Vitamins C & D increase the absorption of calcium, protecting our bones.

What does calcium do in the body? How much calcium per day?

How to increase calcium absorption in the body? What does calcium do in the body? What’s the daily recommended intake of calcium? Can a plant-based diet cause calcium deficiency?

What’s calcium?

Calcium is a mineral. Actually, it’s the most abundant mineral in the body and it’s necessary for life, as calcium has a key role in countless body functions.

Where is calcium stored in the body?

The calcium is stored mainly in the bones and teeth. They are the places where we find calcium. About 99% of the body’s calcium is stored there. The main function of it is to support bones’ structure and proper function.

Role of calcium in body function

The calcium in bones is also used to keep steady amounts of calcium in the body. For instance, calcium in blood and muscle is always regulated. Our bodies regulate it constantly. Even when eating a meal high in calcium, calcium in the blood doesn’t change.

What does calcium do in the body?

Calcium is important for many functions of the body.

To name a few, calcium has a key role to:

  • vascular contraction,
  • the dilatation of blood vessels,
  • muscle function,
  • nerve transmission,
  • signaling between cellular,
  • hormonal secretion,
  • blood clotting,
  • muscle contraction,
  • oocyte activation,
  • have normal heartbeat

Most noteworthy, all these important functions need less than 1% of total body calcium…This means that only 1% of the calcium in our bodies is in the blood.

Calcium and bone function

We know that calcium is important for our bones. Why?

Our bones keep remodeling throughout our life span. Calcium is reabsorbed all the time by bones. Additionally, our bones can store more calcium, or the contrary, lose some calcium. It depends on the age.

Children form new bone tissue. That’s part of the growing process.

On the other hand, the elderly tend to lose bone tissue. That’s because of bone breakdown. The elderly can’t form bone tissue as efficiently as younger people. The result is bone loss. That increases the risk of osteoporosis.

Women who experienced menopause, are at higher risk of developing osteoporosis.


Calcium has a key role in the proper development, growth, and maintenance of bone mass.

Does your body need calcium after exercise?

Moreover, calcium is one of the important electrolytes. What is this important for exercise?

The most known electrolytes are sodium, potassium, chloride, calcium, and magnesium.

They are everywhere in our bodies. We can find them in blood, muscles, or urine.

But why should we worry about them during exercise?

Because they regulate so many body functions:

  • amount of water in the body
  • the acidity of the body
  • muscle function
  • nerve function
  • brain function

But electrolytes may be imbalanced. How?

Most commonly with extreme sweating…

When you run under the hot sun, you sweat. Through sweating, you lose electrolytes. That’s how imbalances are created.

Electrolytes should be in balance, in order to avoid leg cramps, for instance…

It’s important to increase food rich in electrolytes, such as calcium, after extreme exercise.

Furthermore, if you drink too much water, without consuming additional electrolytes, preferable from foods, you may experience a decrease in your athletic performance.

If you want an extra boost, try beet greens. Not only contain many minerals, such as calcium but also contain nitrates, that can help you run longer and more effortlessly…


Water balance and electrolyte balance are necessary for improved athletic performance.

How much calcium do I need per day?

Daily calcium intake demands are different depending on age and sex.

Daily Recommended Calcium intake

According to the National Institutes of Health, Office of Dietary Supplements, the daily recommended calcium intake should be:

0–6 months200 mg200 mg
7–12 months260 mg260 mg
1–3 years700 mg700 mg
4–8 years1,000 mg1,000 mg
9–13 years1,300 mg1,300 mg
14–18 years1,300 mg1,300 mg1,300 mg1,300 mg
19–50 years1,000 mg1,000 mg1,000 mg1,000 mg
51–70 years1,000 mg1,200 mg
71+ years1,200 mg1,200 mg

How many mg of calcium per day

As you can see, most people should consume about 1000 mg of calcium daily.

Teens should only consume more. About 1300 mg. They need more calcium daily, because of bone growth.

Remember…Women after menopause are more vulnerable to osteoporosis. Hence, women in their 50s should consume slightly more mg of calcium per day.

The recommended daily calcium intake for them is 1200 mg.

Is Dairy necessary for healthy bones?

Everybody has heard that dairy is good for us, as they contain calcium. But eating dairy doesn’t mean healthy bones…

Many studies have proven this…

In 2011 scientists published a study to the American Society for Bone and Mineral Research. They didn’t find a connection between milk intake and decreased hip fracture risk in women.

Another study published in The American Journal of Clinical Nutrition showed that cow milk doesn’t reduce hip fractures risk in postmenopausal women. Moreover, a high-calcium diet didn’t reduce the risk of hip fractures.

Your body needs calcium but milk may not be the best option. Whole food not only provides us with calcium but many other micronutrients.

Furthermore, scientists underlined the importance of vitamin D intake for healthy bones. They propose vitamin D supplementation, as most women fail to meet the recommended daily vitamin D intake.

Skip cow’s milk today. There are so many healthier non-dairy sources of calcium. More here.

Calcium intake for greater height

What about teenagers? They need extra calcium for bone growth.

Maybe greater calcium consumption leads to increased bone mass during childhood (6).

Seems like dairy isn’t the only option. Teens should just consume adequate amounts of calcium. There are so many vegan sources.

Moreover, if you consume much milk during teenage years, it doesn’t mean that you would have lower risk of hip fracture later in life (6).

Want tall children? It’s mainly genetics, but high consumption of foods rich in calcium is a good practice. Many plants are a good source.

Bioavailability of calcium

According to a report of the National Academy Press (Dietary Reference Intakes for Calcium and Vitamin D), we absorb only about 30% of the calcium in foods.

This varies though. It depends on the type of food…

Depends on the type of food

Dairy is a good source of calcium. Moreover, we absorb about 30% of them.

The same stands for fortified foods. So, we absorb about 30% of calcium from fortified orange juice, soy milk, or tofu.

What about whole food vegan options? Good news.

The absorption of calcium from some vegetables can double.

We can absorb up to 60% of calcium coming from kale, broccoli, or bok choy.

Do beans, fruits, and veggies inhibit calcium absorption?

Yes, it’s true… Super healthy foods, such as fruits, vegetables, or beans can inhibit calcium absorption. How?

Because they contain phytochemicals that bind to calcium, preventing its absorption. Phytic acid and oxalic acid are the most known compounds that bind to calcium.

On the other hand, these compounds have potent health benefits. More about the health benefits of phytic acid here.

Foods rich in oxalic acid

The number one food rich in oxalic acid is spinach. For this reason, you better eat less of it if you have a history of kidney stones.

A great alternative to spinach is kale. Kale is a dark leafy vegetable, rich in health-promoting phytochemicals, but also low in oxalates (that’s another name of oxalic acid).

Other oxalic acid-rich foods are collard greens, beet greens, sweet potatoes, rhubarb, and legumes.

Oxalic acid binds to calcium inhibiting absorption.

But oxalic acid in different foods has different bioavailability.

For instance, although brewed tea has a high oxalate content, it isn’t bioavailable.

Contrary, peanuts, and almonds have a modest oxalate content, while its oxalate content has increased bioavailability (3).  

Foods rich in phytic acid

Common foods that are rich in phytic acid are cereals, legumes, oilseeds, and nuts. Detailed list here.

Phytic acid has two faces. It is called an anti-nutrient. Why? Because it can inhibit the absorption of minerals, such as calcium.

On the other hand, foods rich in phytates (phytic acid) can be important in the prevention of bone mineral density loss. Scientists said that postmenopausal women who consume many phytate-rich foods can benefit the most (4).

Usually, foods rich in phytic acid are also rich in fiber. Whole-grain products, beans, seeds, nuts, and soy both good sources of phytic acid and fiber.

So, should I avoid veggies, fruits, and beans?

Of course not…

We just should more calcium-rich foods and follow some technics, in order to increase calcium absorption.

Furthermore, scientists suggest that we should eat a variety of foods, in order to have the best results. If we consume many different foods, we’ll avoid inhibiting calcium absorption.


A great variety of food has little or no nutritional effect on calcium absorption. Eat different foods every day…

More calcium, less absorption in the body

The more calcium we consume, the less we absorb. In other words, as calcium intake increases, the efficiency of absorption decreases.

Scientists have reported that the absorption of calcium can range from 60% to less than 30%. 60% with very low calcium intake. Less than 30% with a high intake.

That’s our body’s defensive mechanism, in order to avoid calcium deficiency and calcium toxicity.

Absorption decreases with age

Another factor for calcium absorption is age. As we get older, we absorb calcium less efficiently.

For instance, children absorb 60% of calcium. Their calcium needs are greater than adults. They need it for bone growth.

On the other hand, adults absorb about 20% of calcium.

Only, pregnant women absorb calcium more efficiently. They also have extra calcium needs…

Moreover, as we get older, we can’t absorb calcium.

As mentioned, women older than 50 years should consume more calcium. Not only they don’t absorb calcium, but also they have increased calcium needs.

How can you increase calcium absorption?

There are many factors that can inhibit calcium absorption…

Decrease in Sodium Intake

If you have osteoporosis or experiencing calcium deficiency, maybe it’s a good practice to cut down on salt.

The reason is that high sodium intake increases the losses of calcium by urine.

Consume foods rich in vitamin C

According to a study, published by the American Society for Bone and Mineral Research, vitamin C intake may have a beneficial role in levels of bone mineral density.

Scientists took data from 994 women. Women who took vitamin C had the best results.

Postmenopausal women benefited greatly as well.

But how much vitamin C should you take?

Scientists couldn’t tell. Maybe 1000 mg of vitamin C daily it’s a good dose though.

So, should you take vitamin C supplements? The answer is here.

Firstly, try to eat as many foods rich in vitamin C.

Your body needs Vitamin D

Calcium absorption is improved with vitamin D.

Vitamin D is produced by the skin when exposed to sunlight.

Many studies have shown that supplementation with both calcium and vitamin D has beneficial effects. Calcium and vitamin D can reduce fractures in the elderly.

Contrary, elderly people who don’t consume adequate amounts of calcium and have low vitamin D levels may develop osteoporosis.

In order, to avoid a reduction in bone mass later in life, we should consume adequate amounts of calcium throughout our lives.

Also, it’s beneficial to take vitamin D supplements. According to a study, vitamin D supplementation of 700 – 800 IU daily can reduce the risk of hip fractures in elderly people. Lower dose didn’t have any benefits. For instance, scientists didn’t find fracture prevention when people consumed 400 IU of vitamin D per day (5).

Seems sunlight and vitamin D supplements are the only vital solutions for adequate amounts of vitamin D intake. We can’t depend on food (7).

Finally, we should exercise regularly. It’s critical…

Want healthy bones?

Regular exercise. Also, we need adequate intakes of calcium and vitamin D throughout the life cycle.

Cook your greens

Cooking vegetables is a good practice if you want to increase calcium absorption. Why?

Because some veggies, such as spinach or beet greens are high in oxalic acid. Oxalic acid binds to calcium inhibiting absorption.

In plants, oxalic acid binds to minerals. This new compound is called oxalate.

Oxalate is water-soluble. This means that we can reduce its content by cooking.

The best method is steaming. This way we don’t lose many nutrients in the water, but we can reduce oxalate content by up to 53% (1).

Boiling has better results though. By boiling we can reduce oxalate content by up to 87%. Unfortunately, when boiling, many nutrients are leached in the water.

Finally, baking doesn’t change oxalate content.

If you have a history of the development of kidney stones, you better steam or boil your vegetables. Avoid spinach as well. It’s by far the richest source of oxalates. Oxalates bind to calcium, forming kidney stones.

Avoid excess alcohol intake

Avoid excess alcohol intake, as alcohol reduces calcium absorption.

Also, alcohol inhibits the conversion of vitamin D to its active form. As we mentioned, vitamin D is very important to calcium absorption.

What amount of alcohol tends to affect calcium?

We don’t know. Better consume moderate amounts…

According to the Mediterranean Diet, up to two glasses of red wine, a day for men and one glass for women is beneficial (2).

Especially, red wine is rich in phenolic acids and flavonols, such as myricetin, quercetin, catechin, epicatechin, anthocyanins, and many more. Polyphenols are known for their health benefits.

Tea or coffee in moderate. Avoid Caffeine

Caffeine may be harmful for calcium absorption.

If you consume large amounts of caffeine, it can increase calcium excretion and also reduce calcium absorption.

But low consumption of caffeine has bo negative effect though.

You can have one cup of coffee or two cups of tea daily. This amount of caffeine causes a tiny loss of calcium. Only about 2-3 mg. That’s negligible.


Women in their 50s or pregnant women should avoid consuming large amounts of caffeine-rich foods, such as coffee or tea.


  1. NCBI: Effect of different cooking methods on vegetable oxalate content.
  2. Pubmed: Mediterranean Way of Drinking and Longevity.
  3. A further study of oxalate bioavailability in foods.
  4. Reumatologia-Clinica: The influence of consumption of phytate on the bone mass in postmenopausal women of Mallorca
  5. Fracture prevention with vitamin D supplementation: a meta-analysis of randomized controlled trials.
  6. 2014: Milk Consumption During Teenage Years and Risk of Hip Fractures in Older Adults