Vitamin D intake

VITAMIN D AND THE IMMUNE SYSTEM FUNCTION
Vitamin D has a crucial role in balancing the immune system. For example, vitamin D is a power supply for T cells. When an immune reaction occurs, a phagocytic cell traps the pathogen and presents it to a T cell, producing a VDR that reacts to vitamin D. The receptor binds vitamin D from the blood, awakening the T cell. As a result, helper T cells announce the intruder and killer T cells attempt to restrain the uninvited guest. Without vitamin D, the T cells never awaken from hibernation.

Vitamin D also regulates the genes determining whether a T lymphocyte becomes a killer, helper, or memory cell in the immune system. Vitamin D deficiency is a predisposing factor for autoimmune diseases such as MS, diabetes, psoriasis, intestinal inflammation, and arthritis. Additionally, those suffering from vitamin D deficiency are more likely to catch influenza and the common cold. Vitamin D deficiency also predisposes to silent inflammation linked to many chronic illnesses. On the other hand, a low vitamin D level may also be caused by chronic silent inflammation.

THE VITAMIN D INTAKE GUIDELINES AND ACTUAL NEEDS

In Finland, for example, the official recommended vitamin D intake for adults (18–74) is 10 micrograms (mcg) daily. Taking a separate vitamin D supplement is not recommended. For children between 2 weeks and 2 years, the recommended daily intake is 10 mcg (10 mcg per day from a supplement). From age 2 onwards, the recommended daily intake is 10 mcg (7.5 mcg per day from a supplement). For adults older than 75 years, it is recommended to take a 20 mcg vitamin D supplement throughout the year. For pregnant or breastfeeding women, it is recommended to take a 10 mcg vitamin D supplement daily throughout the year. The average intake of vitamin D from supplements is 18 mcg per day.

In the USA the Food and Nutrition Board (FNB) of the IOM sets the Recommended Dietary Allowance (RDA) based on the amount of vitamin D needed for bone health. Therefore preventing other diseases, such as cardiovascular disease, has not been considered. The recommended vitamin D intake for adults is 15 mcg per day, still 5 mcg more than, for example, in Finland.

The recent Finriski study by the Finnish National Institute for Health and Welfare investigated vitamin D intake in Finland (Rautio et al., 2017). In individuals who did not take dietary supplements containing vitamin D, the blood serum's 25(OH)D level in 2012 was on average 60 nmol/L. In those who took dietary supplements containing vitamin D, the level was average above 70 nmol/L.12 For bone health, the optimal level is above 80 nmol/L. However, the researchers drew the following conclusions: “Working-aged individuals do not require vitamin D supplements provided that they eat fish at least twice per week or regularly use dairy products or margarine spreads with added vitamin D.” Still, based on several study reviews, the optimal vitamin D level is closer to 125–150 nmol/L, particularly in the case of chronic illness. According to Professor of Nutrition from Harvard University, Dr. Edward Giovannucci, the blood serum vitamin D level has been around 125 nmol/L for most human evolution. These days, achieving this level without a vitamin D supplement can be challenging.

The vitamin D intake of Finnish children was compared to their blood levels in the PANIC (Physical Activity and Nutrition in Children) study published in 2016. The study found that the vitamin D intake of Finnish children aged 6–8 was very low: on average only 5.9 micrograms per day. Only 40.8 % took a vitamin D supplement. More than 80 % of the children failed to get the recommended 10 micrograms of vitamin D per day despite drinking milk with added vitamin D. Milk consumption covered almost one-half of the children’s vitamin D intake. One child in five had an S-D-25 level lower than 50 nmol/L, indicating a vitamin D deficiency (the international recommended reference range is 75–150 nmol/L).15 Similar results are seen in other European countries.

According to the American Institute of Medicine (IOM) recommendations, a sufficient vitamin D (calcidiol) level in the blood is 50 nmol/L. Further, IOM states that according to treatment studies, most (97.5 %) of populations in the northern areas achieve this level by taking a daily vitamin D supplement of 15 micrograms. Canadian statisticians have now proven the IOM calculations to be incorrect. Once the studies used by IOM were re-analyzed and the observed statistical error corrected, it became apparent that a daily vitamin D supplement of 15 micrograms is only proven to increase the calcidiol level of the population to the value of 27 nmol/L. The authors note that insufficient daily vitamin D intake guidelines have severe public health consequences and should be re-evaluated.

According to a study published in 2017, the low vitamin D intake guidelines in Finland may be based on an inaccurate statistical analysis. The committee responsible for establishing the Finnish nutritional guidelines is aware of this; however, the recommended intake for vitamin D has not been increased.17 It is therefore highly likely that the Finnish guidelines for vitamin D intake are not current. As recently as in the 1960s, the recommended vitamin D intake was 100 micrograms daily.