| Mushrooms may yield vitamin D bonanza|
|A burst of ultraviolet light can make mushrooms a major source of vitamin D, Australian researchers report.|
Dr Gerald Pang and colleagues from the University of Western Sydney report their findings in the Journal of Agricultural and Food Chemistry.
Mushrooms naturally contain a high level of ergosterol, the precursor for vitamin D.
But the standard practice of producing mushrooms indoors means they are not exposed to sunlight and so the ergosterol is not converted to vitamin D.
North American researchers have developed technology that uses UV light to increase the amount of vitamin D in mushrooms, which have been available in the US since last year, says Pang.
Now, research by Pang and colleagues, funded by the Australian Mushroom Growers' Association and Horticulture Australia Ltd, has confirmed Australian mushrooms also respond to UV light.
Importantly, says Pang, the research shows the vitamin D is stable and lasts 8 days after treatment at room temperature or under refrigeration - a requirement by regulators.
Pang and colleagues tested the impact of irradiating Agaricus bisporus mushrooms with UV-C light from a xenon lamp from between 2 seconds to 30 minutes.
They found that placing the lamp the right distance away and exposing the mushrooms for the right length of time gave no impact on their colour while boosting their vitamin D concentrations.
The researchers will soon study the impact of higher intensity ultraviolet light to reduce the amount of irradiation time required to boost D levels.
Greg Seymour, president of the The International Society for Mushroom Science and general manager of the Australian Mushroom Growers' Association, says evidence suggests 100 grams of irradiated mushrooms could provide the recommended daily intake of vitamin D.
He says he hopes the vitamin-D-rich mushrooms will be available in Australia by the end of the year.
The idea has been met with a mixed response from nutritionists.
"I think it is a clever idea simply because there are so few foods that actually have vitamin D in them," says Catherine Saxelby a Sydney-based consultant nutritionist.
She says despite Australia being a sun-drenched country, vitamin D deficiency is a problem, especially among groups such as the bedridden elderly and dark-skinned veiled women and their children.
"It would be nice to have some other food apart from oily fish, butter and table margarine as our source of vitamin D," says Saxelby.
Nutritionist, Dr Rosemary Stanton, urges a note of caution about the impact of the ultraviolet light on mushrooms.
She says mushrooms are rich in some B group vitamins, which are very sensitive to heat and light.
"You would have to be really careful that it doesn't destroy the B-group vitamins in mushrooms," says Stanton.
She says most people can still get the vitamin D they need without increasing cancer risk by exposing themselves to sun early or late in the day.