Minerals are found in rock formations and in the soil as salts. They pass from the soil to plants and then to the animals that eat the plants. As we consume plants and animals, we obtain the minerals they have accumulated.

The human body requires some minerals in trace quantities while others are required in larger quantities. Zinc, iron, copper, manganese, chromium, selenium and iodine are required in trace amounts while calcium, magnesium, sodium, potassium and phosphorus are required in larger quantities. Each serves a vital function and is required for proper body function.

For minerals to be useful, they must be absorbed into the blood stream, so they can be transported to the cells in the body, where they are absorbed. An excess of some minerals inhibits the absorption of others, so a balanced intake is needed to assure the proper absorption of all minerals. For example, too much zinc can inhibit the absorption of copper and too much calcium can inhibit the absorption of magnesium. Fiber also can affect the absorption of minerals. If one is taking supplements, they should be taken in balance or at different times so they do not interfere with each other.

The following chart lists some of the important minerals, their function and the foods that contain them.

Mineral	Purpose	Source
Boron	Helps calcium uptake and healthy bones	Leafy vegetables, fruits, nuts & grains
Calcium	For strong bones and teeth; maintains regular heartbeat & transmission of nerve impulse; helps muscle growth; prevents cramps and blood clotting	Dairy products, sardines, seafood, green leafy vegetables
Chromium	Metabolizes glucose; aids fat & protein synthesis; helps maintain proper blood sugar	Brown rice, cheese, meat, whole grains
Copper	Aids in formation of bone, hemoglobin and red blood cells; helps maintain healthy nerves	Almonds, avocados, barley, beans, broccoli, garlic, lentils, nuts, oranges, organ meat, raisins, seafood, green leafy vegetables
Iodine	Helps metabolize excess fat; helps physical and mental development; needed for healthy thyroid gland (prevent goiter)	Iodized salts, seafood, kelp, asparagus, garlic, mushrooms
Iron	Needed for hemoglobin production and oxygenation of red blood cells; maintains healthy immune system; aids growth	Eggs, fish, liver, meat, poultry, green leafy vegetables, whole grains
Magnesium	Important for enzyme activity; helps the uptake of other minerals; aids in nerve transmission	Dairy products, meat, seafood, apples, bananas, garlic, nuts, green leafy vegetables, whole grains
Manganese	Aids protein and fat metabolism; promotes healthy nerves; maintains healthy immune system; aids in bone growth	Avocados, nuts, seaweed, whole grains
Molybdenum	Important for nitrogen metabolism and normal cell function	Beans, cereal grains, legumes, peas, dark green leafy vegetables
Phopsphorus	Aids in bone and tooth formation; important for cell growth; aids heart and kidney function	Asparagus, bran, corn, dairy products, eggs, fish, legumes, nuts, seeds, sodas, whole grains
Potassium	Important for healthy nervous system; aids heart function and muscle contraction,	Dairy products, fish, fruit, legumes, meat, poultry, vegetables, whole grains
Selenium	Aids immune system; aids heart and pancreatic function; promotes tissue elasticity	Brazil nuts, broccoli, brown rice, chicken, dairy products, garlic, seafood, vegetables, whole grains
Silicon	Important for bone and tissue formation and cardiovascular function	Alfalfa, beets, brown rice, motherís milk, green leafy vegetables, whole grains
Sodium	Maintains blood pH; aids in stomach, nerve and muscle function	Most foods contain sodium
Sulfur	Protects cells; resists bacteria; disinfects the blood; aids in formation of collagen	Brussels sprouts, dried beans, cabbage, eggs, fish, garlic, meat, onions, wheat germ
Vanadium	Important for cellular metabolism; formation of bones and teeth; reproduction	Fish, vegetable oils, olives,
Zinc	Important for prostate gland function; reproduction; protein synthesis; collagen formation; immune system	Fish, legumes, meats, seafood, poultry, whole grains

The biological clock is located in the suprachiasmatic nucleus (SCN), a distinct group of cells found within the hypothalamus, a small area of the brain near the top of the brain stem. The hypothalamus controls many behaviors including sleeping; eating and drinking; body temperature regulation; immune function and the secretion of hormones (which themselves regulate many bodily processes). The SCN, though, is only one part of the mechanism by which the "time" is kept. There are light receptors found in the retina which have a pathway, called the retinohypothalamic tract, leading to the SCN. A third area is the pineal gland, a pea-like structure found behind the hypothalamus. The pineal gland receives information indirectly from the SCN. It appears that the SCN takes the information on day length from the retina, interprets it, and passes it on to the pineal gland, which secretes the hormone melatonin in response to this message. Nighttime causes melatonin secretion to rise, while daylight inhibits it. The SCN is perhaps the most important mechanism, because if it is destroyed, circadian rhythms disappear entirely.

So what controls the circadian rhythm? The main synchronizer in humans is the light-dark cycle; that is, day and night.

(This article was contributed by Omar R. Othman, a medical student at UMKC.)