The current recommended daily intake of vitamin C — which is based in part on tests carried out in England during the second world war — should be doubled, researchers have suggested.

Currently, the intake of vitamin C recommended by the NHS and the World Health Organization (WHO) is 40mg and 45mg, respectively.

However, researchers from the University of Washington and Harvard Medical School have suggested this figure should be increased to 95mg, after re-examining an initial study into recommended doses of the vitamin carried out in the 1940s.

The author of the new peer-reviewed research, published in the American Journal of Clinical Nutrition in August, concluded that the initial research used methods that would not now be considered reliable.

In the 1944 study, seven volunteers received a daily dose of 10mg, while three had 70mg for nine months, and 10 participants received none. The study concluded that 10mg of vitamin C a day was sufficient to ward off scurvy, which in turn influenced the recommended daily intake used today.

Researcher Philippe Hujoel, a professor at the University of Washington, said that the 1944 trial depleted people’s vitamin C levels during the course of the study, which could have created life-threatening emergencies. Two volunteers were reported to have heart problems following the trial.

The NHS website describes Vitamin C as having three major functions: protecting cells and keeping them healthy, maintaining healthy skin, blood vessels, bones and cartilage, and helping with wound healing.

‘Operation Shipwreck’ was completed by the Sorby Research Institute and was conducted at a time when food was scarce. The aim of the study was to prevent scurvy, rather than maximise health, Professor Hujoel suggested.

Professor Hujoel said: ‘Robust parametric analyses of the [English] data reveal that an average daily vitamin C intake of 95mg is required to prevent weak scar strength [a measure of wound healing capacity] for 97.5% of the population.

‘Such a vitamin C intake is more than double the daily 45mg vitamin C intake recommended by the WHO but is consistent with the writing panels for the National Academy of Medicine and [other] countries.’

He added: ‘It is concluded that the failure to re-evaluate the data [...] may have led to a misleading narrative on the vitamin C needs for the prevention and treatment of collagen-related pathologies.’

Last month, The Pharmacist reported on updated guidance which stated there was no need to take vitamin C alongside oral iron replacement (IRT) therapies.

NHS England has been approached for comment.