What are some natural ways to boost your immune system?

@CheekyBadger A healthy diet and movement. That's it. No supplement, no vitamin, no mineral has been shown to have any notable efficacy against colds and flu. Get immunized, maintain handwashing, mask wearing and social distancing, and you stand a fair chance of scooting through.

@Graylight Healthy diet and exercise is really good - unfortunately in the case of vit D we get the majority of our intake (at least in western countries) through our exposure to sunlight. In winter months, in parts of the world that have swings in the amount of daylight hours (as well as the angle of the sun being lower at it's zenith) the amount of sun available to make vit is vastly reduced - this isn't conjecture, it is verifiable through studies that sample blood). In UK and US at least we know from existing studies that vit D is typically too low for a sizable proportion of the population. A corollary is Japan where diet is much richer in foods containing vit d and levels are much healthier. So if possible to get it in diet then, absolutely, that is best as you get other important nutients too. Vaccines can be effective - but we don't have vaccines for the vast majority of things that cause colds - there are over 200 viruses that can cause a common cold - some are corona viruses (like COVID19), some are influenza virues (like what we refer to as "flu") some are parainfluenza viruses and many are rhinoviruses. It's interesting to note that you can acquire a flu virus but if you have mild symptoms it is just considered a cold - the same virus causing more severe symptoms is what you would call "flu". Most of the symptoms these viruses cause is actually your immune system doing it's thing to rid your body of the foreign invader - e.g. blocked/runny nose or fever.

Washing hands before eating is good practice as there are other pathogens that can be problematic when they get inside you. That isn't going to protect against respiratory viruses though - these are mostly "caught" through breathing them in (not saying you can't get them by touching people's snot etc but those are in a minority). Unfortunately cloth or even surgical masks are not effective in stopping you either transmitting or inhaling them and we think higher density masks have some effectiveness- they won't guarantee that you won't catch something so relying on them isn't good idea. Social distancing is more effective - but as a species we are not designed to live apart and lack of exposure to pathogens can have negative effect on longer term immunity - unless someone is cutting themselves off entirely forever they will have to come in contact with others eventually and when they do they will be exposed to a milleau of different pathogens that their immune system which hasn't had much to do will have to deal with all at once.

@CheekyBadger Bear in mind there's no causative correlation proven between good vit. D levels and better immunity against respiratory pathogens. In particular, as far as I can recall, there's no RCTs showing reduced infection rates, lesser symptoms or shorter recovery times in populations supplemented with vit. D. as opposed to populations with similar characteristics and not supplemented.

@Elessar and that’s my point. Vitamin D is essential, particularly in women. It’s true that we get much of it from the sunlight, but the sunlight doesn’t have to be warm; we still get vitamin D in the winter. Regardless, it’s not linked to Improving respiratory function or listen I know you need breakfast sweetie killing viruses and bacteria. It’s great for other things but not cold and flu prevention.