Calcium, Phosphorus, Magnesium, and Sulfate

Calcium, Phosphorus, Magnesium, and Sulfate

We’ve already covered Sodium, Chloride, and Potassium, but there are four remaining major minerals that we need to talk about! Three of them are important for bone health, and the last one…well, he is just along for the ride. Let’s jump right in to calcium, phosphorus, magnesium, and sulfur!

Major Minerals

Calcium, a major mineral, is found in milk and dairy products.


What does calcium do for my body?

“Milk builds strong bones!” is a phrase we’ve heard our whole lives, and we know that it’s the calcium in milk that offers such an amazing promise! Well, it’s true – calcium’s main function is to build strong bones while we’re young, and maintain strong bones when we’re older. In fact, 99% of the calcium in our body is in our bones and teeth!

A quick lesson on bones, to tie everything together. A bone starts as a thin “web” of collagen – a protein. Calcium forms crystals on this web, hardening and solidifying the tissue to become bone. By childhood, the bones are so rigid that they can support the weight of the child! But bones aren’t solid, as most people believe. They still have a web-like structure, to allow for shock absorption (like when you’re running) and to continuously remodel themselves. Bone is always being broken down and rebuilt, so it’s important to have a steady intake of calcium each day to keep up!

Related Reading: Protein

The bones act like a bank for calcium. They store calcium and use it as part of their structure, but if calcium is needed elsewhere in the body, the bones will break down their structure and donate calcium to the blood. The blood needs to maintain a certain amount of calcium, so if it’s low, it’ll take some from bones. If blood is always taking calcium from the bones, they are breaking down more than they are being rebuilt. After a few years, this could result in brittle bones.

The remaining 1% of calcium in our body is located within fluids. Here, it binds to proteins and activates them to allow them to perform their duties, such as breaking down glycogen to give energy for muscle contractions, nerve impulses, and hormone secretion. Calcium also assists Vitamin K in blood clotting.

Related Reading: Vitamin K

How much calcium do I need?

As adults, our bodies only absorb about 30% of the calcium we ingest, and Vitamin D is required for absorption. Children whose bodies are still growing can absorb up to 60% of the calcium taken in! Vitamin D, stomach acid, and lactose (in infants only) enhance the absorption rate of calcium. A deficiency of Vitamin D, fiber, phytates (in seeds, nuts, and grains) and oxalates (in beet greens, spinach, and sweet potatoes) actually inhibit the absorption of calcium! Phytates and oxalates don’t have a huge impact, though, so don’t limit these whole foods thinking you’re hindering your calcium intake too much!

The RDA for calcium takes this absorption rate into consideration, and is 1000mg for adults. 1200-1300 mg is recommended for children and for women over 50, who are more likely to develop osteoporosis.


A low intake of calcium during childhood can prevent the bones from becoming strong, resulting in stunted growth. Unfortunately, adults won’t have any symptoms of deficiency until later in life, when they have osteoporosis, which could also have been a Vitamin D deficiency.

Related Reading: Vitamin D


Too much of anything isn’t a good thing, and the same is true for calcium. If more than 2,500 mg of calcium is consumed each day, soft tissues could begin to calcify or kidney stones could form.

Where can I find calcium in my diet?

Calcium is found predominantly in milk and milk products, like yogurt and cheese. However, many people choose not to drink milk, or can’t because they are lactose intolerant. Don’t fret! There is a variety of other sources of calcium!

Some nuts and seeds (like almonds and sesame seeds), breads, bok choy, kale, parsley, and broccoli are all great sources of calcium! Oysters and sardines are good seafood choices. Dark green, leafy vegetables do have calcium, but they contain phytates and oxalates that prevent absorption, so they aren’t considered good sources.

Phosphorus, a major mineral, is found in a variety of foods, especially those derived from animals.Phosphorus

What does phosphorus do for my body?

Like calcium, phosphorus is a large part of creating strong bones, but it also does so much more! It’s part of DNA, and therefore required for growth. It’s an integral part in phospholipids, which create every cell membrane. It even assists in energy metabolism, attaching to enzymes and B Vitamins to allow them to become active.

Related Reading: Lipids (aka fats!)

The RDA for phosphorus for adults is 700 mg/day, with an upper limit of 4000 mg/day.


Since phosphorus is found widespread throughout our diets, deficiency is not common. However, symptoms would include muscular weakness and bone pain.


Like calcium, too much phosphorus can lead to calcification of soft tissues, especially the kidneys.

Where can I find phosphorus in my diet?

Phosphorus is widespread throughout almost all foods, but it especially high in animal-derived foods. Sunflower seeds, broccoli, and milk are great sources, too!

Leafy green vegetables like spinach, broccoli, and kale have magnesium, a major mineral.Magnesium

What does magnesium do for my body?

Magnesium is an important mineral for bone health, but it is also in all cells of soft tissues to help with energy metabolism. It helps to build proteins, fats, and DNA. Where calcium promotes muscle contraction and blood clotting, magnesium inhibits them. The two working together help to regulate blood pressure. Finally, magnesium supports the functioning of the immune system.

The RDA for men is 400 mg/day, and for women is 310 mg/day.


Low intakes of magnesium can lead to brittle bones later in life, and could even contribute to heart disease, hypertension, diabetes, and cancer. Central nervous system function can also be affected negatively. Hallucinations and convulsions are symptoms of deficiency.


Magnesium toxicity is rare, but it is very serious and can be fatal. Dehydration and alkalosis are symptoms of a magnesium toxicity. An upper limit has only been set for magnesium from non-food sources. Supplements should not be consumed in amounts greater than 350 mg/day to avoid toxicity!

Where can I get magnesium in my diet?

Magnesium is actually a component of chlorophyll, so many dark, leafy greens are rich in magnesium! Legumes, nuts, and seeds are also great sources, such as pinto beans, peanut butter, and cashews. Halibut and artichoke are also high in the mineral.

Eggs are a good source of sulfate, a major mineral.


Sulfate is the oxidized form of the element sulfur.

What does sulfate do for my body, and where can I find it in my diet?

Sulfate is an important part of the structure of proteins. Without it, our bodies wouldn’t be able to synthesize proteins. Skin, hair, and nails are high in the proteins that contain sulfur. There is no recommendation for daily intake of sulfate, since normal protein intake will meet the body’s needs.

Deficiency and toxicity are not a big concern for sulfate!

Most protein-containing foods provide the sulfate we need, since it’s literally part of the structure of the proteins! Meats, legumes, eggs, nuts, and milk are great sources of sulfate.

There you have it, folks! The major minerals, broken into two parts for you. Sodium, chloride, potassium, calcium, phosphorus, magnesium, and sulfate. Necessary for muscle contraction, nerve impulses, fluid balance, bone mineralization, energy metabolism, and much more!

Did you miss the first part on major minerals? You can find it here:

Major Minerals: Sodium, Chloride, and Potassium

Ready for the next set of minerals?

Continue Reading: The Trace Minerals

Leave a Comment!