Vitamin D in Mushrooms

Mushrooms are an excellent source of vitamin D2. Vitamin D2 provides a vegetarian source of the sunshine vitamin to combat vitamin D deficiency.

Vitamin D deficiency is common in Canada and the northern half of the US. In fact, Statistics Canada estimates that as many as 10 percent of Canadians have inadequate levels of vitamin D in their blood.

Unfortunately, few foods naturally contain vitamin D, so most people need to supplement in order to get the recommended intake of at least 1,000 IU per day during the winter months.

Many of today’s vitamin D3 supplements are synthesized from oil in sheep’s wool—not ideal for the approximately 1.36 million vegetarians in Canada.

Animal-free vitamin D

Thankfully there is one good vegetarian source of vitamin D2: mushrooms. Grown in the wild and exposed to natural sunlight, 3.5 oz (100 g) of morel mushrooms, for example, average 212 IU of vitamin D2.

However, most commercial mushrooms are typically grown rapidly indoors with no light exposure and average just 10 IU of vitamin D2 per 100 g.

Now researchers have found a way to up the vitamin D content of commercially grown organic mushrooms by simply exposing them to UVB light. This light exposure causes the natural ergosterol in the mushrooms to convert to ergocalciferol (vitamin D2) without changing their structural integrity or negatively altering other aspects of their nutritional profile, such as phytosterols, antioxidants, fibre, and an abundance of vitamins and minerals. UVB-exposed mushrooms can pack up to 135 IU per 100 g, nearly as much as the wild-grown variety.

No solvents are used to extract the vitamin D from the mushrooms. Organic vitamin D2 from mushrooms is retrieved through a simple three-step process: grow mushrooms; shine UVB light on mushrooms; dry and grind.

Fact versus fiction

Some have contended that vitamin D2 (the vegan form) is not as well absorbed as D3, but both animal and human studies have shown that vitamin D2 can increase the serum levels of active vitamin D just as well as vitamin D3 can.

The research shows that vitamin D2 works—and works well. In states of deficiency, vitamin D2 and D3 increase bone mineral density and bone volume “with no significant difference due to vitamin D source,” according to researchers from the Department of Medicine at Boston University School of Medicine.