My secret of how to feel good and less sick: get enough sleep (go to bed every day at 11 pm, get up at 6: 30-7: 00 am), eat right (of course, I do not refuse to drink wine or a little whiskey on holidays, but in moderation, or sometimes eat something tasty and harmful). Physical activity is important for the body to work, there is no blood stagnation. Also, in winter, I definitely take multivitamins for 3-4 months, I prefer Optimum Nutrition Opti-Men. But other options for high-quality vitamins can be found here The Best Multivitamin for Men’s Bodybuilding 💊. There are both cheaper and more expensive.