Experts issue warning over this popular winter supplement

Does the ‘sunshine vitamin’ have a dark side? Here’s what you need to know

As sunshine continues to evade us in the UK, many turn to vitamin D supplements in an attempt to keep seasonal flu and the blues at bay. But health experts have warned about little-known side effects of incorrectly taking them.

Vitamin D, often called the “sunshine vitamin” because it is made by the body using sunlight, is found in food such as oily fish, red meat, and egg yolks.

It helps regulate the amount of calcium and phosphate in the body. These nutrients are needed to keep bones, teeth and muscles healthy.

However, due to a lack of daylight hours in UK winters, around one in six people in the UK have vitamin D levels below government recommendations.

The NHS posted on X: "From October to March we can't make enough vitamin D from sunlight, so to keep bones and muscles healthy, it's best to take a daily 10 microgram supplement of vitamin D. You can get vitamin D from most pharmacies and retailers."

Vitamin D is often called the ‘sunshine vitamin’ because it is made by the body using sunlight (Alamy/PA)

Dr Kathryn Basford at Asda Online Doctor told The Independent: “Everyone in the UK can benefit from taking vitamin D during the darker months, as although you can get some vitamin D from what you eat, it’s difficult to get enough through diet alone.

“A lack of vitamin D can lead to tiredness, bone or muscle pain, and recurrent infections, among other things.”

So what do we need to know about the side effects of taking vitamin D?

Dr Basford said vitamin D is unlikely to cause any harm if taken as prescribed by your doctor. However, she added that side effects tend to happen when you take too much vitamin D.

“Taking more than the recommended amount of fat-soluble vitamins like vitamins A, D, E, and K can cause them to build up in your body, leading to toxic effects,” she said. “Toxicity is only a possibility when taking these vitamins as supplements, so getting these vitamins from the sun or your diet won’t lead to this problem.”

The most common side effects include:

• Headache
• Skin reactions
• Stomach pain
• Increased calcium levels
• Nausea

“If you are experiencing any of these, it’s important to talk to your doctor to make sure you are taking the right dose,” she added.

Katherine Elyse Blake, a qualified nutritionist and women’s health consultant, said the most common issues she sees are people taking high doses of vitamin D for long periods without monitoring, and “assuming more is always better”.

She told The Independent: “Vitamin D requirements vary significantly depending on factors such as sun exposure, skin tone, body weight, diet, age, and existing health conditions. A dose that is appropriate for one person may be excessive or unnecessary for another.

“Timing and context matter too. Taking vitamin D very late in the day may interfere with sleep for some people, as it can influence melatonin production. It’s often better tolerated when taken earlier in the day with a meal that contains fat.”

Health experts stress that vitamin D should be taken as prescribed by your doctor (PA Archive)

Incorrect use of vitamin D can also affect the skin. Dr Aiza Jamil, consultant dermatologist, said vitamin D has a “direct, biological role in skin structure and health”.

She explained that the skin is the primary site of vitamin D synthesis, and the only organ capable of producing vitamin D in meaningful quantities without dietary input.

Dr Jamil said: “Vitamin D regulates keratinocyte differentiation and lipid production, which, when it is malabsorbed or incorrectly taken, can cause an impaired skin barrier, dryness, dermatitis, uneven skin tone, and skin texture changes, for example.”

Should I take tablets, sprays or gummies?

There is no doubt that taking vitamin D supplements correctly is beneficial. So which form should you choose?

Dr Basford said: “Tablets are the most widely available option on the market, and are able to deliver higher doses of active ingredients. However, absorption is slower as tablets must be broken down in the stomach and digestive tract.

“Conversely, oral sprays can be much faster in absorption compared to tablets and capsules, as the nutrients are delivered directly into the bloodstream through the mouth. However, sprays may contain sugars or artificial flavours so always check the label and choose a reliable brand.

“Finally, gummies are arguably the most pleasant to take, especially if you are uncomfortable with swallowing tablets. However, they can also contain added sugars and artificial sweeteners, and often have lower nutrient densities compared to tablets.”