New research has dispelled the myth that vitamin D2 and D3 have the same nutritional value, pushing worldwide health authorities to rethink their official guidelines on vitamin D.

The first-ever study of its kind, the research was carried out by the University of Surrey, U.K. to look into which type of vitamin D -- D2 or D3 -- is most effective in raising levels of the vitamin in the body.

Vitamin D3 is derived from animal products, while D2 is plant-based, with the team choosing to use vitamin D-fortified foods for the study.

The team looked at 335 South Asian and white European women, analyzing their vitamin D levels over two consecutive winter periods, a time when the level of the nutrient is known to be low.

The women were split into five groups, with each group receiving either a placebo, a juice containing vitamin D2 or D3 and a biscuit with D2 or D3.

The team found that the levels of vitamin D in women who received vitamin D3 from either juice or a biscuit increased by 75 per cent and 74 per cent respectively compared to those who were given D2 via juice or a biscuit.

Those given D2 saw an increase of just 33 per cent and 34 per cent over the 12-week intervention period.

The researchers noted that both fortified food and drinks like juice had an effect on vitamin levels.

Those who received the placebo however, showed a 25 percent reduction in vitamin D over the same period.

The findings could now have implications for official guidelines around the world, including the U.S. National Institute of Health, which states that the two forms of vitamin D are equally effective.

The retail sector may also need to rethink their products, as many have added D2 to their foods in recent years to meet the need of consumers who choose to up their vitamin D intake with fortified products and supplements.

The team now believes that consuming products that contain vitamin D3, not D2 will help the public reach recommended levels of vitamin D -- which in the U.K., where the study was carried out, currently stands at 10 micrograms per day throughout the year for everyone aged 4 years and older.

Lead author Dr Laura Tripkovic commented on the findings saying, "The importance of vitamin D in our bodies is not to be underestimated, but living in the U.K. it is very difficult to get sufficient levels of it from its natural source, the sun, so we know it has to be supplemented through our diet.

"Those who consume D3 through fish, eggs or vitamin D3 containing supplements are twice as likely to raise their vitamin D status than when consuming vitamin D2 rich foods such as mushrooms, vitamin D2 fortified bread or vitamin D2 containing supplements, helping to improve their long term health."