New research from the BfR Federal Institute for Risk Assessment found that if adults and children 11 years of age and older consume a daily quantity of no more than 100 μg of vitamin D, any impairments to health are unlikely.

This tolerable upper intake level, or UL value, includes the intake of vitamin D from all sources, including supplements, normal dietary intake, and intake from food that has been fortified with vitamin D. If high-dose vitamin D preparations are also consumed, this figure may be exceeded in combination with other sources of the vitamin, according to the study authors.

Vitamin D is formed in the skin following its exposure to sunlight in comparison to the body’s own formation of vitamin D. Dietary consumption generally makes up only a relatively small proportion of the vitamin D supply to the body. An overdose resulting from the body’s own production is not possible, but it can certainly result from the consumption of high doses of vitamin D, such as certain food supplements, according to the study.

This kind of overdose can lead to an elevated calcium value in the blood serum, or hypercalcemia. The clinical symptoms associated with hypercalcemia in humans range from fatigue and muscular weakness to vomiting and constipation and can even lead to cardiac arrhythmias and the calcification of blood vessels. Further, hypercalcemia can lead to kidney stones, kidney calcification, and ultimately, a loss of renal function, according to the study authors.

A daily consumption of 20 μg of vitamin D is adequate to meet the body’s needs for the vast majority of the population. Additionally, the daily consumption of vitamin D preparations containing a 50 μg or 100 μg dose is not necessary.

However, the researchers said it is unlikely that impairments to health will result from the occasional consumption of such high-dose preparations. If such high-dose vitamin D products are consumed on a daily basis over a longer period of time, the latest research does point to an elevated risk to health.

The BfR notes that given an adequate length of time spent outdoors with corresponding exposure of the skin to sunlight, plus a balanced diet, an adequate supply of vitamin D can be achieved by individuals without having to take vitamin D preparations. Further, individuals in risk groups for which a serious lack of vitamin D or a vitamin deficiency requiring medical intervention may be more likely to occur, should first clarify any need to take such preparations with their attending physician or general practitioner.

Vitamin D: consumption of high-dose food supplements is unnecessary. EurekAlert! Published October 20, 2020. Accessed October 22, 2020.