In Australia, especially in sunny Queensland melanoma is all too common. And while you will still see plenty of people toasting themselves to leathery goodness every weekend, the rest of us tend to avoid the sun like the plague. And the end result is widespread deficiency in vitamin D, sometimes called “the sunshine vitamin”. Vitamin D deficiency affects a whopping 31% of women in the northern parts of Australia during winter-spring, which is particularly concerning for those who are pregnant or breastfeeding.
We need vitamin D to maintain calcium and phosphate balance for the health of our bones – vitamin D deficiency puts you at risk of rickets and osteoporosis, both of which are on the rise in Australia. Vitamin D is also important for immunity, central nervous system function and even muscle strength. Plus we have a growing body of evidence to suggest that maintaining normal vitamin D levels is associated with a decreased risk of heart disease, type 2 diabetes, hypertension and colorectal cancer.
So we need vitamin D so we don’t get osteoporosis or heart disease or even cancer, but it comes from the sun, and too much sun exposure *causes* cancer. So what’s a girl to do? Well first of all, moderate sun exposure is useful – you only need to spend 10-15 minutes in the sun to optimise vitamin D levels, no need to cook yourself. But for office workers, getting even that much sunshine is a hard ask, particularly in the winter months when it’s not uncommon to leave home before the sunrises and leave the office after the sun sets.
Food sources of vitamin D include oily fish (salmon, tuna, mackerel, sardines), beef liver, egg yolk (thus confirming my theory that egg white omelette is the devil’s food) and full fat dairy products such as milk and butter. Vitamin D fortified reduced fat dairy products are also appearing on the market, but dietary vitamin D intakes are still low. Most people get barely 10% of their vitamin D from food, relying on sun exposure and supplements to make up the difference.
Eating more fish and eggs is reasonable for some, but if you can’t eat these foods, this is bad news. And that’s why you should be making friends with mushrooms today.
Mushrooms naturally produce vitamin D when they see sunlight, or another source of UV light. But most mushrooms are grown in the dark, so cultivated mushrooms are low in vitamin D. Mushrooms from retail stores can have 1-5 mcg vitamin D per 100g (around 3 button mushrooms), possibly due to UV light exposure in-store. This isn’t too shabby, given that daily requirements for vitamin D are 5-15 mcg, the higher level for older people.
While store-bought mushrooms have a modest amount of vitamin D in store, they are able to generate over 20 mcg per serve after being placed in sunlight for a couple of hours in the midday sun. Research shows that leaving mushrooms in the midday winter sun for about an hour produced about 10 mcg of vitamin D in a 100g serve, which is smack bang in the middle of the daily requirement.
Now if you’re not into irradiating your own mushrooms, there is another option. If freshly harvested mushrooms are exposed to a short burst of ultraviolet light after harvesting they quickly generate vitamin D, while retaining the good looks and nutrition of the mushroom (leaving them in the sun too long causes them to shrivel and brown). These high vitamin D mushrooms are being sold under the very creative name of “Vitamin D Mushrooms”, and are now available in supermarkets in some parts of Australia and New Zealand. A single 100g serve of vitamin D mushrooms provides at least the daily need for vitamin D.
Mushrooms are an easy food to incorporate into your diet, whether chopped finely and hidden in your bolognaise sauce or sautéed with garlic and butter as a side dish to your eggs on toast. Roasted field mushrooms also make a great alternative to burger patties or the bun, depending on what your goals are.