Why we need vitamin DOur bodies cannot function without an adequate supply of vitamin D: its role in our health is too central. The functions of this nutrient include:
- Maintaining normal blood levels of the minerals calcium and phosphorus.
- The absorption from food of calcium, enabling healthy bone growth.
- Stimulating immune cells to release antibodies and thereby encouraging a healthy, responsive immune system.
- Metabolising glucose to fuel our bodies.
- Controlling the growth of cells and nerves.
- Maintaining healthy muscles and joints.
- High blood pressure – also known as hypertension.
- Muscle pain or tremors.
- Tooth pain and gum inflammation.
Foods that are rich in vitamin DSo what foods contain vitamin D? How do you top your levels and make sure you are getting enough? It is more challenging to do so than you might think. As we saw above, our bodies are designed to generate vitamin D from sunlight, and that is a good thing because foods abundant in this nutrient are relatively limited. Let’s take a look at the principal dietary sources of vitamin D.
SalmonThis tasty fish contains plenty of vitamin D: on average, 250- 500 IU (international units) per serving of farmed salmon, or two thirds of the recommended daily amount. Wild salmon is even better, with the average vitamin D content per serving shooting up to around 1,000 IU, comfortably exceeding the recommended daily amount.
HerringThis familiar seafood staple is another fish rich in vitamin D. A single serving of fresh herring offers around one quarter of the recommended daily amount: 216 IU. The picked variety still offers over 100 IU per serving, or 14% of the recommended daily amount.
SardinesCanned sardines are also abundant in vitamin D: an average four ounce can contains more than 175 IU – almost a quarter of the recommended daily amount.
MackerelThis equally familiar oily fish offers at least 360 IU of vitamin D per fillet on average.
TunaNo, we’re still not done with the fish. There’s plenty of vitamin D in a standard 100 gram can of tuna: nearly 270 IU, or around one third of the recommended daily amount.
MushroomsMushrooms are the only plant food to offer a good level of vitamin D. Fungi synthesise vitamin D2 when exposed to sunlight. Just like salmon, wild varieties offer much higher levels than farmed ones – as much as 2,300 IU per serving: that’s 300% of the recommended daily amount. By contrast, farmed varieties may offer as little as a few hundred IU. This is because farmed mushrooms are often grown in the dark, under ultraviolet light.
Egg yolksEgg yolks make an ideal vitamin D source, especially for those who don’t like fish. The yolk of an average single egg contains nearly 40 IU – but this can claim to several hundred in the yolks of eggs produced by free range chickens who are allowed to enjoy some time in the sun. Some chickens are also given vitamin D-enriched feed in order to produce healthier eggs: this should be indicated on the packaging.
Red meatRed meat can also be a good source of vitamin D for those who do eat animal products. That’s not a lot of different foods to choose from. Vegetarians and vegans are at an obvious disadvantage and they may need to rely on dietary supplements and fortified foods to ensure healthy levels of vitamin D. Fortified foods have had nutrients added during the processing or manufacturing stage. A range of supermarket staples, including breakfast cereal, orange juice, soya milk and cow’s milk are routinely fortified with vitamin D to encourage basic levels of health in the general population. On average, such foods offer 50 – 150 IU per serving. Supplements include not only the tablets available in health food stores and supermarkets but also traditional cod liver oil, which provides nearly 450 IU per teaspoon. Cod liver oil is of course not suitable for vegans but it is ideal for those who do not like the taste of fish.
How to test your vitamin D levels at homeIf you want to ensure you’re getting enough vitamin D levels enough vitamin D to stay healthy, it makes sense to discover just how much you are getting. Vitamin D tests for use at home are quick and easy. Take a skin prick blood sample and send this in for full laboratory analysis. Next stop better health!
Medically reviewed by Sian Baker, Dip ION mBANT mCNHC – Written by Beth Giddings (BSc)