His doctor checked him out before and after his experiment. The only noticeable effect was that his vitamin D levels had increased, and so had his girth - by almost five kilograms. His experiment has inspired mixed reactions in the scientific and business community in Australia, where vitamins are a multimillion-dollar industry. Sydney University associate professor in human nutrition, Samir Samman, said the largest body of evidence on vitamin use showed their efficacy was questionable. He pointed to clinical trials of people suffering from cardiovascular disease who were given vitamins A, E, and C, beta-carotene and selenium. "The first really important finding was that these made no effect - that there was no improvement in people taking large amounts of vitamins in relation to cardiovascular disease," Professor Samman said.

"The statistics also showed that large doses of vitamins actually have a small, but statistically significent, increase in mortality for these patients." He said Cloud's experiment came to similar conclusions as other academic research into the efficacy of vitamins. "You find sporadic bits of information promoting this, or saying that this is beneficial if you are being treated for a condition," he said. "But if people are otherwise healthy, and adequately nourished, then why are they taking additional supplements?" Australian Medical Association chairman of the council of general practice, Brian Morton praised Cloud's experiment.

"It may not stand up to a class one evidence test but it is not a bad way of monitoring how effective supplements are for you," Dr Morton said. "I would suggest talking to your GP before you start taking supplements, but if you are going to do it yourself - jot down why you are doing it and what you want to get better. Buy enough for a month and then see if you are any better." Dr Morton said that he rarely suggests vitamins to his patients, unless they are suffering from a serious illness. "If for example, a patient has been treated for cancer, and their appetite and vitamin intake is down because of all those awful side effects, I will suggest a multi-vitamin. "But, otherwise, you should not take them without good reason. Most Australians have the problem that their diet has an excess, not a deficiency, of vitamins."

President of the Vegan Society of NSW Greg McFarlane said it was a myth that people on strict vegetarian or vegan diets need iron and calcium supplements. ‘‘We believe that a well-balanced vegan diet can provide all necessary nutrients except for B12, and so we would recommend taking a B12 supplement. This is because it comes from bacteria - which you can only get either from meat or from dirty food,’’ Mr McFarlane said. Blackmores director of education, Pam Stone, who is also a naturopath, agreed that supplements had to be taken in consultation with a doctor or pharmacist. But she said it was wrong to assume from Cloud's experiment that vitamin supplements had no use. "It comes down to people taking responsibility for their health and well-being, and looking after their diet and overall lifestyle," Ms Stone said.

"You need five serves of vegetables every day, and you can't expect that a multivitamin will [replace] that. Loading "We don't encourage people to indiscriminately self-select supplements. They need advice from a trusted healthcare professional," she said. Follow Life&Style on Twitter @Life_Style_News