Experts issue shocking warning about popular vitamin supplement: 'It could be making your levels LOWER'

People who take a certain form of vitamin D may actually be depleting their natural stores of the essential vitamin, worrying new research has found.

It is currently estimated that around one in six adults in the UK do not get enough vitamin D, with NHS guidelines recommending supplementing the vitamin in the winter months when there is less sunlight.

Scientists found that vitamin D3—which is produced by the body in response to sunlight and found in animal-based foods such as oily fish, egg yolks and liver—is the most efficiently absorbed to boost overall vitamin D levels.

However, millions of people could be taking plant-based vitamin D2—the most common form which is added to fortified foods as it's cheaper to produce—which the researchers found actually decreases levels of vitamin D3 in the body.

Low vitamin D3 levels heighten the risk of bone disorders such as osteoporosis as it helps the body to absorb calcium.

Dr Emily Brown, an expert in nutrition at the University of Surrey and study lead author said: 'We discovered that vitamin D2 supplements can actually decrease levels of vitamin D3 in the body, which is a previously unknown effect.

'This study suggests that subject to personal considerations, vitamin D3 supplements may be more beneficial for most individuals over vitamin D2.

In the study, published in the journal Nutrition Reviews, scientists analysed data from randomised controlled trials and found that taking vitamin D2 supplements led to a reduction in vitamin D3 levels.

In many of the studies, researchers noted that the vitamin D3 levels dropped lower in people taking vitamin D2 compared to those in the control group, who were not supplementing any form of vitamin D.

Professor Cathie Martin, group leader at the John Innes Centre, who was also involved in the study, said: 'This meta-analysis highlights the importance of ensuring plant-based vitamin D3 is accessible in the UK.'

Also known as the 'sunshine vitamin', people can get vitamin D from exposure to sunlight, as well as from foods like oily fish, red meat and egg yolks.

But it is also possible to top up levels through supplements, available for as little as 2p per pill at high-street pharmacies.

While science has long maintained that vitamin D is crucial for keeping bones, teeth, nerves muscles and the immune system healthy, experts say not all vitamin D is created equal—with vitamin D3 playing a vital role in combating inflammation in the body.

The current study supports previous research led by Professor Colin Smith at the University of Surrey, which found that vitamin D2 and D3 work differently in the body.

The study found that vitamin D3 has a modifying effect on the immune system which could help fortify the body against disease and ward off infection.

Prof Colin concluded: 'A healthy vitamin D3 status may help prevent viruses and bacteria from gaining a foothold in the body.'

Previously, world-leading oncologist Dr Justin Stebbing has even suggested that vitamin D could help protect against bowel cancer—a disease that is mysteriously rising among young people.

Dr Stebbing said whilst the vitamin's exact role in cancer prevention is unclear, tests show the nutrient played a crucial role in supporting the immune system and regulating cell growth, including in the bowel.

All of this supports the idea that high vitamin D levels, supported through vitamin D3 supplementation, should help reduce cancer risk.

And data does back this up, with some studies suggesting people with recommended vitamin D levels—which equates to around 10 micrograms a day—are significantly less likely to develop bowel cancer.

Professor Martin Warren, chief scientific officer at the Quadram Institute, who was involved in the current study added: 'Vitamin D deficiency represents a significant public health concern, especially during the winter months.

'This collaborative research effort aligns with our mission to deliver healthier lives through food innovation to enhance the nutrient density of the food we eat.

'Tackling this with the most effective form of vitamin D supplementation or fortification is of the utmost importance to the health of the nation.'

The latest data suggests as many as two in five adults may be vitamin D deficient during the winter months when there are fewer daylight hours.

A lack of the the vitamin can lead to bone problems, including rickets, a condition that causes bone pain, bone weakness and can lead to deformities.

But people should also be careful not to have too much of the nutrient.

As vitamin D helps to absorb calcium, too much can cause a condition known as hypercalcaemia, which can cause damage to the kidneys and heart.

As such the NHS recommends people don't take more than 100 micrograms of vitamin D per day unless specifically advised to by their doctor.