Vitamin D – the ‘sunshine vitamin’ – is a hormone naturally produced from cholesterol when your skin is exposed to sunlight.
What can Vitamin D do for my health?
Research studies are uncovering new benefits of Vitamin D all the time.
There are many known benefits, with some of the main ones being:
Bone strength – strengthens bones and helps prevent osteoporosis and the risk of falls for the elderly
Physical strength – strengthens the upper and lower limbs
Cancer prevention – some studies have highlighted a reduction in the risk of various types of cancer. One study indicated that 1,100IU per day with calcium reduced cancer risk by 60%.
Depression – mild reductions in symptoms have been reported in some studies
Reduced risk of disease – the risk of diabetes, cancer, heart disease, dementia and autoimmune diseases are all reduced with high levels of Vitamin D
Living longer – can help reduce likelihood of many diseases and overall mortality rates
How can I get enough Vitamin D?
Being a fat-soluble vitamin, Vitamin D can be stored by your body over time, but regular top ups are required.
At the time of writing (November 2020), BANT (British Association of Nutrition and Lifestyle Medicine) has recommended daily supplementation for all adults to the UK government. The advice was for a minimum of 600-800 IU per day, increasing to 5000 IU per day if knowingly deficient in Vitamin D or if COVID-19 symptoms were to develop. The UK government has since committed to supplying Vitamin D in supplement form to the most vulnerable in society to help in the fight against COVID-19.
Where should we get Vitamin D from?
From the sun
The best source is generally from sunlight, with 20-30 minutes of exposure at summertime, in a midday sun, providing around 10000 IU a day. However, it's not possible to get and maintain regular levels from sunlight in the UK, especially in darker months and in periods where there's not much sun. This issue is more prevalent than ever in modern life where kids often don't play as much as they used to outside, and adults are generally spending more time indoors too.
The larger the area of skin exposed, the more Vitamin D can be absorbed. Factors that will reduce absorption include use of sunscreen and being behind windows/glass, etc.
General advice for optimising absorption rates is to apply sunscreen before your skin would start to burn. Of course, this advice depends on the intensity of the sun and your own sensitivity to the sun.
The darker your skin colour, the less Vitamin D is absorbed from the sun.
The following video from Cancer Research UK offers some general advice on staying safe in the sun:
From the diet
It is very difficult to obtain significant amounts of Vitamin D from food, which has lead to deficiencies being commonplace in countries that have little sun at certain times of the year. Main sources from food are oily fish, egg yolks and liver, however, you would need to be eating large portions of those to get anywhere near an optimum daily supply. It’s worth bearing in mind that some cereals and dairy items are fortified with Vitamin D.
There are two main forms of Vitamin D available from food:
Vitamin D3 (cholecalciferol): from some animal foods e.g. oily fish, liver, egg yolks.
Vitamin D2 (ergocalciferol): from a selection of mushrooms
Vitamin D3 is generally thought to be the more 'bioavailable' version - meaning the body often utilises it more efficiently. D3 is the form of the vitamin naturally made in the skin from sunlight.
Due to the lack of regular sunlight together with difficulties in gaining high enough levels from food, supplementation is perhaps the best way to make sure we have enough regular Vitamin D in our bodies.
The best option is in the form of Vitamin D3 (preferably in conjunction with vitamin K2).
Vitamins D and K work well together. Vitamin D helps the body to absorb calcium from food and supplements, and vitamin K helps to assist calcium use use by the bones. Vitamin K2 is naturally found naturally in high fat dairy products, liver and even Japanese fermented foods. You will often find vitamin D3 & vitamin K2 (MK-7) together in supplements.
In relation to strength, advice can differ between sources. Following the BANT advice towards the end of 2020, a minimum of 600-800 IU a day is probably wise (rising to 5000 IU a day as a medicinal type dose). The Endocrine Society recommends 400 IU for children aged 0-1 year and 600 IU/day for children aged 1-18 years. 1500-2000 IU is recommended for all men and women older than 18 years, including lactating and pregnant women whose infants are not ingesting vitamin D. Higher doses of vitamin D, given either daily or weekly, are recommended for vitamin D–deficient children and adults, followed by an increase in the daily dose of vitamin D.
It's worth noting that Cod Liver Oil contains a large amount of Vitamin D, but is considered to be a less effective option, due to the large amount of Vitamin A it also contains. Vitamin A is another fat-soluble vitamin that is fairly commonplace in the average diet and larger doses may interfere with effective Vitamin D absorption.
Having your blood levels measured is an accurate way of knowing if you are Vitamin D deficient. Your GP can help you with this test.
Please consult your doctor if you are on prescribed medication that may interfere with Vitamin D, or are being treated for an existing medical condition and unsure about the effect supplementation may have.