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Vitamin D may reduce the risk of respiratory illness by as much as 40 per cent

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Scientists from the University of Colorado have found that older patients who had high doses of vitamin D, the “sunshine vitamin”, were less likely to suffer from respiratory illnesses such as the flu, than those who had lower amounts. The researchers surmised that this is due to vitamin D’s effect on the immune system. 

This latest research builds on a wealth of studies that have looked at the many and varied benefits of the this vitamin. GP and medical nutritionist Dr Sarah Brewer takes us through some of the others.


Have you ever wondered why you get more coughs, colds and respiratory bugs during winter than in summer months? While huddling together indoors may help germs spread more easily, falling vitamin D levels are also to blame for reduced protection.

Vitamin D is involved in the activation of macrophages – the hunter-killer cells that engulf and destroy invading viruses, bacteria and even fungi.  

Low mood

Vitamin D deficiency has been associated with depression and low mood – particularly in winter - as our bodies obtain most of our vitamin D via UVB rays from the sun. Research published in the British Journal Psychiatry found those with the lowest vitamin D levels were up to twice as likely to develop depression as those with highest levels.

Life expectancy

Higher vitamin D levels may help us live longer, according to research in people aged over 50 published in the BMJ. Studies carried out in eight countries, involving 26,000 men and women, found those with the highest vitamin D levels were 57 per cent less likely to die from any medical cause during the research durations than those with the lowest levels.

What dose do I need?

10mcg is the minimum needed to prevent conditions linked with vitamin D deficiency such as muscle and bone aches and pains, osteomalacia (softening of the bones) or rickets.

This is the amount we are advised by Public Health England to take during winter.

While that's great advice as far as it goes, it doesn't take into account how important the vitamin is for a strong immune system and protection against many health issues – such as those discussed above.

There's also increasing evidence some people may need higher doses of 25mcg to 50mcg, particularly the elderly.

If you always use sunscreen, cover up in the sun, have dark skin or are house bound, you may need vitamin D supplements all year round.

Sarah Brewer graduated as a doctor from Cambridge University. Having worked in hospitals and general practice, she gained a Master's degree in Nutritional Medicine from the University of Surrey. She is the author of over 60 popular health books and writes widely on all aspects of health including complementary medicine. More from this expert.

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No statement or article should be understood as providing treatment advice. If you have a health problem consult your GP and check compatibility of new supplements with your GP or Pharmacist if you are taking any prescription medication.

Nutrition Expert sources the latest information and advice from a range of qualified doctors, nutritionists and coaches. We always endeavour to have the most up to date information possible and publish new content weekly. However with the constant research in this field sometimes some of our older articles can become out of date. If you see anything that you believe needs to be updated please let us know via our Contact Us page