Ah, summer. The endless blue skies and days of sunshine can really help us to feel better, both mentally and physically. But the reality for those living in the UK is that the skies can remain cloudy whatever the season. So, what happens to our levels of vitamin D (dubbed the ‘sunshine vitamin’) when it’s more overcast than gloriously sunny? 

We know by now that it’s recommended we take a vitamin D supplement from October to April (the NHS advises all children over the age of one and adults in the UK take a daily dose of 10mg of vitamin D), based on the assumption that from May to September, we’re absorbing enough of the vitamin from the sunshine on our face and arms. 

But when it’s constantly gloomy, are we still getting enough? Should we be supplementing all year round? And even if it’s sunny, are there any benefits to continuing vitamin D supplementation? We turned to the experts for their take and asked if you can ever have too much of a good thing. 

Vitamin D is important for several vital bodily functions, including supporting bone health and improving brain function. Unlike other vitamins, which can be readily absorbed via our diet, our main source of vitamin D is sunlight. 

“The best way to get vitamin D is for our body to make it from direct sunlight during the summer months in the UK (from about March/April to September),” Georgine Leung, a registered nutritionist, previously told Stylist. “This is because the sun has to be high enough in the sky for the ultraviolet B radiation (UVB) to get through to us.”

So, given that the UK is hardly being drenched in sunshine this year, should we be supplementing with vitamin D all year round? 

“During the summer months in England, most people can synthesise enough vitamin D from sunlight exposure,” says GP and dermatologist Dr Thuvan Amuthalingam. “However, several factors can affect this. People with darker skin, including those of African, African Caribbean or South Asian origin, require more sunlight to produce adequate vitamin D. Similarly, the elderly, who may not spend much time outdoors, and those who work indoors or cover their skin for cultural or medical reasons, may also struggle to get enough from sunlight alone.”

Depending on how susceptible you are to deficiency, it might be worth considering a supplement all year round to keep your levels within the optimum range. While most of us can get away with only supplementing in autumn and winter, some groups are more at risk of deficiency. 

“Older adults (people over 65) may need more vitamin D than younger people, as it becomes harder to synthesise vitamin D from the sun as we age,” explains nutritionist Thalia Pellegrini. “Similarly, a BMI of more than 30 is associated with lower levels of vitamin D. People with Crohn’s disease and coeliac disease need additional vitamin D as these conditions impact the absorption of nutrients in the gut.”

If any of these apply to you, you may want to seek professional medical advice as to whether you need to supplement in the summer. 

“Vitamin D is crucial for bone health, immune function and reducing inflammation, and insufficient levels can lead to bone disorders, such as rickets in children and osteomalacia or osteoporosis in adults,” says Dr Amuthalingam. “Therefore, even in summer, some individuals might still benefit from supplements to maintain optimal health.”

So, can we have too much of a good thing? If we’re getting lots of sun and taking a supplement, then yes. But rather than cutting out the supplement entirely, you might just need a different dose. 

“If you’re concerned you’re getting too much vitamin D, the problem is more likely to be that you’re supplementing with too high a dose,” cautions Pellegrini. “And yes, you can take too much. Unlike B and C vitamins, which are water soluable, vitamin D is a fat-soluble vitamin, which means we can’t easily excrete any excess. Vitamin D can be toxic if we take much more than we need over a period of time.”

You can’t overdose on vitamin D through exposure to sunlight alone, but taking too much orally can cause a condition called hypercalcaemia, whereby too much calcium builds up in the body. According to the NHS, this can weaken our bones and damage the kidneys and heart. Symptoms of an overdose of vitamin D can include nausea, vomiting, weakness and frequent urination. 

If you’re concerned that you may have taken too much, seek professional medical advice. This said, these side effects and complications are rare. 

The expert advice is always to seek professional medical advice before supplementing.

“I always recommend doing a vitamin D test once or twice a year,” adds Pellegrini. “They’re inexpensive, easy to do at home and you can know how much vitamin D you actually need. If you spend a lot of time outside in the summer months, your vitamin D levels will be supported. If in doubt, test.”

Images: Getty