"There is much confusion about nutritional supplements and conflicting reports about their benefits, effectiveness, and even safety. This is unfortunate, because I believe that for the vast majority of us, they are fundamental and essential for human survival and optimal health. In fact, the word “vitamin” is derived from “vital amine”— vital components found in our diet without which we can get very sick or die. Yet 90 percent of Americans are deficient in one or more essential nutrients because most of us live on processed, nutrient-depleted food. In fact, 10 percent of us don’t get enough vitamin C to prevent scurvy, a profound nutritional deficiency syndrome first described in sailors who ate no fresh fruits and vegetables, and up to 80 percent have inadequate levels of vitamin D. Let me explain briefly what vitamins and minerals do. They are not drugs, they do not work like drugs, and they cannot be studied like drugs, which is why you hear so much confusing information in the media about nutritional research. Vitamins and minerals are essential components of our biology that make every chemical reaction in our body function, including metabolism and calorie burning. Each chemical reaction requires a catalyst (an enzyme), and each catalyst has a “helper” or cofactor (coenzyme). Vitamins and minerals are those helpers. Without optimal levels of vitamins and minerals, your biochemistry doesn’t run well. Most of our ideas about nutrients revolve around the minimum amount we need to prevent severe deficiency diseases like scurvy or rickets, not the amounts we need for optimal or enhanced biological function and health.  We are starving in the midst of plenty— overfed, undernourished, and never satisfied. When we eat real food, which contains many nutrients, we are more satisfied and eat less. But still, we need a foundational amount of high-quality nutrients to help run our engines. Getting adequate vitamins and minerals helps you burn calories more efficiently, helps regulate appetite, lowers inflammation, boosts detoxification, aids digestion, regulates stress hormones, and helps your cells become more insulin sensitive."

Hyman, Dr Mark (2014-02-27). The Blood Sugar Solution 10-Day Detox Diet (Kindle Locations 1421-1444). Hodder & Stoughton. Kindle Edition.

This Desk Reference by Jen O'Sullivan is very useful to have. 

Most of my discussions around supplements are to make life easier for all of us regarding supporting body and mind in our third-age wellness endeavours. however, the book is a great all-rounder.