Calcium: Overview

Calcium is present in a wide range of foods such as dairy products, dark-green leafy vegetables, sea vegetables, canned salmon, sardines, tofu, dried fruits, nuts (almonds, brazil nuts) and seeds – especially sesame seeds.

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The mineral Calcium (Ca) is one of the most studied and familiar supplement ingredients today.


Most flour is fortified with calcium carbonate so bread and cereals can be a good source.  If you live in an area with hard water, that may be a good source.  Meat is a very poor source of calcium.

Calcium content of foods (mg per 100gm / 3.5oz portion):

Sourcemg per 100gm (3.5oz)
Human Breast Milk33 (low!)
Apricots (dried)67
Beans (can: pinto, black)135
Beet greens (cooked)*99
Blackeye peas55
Broccoli (raw)48
Brussels Sprouts36
Cabbage (raw)49
Carrot (raw)37
Cashew nuts38
Cauliflower (cooked)42
Cow's Milk (whole)276
Swiss Chard (raw)*88
Chickpeas (garbanzos)150
Collards (raw leaves)250
Cress (raw)81
Dandelion greens187
Figs (dried)126
Filberts (Hazelnuts)209
Kale (raw leaves)249
Kale (cooked leaves)187
Lettuce (light green)35
Lettuce (dark green)68
Molasses (dark-213 cal.)684
Mustard Green (raw)183
Mustard Green (cooked)138
Okra (raw or cooked)92
Orange (Florida)43
Peanuts (roasted & salted)74
Peas (boiled)56
Pistachio nuts131
Potato Chips40
Rhubarb (cooked)78
Sesame Seeds1160
Squash (Butternut)40
Sugar (Brown)85
Spinach (raw)*128
Tofu (calcium-set)93
Sunflower seeds120
Sweet Potatoes (baked)40
Turnips (cooked)35
Turnip Greens (raw)246
Turnip Greens (boiled)184
Water Cress151

* NOTE: According to the USDA nutrient database, a cup of cooked spinach has 245mg of calcium and a cup of milk has 290mg.  However, the oxalic acid content of spinach means that only about 5% of its calcium is absorbed – the same is true of other high oxalate greens such as chard and beet greens.

Calcium comes in various forms:

  • Calcium Ascorbate: A salt form of Calcium (9%) with Ascorbic Acid (up to 85% Vitamin C activity).  This is often used when both Calcium and Vitamin C activity is desired.
  • Calcium Aspartate: A salt form of Calcium (20%) with Aspartic acid, an amino acid.
  • Calcium Carbonate: One of the most common sources of Ca, this salt contains 35% Ca.  This form has been used effectively as an antacid because of its alkaline properties.  These properties also make it a poor source for Ca supplementation.  This form of Ca should be used only as a buffering agent.
  • Calcium Chelates: These forms of Calcium are chelated (bonded) to amino acids, proteins, or peptides.  This allows the Ca to enter through the intestinal wall as a protein/ amino acid rather than a metal cation (positively charged ion).
  • Calcium Chloride: A salt form of Calcium (35%) with chloride.
  • Calcium Citrate: A salt/chelate form of Calcium (20-24%) with citric acid.  Calcium citrate is the calcium salt of citric acid.  It is commonly used as a food additive (E333), usually as a preservative, but sometimes for flavor.  In this sense, it is similar to sodium citrate.  Calcium citrate is also used as a water softener because the citrate ions can chelate unwanted metal ions.  Calcium citrate is also found in some dietary calcium supplements.
  • Calcium Gluconate: A salt form of Calcium (9%) with gluconic acid.
  • Calcium Hydroxyapatite: Also called Durapatite or calcium phosphate hydroxide, Calcium hydroxyapatite has been used for both a calcium and phosphorus supplement.  Containing between 34 and 39% Ca, it constitutes the mineral portion of bones.  It is also used to make artificial bones and teeth.

Why it is Recommended

Calcium balance can be affected by a range of other factors, and a number of substances can inhibit the absorption of calcium.  Phytic acid, found in bran, whole cereals and raw vegetables is one of these.  Uronic acid, a component of dietary fiber, and oxalic acid, found in certain fruits and vegetables can also bind calcium.  However, diets habitually high in these acids are not thought to have a major effect on calcium absorption.  Saturated fats can also lessen calcium absorption.

Calcium is lost in the feces, urine and sweat.  Calcium loss is roughly equal to dietary calcium in adults, and reduced if dietary calcium is low.  Adaptation to both high and low calcium intakes occurs automatically, i.e. reduced intake leads to increased efficiency of absorption.  In infants and children calcium is retained for new bone growth.  Calcium is also lost during lactation in breast milk.

Calcium is essential for a healthy Central Nervous System, muscle and cardiac function.  Its deficiency is associated with hypertension and palpitations.  Supplemented calcium replaces the calcium that is lost by chelating substances.


The current USRDA for Calcium is 1000mg.

Calcium can help with the following:


Dental / Oral


IBS (Irritable Bowel Syndrome)

Calcium promotes the contraction of the gut muscles and reduces the amount of water in the intestines, which contributes to better-formed stools.  It is important to note that there are two types of supplemental calcium, which for IBS can have either a laxative or constipating effect: Calcium carbonate contains no magnesium and can help with diarrhea in those with IBS-D; Calcium citrate contains magnesium and can therefore cause diarrhea, so it is recommended for those with constipation (IBS-C).

Environment / Toxicity

Fluoride Toxicity

It has been observed that the ingestion of calcium, vitamin C or vitamin D, individually, is effective in protection from fluoride toxicity to a certain extent.

A double blind control trial was conducted to examine the effect of a combination of calcium, vitamin D3 and ascorbic acid supplementation in fluorosis-affected children.  25 children were selected from an area consuming water containing 4.5ppm of fluoride.  All the children were in the age group 6-12 years and weighed 18-30kg.  They were graded for clinical, radiological and dental fluorosis and relevant biochemical parameters.  Grade I skeletal fluorosis and all grades of the manifestation of dental and clinical fluorosis were observed.

The children were given ascorbic acid, calcium and vitamin D3 well below the toxic dosages in a double blind manner using lactose as a placebo.  Follow up revealed a significant improvement in dental, clinical and skeletal fluorosis and relevant biochemical parameters in these children.  Thus, the study indicated that fluorosis can be reversed, at least in children, by a therapeutic regimen that is fairly cheap, simple and easily available and without any side-effects.


Pregnancy-Related Issues

Children of mothers who took calcium during pregnancy were still reaping the benefits seven years later in one Argentinian study.  Blood pressure was lower in these youngsters – especially among overweight children – than those in the non-supplement-taking group. [Belizan JM, et al. Brit Med J 1997;315(7103): pp.281-5]  Taking calcium may also decrease a woman's chance of developing pre-eclampsia, pregnancy-related hypertension. [Moutquin HM, et al. Can Med Assoc J 1997;157(7): pp.907-19]

A growing baby acquires most of its calcium during the last trimester of pregnancy; an additional amount is needed during breastfeeding.  This translates into a greater need for calcium during and after pregnancy.  A pregnant woman who fails to consume adequate calcium -1,200mg per day is recommended – increases her risk of developing osteoporosis later in life, especially if she becomes pregnant again. [Vandecandelaere M, et al. Rev Med Interne 1997;18(7): pp.571-4]


Low Melatonin Level

Vitamins B3 and B6, as well as calcium and magnesium support the production of melatonin.



Poor Bone Health

Calcium is essential for healthy bones.

Osteoporosis - Osteopenia

As you age, the need for absorbable calcium, in conjunction with other essential minerals and vitamins, can be increased.  One study found that a supplement containing calcium, manganese, zinc and copper prevented bone loss in postmenopausal women, whereas calcium alone was ineffective.  Calcium supplements for osteoporosis should contain other minerals as well, or the form of calcium used should have been proven to be of benefit.

Intake of supplemental calcium (1000mg per day or more) and vitamin D was associated with reduced tooth loss (due to bone loss) over a five year period in a study of 145 healthy subjects aged 65 years and older who completed a 3-year trial of the effect of calcium and vitamin D supplementation on bone loss from the hip, as well as a 2-year follow-up study after discontinuation of the study supplements. [Am J Med 2001;111(6): pp.452-6]

There are products using compounds of calcium which have been proven to reverse osteoporosis.  One such is AdvaCAL®.


Calcium Requirement

Calcium supplements are best taken between meals, ideally right before bed.  Since you can only absorb about 500mg at a time, you may want to use divided doses.  Drink a full glass of water or juice with them.  The form of calcium does not really matter – calcium carbonate or calcium citrate – just don't use the dolomite form, which may be contaminated with lead.  Some people simply take generic TUMS, which is fine.  Studies show that calcium carbonate works just as well as the high profit margin supplements that you can buy.

NOTE: Calcium supplements may interfere with prescription medications or other supplements that you are taking, so try to avoid taking them within a few hours of any other pills.

Organ Health

Not recommended for
Kidney Stones (Urolithiasis)

High levels of urinary calcium, due to an excess of non-absorbable calcium being consumed, can cause crystallization and subsequent stone formation.  Those with a tendency to form calcium stones are advised to abstain from taking non-prescribed calcium pill supplements.

Tumors, Malignant

Prostate Cancer

See the link between Prostate Cancer and Vitamin D.

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Calcium can help prevent the following:


Coronary Disease / Heart Attack

One study showed a 30% to 35% reduction in ischemic heart disease risk in women with a high intake of supplemental calcium.  Dietary calcium achieved no significant change in heart attack risk, the researchers noted.

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