Vitamin D and Calcium absorption

Amongst the essential nutrients required by the human body, vitamin D is unique. Its the only vitamin that we can synthesise following exposure to sunlight. In the past, a disease called rickets which caused bowed legs in children was common in industrial areas, because children rarely saw the Sun and so were deficient in vitamin D. When the connection between vitamin D, sunlight and this disease was discovered in the 1920s, public health initiatives recommended fortifying milk with this nutrient, and taking cod liver oil supplements. As a result, rickets was virtually eradicated in the UK and USA.

One of the most vital functions of vitamin D is the appropriate absorption of calcium from the gut, so you can see why these two nutrients are closely linked. However, although 20-25 minutes outside daily is often suggested, there isn’t an official recommendation of how long you should spend outside in order to get enough vitamin D, because of the risk of skin cancer. Also, if you live at higher latitudes, are older or dark skinned, or it is the middle of winter, then Sun is less likely to provide your daily needs. It’s also important to note that light through a window won’t work, because glass blocks the crucial wavelength that prompts the body to make vitamin D.

So what can we do in order to make sure we have enough vitamin D? Firstly, it may be unappetising, but Cod Liver Oil is one of the best sources around. One tablespoonful contains 1360IU (international units) of vitamin D; which is more than double the daily value for adults. It’s also available in capsules, which is good news for the majority of people who don’t want to taste it!

As for foods, you won’t be surprised to learn that fish is a good source, for example a 100g (3.5oz) salmon fillet contains 450 IU and canned light tuna has around 150 IU for the same weight. But what if you are vegan or vegetarian?

Portobello mushrooms are one of the best vegan sources of this nutrient, with over 450 IU per 100g. Fortified cereal contains around 340 IU per 100g, and firm tofu has rather less, just under 160 IU. Soy milk has around 60 IU. So while there are less foods that contain vitamin D than most other nutrients, it is still possible to avoid both meat products and sunlight and supply your daily needs. However, there are now vegan supplements on the market, so nobody need worry about not getting enough of this vital nutrient!