Vitamin D is essential for bone health, immune function and overall wellbeing. And it becomes even more crucial^[1] as we age.

New guidelines from the international Endocrine Society recommend^[2] people aged 75 and over should consider taking vitamin D supplements.

But why is vitamin D so important for older adults? And how much should they take?

Young people get most vitamin D from the sun

In Australia, it is possible for most people under 75 to get enough vitamin D from the sun throughout the year^[3]. For those who live in the top half of Australia – and for all of us during summer – we only need^[4] to have skin exposed to the sun for a few minutes on most days.

The body can only produce a certain amount of vitamin D at a time. So staying in the sun any longer than needed is not going to help increase your vitamin D levels, while it will increase your risk of skin cancer.

But it’s difficult for people aged over 75 to get enough vitamin D from a few minutes of sunshine, so the Endocrine Society recommends^[5] people get 800 IU (international units) of vitamin D a day from food or supplements.

Why you need more as you age

This is higher than the recommendation for younger adults, reflecting the increased needs and reduced ability of older bodies to produce and absorb vitamin D.

Overall, older adults also tend to have less exposure^[6] to sunlight, which is the primary source of natural vitamin D production. Older adults may spend more time indoors and wear more clothing when outdoors.

As we age, our skin also becomes less efficient^[7] at synthesising vitamin D from sunlight.

The kidneys and the liver, which help convert vitamin D into its active form, also lose some of their efficiency with age. This makes it harder for the body to maintain^[8] adequate levels of the vitamin.

All of this combined means older adults need more vitamin D.

Deficiency is common in older adults

Despite their higher needs for vitamin D, people over 75 may not get enough of it.

Studies have shown^[9] one in five older adults in Australia have vitamin D deficiency.

In higher-latitude parts of the world, such as the United Kingdom, almost half^[10] don’t reach sufficient levels.

This increased risk of deficiency is partly due to lifestyle factors^[11], such as spending less time outdoors and insufficient dietary intakes of vitamin D.

It’s difficult to get enough vitamin D from food alone. Oily fish, eggs and some mushrooms^[12] are good sources of vitamin D, but few other foods contain much of the vitamin. While foods can be fortified with the vitamin D (margarine, some milk and cereals), these may not be readily available or be consumed in sufficient amounts to make a difference.

In some countries such as the United States^[13], most of the dietary vitamin D comes from fortified products. However, in Australia^[14], dietary intakes of vitamin D are typically very low because only a few foods are fortified with it.

Why vitamin D is so important as we age

Vitamin D helps the body absorb calcium^[15], which is essential for maintaining bone density and strength. As we age, our bones become more fragile, increasing the risk of fractures and conditions like osteoporosis.

Keeping bones healthy is crucial. Studies have shown^[16] older people hospitalised with hip fractures are 3.5 times more likely to die in the next 12 months compared to people who aren’t injured.

People over 75 often have less exposure to sunlight. Aila Images/Shutterstock^[17]

Vitamin D may also help lower the risk^[18] of respiratory infections, which can be more serious in this age group.

There is also emerging evidence for other potential benefits, including better brain health^[19]. However, this requires more research.

According to the society’s systematic review, which summarises evidence from randomised controlled trials of vitamin D supplementation in humans, there is moderate evidence^[20] to suggest vitamin D supplementation can lower the risk of premature death.

The society estimates supplements can prevent six deaths per 1,000 people. When considering the uncertainty in the available evidence, the actual number could range from as many as 11 fewer deaths to no benefit at all.

Should we get our vitamin D levels tested?

The Endocrine Society’s guidelines suggest^[21] routine blood tests to measure vitamin D levels are not necessary for most healthy people over 75.

There is no clear evidence that regular testing provides significant benefits, unless the person has a specific medical condition that affects vitamin D metabolism, such as kidney disease or certain bone disorders.

Routine testing^[22] can also be expensive and inconvenient.

In most cases, the recommended approach^[23] to over-75s is to consider a daily supplement, without the need for testing.

You can also try to boost your vitamin D by adding fortified foods to your diet, which might lower the dose you need from supplementation.

Even if you’re getting a few minutes of sunlight a day, a daily vitamin D is still recommended.

References

1. ^{^} more crucial (pubmed.ncbi.nlm.nih.gov)
2. ^{^} recommend (pubmed.ncbi.nlm.nih.gov)
3. ^{^} throughout the year (healthybonesaustralia.org.au)
4. ^{^} only need (healthybonesaustralia.org.au)
5. ^{^} recommends (pubmed.ncbi.nlm.nih.gov)
6. ^{^} less exposure (www.ncbi.nlm.nih.gov)
7. ^{^} less efficient (pubmed.ncbi.nlm.nih.gov)
8. ^{^} harder for the body to maintain (www.sciencedirect.com)
9. ^{^} have shown (www.abs.gov.au)
10. ^{^} almost half (www.ncbi.nlm.nih.gov)
11. ^{^} lifestyle factors (pubmed.ncbi.nlm.nih.gov)
12. ^{^} Oily fish, eggs and some mushrooms (dietitiansaustralia.org.au)
13. ^{^} United States (ods.od.nih.gov)
14. ^{^} Australia (pubmed.ncbi.nlm.nih.gov)
15. ^{^} helps the body absorb calcium (www.ncbi.nlm.nih.gov)
16. ^{^} have shown (pubmed.ncbi.nlm.nih.gov)
17. ^{^} Aila Images/Shutterstock (www.shutterstock.com)
18. ^{^} lower the risk (pubmed.ncbi.nlm.nih.gov)
19. ^{^} better brain health (pubmed.ncbi.nlm.nih.gov)
20. ^{^} moderate evidence (pubmed.ncbi.nlm.nih.gov)
21. ^{^} suggest (pubmed.ncbi.nlm.nih.gov)
22. ^{^} testing (www.ncbi.nlm.nih.gov)
23. ^{^} recommended approach (pubmed.ncbi.nlm.nih.gov)