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What is calcium?
Calcium (Ca) is a chemical element and is an alkaline earth metal. It is essential for all living organisms and is found in many foods. Calcium is the fifth most abundant element in the Earth’s crust and the most abundant mineral in the human body.
What does calcium do for your body?
There is approximately 2-3% of calcium per weight in an adult.
A total of 99% of the calcium is stored in the bones and teeth, supporting its structure. Bones are the largest storage site of calcium in the body and serve as a source of calcium ready to be released in order to maintain a constant balance of calcium in the blood, intracellular fluids and muscles.
The remaining 1% supports the body’s critical metabolic functions such as widening of the blood vessels, regulation of the hearts’ functioning, vascular contraction, contraction and relaxation of the muscles and hormone regulation. Calcium also plays a role in the enzyme function, blood clotting, signaling between cells, and the transmission of messages in the nervous system. (1)
Health benefits of calcium
There are proven health benefits associated with calcium intake. However, there is a number of positive effects that are believed to be the outcome of calcium consumption that science still hasn’t proven.
- Calcium and osteoporosis (bone and teeth health)
Following the official recommended daily calcium requirement is essential for good bone health.
Insufficient calcium weakens the bones.The circulating levels of calcium in the blood is constantly regulated by the bones. They release enough calcium to the bloodstream in order to maintain its equilibrium, since calcium is an important building material.
In the long term, the constant release of calcium from the bones causes them to lose their mass and strength, becoming more prone to fractures.This happens in the case of hypocalcemia – a condition where the calcium levels in blood are lower than recommend due to a low calcium diet, or in situations of renal failure or constant use of diuretics.
While in the short term, a diet low in calcium doesn’t display any obvious symptoms, the long term consequences are much more serious, since it leads to osteopenia, osteoporosis and has an impact on rickets coupled with vitamin D deficiency. (2)
Bone loss also occurs as part of the aging process. The most vulnerable are women, especially those who are thin, physically inactive, elderly and postmenopausal (due to the estrogen levels).
People with a family history of osteoporosis that smoke or drink excessive amounts of alcohol also belong to the risk group of developing bone problems. (3)
An adequate daily supply of calcium, either from diet or supplements, ensures that the calcium homeostatic is maintained and that bones do not need to release calcium.
Please note that exercise is a crucial factor for bone strength. Calcium and vitamin D require physical exercise to have an effect on the bones. Relying exclusively on supplement pills may not have the desired outcome. (4)
There are some claims, linked to the acid-ash hypothesis, that a diet rich in both protein and calcium can cause bone problems.
However, evidence has shown the contrary, that it has positive effects on bone health. (read more..)
- Calcium and mortality from any causes
No association was found between calcium intake and mortality from all causes. (5)
- Calcium and colon cancer
Overall, the evidence, from strong, quality studies, that calcium reduces the risk of colorectal cancer is not concrete.
Nevertheless, there are some strong indications (observational and epidemiological studies) that calcium plays some role.Colon cancer has a long period of development, making it difficult to study.
The observational, epidemiological and experimental studies of the role of calcium in reduction of colorectal cancer risks are currently inconsistent, but there is strong evidence that calcium in dietary or supplemental form may have some protective properties.
More studies such as controlled trials and cohort studies are needed to confirm these findings. (6, 7, 8) Studies have so far shown with some degree of certainty that calcium supplementations might help in preventing the development of colorectal non-malignant tumors, called adenomas. Adenoma is a precursor to cancer. (9)
- Calcium and breast cancer
Calcium intakes of 780-1750mg per day are associated with a decreased risk of cancer in premenopausal women.
However, studies on postmenopausal women are inconsistent.No association was found between calcium intake and mammographic density. (5)
- Calcium and obesity
- Calcium and blood pressure
The release of calcium into the bloodstream causes vasodilation (widening of the blood vessels) and, therefore, reduces the blood pressure. Calcium intake is associated with a lower blood pressure in hypotensive adults but not in normotensive.
A low calcium intake, of 500mg/day or less, in people over 40 years old with hypertension is related to significantly higher risk of hypertension, in comparison with those whose intake is 1100mg or more per day.
Calcium supplementation significantly reduces the systolic blood pressure by 2-4 mm Hg in hypertensive adults compared to adults with no supplementation.
- Calcium and heart health
There is a strong association between a low calcium intake (less than 696mg/day) and the increased death risk caused by ischemic heart disease in white women between 55-69 years of age.
There is also a connection between a low calcium intake (less 500mg per day) and an increased risk of stroke in women in general, in comparison with those who have higher intakes of calcium. (5)
- Calcium and growth
Calcium supplementation is not associated with weight or height gain in children or adolescents. There is, however, evidence of height gain in children that consume more milk which is associated with a combination of high calcium and protein contents. (5)
Food sources of calcium
It is recommended to get your calcium from foods rather than supplements. Supplementation may lead to excessive calcium intake which may have negative health reactions (see below).
The best calcium-rich foods are dairy products such as milk, yogurt and cheese.
Non-dairy calcium rich foods include:
- Leafy green vegetables, such as turnip greens, collards, broccoli, bok-choy or spinach;
- Soy products, such as tofu or soy drinks (calcium fortified), for example, soy yogurt or soy milk;
- Fish with bones, like sardines and salmon;
- Nuts, such as brazil nuts and almonds;
- Seeds, especially sesame, chia seeds, flaxseeds and poppy seeds;
- Calcium fortified foods (check the labels). Please note that many of the calcium fortified foods can be also rich in sugar such as orange juice or breakfast cereals and overall may not be beneficial.
- Coconut water, blood orange, orange, lemon and blackcurrants.
Best food sources of Calcium
|Food||Serving||Amount of Calcium (mg)||% of RDA |
|Rating||% of RDA |
|Cheese||2 oz (56g)||404||40.4||Excellent||40.4||Excellent|
|Poppy seeds||1 oz (28g)||403||40.3||Excellent||40.3||Excellent|
|Cheese ricotta, low fat||1/2 cup (124g)||337||33.7||Excellent||33.7||Excellent|
|Milk, cow's||1 cup (244g)||276||27.6||Excellent||27.6||Excellent|
|Sesame seeds||1 oz (28g)||273||27.3||Excellent||27.3||Excellent|
|Cheese ricotta||1/2 cup (124g)||257||25.7||Excellent||25.7||Excellent|
|Yogurt low fat||1/2 cup (120g)||219.4||21.9||Excellent||21.9||Excellent|
|Turnip greens||1 cup (144g)||197||19.7||Good||19.7||Good|
|Chia seeds||1 oz (28g)||177||17.7||Good||17.7||Good|
|Cuttlefish, cooked||3 oz (85g)||153||15.3||Good||15.3||Good|
|Spinach, cooked||1/2 cup (90g)||142||14.2||Good||14.2||Good|
|Collards, cooked||1/2 cup (95g)||133||13.3||Good||13.3||Good|
|Soy Yogurt||1/2 cup (100g)||132||13.2||Good||13.2||Good|
|Perch, cooked||3 oz (85g)||116.5||11.6||Good||11.6||Good|
|Dandelion greens||1 cup (55g)||103||10.3||Good||10.3||Good|
|Scallops, cooked||3 oz (85g)||97.7||9.8||-||9.8||-|
|Oats, cooked||1/2 cup (117g)||93.5||9.4||-||9.4||-|
|Octopus, cooked||3 oz (85g)||90.1||9||-||9||-|
|Crab, cooked||3 oz (85g)||88.4||8.8||-||8.8||-|
|Soybeans, cooked||1/2 cup (86g)||87.5||8.8||-||8.8||-|
|Clam, cooked||3 oz (85g)||78.2||7.8||-||7.8||-|
|Trout, cooked||3 oz (85g)||73.1||7.3||-||7.3||-|
|Flaxseed||1 oz (28g)||71.4||7.1||-||7.1||-|
|Almonds||1 oz (28g)||70.3||7||-||7||-|
|Pollock, cooked||3 oz (85g)||65.5||6.5||-||6.5||-|
|Navy beans, cooked||1/2 cup (91g)||63||6.3||-||6.3||-|
|Herring, cooked||3 oz (85g)||62.9||6.3||-||6.3||-|
|Soy milk||1 cup (250g)||62.5||6.3||-||6.3||-|
|Pike, cooked||3 oz (85g)||62.1||6.2||-||6.2||-|
|Amaranth, cooked||1/2 cup (123g)||58||5.8||-||5.8||-|
|Coconut water||1 cup (240g)||57.6||5.8||-||5.8||-|
|Egg large||2 large (100g)||53||5.3||-||5.3||-|
|Lobster, cooked||3 oz (85g)||51.9||5.2||-||5.2||-|
|Halibut, cooked||3 oz (85g)||51||5.1||-||5.1||-|
|Blood orange||medium (121g)||48.4||4.8||-||4.8||-|
|Kale, cooked||1/2 cup (65g)||46.8||4.7||-||4.7||-|
|Arugula||1 cup (28g)||44.8||4.5||-||4.5||-|
|Brazil nuts||1 oz (28g)||44.8||4.5||-||4.5||-|
|Beet greens||1 cup (38g)||44.5||4.5||-||4.5||-|
|Carp, cooked||3 oz (85g)||44.2||4.4||-||4.4||-|
|Rhubarb||1 stalk (51g)||43.9||4.4||-||4.4||-|
|Crayfish, cooked||3 oz (85g)||43.4||4.3||-||4.3||-|
|Watercress||1 cup (34g)||40.8||4.1||-||4.1||-|
|Chickpeas, cooked||1/2 cup (82g)||40.2||4||-||4||-|
|Pinto beans, cooked||1/2 cup (85,5g)||39.3||3.9||-||3.9||-|
|Lemon||1 oz (28g)||37.5||3.8||-||3.8||-|
|Bok choy||1/2 cup (35g)||36.8||3.7||-||3.7||-|
|Green cabbage, cooked||1/2 cup (75g)||36||3.6||-||3.6||-|
|Haddock, cooked||3 oz (85g)||35.7||3.6||-||3.6||-|
|Snapper, cooked||3 oz (85g)||34||3.4||-||3.4||-|
|Shrimp, cooked||3 oz (85g)||33.1||3.3||-||3.3||-|
|Broccoli florets, cooked||1/2 cup (78g)||32.2||3.2||-||3.2||-|
|Hazelnuts||1 oz (28g)||31.9||3.2||-||3.2||-|
|Red cabbage||1/2 cup (75g)||31.5||3.2||-||3.2||-|
|Abalone, cooked||3 oz (85g)||31.5||3.1||-||3.1||-|
|Tofu||1 cup (100g)||31||3.1||-||3.1||-|
|Blackcurrants||1/2 cup (56g)||30.8||3.1||-||3.1||-|
|Pistachios||1 oz (28g)||30.8||3.1||-||3.1||-|
|Parsnip, cooked||1/2 cup (78g)||28.9||2.9||-||2.9||-|
|Brussels sprouts, cooked||1/2 cup (78g)||28.1||2.8||-||2.8||-|
|Mussel, cooked||3 oz (85g)||28.1||2.8||-||2.8||-|
|Adzuki beans, cooked||1/2 cup (100g)||28||2.8||-||2.8||-|
|Green beans, cooked||1/2 cup (62,5g)||27.5||2.8||-||2.8||-|
|Walnuts||1 oz (28g)||27.4||2.7||-||2.7||-|
|Sweet potato, cooked||1/2 cup (100g)||27||2.7||-||2.7||-|
|Bread, mulitgrain||1 slice (26g)||26.8||2.7||-||2.7||-|
|Kiwifruit skin on||1 medium (76g)||25.6||2.6||-||2.6||-|
|Radish||4 medium (100g)||25||2.5||-||2.5||-|
|Kidney beans, cooked||1/2 cup (88,5g)||24.8||2.5||-||2.5||-|
|Squash, cooked||1/2 cup (90g)||24.3||2.4||-||2.4||-|
|Currants, dried||1 oz (28g)||24.1||2.4||-||2.4||-|
|Macadamia||1 oz (28g)||23.8||2.4||-||2.4||-|
|Rye||1 slice (32g)||23.4||2.3||-||2.3||-|
|Black beans, cooked||1/2 cup (86g)||23.2||2.3||-||2.3||-|
|Figs||1 large (64g)||22.4||2.2||-||2.2||-|
|Eel, cooked||3 oz (85g)||22.1||2.2||-||2.2||-|
|Green peas, cooked||1/2 cup (80g)||21.6||2.2||-||2.2||-|
|Fennel||1/2 cup (43,5g)||21.3||2.1||-||2.1||-|
|Turkey, cooked||3 oz (85g)||21.3||2.1||-||2.1||-|
|Blackberries||1/2 cup (72g)||20.9||2.1||-||2.1||-|
|Asparagus, cooked||1/2 cup (90g)||20.7||2.1||-||2.1||-|
|Carrot||1 medium (61g)||20.1||2||-||2||-|
|Celery||1/2 cup (50g)||20||2||-||2||-|
|Coconut milk||1/2 cup (120g)||20||2||-||2||-|
|Jackfruit||1/2 cup (82,5g)||19.8||2||-||2||-|
|Pecans||1 oz (28g)||19.6||2||-||2||-|
|Lentils, cooked||1/2 cup (99g)||18.8||1.9||-||1.9||-|
|Chocolate 70% cocoa||0.5 oz (13,3g)||18.7||1.9||-||1.9||-|
|Cumin||1 tsp (2g)||18.6||1.9||-||1.9||-|
|Pumpkin, cooked||1/2 cup (122,5g)||18.4||1.8||-||1.8||-|
|Heavy cream||1 oz (28g)||18.2||1.8||-||1.8||-|
|Dates, pitted||1 oz (28g)||18||1.8||-||1.8||-|
|Chard||1 cup (36g)||17.9||1.8||-||1.8||-|
|Grouper, cooked||3 oz (85g)||17.9||1.8||-||1.8||-|
|Veal lean, cooked||3 oz (85g)||17.8||1.8||-||1.8||-|
|Boysenberries||1/2 cup (66g)||17.8||1.8||-||1.8||-|
|Artichokes, cooked||1/2 cup (84g)||17.6||1.8||-||1.8||-|
|Beef, lean||3 oz (85g)||17||1.7||-||1.7||-|
How much calcium do I need?
The daily calcium requirement varies depending on a few factors:
- If on a formula, infants need more calcium since the calcium from the formula is not as well absorbed as from the mother’s milk;
- Young children have high calcium needs since their skeletal system is still growing;
- Teenagers need more calcium, since this is a crucial time for building the peak bone mass. Future bone health (including the risk of osteoporosis) depends on how dense the bones get during these years.
- Pregnancy requires more calcium for the development of the baby;
- Aging is an inevitable cause of bone loss. A calcium rich diet slows down the age-related bone loss.
- Women tend to have a greater bone loss than men, especially close to menopause.
- People with a larger body frame require more calcium than people with a smaller body frame.
Recommendations for Calcium (mg/day)
|Life Stage||Age||RDA for men||UL for men||RDA for women||UL for women|
|Infants||0-6 months||200 (AI)||1,000||200 (AI)||1,000|
|Infants||6-12 months||260 (AI)||1,500||260 (AI)||1,500|
|Adults||> 70 years||1,200||2,000||1,200||2,000|
What can too much calcium cause?
Daily intake recommendations for calcium
- Calcium and gastrointestinal upsets
Too much calcium may cause bloating and constipation. Calcium supplementation should not exceed the recommended daily allowance. (1)
- Calcium and prostate cancer
Higher calcium intake and dairy foods or both by men (>1,500 mg or >2,000 mg per day) is slightly associated with an increased risk of developing prostate cancer compared to intakes of 500-1000 mg per day. The studies are inconsistent, however, and more studies are suggested to confirm these findings. (5)