Sources and bioavailability

Food sources of essential minerals/trace elements:

• Generally, high levels in fibre-rich foods: whole grain products, fruit, vegetables.

• Lowest levels in refined foods, oils, fats, sugar-rich foods and alcoholic drinks.

Good sources are

• Magnesium: vegetables, legumes, whole grain.
• Zinc: associated with protein (except for fish - why?)
• Selenium: imported grain, fish, meat, milk
• Copper: grain, vegetables
• Chromium: grain, vegetables
• Iodine: milk, cheese, fish, iodinated salt
• Iron: grain, bread, meat, eggs

Bioavailability -how well does the nutrient reach its ’target organ’?

External factors influencing bioavailability:

• Total amount present in food
• Solubility
• Binding to fibre etc.
• Oxidation level (Fe, Cr, Mn)
• Synergism/antagonism
• Chelation, for example with amino acids

Intrinsic (physiological) factors influencing bioavailability:

• Genetic variation – inter-individual differences
• Particular diseases
• Age
• Sex
• Metabolic state – growth, pregnancy etc.
• Nutritional state (e.g. poor status can lead to increased Fe uptake, but decreased Zn absorption)
• Physiological stress
• Conditions in digestive tract (pH, bacterial flora)