9.1: Major Minerals

Major minerals, also known as macrominerals, are essential nutrients that the body requires in amounts greater than 100 mg/day to carry out vital physiological functions. These minerals play critical roles in building and maintaining strong bones and teeth, regulating fluid and electrolyte balance, supporting nerve transmission and muscle contraction, and enabling key metabolic processes. The major minerals include calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur, each contributing uniquely to overall health.

Calcium

Calcium is the most abundant mineral in the body, accounting for 2.2 pounds of the average adult’s body weight. The majority (>99%) of calcium in the body is stored in the bones and teeth to provide structural strength, while the rest is found in the blood and other tissues.

Dietary Sources

The RDA for calcium (people ages 19-50) is 1,000 mg/day for both men and women. Calcium is abundantly found in dairy products such as milk, yogurt, and cheese, fortified plant-based milks, leafy greens like kale and bok choy, and almonds (Figure 9.1). Overall, animal-based foods are much richer sources of calcium.

The bioavailability of calcium is increased by vitamin D, which aids in its absorption. However, bioavailability is decreased by age, as absorption of calcium tends to decrease after the age of 50 (the RDA raises to 1,200 mg/day for individuals aged 51+). The presence of oxalate and phytate compounds in foods also inhibits absorption of calcium. These compounds chelate (bind) calcium and make it unavailable for absorption. For example, spinach is a great source of calcium, but has a lot of oxalates in it that prohibit that calcium from being absorbed. Oxalates tend to be found in many vegetables, teas, and cocoa, while phytates are found in many whole grains and nuts.

Figure 9.1 Examples of dairy and non-dairy food sources of calcium. Image by Brookepinsent is licensed under Creative Commons Attribution Share-Alike 4.0 International license.

Important Roles

Calcium is a main component of hydroxyapatite, the mineral matrix of bones and teeth (and storage depot for calcium). Calcium aids to maintain the structure of the skeleton and strength of the bones and teeth. Calcium also has a number of regulatory functions. For example, it works with vitamin K for blood clot formation, activating clotting factors in the coagulation cascade. Calcium is important for nerve impulse transmission is essential for all types of muscle contraction.

Due to calcium’s significant role in structure, nerve signaling and muscle contraction, it is crucial that calcium levels in the blood are maintained at a homeostasis (Figure 9.2). If calcium levels are low in the blood, the parathyroid gland releases parathyroid hormone (PTH). PTH stimulates the conversion of 25-hydroxyvitamin D3 to active vitamin D (calcitriol) in the kidneys. Calcitriol and PTH then work together to stimulate: increased calcium absorption in the small intestine, decreased calcium excretion in the urine, and increased bone breakdown (resorption) by osteoclasts and release of calcium into the blood. Conversely, if blood calcium is high, the thyroid gland releases the hormone calcitonin. Increased calcitonin then leads to decreased calcium absorption in the small intestine, decreased bone breakdown, and increased calcium excretion through the urine.

Figure 9.2 Calcium homeostasis is primarily regulated by parathyroid hormone (PTH). Figure 6.24 by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix, OpenStax from Anatomy and Physiology 2e (2022) is licensed under the Creative Commons Attribution 3.0 Unported license Read image transcript.

Consequences of Deficiency and Toxicity

Calcium deficiency manifests in similar ways as discussed for vitamin D. In children, calcium deficiency can lead to poor bone development and increase the risk of rickets. In adults, it may contribute to osteopenia (moderate loss of bone mass) or osteoporosis, progressive bone loss that causes bones to become weak, fragile, and at risk for fractures. Calcium deficiency can also result in muscle pain, muscle spasms, abnormal heart rhythms, and tingling sensations.

Toxicity typically results from excess calcium consumption through supplementation. This may lead to constipation, development of kidney stones, and impaired absorption of other minerals such as iron and zinc.

Health Note

Calcium is key for strong bones and teeth, and muscle contraction too.

Fun Fact

99% of the calcium in your body is stored in your bones!

Phosphorus

Phosphorus is a major mineral that is a component of phospholipids and associated with nearly all body structures. It is sometimes added to foods to promote moisture retention, smoothness, and taste.

Important Roles

In addition to its importance in the structure of phospholipids, phosphorus works alongside calcium to build bones and teeth. It also plays key roles in energy metabolism as part of DNA and RNA synthesis, and maintaining acid-base balance.

Phosphorus levels are regulated in a similar manner as calcium with PTH, calcitriol, and calcitonin. If blood levels of phosphorus are low, PTH and calcitriol increase absorption in the small intestine and resorption from bones. If levels are high in the blood, calcitonin stimulates the bone building activity of osteoblasts which take up phosphorus from the blood.

Dietary Sources

The RDA is established as 700 mg/day for both women and men. It is abundant in food sources such as meat, poultry, fish, dairy, nuts, legumes (Figure 9.3), and processed foods (which often contain phosphate additives). For example, a typical cola drink has 50 mg phosphorus (labeled as phosphoric acid), though it’s certainly not a good idea to rely on soft drinks for phosphorus intake!

Figure 9.3 Animal products are rich sources of phosphorus. Image modified from photo by FERMOSERGIO from Pixabay.

The bioavailability of phosphorus is high in most foods, though it is more difficult to absorb from seeds and grains due to the presence of phytates.

Consequences of Deficiency and Toxicity

Deficiency of phosphorus is quite rare, but can occur with certain genetic conditions, medical conditions, or malnutrition. Symptoms may include bone pain, muscle weakness, and irregular breathing. In terms of toxicity, the chronic intake of excess phosphorus, usually from supplements or processed foods, can disrupt calcium balance and lead to bone loss.

Health Note

Phosphorus works with calcium to build bones and plays a role in energy metabolism.

Fun Fact

Phosphorus is found in every cell in your body—mostly as part of ATP, your energy currency.

Magnesium

Magnesium is a vital mineral involved in over 300 biochemical reactions in the body. Magnesium is widely promoted as a supplement, mainly for its calming effects on the nervous system. It is often marketed as a natural remedy for stress, anxiety and insomnia. During stressful periods, the body uses more magnesium, and some research suggests that low magnesium levels may worsen stress responses and disrupt sleep. Supplements like magnesium glycinate or magnesium citrate are frequently used to support relaxation and better sleep.

Important Roles

Magnesium is involved in a variety of processes. It contributes to the structural development of bone, plays a central role in energy production, protein synthesis, and nerve transmission. It is especially important in muscle function in heart tissue, keeping the heartbeat steady. In muscle, calcium binds to proteins such as troponin C and myosin. This changes the shape of these proteins, which generates a muscle contraction. Magnesium acts as a natural calcium blocker and competes with calcium for these same binding spots to help relax your muscles. If your body doesn’t have enough magnesium to compete with calcium, your muscles may contract too much, causing cramps or spasms.

Figure 9.4 Nuts, seeds, cocoa, and vegetables are rich sources of magnesium. Photo by FotoshopTofs from Pixabay

Dietary Sources

The RDA for magnesium is established as 320 mg/ day for women and 420 mg/day for men. It is found in food sources such as fish like halibut, whole grains, nuts, seeds, leafy green vegetables, and dark chocolate (Figure 9.4).

Consequences of Deficiency and Toxicity

Magnesium deficiency can cause muscle cramps and irregular heartbeat, fatigue, migraines, and in severe cases, seizures. Toxicity is typically rare from food sources, though is possible with supplements or medications (such as antacids like milk of magnesia). Associated symptoms are typically GI related, including diarrhea and nausea.

Health Note

Magnesium supports muscle and nerve function and over 300 enzyme systems. It may help improve sleep and reduce muscle cramps.

Fun Fact

About 60% of the body’s magnesium is stored in the bones, highlighting its role in bone structure alongside calcium and phosphorus.

Sodium

Sodium, like many other minerals, is important for nerve transmission and muscle contraction. It also plays a crucial role in fluid balance. Sodium comprises approximately 40% of table salt, the other 60% being chloride. Perhaps unique to sodium — this is not a nutrient you typically need to look for in foods, it will find you!

The majority of sodium absorption occurs in the small intestine, though the colon does actively absorb sodium as well. Because water follows sodium in the body — without colonic absorption, large amounts of water would be lost in the feces resulting in diarrhea and dehydration.

Important Roles

Sodium plays a crucial role in nerve impulse transmission. When a nerve cell is stimulated, sodium channels in the cell membrane open, allowing sodium ions to rush into the cell. This influx of sodium causes a change in the electrical charge across the membrane, a process called depolarization, which propagates as a nerve impulse or action potential. Similarly, sodium plays a vital role in muscle contraction by initiating the action potential that triggers the process. When a nerve impulse arrives at the neuromuscular junction, the neurotransmitter acetylcholine is released and binds to receptors on the muscle fiber membrane. This causes sodium channels to open, sodium to flood into the cell, and this influx depolarizes the membrane and sends an action potential along the muscle fiber for eventual muscle contraction.

Sodium is also crucial for maintaining fluid balance in the body, maintaining both blood volume and blood pressure. It is the primary electrolyte in the extracellular fluid and helps regulate the distribution of water between the outside and inside of cells.

The kidneys play a key role in sodium (and water) balance, working with hormones to adjust sodium and water excretion to maintain homeostasis. If sodium levels in the blood are low (hyponatremia), the adrenal glands will increase secretion of the hormone aldosterone. Aldosterone then stimulates the kidneys to decrease sodium excretion in the urine, and therefore increase sodium reabsorption, to bring blood sodium levels to homeostasis (Figure 9.5). Alternatively, if blood sodium levels are high (hypernatremia), the adrenal glands will decrease their release of aldosterone. Low aldosterone levels then favor increased sodium excretion in the urine to bring blood sodium levels down.

Figure 9.5 Regulation of sodium levels by the hormone aldosterone targeting the kidneys to impact sodium excretion. Image by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix, OpenStax (2013) is licensed under the Creative Commons Attribution 3.0 Unported license.

Dietary Sources

Although there is great interest in the effects of salt in the diet, data are insufficient to establish RDAs for sodium. The adequate intake levels are 1,500 mg/day for both men and women. Processed foods provide the majority of sodium to the diet (this is also true of chloride, as foods that contribute sodium to the diet are also good sources of chloride). Table salt is also a rich source of sodium, with one teaspoon of salt containing more than 2,000 mg (Figure 9.6). Other sources include canned soups, ham, many condiments, and snack foods like potato chips. The average individual consumes approximately 3,400 mg of sodium per day.

Figure 9.6 Table salt is a rich source of sodium (and chloride). Image from Pixabay.

Consequences of Deficiency and Toxicity

Sodium deficiencies due to inadequate food intake are fairly uncommon, though can be caused by inadequate salt intake. It is much more common as a result of the loss of sodium from extreme sweating or excessive water consumption not accompanied by adequate sodium intake. Deficiency can also occur in stations of vomiting and diarrhea. Symptoms include headache, dizziness, nausea, muscle cramps, and confusion.

High sodium intake is associated with increased blood pressure (hypertension). With a higher sodium concentration in the blood, there will be a higher blood volume, and increased blood pressure. This increases the risk for cardiovascular disease and stroke.

Health Note

Sodium is important for fluid balance, nerve impulses and muscle contractions.

Fun Fact

While essential, most Americans consume double the recommended sodium intake!

Chloride

Chloride is a mineral that is typically found in foods with sodium, including table salt (sodium chloride).

Category	Mineral	Key Functions
Major Minerals	Calcium	Bone and teeth formation Muscle contraction Nerve function Blood clotting
	Phosphorus	Bone and teeth structure Energy metabolism
	Magnesium	Muscle and nerve function Bone health
	Sodium	Fluid balance Nerve transmission Muscle function
	Chloride	Fluid balance Stomach acid production
	Potassium	Fluid balance Muscle contraction Heart function
	Sulfur	Component of some amino acids and vitamins
Trace Minerals	Iron	Oxygen transport Energy metabolism
	Zinc	Immune function Wound healing
	Copper	Iron metabolism Antioxidant activity
	Iodine	Thyroid hormone production
	Selenium	Antioxidant activity Thyroid function
	Fluoride	Tooth enamel formation and protection
	Chromium	Enhances insulin action
	Manganese	Metabolism Antioxidant function
	Molybdenum	Enzyme function in metabolism

Important Roles

Chloride helps maintain fluid and electrolyte balance, working with sodium to regulate the proper amount of fluid inside and outside of the cells, and maintain blood volume and pressure. Chloride is a key component of hydrochloric acid (HCl) in the stomach, thereby playing a major role in digestion as HCl is important in maintaining the acidity of the stomach, digesting proteins, and killing ingested pathogens.

Dietary Sources

The RDA for chloride is 2,300 mg/day. Chloride is found in table salt and other food sources such as seaweed, rye, tomatoes, celery, and many processed foods.

Consequences of Deficiency and Toxicity

Chloride deficiency is uncommon, though may occur in situations of vomiting or diarrhea. Symptoms include muscle cramps, loss of appetite, and lethargy. Toxicity from high levels of chloride is most commonly seen with excessive salt intake. Like sodium, this would contribute to hypertension and fluid retention.

Health Note

Chloride helps maintain fluid balance and is part of stomach acid.

Fun Fact

Chloride makes up half of table salt (sodium chloride)!

Potassium

Potassium is the most abundant cation in intracellular fluids. It is crucial for maintaining fluid and electrolyte balance, and works closely as a partner with sodium and chloride to maintain that fluid balance.

Important Roles

The main role of potassium in the body is to help maintain normal levels of fluid inside the cells while sodium maintains normal fluid levels outside of cells. Potassium is also important in muscle contraction, particularly the heart and supporting normal blood pressure. It is important for nerve function and energy metabolism as well.

Potassium levels are regulated with the action of aldosterone (Figure 9.5). In response to elevated blood potassium levels (hyperkalemia), aldosterone is released from the adrenal glands. Aldosterone targets the kidneys to excrete potassium in the urine, thus normalizing blood potassium levels. Conversely, low blood potassium levels (hypokalemia) results in the decrease of aldosterone and reabsorption of potassium by the kidneys.

Figure 9.7 Examples of food sources of potassium (K). Image by Arcturus525 from Pixabay.

Dietary Sources

The adequate intake level for potassium has been determined to be 4,700 mg/day for both women and men. It is abundant in fruits such as bananas, oranges, and cantaloupe, as well as vegetables like potatoes, spinach, and tomatoes. Potassium can also be obtained from dairy sources, legumes, and nuts (Figure 9.7).

Consequences of Deficiency and Toxicity

Potassium deficiency most commonly occurs with prolonged diarrhea and/or vomiting, or in individuals using diuretics. Diuretics are drugs that help the body eliminate water by increasing urine formation and are often taken to help lower blood pressure. Symptoms of potassium deficiency may include weakness, fatigue, muscle cramps, and abnormal heart rhythms. Toxicity from potassium is rare from food intake, but can occur with high dosage supplementation or conditions of kidney dysfunction. This typically impacts the heart, potentially causing a slowed heart rate and heart arrhythmias.

Health Note

A potassium-rich diet is associated with lower blood pressure and a reduced risk of stroke. For this reason, potassium is considered a "nutrient of public health concern" in populations where intake is commonly below recommended levels.

Fun Fact

Bananas are famous for potassium—but potatoes and beans have more!

Sulfur

Sulfur is among the most biologically abundant elements in the human body. It plays a role in functions including cellular signaling, detoxification of free radicals, structural support, and energy production.

Important Roles

Sulfur is a component of amino acids like methionine and cysteine, which are building blocks of protein. It is also a component of vitamins like thiamin and biotin. Sulfur is important for the synthesis of glutathione, a powerful antioxidant that protects cells from free radical damage. It also aids in the overall detoxification process of the liver to rid of the body of harmful substances and waste products.

Dietary Sources

While there is no RDA established for sulfur in the diet, it can be found in protein-rich foods like meat, fish, poultry, eggs, legumes, and dairy. It can also be found in vegetables such as onions, garlic, kale, and broccoli.

Consequences of Deficiency and Toxicity

Sulfur deficiency is not typically seen, as average protein intake will meet an individual’s sulfur needs. There have been no well-documented deficiency symptoms in humans. There are also no known toxic effects from dietary intake, though excessive supplementation may cause diarrhea and foul-smelling gas.

Health Note

Sulfur is needed for certain amino acids and detoxification pathways.

Fun Fact

The smell of rotten eggs? That’s sulfur at work!