Major Minerals: Functions, Sources, Bioavailability, and Health Implications

Major Minerals in Human Nutrition

Introduction to Minerals

Minerals are inorganic elements essential for human nutrition and play critical roles in various physiological processes. Out of the 92 naturally occurring elements, 14 are essential for body function. These minerals are categorized based on the amount required by the body: major minerals (macrominerals) and trace minerals (microminerals).

• Major minerals: Needed in amounts greater than 100 mg/day; at least 5 grams present in the body.

• Trace minerals: Needed in amounts less than 20 mg/day; less than 5 grams present in the body.

Major minerals include: Calcium, Sodium, Potassium, Chloride, Phosphorus, Magnesium, and Sulfur.

Properties of Minerals

• Minerals are single molecules containing only atoms of the same element.

• They are found as individual ions or as inorganic compounds (do not contain carbon).

• Minerals are not destroyed by heat, acid, oxygen, or ultraviolet light and remain intact during digestion.

• They generally do not change shape or structure during biological functions.

Bioavailability of Minerals

Bioavailability refers to the degree to which a nutrient from food is absorbed and utilized in the body. Several factors influence mineral bioavailability:

• Nutritional status (deficiency increases absorption)

• Competing minerals in the intestinal tract

• Binders (e.g., phytates, oxalates, polyphenols) can reduce absorption

• Enhancers (e.g., vitamin C for iron, vitamin D for calcium, animal protein for zinc)

Factors That Increase Bioavailability	Factors That Reduce Bioavailability
Deficiency in a mineral increases absorption	Binders (e.g., oxalates in foods)
Cooking increases bioavailability in legumes	Phytates in nuts, whole grains, legumes
Vitamin C increases iron absorption	Polyphenols in tea and coffee
Vitamin D increases absorption of calcium, phosphorus, magnesium	Supplementation of single minerals affects absorption of competing minerals

Functions of Major Minerals

• Fluid and electrolyte balance

• Blood formation

• Building healthy bones and teeth

• Maintaining a healthy immune system

• Enzyme cofactors (e.g., antioxidant systems, energy production, muscle contraction, nerve transmission)

• Structural growth

The body maintains tight control over mineral balance via the gastrointestinal tract (regulates absorption) and kidneys (excrete excess and reabsorb minerals).

Toxicity of Minerals

• High intakes of minerals can be toxic, causing illness or death.

• Toxicity is rare from food sources and usually results from excessive supplementation or certain medical conditions.

Overview of Major Minerals

Major Mineral	Metabolic Function	Daily Needs (19+ yrs)	Food Sources	Toxicity Symptoms	Deficiency Symptoms
Sodium (Na+)	Major cation outside cell; regulates body water and blood pressure	1,500 mg/day	Processed foods, table salt	Edema, hypertension (UL: 2,300 mg/day)	Headache, nausea, vomiting, fatigue
Chloride (Cl-)	Major anion outside cell; part of HCl in stomach; maintains fluid balance	2,300 mg/day	Processed foods, seaweed, table salt, rye	Vomiting (UL: 3,600 mg/day)	Rare, but symptoms include shallow breathing, muscle weakness
Potassium (K+)	Major cation inside cell; regulates body water and blood pressure	4,700 mg/day	Unprocessed foods, fruits, vegetables, meat, dairy, nuts	Irregular heartbeat, heart damage	Muscle weakness, cramps, glucose intolerance, irregular heartbeat, paralysis
Calcium (Ca2+)	Formation of bones and teeth, muscle contraction, nerve conduction, blood clotting, heart and nerve function	1,000 mg/day	Milk, dairy, green leafy vegetables, broccoli, salmon, sardines, calcium-fortified soy/rice milk	Constipation, impaired kidneys, calcium deposits (UL: 2,500 mg/day)	Bone loss, bone fractures
Phosphorus (PO43-)	Formation of bones and teeth, part of DNA/RNA, ATP, acid-base balance	700 mg/day	Meat, fish, poultry, eggs, cereals	Decrease in bone mass, calcium deposits in tissues (UL: 4,000 mg/day)	Muscle weakness, bone pain
Magnesium (Mg2+)	Cofactor in enzymatic reactions, muscle contraction, nerve conduction	Women: 310 mg/day; Men: 400 mg/day	Green leafy vegetables, whole grains, nuts, dairy, fruit	Diarrhea, cramps, nausea (UL for supplements: 350 mg/day)	Weakness, confusion, seizures, depression, irregular heartbeat
Sulfate (SO42-)	Part of keratin in hair and nails, collagen formation, acid-base balance, cellular respiration	None established	All protein-containing foods, meat, fish, poultry, eggs, legumes, nuts, dairy	May promote ulcerative colitis (no UL)	None known

Detailed Focus: Sodium, Chloride, and Potassium

Sodium (Na+)

Functions

• Major electrolyte and cation in extracellular fluid

• Regulates blood volume and pressure

• Transmits nerve impulses and participates in muscle contraction

• Helps transport nutrients

• Preserves food and enhances flavor

Absorption and Regulation

• 95–100% absorbed in the small intestine

• Blood levels regulated by the kidneys (aldosterone hormone)

• Small losses through perspiration

Dietary Needs and Sources

• AI: 1,500 mg/day for adults up to 51 years

• 77% from processed foods, 12% from natural sources, 5% added during cooking, 6% at the table

Health Implications

• Excess: Hypertension, hypernatremia, osteoporosis, fluid retention, weight gain, stomach ulcers/cancer

• Deficiency: Rare; can cause hyponatremia (headache, muscle weakness, fatigue, seizures, death)

Reducing Intake

• Follow DASH or Mediterranean diets

• Read food labels (low sodium: <140 mg/serving; sodium-free: <5 mg/serving; reduced sodium: 25% less; light: 50% less)

• Limit processed foods, use herbs and sodium-free seasonings

Chloride (Cl-)

Functions

• Major anion in extracellular fluid

• Maintains fluid balance

• Assists in removal of CO2 from blood

• Helps keep blood pH normal

• Part of hydrochloric acid in the stomach

Dietary Needs and Sources

• AI: 2,300 mg/day for adults (19–50 years)

• Sources: Table salt, processed foods, seaweed, tomatoes, olives, lettuce, celery, rye

Health Implications

• Toxicity: Rare, but can occur with severe dehydration (UL: 3,600 mg)

• Deficiency: Rare; can occur with prolonged vomiting/diarrhea or diuretic use (symptoms: shallow breathing, muscle weakness, spasms, twitching)

Potassium (K+)

Functions

• Major cation in intracellular fluid

• Maintains fluid and pH balance

• Muscle contraction, nerve impulse conduction, regular heartbeat

• Lowers high blood pressure by promoting sodium excretion

• Preserves calcium and phosphorus in bones, reduces kidney stones

Dietary Needs and Sources

• AI: 4,700 mg/day for adults

• Sources: Unprocessed foods, fruits, vegetables, meat, dairy, nuts

Health Implications

• Toxicity: Hyperkalemia (irregular heartbeat, heart damage, death); usually from supplements or kidney dysfunction

• Deficiency: Hypokalemia (muscle weakness, cramps, glucose intolerance, irregular heartbeat, paralysis); caused by vomiting, diarrhea, eating disorders

Summary Table: Sodium and Potassium Content in Whole and Processed Foods

Whole Food	Na+ Content	K+ Content	Processed Food	Na+ Content	K+ Content
Baked potato, medium	10 mg	870 mg	Hash browns, one serving	746 mg	513 mg
Orange juice, 1 cup	2.5 mg	496 mg	Orange soda, 1 cup	30 mg	5 mg
Milk, 1 cup	107 mg	366 mg	Vanilla pudding, 1 cup	156 mg	170 mg
Tri-tip, 3 oz	141 mg	370 mg	Beef jerky, 3 oz	1,320 mg	356 mg
Strawberries, 1 cup	1.5 mg	233 mg	Strawberry pie, 1 serving	284 mg	110 mg
Green beans, 1 cup	6 mg	230 mg	Green beans, canned, 1 cup	376 mg	183 mg
Oatmeal, 1 cup	3.1 mg	166 mg	Oat cereal, 1 cup	864 mg	184 mg

Conclusion

Major minerals are vital for maintaining fluid balance, bone health, nerve transmission, and many other physiological functions. Understanding their sources, functions, and the consequences of deficiency or excess is essential for promoting optimal health and preventing disease.