Should You Be Taking a Vitamin D Supplement?

I often get asked by friends and colleagues whether it’s worthwhile taking vitamin and other dietary supplements. On the whole, if you have a healthy, balanced diet they are not needed (unless recommended by your doctor). However, there is one exception to this, and that’s why the NHS recommends that everyone in the UK should take a Vitamin D supplement through the autumn and winter.

Why do I need Vitamin D?

Vitamin D helps regulate the amount of calcium and phosphate in the body, which allows us to build healthy bones and muscles. Maintaining adequate amounts of the vitamin is essential for bone health, especially for older adults who are at risk of developing osteoporosis (thin bones). This is why some older people are prescribed a combination of vitamin D and calcium by their doctor, as this provides the building-blocks for healthy bones.

Vitamin D is also needed to maintain a healthy immune system, allowing us to fight off infections. It’s also thought to have a role in how our nerves function.

Why should I take a Vitamin D supplement?

Vitamin D is one of a small number of fat soluble vitamins, and although it is present in some foods, our bodies create much of the vitamin D we need when UVB rays from outdoor sunlight strike the skin and react with a protein, making the active form of the vitamin.

Even when we take vitamin D by mouth (whether in food or as a supplement), it is in the inactive form, and it undergoes changes in the liver to convert into the active compound that our bodies can use. Interestingly, Vitamin D synthesis by the liver is not adversely affected by age, however synthesis from the skin is.

Which foods contain Vitamin D?

Vitamin D can be found in small amounts in oily fish, red meat and egg yolks. Breakfast cereals and some fat spreads are also fortified with it. In the US and Canada cow’s milk has vitamin D added to it, but this does not happen in the UK.

• Oily fish: Salmon, mackerel, and sardines.
• Red meat: Beef and lamb.
• Egg Yolks

I wear sunscreen all the time. Does this mean that I need extra Vitamin D all year round?

No it doesn’t. Although many sunscreens block UVB, scientific studies have shown that even higher factors don’t stop 100% of UVB rays, meaning we can get the vitamin D we need and still protect against skin cancer.

UVB rays do not penetrate glass, so sitting by a window on a sunny day isn’t beneficial; sunlight or daylight lamps don’t produce UVB either.  

Can I accidentally take too much Vitamin D?

A dose of 10 micrograms per day is recommended by the NHS for everyone through the autumn and winter months, but it is safe to take up to 100 micrograms per day. If you are prescribed Vitamin D by your doctor the dose may be higher, but this will be for a clinical reason so you should continue.

If you take several supplements you should check the amount of vitamin D in them so that you aren’t accidentally taking too much.