Micronutrients – Vitamins

Introduction

Micronutrients are, as the name suggests, those needed by the body in smaller quantities. (Macro meaning large and micro meaning small). Vitamins and minerals fall into this category. (We also need water and oxygen, but I’ll take those as read).

There are 13 vitamins in total: A, B1, B2, B3, B5, B6, B7, B9, B12, C, D, E and K. The fat-soluble vitamins are A, D, E and K and, as their name suggests, they are found in fats and need to be consumed in/with fats for their absorption. The water-soluble vitamins are vitamin C and the vitamin B group, which comprises: B1 (thiamine); B2 (riboflavin); B3 (niacin); B5 (pantothenic acid); B6 (pyridoxine); B7 (biotin); B9 (folic acid) and B12 (cobalamin). Biotin is sometimes called vitamin H.

Water soluble vitamins are easily lost, as the body loses water (through sweat, urine and faeces) and, therefore, we need to ensure that we get sufficient vitamins B and C each day. Fat soluble vitamins can be stored by the body, but we should still be at least averaging the recommended minimums daily, so that we don’t fall behind.

Recommended Daily (or Dietary) Allowances (RDAs), of foods and supplements have traditionally been set by government health bodies in the US, UK, and Europe. In the US, RDA stands for "Recommended Dietary Allowance”, which is established for each vitamin and mineral by the Food and Nutritional Board of the National Academy of Sciences and the Food and Drug Administration (FDA).

In 1979, the UK Department of Health proposed an RDA for vitamins A, C, and D, three of the B vitamins, and two minerals (calcium and iron) (Ref 1). In 1993, the European Union (EU) issued a directive on food labelling for its members, which included RDAs for 12 vitamins (excluding K) and 6 minerals (calcium, phosphorus, iodine, iron, magnesium, and zinc) (Ref 2). In 2004, the World Health Organisation (WHO) published RNI’s – Recommended Nutritional Intakes – for all 13 vitamins and a selection of minerals (calcium, iodine, iron, magnesium, selenium and zinc) (Ref 3).

For the table in this note, I have used the US RDAs, as these are up-to-date and more complete (Ref 4). Recommended amounts differ for males and females and people of different ages. I have taken the higher of the recommendation for either males or females in the 19-65 age group. This is usually the figure for males. Pregnant women have even higher RDAs for certain nutrients and older or younger people sometimes have additional needs. However, the RDA for males or females aged 19-65 will cover the vast majority of the population and will serve well as an indication of the minimum amount of each nutrient that we require on a daily basis. The RDAs for males and females are invariably the same and any differences are small.