Why is Vitamin D ('the sunshine vitamin') important for our health? Why might we be at risk of Vitamin D deficiency as we get older? What can we do to avoid this?  

What happens if we don’t get enough Vitamin D?

This can have effects at different stages throughout our life:

• During pregnancy Vitamin D insufficiency is common during pregnancy. Whether this increases health risks is still being researched. A review of existing research in 2016 found some but not all studies suggested an association between Vitamin D deficiency and pre-eclampsia (a complication that can arise during pregnancy, with symptoms including high blood pressure). Where Vitamin D was combined with calcium the evidence of benefit here appeared more consistent. A review of published evidence in 2012 even suggested that Vitamin D deficiency in pregnancy or early childhood may increase the chances of autism in children who are genetically predisposed, although more research is needed here.
• For children Vitamin D deficiency can cause rickets (osteomalacia) – a softening and weakening of the bones which can lead to fractures and deformity. 
• During our lives Vitamin D appears to affect how well our immune system functions. Lack of vitamin D in the winter months may play a part in the higher rates of flu infection. As the Harvard Gazette reported in 2017, Vitamin D may reduce the risk of colds and flu. 
  
• For the elderly in particular, too little Vitamin D and calcium can result in bone loss and hip fractures. Vitamin D deficiency may also be associated with muscle weakness, particularly as muscle mass reduces from the age of 40, putting elderly people at increased risk of falls and fractures.
• Vitamin D may even help us live longer - according to one study carried out in 2007 the concentrations of Vitamin D in serum of a group of women, who were receiving Vitamin D supplement, were closely linked with the increased length of the telomere (an indicator of longevity). And a systematic review published in 2014 found that Vitamin D3 seemed to decrease mortality in elderly people living independently or in institutional care – although it recommended that more research was needed.

Vitamin D and respiratory infections 

In a study published in the British Medical Journal in 2017, researchers examined data from trials involving almost 11,000 participants from all over the world. They considered the effect of vitamin D on acute respiratory illnesses, such as bronchitis, pneumonia, ear infections and the common cold. The analysis showed that regular supplements resulted in a 12 per cent reduction in the number of people suffering an acute respiratory tract infection. Meanwhile, for people with the lowest levels of Vitamin D, supplements cut their risk by 50%. 

What are the effects of age? 

As we become older we may face special problems in getting enough Vitamin D:

• As we age our skin becomes thinner. Because Vitamin D from sunlight is processed through the skin this means our skin produces less Vitamin D than when we’re younger.
  
• Changes in lifestyle can also limit access to sunlight e.g. less outdoor activity or even being housebound, and the type of clothing we wear.
• We may also eat a less varied diet, with a lower natural vitamin D content. 
• Finally, our kidneys may produce less of an important metabolite of Vitamin D because our kidneys function less efficiently with age.   
  

These changes potentially put older people at risk of vitamin D deficiency, especially in the winter. If you can afford it, a winter holiday to somewhere sunnier may help top up your Vitamin D.

How much Vitamin D do we need?

A blood test is the usual way to identify your Vitamin D level. Most NHS Trusts classify Vitamin D levels as follows: below 25 nmoL/L is Deficient; 25 – 50 nmpL/L is Insufficient; 50 – 75 nmol/L is Adequate; and above 75 nmoL/L is Optimal. 

What are the main sources of Vitamin D?

Exposure to sunlight is the most important source. It helps the skin make vitamin D. During the UK summer (April – October), the NHS advises short daily exposure to the sun. That’s 10 – 15 minutes per day between 11am and 3pm. The amount depends on your skin type. More if you have dark skin, less if you have very fair skin. This needs to be without sunscreen or cosmetics containing sunscreen. And exposure means receiving sunlight on large surface areas such as arms and legs (not just the face).

Once you’ve topped up your Vitamin D then either stay out of the sun or add sunscreen or cover up, to keep your skin safe. 

The best dietary sources include cod liver oil as well as oily fish such as herring, sardines, mackerel, salmon and tuna. Egg yolks, mushrooms and liver contain smaller amounts. Vitamin D can also be found in foods such as fortified milk and cereals. 

Should we take Vitamin D supplements?

Exposure to recommended levels of sunshine and a diet rich in vitamin D should usually provide adequate levels. The NHS doesn’t normally recommend supplements. However it does recommend Vitamin D supplements for some specific groups of people e.g.

• Those over 65
• Those with darker skin or not exposed to much sun
• Pregnant and breastfeeding women 

For the UK it also recommends Vitamin D for people generally between October and March, as there isn't enough sunshine to provide enough Vitamin D.

Don’t overdose on Vitamin D supplements though, as that can cause a range of side effects, from nausea and vomiting to kidney problems.  The daily dose recommended by the NHS is 10 micrograms.

What about Calcium as a partner to Vitamin D?

Calcium and Vitamin D are an important combination. Calcium is important for strong bones and Vitamin D helps our body break down and absorb calcium.

For patients with Vitamin D deficiency in institutionalized settings, whose intake of Vitamin D and calcium is supervised, this seems helpful in reducing fractures. And this also seems to reduce falls, particularly in older women.   

Recent controversy about Vitamin D supplementation

A 2016 review in the British Medical Journal suggested that Vitamin D supplementation on its own (e.g. without calcium) may not be as helpful as previously proposed. In particular the authors argued there is no evidence that taking vitamin D supplements alone reduces the risk of fractures or falls, or improves bone strength.

The NHS reviewed this report. It agreed that ideally we can get all the vitamin D we need through a combination of diet and sensible exposure to sunlight and that the evidence does not show that people with normal levels of vitamin D benefit from taking supplements. However, it then  went on to make the point that we don’t live in an ideal world and that many people in the UK eat unhealthy, vitamin D-poor diets and also don't get enough exposure to sunlight.The NHS also noted that people with darker skin, from African, Afro-Caribbean, and south Asian backgrounds, may not get enough vitamin D from sunlight in the summer and should also consider taking a supplement all year round. The advice from the NHS therefore remains to take a Vitamin D supplement during at least the autumn and winter months – while being alert for possible signs of excessive vitamin D levels causing a build-up of calcium in the blood (hypercalcemia). Warning signs and symptoms loss of appetite, feeling and being sick.

 So what steps should we take? 

• Expose our arms and face to the sun for 10 – 15 minutes per day in the summer, depending how dark our skin is (this figure applies to the UK and may need reducing in countries where the sun is stronger). 
• Include vitamin D rich food in our diet each week – especially oily fish. 
• Take a Vitamin D supplement regularly if we are in ‘at risk’ group e.g. over 65, institutionalised, wearing enveloping clothing, pregnant or dark-skinned.
• If we are not in an 'at risk' group and are in the UK take a Vitamin D supplement (10 mcg) between October and March, to compensate for the lack of sunshine.
• Don’t overdose on supplements, as there can be side effects.
• If we can afford it, winter holidays in the sun can also help. 

Richard Franklin May 2017. Next review date April 2022.