For me, I used to take Centrum (a popular multivitamin my dad had me take since I was 10 or so) daily for decades, I stopped several months ago when I ran out and was too lazy to get more. I felt no different. I would assume I'd feel a deficiency not taking it but I never did. I started having doubts, so I changed things up a bit.
What I take now as supplements, not all daily, but often:
- Protein supplements for exercise (whey isolate only with no flavor and minimal ingredients)
- Iodine, a drop a day, the only daily one I still use because I can feel when I don't
- Milk thistle for my liver - I like to eat a lot of toxic raw seafood like oysters and it seems to help
- Fuck loads of B-vitamins after I drink since alcohol burns B-vitamins fast af
For avoiding:
- Fluoride - I buy expensive water filters to get rid of fluoride. If you take care of your teeth, there is no need for it. It can only harm you.
- Tap Water - Similar to above because I live in SoCal and sewage is treated and dispensed as drinking water. The pharmaceuticals are not filtered well at city level, so I filter them myself. I used to take my male cat to the vet for urinary crystals (kidney stones for humans) multiple times/year, I started filtering it with good filters, never had a problem with him since. Thousands of dollars lost to him not being able to pee from drinking tap water, never has an issue with properly filtered water. Please do the same. I may gift you a filter if you need if you have cats and message me if you can't afford it.
Well, zinc is very much a necessary nutrient. Zinc is used by the body to maintain hair and skin, to regulate the immune system and mood, and the production of testosterone.
So in the case of men, zinc plays a big part in developing and sustaining muscle mass, sexual stamina, fertility, growth of facial hair, and contributing toward baldness. Testosterone also plays a part part in female biology, but I've never bothered to read up on that one.
You've got to be careful about dose though. Zinc toxicity is nasty. Overdoses will cause all kinds of painful stomach issues. A too-high dose over a long period can block your body from using iron and other good metals in your diet, which can cause severe anemia.
But to answer your question about zinc and the cold virus, I'd take a guess and say that if you already have proper levels of zinc in your diet, you won't benefit from taking more. In fact, nutrient deficiencies might be the reason your friend's brother is getting sick in the first place.
Edit: and on the subject of alcohol, consider taking some magnesium too. Alcohol makes you pee out more magnesium than normal