THE CONTEXT
Minerals support physiologic and biochemical functions. Adequacy depends on dietary variety, geographic food sources and losses, while excessive intake can cause toxicity.
Requirements and dietary supply
•
Many essential minerals are widely distributed in foods, and most people eating a mixed diet are likely to obtain adequate amounts.
•
Requirements range from grams per day for sodium and calcium to milligrams per day for iron and zinc, and micrograms per day for trace elements.
Geographic sources and deficiency
•
Mineral deficiencies can occur when foods come from a single region with mineral-deficient soil; iodine and selenium are examples.
•
Obtaining foods from a variety of regions makes mineral deficiency less likely.
Iron deficiency and overload
•
Iron deficiency is an important worldwide problem because high losses, such as heavy menstrual blood loss or losses associated with intestinal parasites, can be difficult to replace through dietary intake.
•
The passage states that 10% of the population, and more in some areas, are genetically at risk of iron overload.
•
When iron-binding protein capacity is exceeded, iron ions in free solution undergo nonenzymic reactions that generate free radicals.
Other effects of excess
•
Foods grown in soil containing high selenium levels can cause selenium toxicity.
•
Excessive sodium intake causes hypertension in susceptible people.