Healthy young people normally make sufficient amounts of conditionally essential molecules in the body, although the levels are not always optimal. With inadequate levels of minerals or vitamins, key enzymes in biochemical pathways may not function optimally.
There are thousands of dietary supplements on the market, including 40+ essential nutrients alone and in various combinations, i.e. vitamins, minerals, trace elements and fatty acids. However, a number of other nutrients are "conditionally essential", meaning that the body normally can make these molecules, but some people do not make optimal amounts. Examples are L-carnitine, alpha-lipoic acid, the methyl donor betaine, chondroitin sulfate, coenzyme Q10, choline, amino acids such as tyrosine or arginine, and "essential" sugars normally formed in the body.
Healthy young people normally make sufficient amounts of conditionally essential molecules in the body, although the levels are not always optimal. With inadequate levels of minerals or vitamins, key enzymes in biochemical pathways may not function optimally. Due to genetic mutations, some enzymes may have increased needs for certain cofactors (vitamins), which can prevent them from functioning optimally. Some enzymes only function normally when supplied with cofactors in greater amounts than normally required. If supplements of essential nutrients prove insufficient for optimal enzyme function, "conditionally essential" nutrients may be added as part of a comprehensive, therapeutic program.
Reasons for high-dose supplements of micronutrients.
1. The agricultural revolution has reduced food quality
The transition from an existence as hunter and gatherers to urban agriculture around 10,000 years ago began an epoch when foods were mass-produced but had lower nutritional density, compared with the previous food eaten by our ancestors. The nutritional density in many foods has fallen significantly since human societies transformed from hunter-gatherers into resident farmers. This is especially true in the last 60-70 years after agriculture was changed from small, versatile ecologically driven family farms to large, chemical-based, industrial agriculture.
Reduced nutritional density in many foods, combined with the use of refined "foods" like sugar, white flour and refined oils, places a greater priority on eating the most nutritious foods. Farm produce grown organically generally has higher levels of essential nutrients such as trace minerals because the soil contains higher levels of trace minerals and the produce grows slower and thus has more time to absorb nutrients from the soil. Examples of nutrient dense foods are sardines, wild salmon, shellfish, eggs, liver, kale, collards and spinach, sea plants (seaweed), garlic, blueberries, and dark chocolate.
2. Nutritional content of food varies with geographical location
Nutritional density varies considerably geographically between different regions, even with the same agricultural methods. The soil in areas with relatively low rainfall may in some cases contain an extremely high concentration of minerals, which is reflected in the plants growing there.
Research shows that when the soil gets depleted of magnesium from heavy use, this essential mineral is not included in soil amendment with fertilisers. Produce grown in soil with an adequate level of magnesium will contain more magnesium than produce grown in soil deficient in magnesium. Magnesium supplements (chloride, malate or citrate) can provide an adequate level when vegetables grown in soil with adequate magnesium are not available.
3. Stress and the modern lifestyle increase the need for nutrients
Mental stress increases the excretion and hence the need for many nutrients. Among the most important are magnesium and vitamin C, both of which are used by the body in larger quantities during periods of physical and mental stress.
Vitamin C protects the brain and nervous system from damage caused by stress because the synthesis and maintenance of chemical neurotransmitters such as adrenaline and noradrenaline requires adequate levels of vitamin C.  Vitamin C is also needed to repair collagen which is essential for skin, blood vessels, bones and joints, and muscles. When these are damaged by physical stress, extra vitamin C is necessary.
In this modern era, processed food are almost inevitable. Processing of food reduces its nutritional content, and the finished products are often based on fractions of the original foods. One example is milling grain to make white flour, which has a lower nutritional density than whole grain flour. The reduction in nutritional value has accelerated since whole foods are now divided into pieces, for example, boneless chicken breast.
4. Environmental pollutants increase the need for nutrients
The need for efficient detoxification and excretion is greatly increased by environmental pollution from the chemical industry, herbicides and pesticides used by industrial agriculture, antibiotic treatment of animals, transport, and plastic packaging. In our polluted world, the increased toxic load may be compensated for by an increase in nutrients to promote detoxification. One can respond by taking large doses of supplements of essential nutrients, for example, antioxidants vitamin C and E, and an adequate dose of selenium, which help the body detoxify harmful chemicals. Also helpful is regularly taking sauna baths, fasting periodically, and eating an excellent diet that includes generous portions of dark green leafy vegetables and colourful vegetables and fruits.
5. An optimal nutrient intake promotes health and delays ageing.
A spokesperson for optimal nutritional intake is the well-known biochemist Bruce Ames, who proposed the "triage theory of nutrients," in which enzymes responsible for cell maintenance functions evolved to have lower affinity for the essential vitamin and mineral cofactors than the enzymes responsible for short-term survival, to preserve life during times of famine.
Thus, higher levels of vitamins and minerals may delay mitochondrial ageing, speed up the repair of large molecules such as DNA and collagen, and generally improve other cellular functions. This is an important rationale for taking higher doses of vitamins and minerals than recommended reference intakes. Dietary supplements can slow the ageing process, in part by reducing the harmful effects of free radicals, known to be involved in many diseases such as cardiovascular disease and cancer. Naturally-occurring hormones and/or supplements of cofactors needed for optimal hormone production in the body can have a significant life-prolonging effect if the body produces less than optimal amounts. This is especially relevant for those with a genetic predisposition for disease.
An optimum intake of all nutrients is difficult to achieve even for those who eat almost exclusively an excellent diet of nutrient dense foods, such as meat and innards, fish, shellfish, fowl, eggs, nuts, mushrooms, and vegetables, berries and nutritious fruits. Some nutrients such as folic acid or carotenoids in vegetables are absorbed better from processed than unprocessed foods. Although vegetables are often considered to be a good source of vitamins, for example vitamin A from carrots, vitamin A is only found in animal products such as liver, egg yolk, fish cod and cod liver oil. Although eating raw vegetables is helpful for several reasons (vitamin C, fiber, microbiota), carotenoids (alpha/beta-carotene, lutein, lycopene) in vegetables are less well absorbed from raw than cooked food and better absorbed in the presence of added fat. Nutrients in vegetables are better absorbed when finely chewed, graded, or mashed and cooking and grinding meat reduces the energy required to digest it and increases nutrient absorption.