While the NHS recommends taking this pill daily through the autumn and winter, too much of it could do more harm than good.
Vitamin D is an essential nutrient needed to regulate the amount of calcium and phosphate in the body. This helps to keep bones, teeth and muscles healthy and prevent conditions such as rickets.
The majority of vitamin D we need comes from exposure to UV rays found in sunlight. This does mean that during the autumn and winter Brits can be at risk of not getting enough vitamin D.
As a result many of us will take vitamin D supplements at this time of year with the NHS actually recommending supplementation between October and March for this reason. However, one expert revealed that you need to take care in the amount of vitamin D you consume – with an excess also causing “dangerous” health issues.
In the most recent Zoe Health podcast, Professor Tim Spector explained more. Responding to the question “can I do myself any harm” by taking too much vitamin D, he said: “So we didn’t think there was, but in the last 10 years there have been several trials.
“And in these trials, they’ve shown that the group that were having vitamin D, by injections or large amounts by mouth, had increased fractures and increased falls, and they weren’t expecting that result. So you can overdose on these and increasingly in clinics we’re seeing people who are self-medicating from the internet.
“You can get very high dose tablets from the internet. These are very dangerous because you do accumulate vitamin D in your body.
“It doesn’t just get peed out like some other B vitamins. And that can cause real problems: nerve problems, muscle problems, and because it’s called a vitamin people think it’s harmless.”
One study referenced by Prof Spector was published in the Journal of the American Medical Association (JAMA) in 2018. It analysed data from 62 trials around vitamin D dosage and falls.
It concluded: “Vitamin D supplementation interventions had mixed results, with a high dose being associated with higher rates of fall-related outcomes.” Another study from 2010, that was also published in JAMA, trialled the effect of taking 500,000 international units (IU) of vitamin D3 daily compared to a placebo.
This is far over the NHS recommendation of 400 IU to 2,000 IU a day. The study, of 2,892 people, found an “increased risk of falls and fractures” among those taking the vitamin D3.
As part of the podcast episode, Dr Federica Amati added that the amount of vitamin D we should be taking will vary depending on the person and their diet. She said: “It’s hard to even measure how much vitamin D we have in our bodies. So it’s not a simple answer.
“These recommended amounts to take as supplements excludes any exposure to sunlight and any food. So already these recommendations are aiming at helping people who have very little sunlight exposure and maybe don’t have the right foods in their diet to include vitamin D.”
The NHS says that 10 micrograms (400 IU) of vitamins D a day will be enough for most people. “Do not take more than 100 micrograms (4,000 IU) of vitamin D a day as it could be harmful,” it says.
The NHS adds: “Taking too many vitamin D supplements over a long period of time can cause too much calcium to build up in the body (hypercalcaemia). This can weaken the bones and damage the kidneys and the heart.”
