How much of each vitamin and mineral do we need?
For every person who asks this question, the answer will be slightly different. Each one of us has different needs and different ways of meeting those needs – a unique combination of stress and biochemical individuality. Genetic factors play an important part in this. For example, recent research indicates that as many as 5 to 15 per cent of people may have a particular type of genetic mutation in the DNA which codes for an enzyme involved in the metabolism of an amino acid known as homocysteine. This leads to higher homocysteine concentrations and therefore an increased risk of heart disease, and in women, of having babies with neural tube defects. Because folate and other B vitamins are involved in homocysteine metabolism, such people have higher folate requirements than those who do not have this type of genetic mutation, and may need supplements. Future research may show the presence of other common genetic variations, which throws doubt on the concept of assuming normality for nutrient requirements in any population.
Lifestyle factors also play a part. Someone who smokes or has a history of illness will have greater vitamin and mineral needs than someone who does not. The nutrient needs of an Olympic athlete are different to those of someone who sits on the couch and watches TV all day. Needs also vary according to sex, age and specific life events; a pregnant woman needs more iron than an elderly woman. Stress, disease, prescription drugs, environmental factors and intense physical activity can also raise requirements.
People vary in their ability to absorb and metabolize different nutrients. One person’s genetic make up may mean they get enough vitamin C from an average diet whereas another would benefit from taking a supplement. The amounts and types of food people eat and the way they cook also affects the ability to obtain enough nutritional value from food.