A high daily dose of vitamin D may reduce your risk of being admitted to hospital. But the results are based on a relatively short study, and the researchers can鈥檛 be certain that the supplements were responsible.
Vitamin D is naturally made in the skin during exposure to sunlight and is found in some foods, such as egg yolks and oily fish. The compound is important for building healthy bones and helping the immune system ward off infections. Some studies have also linked it to a reduced risk of autoimmune conditions, such as rheumatoid arthritis and psoriasis.
Health organisations such as the UK鈥檚 national health services recommend that adults take 10 micrograms, or 400 international units (IU), of vitamin D every day, while the National Institutes of Health in the US advises that most adults take 600 IU, with both bodies cautioning against taking more than 4000 IU per day. Taking too much vitamin D can cause a harmful build-up of calcium in the blood, leading to symptoms such as nausea and kidney stones.
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But at the University of Pennsylvania and his colleagues recently found that a daily dose of 5000 IU may . They wondered whether this higher-than-recommended dosage may also lower other risks, such as that of being hospitalised.
To explore this idea, the team asked 196 adults to take 5000 IU of vitamin D3, the form of the compound that animals make, every day for around nine months. The adults, aged 47 on average, were aware of the vitamin D dose they were taking. As vitamin D takes a while to build up in the blood, the team analysed data on each participant鈥檚 healthcare visits from two months after the first dose until the end of the study period.
The researchers also analysed the data of more than 1900 people who weren鈥檛 given the 5000 IU daily dose of vitamin D or any other pill, such as a placebo tablet. However, they were free to take vitamin D supplements if they wished. Given vitamin D鈥檚 potential benefits, 鈥渋t wouldn鈥檛 be ethical to tell people not to take any supplement鈥�, says LaRiccia.
Towards the end of the study, around a fifth of the participants in the control group responded to a survey that asked about any vitamin D use, with 311 saying they had been taking a supplement. Across this group, the average reported dose was 1318 IU and the average age was 50.
Over the 10-month study, those who were given the 5000 IU dose had a lower risk of being hospitalised due to any cause, and had to visit the emergency room or be admitted to intensive care less often compared with those in the other group.
However, LaRiccia says the team can鈥檛 rule out the marginal age difference as a possible cause of these results, with those in the high-dose group potentially avoiding hospital because they were on average three years younger.
The ethnicities of people in the two groups also differed, with fewer Hispanic and Latino people in the high-dose group, which may have affected the results, he says. There were no substantial differences in their underlying health at the start of the study, however.
While the findings are promising, the study was relatively small, says at Harvard University. It also didn鈥檛 account for the placebo effect, she says. This can occur when a person鈥檚 symptoms lessen after taking something that they believe to be an effective treatment.
While none of the participants reported experiencing any side effects, the study period was too short to monitor any long-term safety issues of such a high daily dose of vitamin D, says Manson. 鈥淎ssessing long-term safety can take several years and [requires] large study populations,鈥� she says.
medRxiv
