Every time you move, the body releases adrenaline, so you are not far wrong in your line of thought. The adrenal glands produces around 180 different hormones including adrenaline, so protecting or even attempting to improve their function would be a logical natural pain killing route to take. Hint they are layer upon layer of epithelial cells. Of course other factors like the body attacking itself is also a problem which the adrenal glands alone cant "fix", for example too much sodium increases the Th17 cells to the point they start attacking the body. T cells from Thymus, B cells from bone marrow. However considering civilisations & Religions have existed for over 10,000years dating back to Sumerian times, observation was the only "scientific" methods available at the time, and Religions had to keep their followers healthy for the next attack, so looking into different religious fasting methods could also improve health outcomes. The world record for a water only fast, still in the Guinness book of world records is 382days, carried out in 1971 at the University of Dundee. Having done an 18day water only fast myself and felt like a teenager again, I'd highly recommend investigating it to others. A US movement in the 1950's called the Hygienists and Shelton were big advocates. Also consider the immune system attacks the food we eat, so as our immune cell count falls during a fast, are there still more immune cells now working solely removing damaged cells from the body? Its suggested viruses need carbs as noted by the use of the Keto BCAA Lysine for Cold Sores, bacteria builds biofilms when they go dormant in the body but are not impenetrable to the attacking immune system either. So there seems to be some merit with a water only fast for some, however sudden death is a risk to those with undiagnosed conditions, a bit like we see with some seemingly healthy people dying of covid. Either way, the human body, in fact any lifeform is an extremely complex biochemical and electrical real time puzzle where many chemicals play their part in lengthening life spans or shortening life spans. I wouldnt bet my life on just one supplement, unlike Linus Pauling and Vit C, its effects like all supplements, need to be put in context in the scheme of things keeping us alive, healthy and happy.