Yes, most definitely. I cut all bread and pasta from my diet long ago and try to eat mostly meats, beans and greens. Mood changes are noticeable. Vitamin D supplements, however, are still quite important. I don't mean to sound like a self-medicating quack here, but there is a chance that many severe cases of covid are somehow linked to vtm D deficiency. My dad has been taking it for years, prescribed by his doctor, and my mom started taking it recently prescribed by her (different) doctor, precisely because it might prevent covid complications. The latter said there is absolutely no harm in me taking it as well, even though I'm not in any risk group.I agree with @rizen suha on eating natural; however, to get your vitamin D levels into the green zone during winter, I think you have to take it as a vitamin D3 supplement (optimally in an oily solution), because you can't get it directly from food, and as we know, in the sunny season, the body is able to make it from the sunlight on the skin. I like fiber-rich foods, too.
And I double down on the cold showers. It's good stuff.