Top up your vitamin D

Vitamin D – or the sunshine vitamin, as it’s often called – is an essential nutrient for all of us. It gets its nickname from the fact that our bodies need exposure to sunlight to make it.

Why do we need it? Vitamin D is important for keeping bones and muscles healthy, protecting muscle strength and supporting healthy immunity. A deficiency can lead to bone problems such as rickets (which causes bowed legs) in children, and muscle weakness and painful or tender bones in adults. Conversely, the benefits of getting enough vitamin D are wide ranging, from a lower incidence of depression and certain cancers to the decreased severity of Covid-19 symptoms.

It’s also worth noting that a study published by the Alzheimer’s Association suggests vitamin D sufficiency may lower your risk of dementia, especially if you are older and female. When researchers analysed data from more than 12,000 people with an average age of 71, they discovered that women who had taken a daily vitamin D supplement were 50% less likely to develop dementia over 10 years than those who had not.

Unlike other vitamins, for which the main intake is through food, around 90% of our vitamin D comes from the action of sunlight (specifically UVB light) on our skin – the same UV light that causes skin to burn. Fortunately, it doesn’t take much sun exposure for the body to produce vitamin D. A study published in the journal Nutrients estimates that, for white-skinned people, exposing about one-third of the skin area (equivalent to face, hands, forearms and lower legs) unprotected for just nine minutes a day from March to September will provide adequate levels. Darker skin tones are likely to need more time – up to 25 minutes.

Interestingly, getting more sun doesn’t mean you’ll get more vitamin D. Instead, it puts you at risk for ageing and skin cancer, which is why the British Association of Dermatologists advises using a sunscreen with SPF 30 or higher. The question then is whether using sunscreen all the time can stop the body from making vitamin D and potentially cause a deficiency?

To answer this question, researchers from King’s College London divided participants based in Poland into four groups. Three of the groups went on a week-long holiday to sunny Tenerife. The first group of 20 participants received a broad-spectrum sunscreen (SPF 15) providing a balance of UVA and UVB protection. (‘Broad spectrum’ means the sunscreen protects against both UVA and UVB light.) UVB rays cause sunburn and skin cancer, while UVA rays are the ones that prematurely age your skin. (Incidentally, SPF only indicates protection against UVB, so a sunscreen not labelled broad spectrum may not offer UVA protection.) The second group of 20 individuals received a non-broad-spectrum sunscreen, which also had an SPF 15, but offered low UVA protection. The third group comprised 22 participants who used their own sunscreen with no instructions on how to apply it. The fourth group, the control group, remained in Poland.

The participants in the first two groups had their blood tested 24 hours before and 48 hours after they returned from Tenerife. The study found that SPF 15 sunscreens applied at sufficient thickness to prevent sunburn allowed a ‘highly significant’ improvement in vitamin D levels. “Data from this study and others suggests that using sunscreen will not impact vitamin D synthesis,” confirms consultant dermatologist Dr Anjali Mahto. “In real life, people apply less sunscreen than the amount [this study] tested at. So, it is likely that standard sunscreen use, even at a higher factor such as SPF 50, is unlikely to compromise vitamin D synthesis.”

Apart from sun exposure, diet is the other means of getting your vitamin D. You can find it in fresh or tinned oily fish (such as salmon or sardines), egg yolks and mushrooms exposed to UV light (see ‘Growing Protection’, left). The vitamin is also added to certain fortified breakfast cereals, plant-based dairy alternatives and vegetable spreads.

“If you have a darker skin tone or don’t get much sun, then year- round supplementation is recommended,” says consultant dermatologist and nutritionist Dr Thivi Maruthappu. “It is simple and inexpensive.”

If you take steps to protect your skin – using a ‘high protection’ sunscreen of at least SPF 30 as well as wearing a hat, T-shirt and sunglasses, and seeking the shade between 11am and 3pm – spending time in the sun is a great way to get some extra vitamin D. And rest assured: sun protection does not prevent your body from making this vital nutrient. Away from the sunlight, try adding vitamin D-rich foods to your diet and taking a daily vitamin D supplement.

About the author: Anita Bean is a registered nutritionist. She has worked with the London Marathon and is the author of The Vegan Athlete’s Cookbook and The Runner’s Cookbook.

GROWING PROTECTION

Mushrooms exposed to UV light can make vitamin D, much like human skin. Look for ‘vitamin D-enriched’ on the label, or buy regular mushrooms (any variety) and leave them in a sunny spot for up to 60 minutes between the hours of 10am and 3pm during spring and summer months.

PLANT OR ANIMAL?

There are two forms of vitamin D in supplements: D2 (ergocalciferol) and D3 (cholecalciferol). D2 is found in plants, while D3 can come from animal sources – although vegan D3 supplements are derived from lichen. Some studies have shown that vitamin D3 supplements are better at raising vitamin D levels compared to D2.