Just 12 percent claimed they are very familiar with the sources of Vitamin D, while only 38 percent realise that late April to September are the months you can get Vitamin D from sunlight.
A further one in ten adults admitted to feeling as, or more, anxious about their health this coming winter.
Less than one in five (16 percent) were aware vitamin D can be found in red meat, while just a tenth could name mushrooms as a source.
More than half (55 percent) were also clueless about how much of each vitamin they should be taking in every day.
The research was commissioned by Warburtons to highlight its “Half and Half” range.
Dr Zoe Williams, who helped the development of the report, said: “Addressing Vitamin D deficiency in the UK is clearly of importance to the nation’s health so it’s great to see Warburtons raising the issue with this report.
“It really highlights how much there is to do to increase the public’s knowledge about Vitamin D.
“Just expecting people to buy over the counter supplements is not sufficient action, especially since those most affected are the least likely to be able to do so.
“More focus needs to be put on education, free access to vitamin D supplementation and fortification of foods.
“These are three very important easily accessible solutions in helping to reduce the deficiency levels in the UK.”
The study also found 29 percent of adults believe wearing sunscreen can stop the production of vitamin D in the body – which is incorrect.
It also emerged that one in ten adults believe vitamins are responsible for providing the body with energy – and just under a tenth strongly agree that “the more vitamins you take, the better”.
Warburtons’ chairman, Jonathan Warburton, said: “The findings of our report have shown just how important it is to ensure the nation is receiving the right levels of vitamin D.
“We hope the findings of the study and the insight from healthcare professionals will help shine a light on this important issue.
“It will help us all respond to one of the most challenging and unresolved issues of the pandemic – how we create a healthier, more resilient nation in the days, months and years ahead.”