Vitamin D, our health, and ageing



In this article, we look at why we need Vitamin D, and describe some of the effects if we don’t get enough of it.

  • What are the major sources of Vitamin D?
  • The effects of Vitamin D deficiency at different stages of life
  • What are the effects of age?
  • How much Vitamin D do we need?
  • Should we take Vitamin D supplements?
  • What about a calcium+Vitamin D combination?
  • What can we do to ensure we get enough Vitamin D?


What are the major sources of Vitamin D?




Exposure to sunlight is the most important source of Vitamin D, as it helps the skin make Vitamin D. 


During the UK summer (April to October), the NHS advises short daily exposure to the sun. That’s 10 to 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 exposure needs to be without sunscreen or cosmetics containing sunscreen – ‘exposure’ means receiving sunlight on large surface areas such as the arms and legs, and not just the face. 


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


The best dietary sources include cod liver oil, as well as oily fish such as herring, sardines, mackerel, salmon, and tuna (fresh, not tinned). Egg yolks, mushrooms and liver contain smaller amounts. Vitamin D can also be found in foods such as fortified milk (i.e., with added vitamins and minerals) and cereals.


The effects of Vitamin D deficiency at different stages of life

Not getting enough Vitamin D at different stages in our life can have negative effects on our health:

During pregnancy

Vitamin D insufficiency is common during pregnancy and can result in health complications.

In a 2022 review of Vitamin D and pregnancy studies, deficiency of the vitamin was shown to be associated with pre-eclampsia (a complication involving high blood pressure and high levels of protein in the urine), and possibly also gestational diabetes mellitis, higher incidence of caesarean section and of preterm birth, although the evidence for these latter conditions is mixed.

There is increasing evidence that Vitamin D deficiency in pregnancy and early childhood can also lead to the occurrence of autism spectrum disorder (ASD). ASD is a neurodevelopmental disorder that can lead to severe social behavioural difficulties, narrow interests and repetitive, stereotypes behaviours.

For children

Vitamin D deficiency can cause rickets (osteomalacia) – a softening and weakening of the bones – which can lead to fractures and deformity. Also, lower respiratory tract infections, such as bronchiolitis in early childhood, have been associated with low levels of Vitamin D.

During our lives 

Vitamin D also plays a role in the immune system’s response to infections. Lack of Vitamin D in the winter months may therefore play a part in higher rates of flu infection. In support of this, a 2021 study that pooled together findings from 43 studies showed that taking Vitamin D supplements reduced the risk of having one or more acute respiratory infections. However, the amount of this protective effect varied between studies.

However, Vitamin D supplementation appears to have no significant impact on the risk of Covid-19 infection, although it does have a significant protective effect against admission to an intensive care unit, and death.

Later in life

For the elderly in particular, too little Vitamin D and calcium can result in bone loss and hip fractures. Vitamin 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. However, the evidence here is mixed.

Vitamin D may even help us live longer. The findings of a 2021 review suggest that higher Vitamin D concentrations (which can be achieved by taking supplements) are associated with longer telomere length – telomeres are part of our genetic make-up and an indicator of longevity. This highlights the vitamin’s potentially beneficial effects on ageing and age-related diseases.

However, in a pooled analysis of 52 trials, an association between Vitamin D supplementation and mortality from any cause was not indicated when compared with placebo or no treatment, although the risk of cancer death was reduced by16%.


What are the effects of age?

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

  • As we age our skin becomes thinner. Because Vitamin D from sunlight is processed through the skin this means that our[2]  skin may produce less Vitamin D.
  • Changes in lifestyle can also limit access to sunlight, for instance, less outdoor activity or 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. Limited sun exposure, fortified foods such as dairy products and cereals, and supplementation with Vitamin D can all help to top up your Vitamin D.


How much Vitamin D do we need?

A blood test is the usual way used to identify Vitamin D levels. The National Institute for Health and Care Excellence (NICE) defines Vitamin D thresholds in respect to bone health like this



Should we take Vitamin D supplements?

Exposure to recommended levels of sunshine and a diet rich in Vitamin D should usually provide adequate levels during the summer.

However, some people will not make enough Vitamin D from sunlight because they have little or no exposure, or they are from African, Afro-Caribbean, or South Asian backgrounds and have a darker skin. In these cases, the NHS recommends taking a daily supplement of Vitamin D.

The NHS also recommends a daily Vitamin D supplement for people in the UK between October and March, as the sun is not strong enough for the body to make Vitamin D. 


Taking too many Vitamin D supplements 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 a Calcium+Vitamin D combination?

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. 

Supplementation with calcium, Vitamin D, or both in combination, has been reported as not preventing fractures in community-dwelling adults. Vitamin D with calcium is, however, associated with an increase in the incidence of kidney stones.

However, in a 2021 randomised, controlled trial, residents of 30 aged-care facilities who received additional calcium in the form of dairy foods, had a reduced risk of falls and fractures, compared to those of another 30 similar care facilities who received their usual diet. All residents (N=7,195) in both groups also received routine Vitamin D supplementation.


What can we do to ensure we get enough Vitamin D?

  • Expose our arms and face to the sun for 10 to 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 an ‘at risk’ group e.g., over 65, institutionalised, wear clothing that prevents exposure to the sun, pregnant, or dark-skinned.
  • If we are not in an 'at risk' group and are in the UK, take a Vitamin D supplement (10 micrograms) between October and March, to compensate for the lack of sunshine.
  • Don’t overdose on supplements, as there can be negative side effects.


Barbara Baker, July 2023. Next review date: June 2028


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