Both full-fat cheddar cheese and low-fat cheese fortified with high-dose vitamin D produced rises in blood vitamin D similar to a liquid vitamin D supplement, according to a study with 80 people published in the Journal of Nutrition .
The vitamin is produced in the body on exposure to sunlight, but increasing vitamin D levels via sunlight or supplements has been a source of ongoing debate.
In the US, where over 1.5 million people are diagnosed with skin cancer every year, experts are pushing supplements, claiming recommendations for sun exposure are "highly irresponsible".
Another push for supplements comes from the fact that intakes are low from dietary sources coupled with a lack of sunshine in northern climates, has led to estimates that as much as 60 per cent of northern populations may be vitamin D deficient.
In adults, vitamin D deficiency may precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases.
Another avenue that has been explored is the fortification of certain foods, predominantly dairy.
Fortification of fluid milks and margarine products was made mandatory in Finland in 2003-2004, while other European countries do not allow for any fortification.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol.
Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
Cheesy results According to Dennis Wagner, lead author of the new study, "there is a need to increase the options for vitamin D fortification."
Wagner and co-workers from the University of Toronto, Mount Sinai Hospital, the Egyptian National Research Centre, the University of Saskatchewan, and Ryerson University tested the effects of fortified cheeses to offer bioavailable vitamin D, and compared this to supplements.
The 80 participants were randomly assigned to receive weekly servings of fortified cheddar cheese (34 g), fortified low-fat cheese (41 g), or a vitamin D supplement consumed with or without food, placebo cheddar cheese, or placebo supplement Each intervention provided a dose of 4,000 International Units of vitamin D (cholecalciferol).
In both placebo groups the blood levels of 25(OH)D declined by, on average, 4.3 nanomoles per litre.
On the other hand, all groups receiving the vitamin D interventions experienced significant increases, compared to placebo.
Indeed, 25(OH)D levels increased by 65.3 and 69.4 nanomoles per litre in the fortified full-fat cheddar cheese and low-fat cheese groups, respectively.
In the dietary supplement groups consumption with or without food led to 25(OH)D increases of 59.3 nanomoles per litre.
Statistically, there was no difference between any of the fortification groups.
"These data demonstrate that vitamin D is equally bioavailable from fortified hard cheeses and supplements, making cheese suitable for vitamin D fortification," concluded the researchers.
Source: Journal of Nutrition July 2008, Volume 138, Pages 1365-1371 "The Bioavailability of Vitamin D from Fortified Cheeses and Supplements Is Equivalent in Adults" Authors: D. Wagner, G. Sidhom, S.J. Whiting, D. Rousseau, R. Vieth