The major minerals calcium, phosphorus, magnesium, and sulfur play essential roles in human health by supporting the structure, regulation, and metabolic activities of the body. Although they are often discussed in relation to bone health, these minerals extend far beyond the skeleton and are critical for daily physiological function.

Sulfur is unique among the major minerals. It is not consumed as a free mineral in foods but is found exclusively as a component of certain amino acids—most notably methionine and cysteine. Through these amino acids, sulfur contributes to protein structure and function but has no independent physiological role outside of its presence in amino acids and the compounds derived from them.

Calcium: More Than Just Bones

Calcium is the most abundant mineral in the human body. More than 99% of the body’s calcium is stored in bones and teeth, where it provides structure and strength. The remaining 1% is found in the blood and soft tissues—but this small amount performs some of the body’s most critical life-sustaining functions.

Because calcium in the blood is essential for survival, the body tightly regulates blood calcium levels. If blood calcium drops, the body quickly responds by pulling calcium from bone through a process called bone resorption. In this way, bone tissue acts as a “calcium bank,” releasing stored calcium to keep blood levels normal.

This is why:

• Bone health depends on adequate dietary calcium intake, and

• Blood calcium levels do not always reflect how much calcium you consume in your diet.

Building and Maintaining Bones and Teeth

Calcium’s most well-known function is to build and strengthen bones and teeth. When bone is first formed during growth or remodeling, it begins as a soft, protein-rich material called osteoid. Specialized bone cells (osteoblasts) deposit calcium and phosphorus salts onto this protein framework, a process called bone mineralization.

About 65% of bone tissue is made of mineral salts, primarily calcium phosphate. This mineral content gives bone its hardness and strength.

If dietary calcium intake is too low:

• Bone mineral content decreases

• Bones become weaker and more brittle

• Risk of fractures increases

Higher mineral content corresponds to greater bone mineral density (BMD) and stronger bones.

Nerve Transmission

Calcium plays a key role in the transmission of nerve impulses. It helps electrical signals move from one nerve cell to another. Without calcium, communication between nerves would not function properly.

Muscle Contractions

Calcium is essential for muscle movement. Inside muscle cells, calcium allows two proteins—actin and myosin—to interact, which produces contraction. Every heartbeat, every step, and every breath depends on calcium.

Blood Clotting

Calcium activates clotting factors in the blood. These clotting factors help form a clot at the site of injury, preventing excessive blood loss and allowing damaged tissue to heal.

Hormonal Regulation of Blood Calcium

Other Health Benefits of Calcium

In addition to building and maintaining strong bones and teeth, calcium may provide several other health benefits. Research continues to explore these relationships, and while some findings are well supported, others remain under investigation.

Calcium and Cancer Risk

Higher calcium intakes are associated with a lower risk of colon cancer, possibly because calcium helps limit the growth of colon polyps that can develop into cancer. In contrast, research on calcium and prostate cancer is mixed. Some studies suggest that very high calcium intake may increase the risk, while others show no clear link. More research is needed to better understand this relationship. ^[1]

Calcium and Blood Pressure

Multiple studies show that higher calcium intake is associated with modest reductions in blood pressure. In pregnancy, consuming about 1,000 mg of calcium per day reduces the risk of gestational hypertension and preeclampsia, particularly among women with low baseline calcium intake or higher risk. Evidence from randomized controlled trials supports calcium supplementation as a safe and effective strategy to lower hypertensive complications and related adverse outcomes during pregnancy. ^[2]

Calcium and Cardiovascular Health

Emerging research suggests that higher calcium intake may improve certain cardiovascular risk factors, such as elevated cholesterol levels and obesity. However, the current evidence is limited and sometimes conflicting. More well-designed clinical trials are needed before firm conclusions can be made.

Calcium and Kidney Stones

Dietary calcium may actually help prevent kidney stones. Calcium binds to oxalate—a compound found in plant foods such as spinach and parsley—in the digestive tract. When calcium binds to oxalate in the intestine, less oxalate is absorbed into the bloodstream, reducing the risk of kidney stone formation.

Importantly:

• Calcium from food sources appears protective.

• Calcium supplements, particularly in high doses, may increase kidney stone risk in susceptible individuals.

This distinction highlights the importance of obtaining nutrients primarily from whole foods whenever possible.

While calcium is best known for its role in bone health, research suggests it may also influence cancer risk, blood pressure, kidney stone formation, and cardiovascular health. However, not all associations are equally strong, and excessive intake does not necessarily provide additional benefit. As with many nutrients, balance and adequacy—rather than excess—are key.

Groups at Risk for Calcium Deficiency

Calcium may not receive much attention outside of discussions about bone health, yet it plays an important role during the college years. Adolescent girls and older adults are the groups most likely to have inadequate intakes, and the effects of low intake often appear later in life as reduced bone strength. Despite strong evidence supporting calcium’s benefits—particularly for bone health—most Americans do not meet recommended intake levels. In fact, females over age nine consume only about 70% of the recommended amount, making young adulthood an important period for establishing dietary habits that support lifelong bone health.

Groups at higher risk include:

• Adolescents, especially girls, whose dairy intake often declines during the teen years

• Amenorrheic women and female athletes, where low estrogen, inadequate intake, and high physical stress can reduce bone density

• Older adults, due to reduced calcium absorption, less active vitamin D, dietary changes, and lower sun exposure

• Postmenopausal women, because decreased estrogen increases bone loss and reduces calcium absorption

• Lactose-intolerant individuals, who may avoid dairy products

• Vegans, whose diets may be lower in calcium and include compounds that reduce calcium absorption

For those who avoid dairy, calcium needs can still be met through calcium-rich plant foods, fortified foods, and lactose-free or low-lactose dairy options.

Calcium Supplements: Which One to Buy?

Many people choose to fulfill their daily calcium requirements by taking calcium supplements. Calcium supplements are sold primarily as calcium carbonate, calcium citrate, calcium lactate, and calcium phosphate, with elemental calcium contents of about 200 milligrams per pill. It is important to note that calcium carbonate requires an acidic environment in the stomach to be used effectively. Although this is not a problem for most people, it may be for those on medication to reduce stomach-acid production or for the elderly who may have a reduced ability to secrete acid in the stomach. For these people, calcium citrate may be a better choice. Otherwise, calcium carbonate is the cheapest. The body is capable of absorbing approximately 30 percent of the calcium from these forms.

Diet, Supplements, and Chelated Supplements

In general, calcium supplements perform less well than dietary sources of calcium in providing many of the health benefits linked to higher calcium intake. This is partly due to the fact that dietary sources of calcium provide additional nutrients with health-promoting properties. It is reported that chelated forms of calcium supplements are easier to absorb as the chelation process protects the calcium from oxalates and phytates that may bind with the calcium in the intestines. However, these supplements are more expensive and only increase calcium absorption by up to 10 percent. In people with low dietary intakes of calcium, calcium supplements have a negligible benefit on bone health in the absence of a vitamin D supplement. However, when calcium supplements are taken along with vitamin D, there are many benefits to bone health: peak bone mass is increased in early adulthood, BMD is maintained throughout adulthood, the risk of developing osteoporosis is reduced, and the incidence of fractures is decreased in those who already had osteoporosis. Calcium and vitamin D pills do not have to be taken at the same time for effectiveness. But remember that vitamin D has to be activated and in the bloodstream to promote calcium absorption. Thus, it is important to maintain an adequate intake of vitamin D.

The Calcium Debate

A recent study published in the British Medical Journal reported that people who take calcium supplements at doses equal to or greater than 500 milligrams per day in the absence of a vitamin D supplement had a 30 percent greater risk for having a heart attack.^[4]

Does this mean that calcium supplements are bad for you? If you look more closely at the study, you will find that 5.8 percent of people (143 people) who took calcium supplements had a heart attack, but so did 5.5 percent of the people (111) people who took the placebo. While this is one study, several other large studies have not shown that calcium supplementation increases the risk for cardiovascular disease. While the debate over this continues in the realm of science, we should focus on the things we do know:

1. There is overwhelming evidence that diets sufficient in calcium prevent osteoporosis and cardiovascular disease.
2. People with risk factors for osteoporosis are advised to take calcium supplements if they are unable to get enough calcium in their diet. The National Osteoporosis Foundation advises that adults age fifty and above consume 1,200 milligrams of calcium per day. This includes calcium from both dietary sources and supplements.
3. Consuming more calcium than is recommended is not better for your health and can prove to be detrimental. Consuming too much calcium at any one time, be it from diet or supplements, impairs not only the absorption of calcium itself, but also the absorption of other essential minerals, such as iron and zinc. Since the GI tract can only handle about 500 milligrams of calcium at a time, it is recommended to split calcium supplements rather than taking a few all at once to meet the RDA.

Dietary Reference Intake for Calcium

The recommended dietary allowance (RDA) of calcium is 1000 milligrams for college-age adults. The RDA is elevated to 1,300 milligrams per day during adolescence because this is the life stage with the most rapid bone growth. Studies have shown that a higher intake of calcium during puberty increases the total amount of bone tissue that accumulates in a person. For women above age fifty and men older than seventy-one, the RDAs are also a bit higher for several reasons, including that as we age, calcium absorption in the gut decreases, vitamin D3 activation is reduced, and maintaining adequate blood levels of calcium is important to prevent an acceleration of bone tissue loss (especially during menopause. ^[5]

In the typical American diet, most calcium comes from dairy products, especially cheese and milk.

• One slice of cheddar or Swiss cheese provides about 200 mg of calcium.

• One cup of nonfat milk contains about 300 mg, which is roughly one-third of the Recommended Dietary Allowance (RDA) for most adults.

Many foods are also fortified with calcium, including:

• Breakfast cereals

• Soy milk and other plant-based beverages

• Orange juice

These fortified products may provide one-third or more of the daily recommended intake per serving.

Although dairy products are the primary source of calcium in the U.S. diet, many non-dairy sources are available, allowing people to meet their calcium needs through a variety of dietary patterns.

In the typical American diet, calcium is mostly obtained from dairy products, especially cheese. A slice of cheddar or Swiss cheese contains just over 200 milligrams of calcium. One cup of nonfat milk contains approximately 300 milligrams of calcium, which is about a third of the RDA for calcium for most adults. Foods fortified with calcium, such as cereals, soy milk, and orange juice, also provide one-third or greater of the calcium RDA. Although the typical American diet relies mostly on dairy products for obtaining calcium, there are other good non-dairy sources of calcium.

Calcium Bioavailability

In the small intestine, calcium absorption primarily takes place in the duodenum (first section of the small intestine) when intakes are low, but calcium is also absorbed passively in the jejunum and ileum (second and third sections of the small intestine), especially when intakes are higher. The body doesn’t completely absorb all the calcium in food. Interestingly, the calcium in some vegetables, such as kale, brussels sprouts, and bok choy, is better absorbed by the body than that in dairy products. About 30 percent of the calcium in milk and other dairy products is absorbed.

The greatest positive influence on calcium absorption is an adequate intake of vitamin D. People deficient in vitamin D absorb less than 15 percent of calcium from the foods they eat. The hormone estrogen is another factor that enhances calcium bioavailability. Thus, as a woman ages and goes through menopause, during which estrogen levels fall, the amount of calcium absorbed decreases and the risk for bone disease increases. Some fibers, such as inulin, found in jicama, onions, and garlic, also promote calcium intestinal uptake.

Chemicals that bind to calcium decrease its bioavailability. These negative effectors of calcium absorption include the oxalates in certain plants, the tannins in tea, phytates in nuts, seeds, and grains, and some fibers. Oxalates are found in high concentrations in spinach, parsley, cocoa, and beets. In general, calcium bioavailability is inversely correlated with the oxalate content of foods. High-fiber, low-fat diets also decrease calcium absorption, an effect likely related to how fiber and fat influence the time food spends in the gut. Anything that causes diarrhea, including illness, medications, and specific symptoms of old age, decreases gut transit time and therefore reduces calcium absorption. As we get older, stomach acidity sometimes decreases, diarrhea occurs more often, kidney function is impaired, and vitamin D absorption and activation are compromised, all of which contribute to reduced calcium bioavailability.

Phosphorus: Where Energy Meets Structure

Phosphorus is present in our bodies as part of a chemical group called a phosphate group. These phosphate groups are essential as structural components of cell membranes (as phospholipids), DNA and RNA, energy production (ATP), and regulation of acid-base homeostasis. Phosphorus, however, is mostly associated with calcium as a part of the mineral structure of bones and teeth. Blood phosphorus levels are not controlled as strictly as calcium, so PTH stimulates renal excretion of phosphate to prevent it from accumulating to toxic levels.

Dietary Reference Intakes and Sources of Phosphorus

Compared with calcium, most Americans are not at risk of a phosphate deficiency. Phosphate is present in many foods popular in the American diet, including meat, fish, dairy products, processed foods, and beverages. Phosphate is added to many foods because it acts as an emulsifying agent, preventing clumping, improving texture and taste, and extending shelf life. The average intake of phosphorus in US adults ranges between 1,000 and 1,500 milligrams per day, well above the RDA of 700 milligrams per day. The UL set for phosphorus is 4,000 milligrams per day for adults and 3,000 milligrams per day for people over age seventy.

Magnesium: Powering Enzymes, Muscles, and Nerves

Approximately 60 percent of magnesium in the human body is stored in the skeleton, making up about 1 percent of mineralized bone tissue. Magnesium is not an integral part of the hard mineral crystals, but it does reside on the surface of the crystal and helps maximize bone structure. Observational studies link magnesium deficiency with an increased risk for osteoporosis. A magnesium-deficient diet is associated with decreased levels of parathyroid hormone and the activation of vitamin D, which may lead to an impairment of bone remodeling. A study in nine hundred elderly women and men did show that higher dietary intakes of magnesium correlated to an increased BMD in the hip.^[6] Only a few clinical trials have evaluated the effects of magnesium supplements on bone health and their results suggest some modest benefits on BMD.

In addition to participating in bone maintenance, magnesium has several other functions in the body. In every reaction involving the cellular energy molecule, ATP, magnesium is required. More than three hundred enzymatic reactions require magnesium. Magnesium plays a role in the synthesis of DNA and RNA, carbohydrates, and lipids, and is essential for nerve conduction and muscle contraction. Another health benefit of magnesium is that it may decrease blood pressure.

Many Americans do not meet the recommended dietary intake of magnesium. Some observational studies suggest mild magnesium deficiency is linked to increased risk for cardiovascular disease. Signs and symptoms of severe magnesium deficiency may include tremor, muscle spasms, loss of appetite, and nausea.

Dietary Reference Intake and Food Sources for Magnesium

The RDAs for magnesium for adults between the ages of nineteen and thirty are 400 milligrams per day for males and 310 milligrams per day for females. For adults above the age of thirty, the RDA increases slightly.

Dietary Sources of Magnesium

Magnesium is part of the green pigment, chlorophyll, which is vital for photosynthesis in plants; therefore, green leafy vegetables are a good dietary source of magnesium. Magnesium is also found in high concentrations in fish, dairy products, meats, whole grains, and nuts. Additionally, chocolate, coffee, and hard water contain significant amounts of magnesium. Most Americans do not meet the RDA for magnesium. Typically, Western diets lean toward low fish intake and an unbalanced consumption of refined grains rather than whole grains.

Summary of the Major Minerals 

Attributions

This section is an adaptation of “Calcium”, “Phosphorus”, and “Magnesium” in Human Nutrition: 2020 Edition by University of Hawai‘i at Mānoa Food Science and Human Nutrition Program licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.