Requirements

Figure Typical relationship between intake of a nutrient and health

Importance of dose:

"All substances are poisons, there is none which is not a poison. The right dose differentiates a poison from a remedy". Paracelsus (1493-1541)

-How much do we need? -How much is too much?
Doses are important.
An intake around the recommended level is OK, but it may be only a short step to too much.
As a rule of thumb, the maximum intake should be 3x the recommended level.

In recent years, Nordic countries, EU and USA have published upper limits for intake of vitamins and minerals.
Values are strikingly similar. The size of the ’safe window’ varies from substance to substance.

Meltzer HM et al. (2003)

The tolerance limits are not based on levels that give acute toxic symptoms, but on ’negative health effects’. These can be observed at much lower doses than those that give acute toxic effects.
For example, there may be no clear symptoms of toxicity with an intake of 500 mg/day of zinc for several months. But already at 50 mg/day there are negative effects on absorption of Cu and Fe, and so the upper level is set at 45 mg/day.

Excessive intake of minerals is seldom seen with a normal, well-composed diet.
In this part of the world, it is just possible,

• with intake of high dose supplements
• with intake of enriched foods
• with special foods, such as seaweed (iodine).

Requirements and recommendations

• USA: Dietary Reference Intakes Dietary guidance
• Nordiske anbefalinger 1996 - revised in autumn 2004
• Norske anbefalinger

Table of Actual and recommended intake of trace elemements in the nordic countries

Assessing whether a person has too low an intake is difficult, for the following reasons:

• In Europe, at least, serious deficiency is rare.
• Sub-clinical deficiency (without clear symptoms) is difficult to diagnose.
• There are generally no good, reliable biomarker assays for status of minerals and trace elements.

It is possible to estimate whether a person has too low an intake from questions about lifestyle, diet, health status, and belonging to a special group such as:

• those who eat too little: slimmers, sick, young women
• those who eat an unbalanced diet: people with food allergies, vegetarians (?), young people (unhealthy food)
• those with increased requirements: pregnant/nursing women, those who use certain medicinal drugs.

Figure
Recommended intakes of minerals and trace elements (Nordic Nutrition Recommendations (NNR) 2004)