Last time we looked at determining elemental calcium content in Part 1 of Understanding Different Types of Calcium, what the solubility/bioavailability of various forms of calcium means for us, and factors that affect calcium absorption in our bodies. Now let’s attempt to dissect the various types of calcium so you can understand your choices better.
Choosing the Right Form of Calcium for You
There are other forms of calcium on the market than those listed below, but these are some of the most common forms found in supplements.
This is a common form of calcium which is an alkaline-based compound found in rocks, limestone, marine animal shells, pearls, eggshells and snails. It is found in many calcium supplements and is even found in antacids like Tums, Rolaids, etc. because of its alkaline nature. It is also the type of calcium found in coral calcium, which has received much attention for exaggerated health claims. There is no research to confirm that coral calcium is in fact a better form of calcium than other forms. Calcium carbonate provides one of the highest concentrations of elemental calcium (35-40%). For example, a calcium carbonate supplement contains 40% elemental calcium; this means that 1,250 milligrams (mg) of calcium carbonate will provide 500 mg of elemental calcium. This is the reason why many supplements use calcium carbonate: it gives the appearance of a high elemental calcium content and doesn’t take up much space in the capsule or tablet. Yet it has poor solubility in water and requires extra stomach acid production to be absorbed. Calcium carbonate’s bioavailability in humans has been measured as high as 40%, but also as low as 15%. Because of its low solubility, and perhaps because of its inconsistent absorption rate, it is generally considered to be one of the least bioavailable forms of calcium.
Key Takeaway: This form is great for people with excess stomach acid (although note that just because you have heartburn or ulcers doesn’t mean you have excess stomach acid!), and it is okay if you are not very concerned with how much calcium you are actually absorbing, since it can vary among individuals. Be aware that just because the label calcium content looks high doesn’t mean that’s what you’re absorbing.
Unlike the alkaline qualities that calcium carbonate offers, calcium citrate has a base that is acidic in terms of pH value. Due to its acidity, it requires less natural stomach acids to be produced in order for it to be absorbed. An analysis of 15 randomized trials concluded that calcium citrate was absorbed 22% to 27% better than calcium carbonate, whether taken on an empty stomach or with food. Calcium citrate is about 20% calcium, and is thought to have a bioavailability of about 40%.
Key Takeaway: This is a better form than carbonate for people with low stomach acid or people over the age of 50.
Oyster Shell Calcium/Bone Meal/Dolomite
Although it may seem to be a natural form of calcium, and therefore higher in absorbable calcium, the calcium in the oyster shells as well as in bone meal and dolomite, are more susceptible to have toxic levels of lead due to difficulty in maintaining quality control. It is better to avoid these natural forms of calcium. The main form of calcium in these products is calcium carbonate.
Key Takeaway: Similar to calcium carbonate. While it may provide some extra trace minerals, do not use these forms if heavy metal toxicity is a concern for you.
It would be necessary to take large amounts of calcium gluconate to obtain calcium requirements as it is only 9-13% elemental calcium, meaning you would need to take several tablets or capsules to get a good amount of calcium. It is not certain how bioavailable this form of calcium really is. One human study showed that calcium gluconate increased blood levels of calcium only slightly more than calcium carbonate.
Key Takeaway: If calcium carbonate works well for you, this form may work even better, although you may need to take more capsules or tablets to get an adequate amount.
This is present in foods such as aged cheese and baking powder. It is common for this form of calcium to be used as an antacid and is added to fruits to maintain their firmness and extend their shelf life. The bioavailability of this form of calcium is acceptable because it can be absorbed at various pH’s in the body; one study found that it is as bioavailable as calcium from milk. However, it has a relatively low amount of elemental calcium of 9-13%.
Key Takeaway: Calcium carbonate may be more favourable, given the numbers. Best not used by those with lactose intolerance.
Calcium Phosphate also has an absorption level similar to that of calcium carbonate and has an elemental calcium amount of 31-38%.
Key Takeaway: Comparable to calcium carbonate.
Originally found in the yogurt from Bulgaria and regions nearby, the Japanese were able to identify this unique form of calcium and its ability to help absorb additional calcium and increase bone mineral density. It also increases the production of equol, a compound that has beneficial bone health effects. This form of calcium is also referred to as lactobionic acid and is not considered to be a useful source of calcium since it contains only 5% calcium. Rather, it is known for its unique ability to help the body absorb more calcium from the diet and from supplements without necessarily increasing calcium intake above 1000 mg per day, therefore preventing calcium from accumulating in the blood vessels. It does this by binding to calcium ions from food in the stomach, intestines and the blood and helping to take them to the site where they are needed most, in the bone. The solubility of this form of calcium is sixty five times higher than other forms of calcium like citrate, which is considered one of the most bioavailable forms.
Key Takeaway: Use this form if you are concerned with the adverse cardiovascular effects of excess calcium, or if you are trying to maximize your calcium absorption from food or supplements without taking the full 1000 mg/day recommended for bone health.
This is formed from the calcium salt of citric acid and malic acid consisting of variable composition. Although calcium citrate-malate contains only about 26% elemental calcium, its bioavailability has been measured as high as 42%, and it also has the most consistently high bioavailability (consistently over 35%) across human studies. Because of this, it is one of the most heavily studied forms of calcium in the area of bone health and considered the most effective vegetarian form of calcium. Calcium citrate-malate’s bioavailability is possible due to its water-solubility and its method of dissolution. Upon being dissolved, it releases calcium ions and a calcium-citrate complex. Calcium ions are directly absorbed into intestinal cells. The special structure of calcium citrate-malate makes it 6 to 9 times more easily dissolved in the stomach than plain calcium citrate, with an absorption rate of 36-37% in tablets and capsules, or higher if dissolved in orange juice. Calcium citrate-malate is well-absorbed taken with or without food.
Key Takeaway: If calcium citrate works well for you, this form may be even better. This form is recommended for individuals who have low levels of stomach acid, for those who are older, who are taking stomach acid blockers, or who have absorption or inflammatory bowel disorders. Considered the best vegetarian calcium source.
Calcium Hydroxyapatite and Microcrystalline Hydroxyapatite Complex
Although many foods provide various calcium salts, human and animal bones are the only natural source of calcium hydroxyapatite. Be aware that there is a synthetic form of calcium hydroxyapatite called calcium orthophosphate: this is not the same as microcrystalline hydroxyapatite complex (MCHC). The calcium found in MCHC from bone is actually not a salt or a chelate form; it is elemental calcium woven into the complex of other minerals and proteins that make up bone, such as phosphorus, magnesium, potassium, zinc, trace minerals, collagen, osteocalcin and other proteins that function as bone growth factors. To preserve its full spectrum of nutrients and minerals, the bone extract needs to be processed at very low temperatures.
The calcium content of MCHC varies but is around 22%, and although a couple studies showed lower bioavailability of this form of calcium compared to some calcium salts, multiple recent and older studies have shown that supplementing with MCHC has superior bone-preserving and bone-building effects over years of use compared to calcium carbonate or other calcium salts. It actually inhibits bone loss and increases bone density. The benefits of MCHC are due not only to its calcium content, but also to the growth factors, peptides, mucopolysaccharides and other minerals and micronutrients that work together to target bone-maintaining and building processes. Therefore, MCHC is not just a calcium source but an almost-complete bone-building supplement in itself. And isn’t bone health the main reason most of us are concerned with calcium in the first place? However, it is not suitable for vegetarians or vegans as it is sourced from animal bones. The highest quality MCHC is sourced from New Zealandsince they have best farming practices and have never had an incidence of BSE (mad cow disease).
Key Takeaway: Given that this form of calcium also contains other minerals and growth factors that stimulate bone growth, this may be the best source of calcium for those concerned with increasing their bone density. However, it may not be suitable for vegetarians or vegans, or for those who have difficulty with taking a large number of capsules.
Putting It All Together
When considering the best method to get your calcium, keep in mind the calcium type, amount, and quality as well as other lifestyle factors that could affect your calcium absorption. In addition, remember that it’s not always just about the calcium, but other important nutrients that enhance its effectiveness within the body that matter too. You might also try combining various forms of calcium (ie. calcium lactobionate with calcium hydroxyapatite or calcium citrate-malate) or rotating forms to get a specific desired effect, depending on your goals.
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