Vitamin D supplements don't help ward off colds and flus: research

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Vitamin D supplements will not protect Australians from catching colds, flus and other respiratory infections, new research has found.

The findings come after a five-year clinical trial, led by Brisbane’s QIMR Berghofer Medical Research Institute, involving 16,000 Australians aged between 60 and 84.

The trial was the largest of its kind to study the relationship between vitamin supplements and respiratory infections.

Each participant was asked to take a capsule once a month for five years – half were given a vitamin D supplement, while the other half were given a placebo or sugar tablet.

At the end of every year, participants completed a health survey detailing any major illnesses or medical events.

Some 2600 participants were also asked to keep a daily diary during winter to record general observations of their health, particularly if they had cold or flu symptoms.

Lead researcher, Professor Rachel Neale said while the findings showed taking vitamin D did not stop people from getting respiratory tract infections, there was some evidence that it reduced the length and severity of infection.

“The key message is that if you are not vitamin D deficient, taking vitamin D is unlikely to stop you from getting a head cold or the flu,” Professor Neale said.

“It may reduce the length of it a little bit, but not enough to really warrant taking vitamin D if you’re not already vitamin D deficient.”

‘More is not better’

Professor Neale said the findings did not surprise her.

“There’s been quite a lot of controversy over vitamin D and how much of it we need in our bloodstream,” she said.

A woman sits at a desk.
Professor Rachel Neale says the research trial was the largest of its kind.(Supplied: QIMR Berghofer Medical Research Institute)

“The findings of this, which suggest that more is not better, would indicate that we shouldn’t just go out and routinely supplement the whole Australian population,” she said.

“It does tell us that being aware of avoiding vitamin D deficiency is important.

The data will be used to inform public policy and clinical care.

Participant Erica French was eager to join the clinical trial after being given conflicting advice about vitamin D consumption.

“I was hearing a lot of different information,” she said.

“First of all I’ve got my own doctor telling me, ‘no more sun Erica … hat, sunscreen, cover up, keep an umbrella over yourself’.

“Then on the other hand … the other information you read is that you’ve got to have some sun exposure every day to get your vitamin D up, so I’m thinking, ‘I don’t get this, which is the way I’m supposed to go?'”

She said she remembered being “sick-free” for five years during the trial.

“I can remember saying to my doctor that I thought I was really healthy,” Ms French said.

“I think it’s good to know that we don’t have to be putting vitamin D in our cereal or our milk or whatever else – that we are as a nation mostly getting enough, and that by taking extra we’re maybe doing other things, but not necessarily helping with respiratory tract infections.

“I am not sure that it’s fully answered all of my questions … but it has helped.”

The Institute’s five-year trial concluded just before the coronavirus pandemic took hold across the world, killing nearly 2 million people to date.

Despite this, Professor Neale said the results were still relevant in a time when immune systems have never needed to be stronger.

“We didn’t measure coronavirus … but we can kind of extrapolate,” she said.

“Our finding of a reduced length and severity of infection, albeit a small reduction, indicates that perhaps vitamin D does influence the immune system in people.

“And that means that in people who are vitamin D deficient, if we were to treat their deficiency, that might have some benefit for their immune system and arguably some benefit for the coronavirus.”

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Written by ABC News


Total Comments: 8
  1. 1

    When I had the last bloods, the Dr told me I am the only person he has seen that does not have a vitamin D deficiency. I do take regular vitamins and go walking, but do not take a vitamin d supplement on its own. (touch wood) I don’t get colds/flu but am autoimmune, so have to look after myself.

  2. 1

    Mystified why this trial was based on one Vitamin D pill per month. All advice I have read on this topic recommends taking a maintenance dose equivalent to 1000 IU per day (one pill), rising to 3000 IU per day or more in cases where low D content in blood is detected. I’ve been taking 2000 IU per day for months (age 76) with no flu symptoms and no side effects.

  3. 2

    Yes most information on Vitamin D and SARS coronavirus 2 says that ideally the supplements should be taken daily but if not, then weekly. So called monthly Bolus shots are not shown to be effective. As noted by the earlier poster, a lot of Australians are Vitamin D deficient, in part because we avoid the sun and use sunscreens to reduce the likelihood of developing skin cancer. Also, given the real problems with Covid arise when you have a severe case, why be so dismissive of the effect of reducing severity – no-one ever suggested Vitamin D operates as a vaccine against these viruses.

  4. 4

    ““And that means that in people who are vitamin D deficient, if we were to treat their deficiency, that might have some benefit for their immune system and arguably some benefit for the coronavirus.””

    Who did this trial, Peter Evans? The paragraph “We didn’t measure coronavirus … but we can kind of extrapolate” is most certainly a scientific breakthrough. Not. I had a desk job and my doctor prescribed Vitamin D and now that I am retired, he has taken me off it. I might add that the dosage was daily, not monthly. I note that Professor Rachel Neale qualified as a Veterinarian and her further studies were about cutaneous squamous cell carcinoma. She is a lot better qualified than I am to be making medical statements but I can’t see any of her qualifications allowing her to be classed as an expert on coronavirus treatment. Seems our ABC has once more been dazzled by a person’s university degree joined with the magic name “Oxford”.

  5. 1

    The headline doesn’t agree with the text – the latter being mainly correct.

    Many – maybe most – people are deficient in vitamin D.
    That’s because we don’t wander about outside in the nuddy as much as nature intended.

    People who are deficient in vitamin D *will* benefit from supplements.
    The minority who are not will not.

    There has been a clear link established between those who suffer when infected with COVID and those who are deficient in vitamin D. Sadly big pharma doesn’t stand to make any money on vitamin D supplementation – if they did it would be a different story.

  6. 0

    I have been taking a Calcium + vitamin D supplement for more years than I can remember, I am 83 years young and in very good health, I also take a range of other vitamins so I can regulate the dosage.

  7. 0

    I too am over 80, and have been taking Vit D for years…..I was found to be deficient 10 years or more ago….I do not like to spend a lot of time in the sun….. so I just take 1000 u/s once a day….job done. I just buy mine at one of the major supermarkets.

  8. 0

    This is the first I’ve heard of Vitamin D having anything to do with colds or flu. I’m nearly 80 and Vitamin D deficient, so take pills.



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