First and foremost: your body must be able to absorb calcium from food for it to be utilized in the body. However, the most sources of bioavailable calcium are of the animal origin. Due to the fact that calcium is a mineral of vital importance, vegans often take calcium pills. The absorption of calcium from most commonly used dietary supplements is very similar. This is contrary to what many calcium supplement manufacturers claim in their promotional materials.
The forms that are taken by mouth include calcium carbonate, calcium acetate, calcium citrate, calcium gluconate, calcium lactate and calcium phosphate.
Calcium carbonate provides one of the highest concentrations of elemental calcium (35-40%) – the fifth most abundant element by mass in the Earth’s crust. The best known form of it is chalk. It’s the cheapest type and therefore most widely used. However, it has poor solubility in water (try to dissolve chalk in water) and requires extra stomach acid production to be absorbed. Due to its dependence on stomach acid for absorption, calcium carbonate is absorbed most efficiently when taken with food, whereas calcium citrate is absorbed equally well when taken with or without food. It is suggested that calcium carbonate’s bioavailability is between 40 and 15%. Due to this fact calcium carbonate is generally considered to be one of the least bioavailable forms of calcium.
Calcium citrate can be taken without food. Calcium citrate has about 21% of elemental calcium: 1000mg will provide 210mg of calcium. It is more expensive than calcium carbonate and more of it must be taken to get the same amount of calcium. Bioavailability of calcium citrate is found to be equal to that of the cheaper calcium carbonate.
Supplementation is generally only required when there is not enough calcium in the diet. Calcium gluconate side effects include nausea, constipation, upset stomach. Rapid intravenous injections of calcium gluconate may cause hypercalcaemia, which can result in vasodilation, cardiac arrhythmias, decreased blood pressure, and bradycardia. Extravasation of calcium gluconate can lead to cellulitis. Intramuscular injections may lead to local necrosis and abscess formation
Calcium lactate has similar absorption as calcium carbonate, but is more expensive. Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements.
Calcium phosphate is the principle form of calcium found in bovine milk. In milk it is found in higher concentrations than would be possible at the normal pH because it exists in a colloidal form in micelles bound to casein protein with magnesium, zinc and citrate – collectively referred to as colloidal calcium phosphate. Seventy percent of bone consists of hydroxyapatite, a calcium phosphate mineral (known as bone mineral). Tooth enamel is composed of almost ninety percent hydroxyapatite. Calcium phosphate costs more than calcium carbonate, but less than calcium citrate. Microcrystalline hydroxyapatite is one of several forms of calcium phosphate used as a dietary supplement. Hydroxyapatite is about 40% calcium. Unlike most other compounds, the solubility level of calcium phosphate becomes lower as temperature increases because heating causes precipitation.
Vitamin D is added to some calcium supplements. Proper vitamin D status is important because vitamin D is converted to a hormone in the body, which then induces the synthesis of intestinal proteins responsible for calcium absorption.
And now let’s see what calcium supplement pills are made of.
A regular 500mg calcium supplement tablet with vitamin D is made from:
- calcium carbonate
- maltodextrin – a digestible polysaccharide (sugar actually) which is moderately sweet and commonly used for the production of soft drinks and candy
- mineral oil – a mineral oil from a mineral source, particularly a distillate of petroleum, which is not approved in food products in many countries, and incidental amounts in foods are carefully regulated; it is typically used for the glossy effect it produces, and to prevent the candy pieces from adhering to each other.
- hypromellose – an emulsifier, thickening and suspending agent, and an alternative to animal gelatin
- glycerin – a non-toxic soluble in water substance from lipids that is widely used in the food industry as a sweetener and in pharmaceutical formulations
- cholecalciferol – one of the five forms of vitamin D
- polyethylene glycol – a polyether compound with many applications from industrial manufacturing to medicine
- carnauba wax – a wax of the palm leaves
Calcium supplements might help you meet your calcium requirements. Or might do you more bad than good. Let’s see.
Side effects of calcium supplement pills
General side effects can include: constipation, upset stomach, nausea, loss of appetite, unusual weight loss, mood changes, bone or muscle pain, headache, increased thirst and urination, unusual tiredness and weakness.
- Calcium and phosphate have to be in balance in the body: too much calcium can throw this balance off and cause harm.
- Under-active thyroid gland: If a person under thyroid hormone replacement treatment, calcium can interfere with it and cause harm.
- High calcium blood level (hypercalcemia): People having this health condition should avoid calcium supplements.
- Kidney conditions: Calcium supplementation can increase the risk of having too much calcium in the blood in people with poor kidney function.
- Smoking: People who smoke absorb less calcium than non-smokers.
- Heart attack risk: It’s not sure fact, but there may be a link between calcium supplements and heart disease.
- Excess of calcium from supplements, fortified food and high-calcium diets, can cause milk-alkali syndrome, which has serious toxicity and can be fatal. Some studies suggest a correlation between high calcium intake (2000mg per day, which is equivalent to six or more glasses of milk per day) and prostate cancer.
Vegans are advised to eat three servings a day of a high-calcium food. Just to remind you that the well-absorbed calcium sources for vegans are: seaweeds (such as wakame) calcium-fortified soy milk and juice, calcium-set tofu, soybeans, almonds or hazelnuts, broccoli, collards, Chinese cabbage, kale, and green leafy vegetables (such as rocket, kale, bok choy, mustard greens and parsley). Do not forget that spinach is not a good source of calcium because calcium is bound to oxalates and therefore poorly absorbed. Also, make sure you consume enough vitamin D, which is needed for calcium absorption.
To take calcium supplement pills or not to take – that is the question.