See the following article. I hadn't seen before today, but this is one of the papers that reinforces the reason for and the ways I fight seasonal flu:
Vitamin D supplements protect against acute respiratory infections including colds and flu, according to a study. The study provides the most robust evidence yet that vitamin D has benefits beyond bone and muscle health.
www.sciencedaily.com
Thanks for the link. I've read it twice so far, and I'm comparing it to the
original paper published in The British Medical Journal (BMJ).
In short, I didn't like the Science Daily's version of the conclusions, or the original BMJ paper at all. My objections are based on conclusions that I believe are unwarranted based on weak correlations with multiple studies. And there also are statistical weaknesses brought on too much variation in the overall participant populations among 25 different studies.
This paper was what is known as a meta-analysis. It compared a large number of different studies and reviews of studies. It mentioned over 11,321 participants, of whom they had access to individual participant data (IPD) for 10,933 (97%). But there is a major problem because those groups of participants were not all from the same or similar enough participant population. To make any meaningful conclusions that have statistical significance, the groups of participants must represent at least a similar subsets of the overall population. I realize that this kind of statistical significance problem puts most people to sleep, but in clinical studies, it is of enormous importance. I think they failed at that.
This analysis included 25 clinical trials conducted in 14 countries including the UK, USA, Japan, India, Afghanistan, Belgium, Italy, Australia and Canada. Did they all study the same or very similar population of participants?
Furthermore, the 25 individual trials yielded conflicting results, with some reporting that vitamin D protected against respiratory infections, and others showing no effect.
A total of 5 aggregate data meta-analyses incorporating data from up to 15 primary trials have been conducted, of which 2 report statistically significant protective effects for Vitamin D, and 3 report no statistically significant difference in effects.
If 5 previous reviews produced conflicting results, 2 reported protective effects and 3 didn’t, how can this group of authors find agreement across the board by using different number crunching methods? Despite that, the Science Daily report claims these results are “worthy of serious debate”. The BMJ paper didn’t use such strong language, and made more modest claims about the results.
Here is my biggest problem. The Science Daily report said “Overall, the reduction in risk of acute respiratory infection induced by vitamin D was on a par with the protective effect of flu vaccine against flu-like illnesses.” If you dismiss yearly flu vaccines as ineffective, how can you choose Vitamin D supplements over the vaccines based on efficacy? I don’t see how both can be true.
This BMJ paper was published in 2017. I don’t read the vitamin supplement literature, but I wonder if anyone else has tried to follow up on this report. I’d like to see a clinical trial testing 4 groups of similar participants with the following:
- Group 1 receives the yearly flu vaccine.
- Group 2 receives Vitamin D supplements.
- Group 3 receives both flu vaccine and Vitamin D supplements.
- Group 4 receives neither vaccine nor vitamin. They are the control arm.
Test all of them for any reduction of risk of acute respiratory infections.
