Vitamin D: how to get enough safely

In aid of Sun Awareness Week, taking place May 8–14, nutritionist Kim Pearson explains how to identify vitamin D deficiency and how you can help clients get back on track.

We’re constantly warned of the damaging and ageing effect of the sun’s rays on our skin, but by avoiding sun exposure completely, could we be doing ourselves more harm than good?

Exposure to UVB radiation provides the mechanism for more than 90% of the vitamin D production in most individuals, but wearing a sunscreen with an SPF as low as eight reduces the skin’s production of vitamin D by an incredible 95%.

Vitamin D is actually a prohormone and is essential for numerous functions throughout the body. It plays a key role in calcium metabolism, making it integral to bone health. It is essential for healthy neuromuscular, cardiovascular and immune function, respiratory system function and cognitive function.

Vitamin D is also vitally important to skin health, as it is directly involved in proliferation and differentiation of keratinocytes. If adequate amounts of vitamin D are not available, epidermal cells cannot differentiate optimally.

How common is Vitamin D deficiency? 

Vitamin D deficiency is more common than previously believed, and it’s on the rise. The Centers for Disease Control and Prevention reported that between 1988 and 1994, only 40% of Caucasian Americans had insufficient vitamin D levels. This soared over the next decade and between 2001 and 2004, some 70% of Caucasian Americans and 90-95% of African Americans were estimated to have insufficient vitamin D.

In Britain, there has been a re-emergence in recent years of rickets, a disease caused by vitamin D deficiency. In January 2011 Dame Sally Davies, the government’s chief medical officer, recommended all children aged six months to five years should be given vitamin D supplements, especially during winter months when the opportunity for sun exposure is reduced. Advice for children to wear a high factor sunscreen and remain covered up while outdoors are partly felt to be behind the reason for the re-emergence of rickets.

Epidemiologic evidence also links vitamin D deficiency to autoimmune disease, cancer, cardiovascular disease, depression, dementia, infectious diseases, musculoskeletal decline, and more. Common manifestations of vitamin D deficiency are lower back pain, muscle aches, and throbbing bone pain. More subtle signs may include fatigue and an increased susceptibility to infection. However, an individual may be completely asymptomatic and still be deficient.

What can cause a deficiency?

In addition to reduced sun exposure, pregnancy and breastfeeding can increase the risk of vitamin D deficiency, as can wearing full coverage clothing or spending a lot of time indoors. Children under five and adults over 65 are also at an increased risk. The darker a person’s skin type, the lower their ability to synthesise vitamin D.

In a modern world where migration is common, people whose skin type has adapted to prevent excess vitamin D synthesis in their native, sunny environment are particularly prone to deficiency when living in a sundeprived country such as the UK. My client list comprises a diverse ethnic background. Muslim women who cover themselves for religious reasons are often found to be vitamin D deficient. My Asian clients with Fitzpatrick IV-V skin type are also commonly deficient. That said, I have also seen plenty of Fitzpatrick Type I clients with low or borderline vitamin D levels.

Most of us spend a significant proportion of our time indoors, meaning that regardless of skin type, anyone can be affected.

How can I help my clients get more vitamin D?

Vitamin D levels can be assessed using a simple blood test. Ingested and cutaneously produced vitamin D is quickly converted to 25(OH)D, but only a small fraction of 25(OH)D is converted to 1,25(OH)2D, its active metabolite.

Therefore, measuring the total 25(OH)D level is the best test to assess levels of vitamin D. I routinely test my clients’ levels through The Doctor’s Laboratory (TDL), but a number of laboratories offer this service.

Of the last 20 clients that I have tested, six were deficient, six had suboptimal levels and just eight had optimal levels. Those with optimal levels were usually either supplementing, or spent a significant amount of time abroad.

The dosing strategy for correcting vitamin D deficiency differs to that for most other nutrients. Normally we take a “little and often” approach, supplementing nutrients regularly while also increasing dietary sources. However, for individuals with vitamin D deficiency, treatment may include oral supplementation of one 50,000 IU dose per week for eight weeks. After vitamin D levels normalise, a daily maintenance supplement of 800 to 1,000 IU vitamin D3 is usually sufficient.

Vitamin D3 is the type that most experts agree should be used. Humans synthesise vitamin D3 in response to sunlight so it is the most natural form to supplement.

Unfortunately, there are few good quality, natural sources of vitamin D. Eggs and oily fish, such as wild salmon, sardines and mackerel, provide vitamin D, but most other food sources come in the form of highly processed fortified foods such breakfast cereals, which I don’t personally recommend.

How much time should clients spend outside? 

There’s no doubt that most of us could benefit from spending a more time outdoors. Making a conscious effort to tear ourselves away from a screen and get out for a short daily walk could improve our health and wellbeing in many ways.

As with many things in life, the key to safe, vitamin D-promoting sun exposure is moderation. The NHS Live Well website advises short daily periods of sun exposure without sunscreen during April to October between 11am and 3pm.

It adds, “Evidence suggests that about 10 to 15 minutes is enough for most lighter-skinned people – and is less than the time it takes you to start going red or burn.”

That said, we often (quite rightly) advocate daily use of sunscreen as part of a skincare regime and in doing so could be inadvertently reducing our client’s ability to synthesise vitamin D from the sun. Therefore, recommending a daily vitamin D3 supplement, especially during winter months, is something you might wish to consider.

Your vitamin D checklist: 

• Know the individual’s vitamin D level by running a blood test
• Recommend that skin is exposed to sunlight daily
• If applying sunscreen to the face, it could be the arms that are exposed (of course – at a level that doesn’t cause redness or burning)
• Advise that oily fish and eggs are included in the diet regularly
• Recommend a vitamin D3 supplement at a dose to suit the needs of the individual. Most of us can benefit from consistent supplementation, regardless of the time of year.