if dairy products enriched with D vitamin and/or fish is not consumed daily during this period.

Pregnant people, nursing mothers and people under 18 and over 74 should take vitamin D3 supplements all year. It is recommended to give 10μg to children under 2 years and from then on 7.5μg until they are 18. Pregnant people and nursing mothers should take 10μg.

The largest daily dose is recommended for the people over 74 – 20μg or 800IU, because in older age people spend less time outside and the vitamin D3 production from sunlight is 70% lower compared to younger people.

Due to individual characteristics it’s sometimes more difficult to find the proper dose and the above guide might not help. That is why we have done blood analyses at our clinic to determine the vitamin D level and adjusted the “treatment” based on the results.

You must also take in to account that sometimes there are disruptions in the absorption of vitamin D (anorexia, celiac disease), in its production (liver and kidney diseases) or the problem is caused by side effects of some medicines (corticosteroid, epilepsy medicine) – again, individual analyses are necessary to determine possible solutions.

In conclusion I would like to add that there are people (especially among the sales reps of different vitamin manufacturers) who recommend taking a considerably larger dosage of vitamin D than mentioned above by reasoning that vitamin D helps to prevent many diseases. And indeed, there are studies that claim that vitamin D deficiency may increase the risk of cardiovascular diseases, depression, tumours, asthma, allergies, etc., but the credibility of these studies is low which is why scientific publications do not recommend high vitamin D dosages and the highest recommended dose for an adult is according to different sources 100 (-200)μg, that is 4000(-8000)IU. It is natural that these numbers will be adjusted if the studies carried out at the moment or in the future provide a basis.

I wish you strong bones and lots of health!

Ingmar Lindström | General Practitioner