Calcium: Benefits, Food Sources and When You Need Supplements

5 minutes

Calcium is needed for more than bones: it supports muscles, nerves and blood clotting. We explore adults' daily needs, whether food can meet them, why blood tests do not reveal calcium stores and when supplements may be needed.

21 June 2025

Unagrande Yoga Expert

1100

What is calcium?
Why your body needs calcium
Daily calcium intake
Foods that contain calcium
How calcium is absorbed
Who needs to pay particular attention to calcium?
Signs of calcium deficiency
Which test measures calcium levels?
How to choose and take a supplement
Combining calcium with vitamin D, magnesium and K2
The risks of too much calcium
Frequently asked questions
Key points about calcium

Calcium usually comes to mind when we talk about strong bones. But its role does not end there: muscles, the nervous system and blood clotting need it too. Buying the bottle with the highest dose is not the best way to “look after your bones”.

Most adults can obtain the calcium they need from ordinary food. Cramps, brittle nails or poor dental health do not, on their own, prove a deficiency. Let us look at daily calcium needs, which foods help meet them and when a supplement may be useful.

At a glance: the Russian dietary reference value is 1,000 mg of calcium a day for adults and 1,200 mg from age 65. This is the total from food and supplements. If your diet already meets your needs, an extra 1,000 mg in tablets is unnecessary. Age thresholds and recommendations vary by country.

What is calcium?

Calcium is the most abundant mineral in the body. Almost all of it is stored in bones and teeth. Bones provide both a framework and a reserve: the body continually removes calcium from them and deposits it again to maintain stable blood levels.

The body cannot make calcium, so it must be supplied regularly through food. Supplements are needed only when the diet does not meet requirements or there is a medical indication.

Why your body needs calcium

Calcium's best-known role is building and renewing bone tissue. It also:

contributes to muscle contraction, including the heart muscle;
helps transmit nerve impulses;
is necessary for normal blood clotting;
supports cellular enzymes and signalling;
maintains the structure of bones and teeth.

Calcium does not work alone. Bone health also depends on vitamin D, adequate protein, physical activity and hormone balance. A single supplement cannot replace a balanced diet or osteoporosis treatment.

Daily calcium intake

According to Russian dietary reference values, adults need:

Age	Calcium per day
18–64 years	1,000 mg
65 years and older	1,200 mg

This is the daily total from all sources: dairy products, fish, vegetables, fortified foods and, where needed, supplements. Other countries use different age thresholds: US guidance recommends 1,200 mg for women from age 51 and for all adults over 70, with 1,000 mg for other adults.

A dietary reference value and a treatment plan are not the same thing. With osteoporosis, kidney disease, parathyroid disorders, pregnancy or breastfeeding, discuss recommendations separately with your doctor.

Foods that contain calcium

It is easier to obtain calcium from several foods throughout the day than from one “record holder”. Good sources can include milk and fermented dairy products, cheese, fish with soft edible bones, fortified plant drinks and tofu, and certain pulses, vegetables, nuts and seeds.

Approximate calcium amounts in typical portions:

Food and portion	Calcium
Plain yoghurt, 150 g	about 207 mg
Milk, 200 ml	about 236–244 mg
Hard cheese, 30 g	about 240 mg
Mozzarella, 60 g	about 242 mg
Sardines with bones, 60 g	about 240 mg
Canned salmon with bones, 85 g	about 181 mg
Calcium-fortified soya drink, 200 ml	about 240 mg
Tofu made with calcium salts, ½ cup	about 253 mg
White beans, cooked, 200 g	about 132 mg
Broccoli, 120 g	about 112 mg
Almonds, 30 g	about 75 mg
Chia seeds, 1 tablespoon	about 76 mg

These figures are approximate: amounts depend on the variety, recipe and manufacturer. Checking the labels of plant drinks and tofu is especially important. An unfortified drink may contain ten times less calcium, and the salts used in making tofu affect its calcium content.

Can you get all the calcium you need from food?

Yes. For example, a serving of plain yoghurt, a glass of milk, 30 g of hard cheese, a portion of sardines and some beans throughout the day provide about 1,050 mg of calcium together.

It is also possible without dairy products. Two glasses of fortified soya drink, calcium-set tofu, beans, broccoli and a small portion of almonds provide around 1,000 mg. Here, checking the ingredients is particularly important. Remember to shake the plant drink carton: added calcium can settle at the bottom.

The practical point is that food can meet your needs. If you eat few dairy or fortified products, fish with bones or other calcium sources, first estimate what your usual menu provides, then consider whether a supplement is needed.

How calcium is absorbed

The calcium amount on a label is not the same as the amount your body absorbs. Absorption depends on the food's composition, portion size, age, vitamin D status and digestive health.

Vitamin D helps with active calcium absorption in the intestine.
Oxalates bind some calcium. This is why calcium from spinach is absorbed less well than calcium from milk, broccoli or kale.
Large single doses of supplements are absorbed less efficiently than smaller doses: no more than 500 mg of elemental calcium at a time is generally recommended.
Age also matters: absorption efficiency gradually decreases with age.

You do not need to build your diet around perfect combinations or worry about every food containing phytates. With a varied diet and calcium sources several times a day, individual interactions usually do not become a problem.

Who is at greater risk of inadequate calcium intake?

Someone may obtain too little calcium if they:

do not consume dairy or fortified products;
follow a very restrictive diet;
have a cow's milk protein allergy or significant lactose intolerance and have not found alternatives;
have a condition that impairs nutrient absorption;
have undergone bariatric surgery;
are older;
have low vitamin D levels;
take certain medicines long term that affect bones or calcium metabolism.

After menopause, bone loss accelerates as oestrogen levels fall. This does not mean every woman automatically needs a high calcium dose: diet, osteoporosis risk factors and medical indications should be assessed first.

Signs of calcium deficiency

An important distinction is that low calcium intake and low blood calcium are not the same thing.

If food provides too little calcium for a long time, the body maintains blood levels by drawing on its bone reserves. A person may therefore feel nothing, while bone mineral density gradually falls and fracture risk increases.

Cramps, brittle nails, tooth decay, hair loss, irritability and tiredness are nonspecific. They have many possible causes and cannot be used to diagnose inadequate calcium.

True hypocalcaemia, meaning low blood calcium, is more often related to disease, disturbances in vitamin D or magnesium metabolism, parathyroid function, serious illness or medicines than to an ordinary diet. It may cause tingling around the mouth and in the fingers, muscle spasms and, in severe cases, seizures and abnormal heart rhythms. These symptoms require medical assessment.

Which test measures calcium levels?

A blood test can measure total or ionised calcium. But a normal result does not mean the diet contains enough calcium or that the bones are receiving everything they need. The body regulates blood calcium very tightly, partly by drawing on bone tissue.

This is why a “calcium test” prompted only by brittle nails or a wish to check your diet is usually not very informative. A doctor may request total calcium, albumin, ionised calcium and other tests when a calcium metabolism disorder is suspected.

Bone mineral density is assessed with a scan called densitometry, or DXA. This is not a test for dietary calcium deficiency either, and it is not an examination every young, healthy person automatically needs.

How to take calcium correctly

If a supplement is needed, do not start by choosing the largest bottle. First assess how much calcium your food already provides, then replace only the shortfall.

Calcium carbonate or citrate

Calcium carbonate contains about 40% elemental calcium. It is absorbed better with food and is more likely to cause bloating or constipation.
Calcium citrate contains about 21% elemental calcium, depends less on stomach acidity and can be taken without food. It is often chosen for low stomach acid or poor tolerance of carbonate.

The words “500 mg calcium citrate” on the front of a pack do not always mean 500 mg of calcium itself. Check the amount of elemental calcium in the ingredients or nutrition information.

How much to take at once

Supplemental doses of up to 500 mg of elemental calcium at a time are absorbed best. If a doctor prescribes more, the daily amount is usually divided into several doses.

Morning or evening?

There is no universal “best time”. Take carbonate with food; citrate can be taken with or without food. Following the prescribed dose and accounting for other medicines matter more.

How long to take it

The duration depends on the reason for prescribing it. A supplement is not necessarily needed for life: if your diet changes and meets your needs, the regimen can be reviewed with your doctor.

Should calcium be combined with vitamin D, magnesium or K2?

You do not automatically need a whole collection of supplements alongside calcium.

Vitamin D

Vitamin D is necessary for active calcium absorption, but this does not mean everyone needs identical doses of both nutrients. Diet and indications should be assessed first. Read more in “Vitamin D: Why You Need It, How to Take It and When to Test”.

Magnesium

Magnesium contributes to bone metabolism, but does not need to be added automatically to every calcium supplement. For more on daily intake, foods and supplements, see “Magnesium: Supporting Energy, Calm and Health”.

Vitamin K2

There is no universal recommendation to take calcium only alongside K2. People taking anticoagulants that are vitamin K antagonists must not start or stop vitamin K supplements themselves.

Medicines

Calcium can interfere with the absorption of levothyroxine, some antibiotics and other medicines. Calcium and levothyroxine, for example, are generally separated by at least four hours. Follow the interval in the specific medicine's instructions or your doctor's prescription.

The risks of too much calcium

It is difficult for a healthy person to obtain a dangerous excess of calcium from ordinary food. Problems are more often related to unnecessarily high supplement doses or diseases that raise blood calcium.

Possible signs of hypercalcaemia include:

nausea and constipation;
weakness and tiredness;
intense thirst and frequent urination;
impaired kidney function;
confusion;
abnormal heart rhythms in severe cases.

NASEM sets the upper intake level from all sources at 2,500 mg a day for adults aged 19–50 and 2,000 mg for adults over 50. This is a safety boundary, not a beneficial target.

Evidence linking calcium supplements to kidney stones and cardiovascular disease is mixed. There is no convincing reason to take a high dose “just in case”. Discuss supplements with a doctor if you have kidney stones, kidney disease or high blood calcium.

Frequently asked questions

Is cottage cheese the best source of calcium?

Not always. Curd cheese such as tvorog often contains less calcium than milk, yoghurt or hard cheese, and the amount depends on how it is made. It remains a useful protein food, but should not be considered the only or main calcium source.

What should you choose with lactose intolerance?

Lactose-free milk contains approximately as much calcium as regular milk. Some people also tolerate yoghurt and hard cheese. Alternatives include fortified plant drinks, calcium-set tofu and fish with soft edible bones.

Can you obtain enough calcium on a plant-based diet?

Yes, but the diet needs more careful planning. Useful sources include fortified plant drinks, tofu made with calcium salts, white beans, broccoli, kale, almonds and seeds. Check the calcium amount per portion as well as the product name.

Does coffee leach calcium from your bones?

Caffeine can slightly reduce calcium absorption, but one cup of coffee does not “wash out your bones”. Overall calcium intake, vitamin D status, physical activity and avoiding smoking matter much more.

Should you take calcium to prevent osteoporosis?

Not automatically. Adequate calcium intake matters, but one supplement does not guarantee protection against fractures. Osteoporosis prevention includes diet, vitamin D when indicated, resistance and weight-bearing exercise, avoiding smoking, assessing fall risk and, when necessary, medication.

Can you take calcium without a blood test?

Assessing your diet is more useful first, because a blood test does not show dietary calcium stores. A small supplement to fill an established dietary shortfall may sometimes be discussed without a test, but high doses and long-term use are best agreed with a doctor.

Can you take calcium with iron?

Ordinary foods containing calcium and iron do not need to be kept apart. If both supplements are prescribed, they are often taken at different times to avoid reducing iron absorption. The exact interval depends on the products and is given in their instructions. Read more about iron in “Iron: Supporting Energy, Concentration and Vitality”.

Key points about calcium

Russian dietary reference values recommend 1,000 mg of calcium a day for adults and 1,200 mg from age 65, counting all sources.
Ordinary food can meet your needs, including without dairy products.
Cramps, brittle nails and poor dental health do not, on their own, prove calcium deficiency.
A normal blood calcium result does not show whether there is enough calcium in the diet or bones.
A supplement is primarily needed to fill the gap between dietary intake and requirements.
Carbonate is taken with food; citrate depends less on stomach acidity.
No more than 500 mg of elemental calcium is generally taken at once.
Vitamin D matters for calcium absorption, but calcium, magnesium and K2 do not automatically need to be taken as a set.
High supplement doses “just in case” do not improve health and may cause harm.

Calcium matters, but looking after your bones starts before taking a tablet. First look at the calcium sources already on your menu, add foods to cover any shortfall, and then decide whether a supplement is needed.