CAUTION: Vitamin C should probably be taken on an empty stomach by most people, because it can increase iron absorption. Most men do not need increased hermatocrit/hemoglobin and/or iron stores (ferritin), due to red meat consumption and other factors. Elevated iron levels have been implicated in heart disease and various brain conditions. (Iron literally "rusts" the body.) There is also a study out there that shows, if you have over 10% fat in your stomach, Vitamin C can actually increase nitrosamine formation. (This is a controversial finding however.)
You seem to stress the importance of sunlight as a source of vitamin D. I live in Finland where you get high sunlight only for short periods during the summer, and none for most of the year.
In your book you say “We can also ﬁnd vitamin D in food sources like dairy or in supplements, but the best way to receive vitamin D is naturally”, but you never explain why food-derived D is so unnatural. I eat mackerel, sardines, cod liver and lots of eggs weekly, all of these are supposed to be sources of vitamin D. Do you think I should still supplement on top of these (if I can’t or don’t want to get lots of sun exposure)?