Calcium citrate is highly soluble and bioavailable forms (they are chelates) of these minerals that have much greater absorption rates than other common forms of calcium and magnesium supplements (and low interaction levels with other minerals as compared to other common forms of these supplements). Calcium Citrate is a chelated mineral. It is basically calcium wrapped with a covering derived from citric acid. Calcium citrate is 21% calcium. Because of the chelation it is better absorbed than calcium carbonate.
Calcium citrate is a high-quality calcium source for food fortification. Its main characteristics are good solubility at low pH, a neutral taste and flavor profile, high calcium content and excellent bioavailability. Besides the standard powder product, Calcium citrate is also supplied as a micronized (ultra-fine) granulation that will dissolve even more quickly in acidic applications.
Calcium citrate is most often used by the informed consumer who understands the importance of getting calcium into the bloodstream where it is used to maintain and re-mineralize bone. Calcium Citrate is essential for the development and maintenance of strong bones. Calcium is also essential for teeth. Especially for teen and young adult women, adequate calcium in a healthful diet can reduce the risk of osteoporosis later in life.
Calcium is a key mineral in the human body, necessary
for the normal growth and development of the skeleton as well as for
teeth, nerve, muscle and enzyme functions. As the body’s calcium
absorption capabilities reduce with age, it is vital for older individuals
to have a sufficient calcium intake. Calcium requirements vary throughout
an individual’s life and for different population groups. However,
it is generally evident that a significant proportion of the population
in Western countries fails to achieve the recommended calcium intakes.
Poor dietary habits are seen to be responsible for this situation, especially
when fast-food consumption dominates much of the population’s menu.
Various studies, including “The Mineral Fortification of Foods,”
published in 1999 by Leatherhead International Ltd., Surrey, UK, showed
that a significant proportion of the population groups failed to achieve
the calcium intakes in Western countries. This observation is thought
to be one of the leading factors causing osteoporosis, and was noted
in a 1991 article from the American Journal of Clinical Nutrition titled
“Calcium Metabolism and Calcium Requirements During Skeletal Modeling
and Consolidation.” As a consequence, national authorities all
over the world recently have reconsidered recommendations in order to
take remedial measures against calcium deficiency and, accordingly,
to reduce the risk of osteoporosis. In this respect, the United States
National Institutes of Health (NIH) has increased the amounts of optimal
daily calcium intake and defined specific values for each population
group. For example, calcium intake should be 1,000 mg/day for adults
(25 to 65 years of age) and as much as 1,500 mg/day for seniors (older
than 65 years) or lactating women.
There are several options to avoid calcium deficiency by increasing
the daily calcium intake: A balanced diet with calcium-rich foods, such
as milk, dairy products and certain vegetables (broccoli, Chinese cabbage,
legumes), would be the best solution. However, this would require a
profound change in dietary habits of Western society. Another possibility
would be consuming food products fortified with calcium. The third option
is the intake of calcium-supplement products.
Common calcium sources
There are different calcium sources commercially available for use in
food and dietary supplements:
• inorganic salts such as calcium carbonate and calcium phosphate;
• organic salts such as calcium citrate, calcium lactate, calcium
lactate gluconate and calcium gluconate.
Other forms of calcium commonly supplied for fortification and supplementation
are calcium gluconate in its anhydrous form, as well as calcium lactate
Tricalcium citrate (TCC), commonly referred to as calcium citrate, is
a high-quality calcium source for food fortification. Its main characteristics
are good solubility at low pH, a neutral taste and flavor profile, high
calcium content and excellent bioavailability. Besides the standard
powder product, TCC is also supplied as a micronized (ultra-fine) granulation
that will dissolve even more quickly in acidic applications.
The selection of the appropriate salt for a specific application is
usually based on the consideration of a number of properties associated
with the respective product, such as solubility, taste, calcium content
and bioavailability. Economic considerations are another important factor
to review before making a decision.
Solubility. There are calcium salts with
a rather good solubility, including calcium gluconate and calcium lactate,
but their drawback is a low calcium content. Calcium salts with high
calcium content, on the other hand, are poorly soluble. TCC offers a
good combination: It shows a high calcium level and moderate solubility.
Solubility is strongly influenced by the pH of the system, since the
solubility of calcium salts typically increases with decreasing pH.
TCC shows improved solubility at pH values below 4.5, as found in orange
And contrary to other salts, TCC is more soluble at low temperatures,
which can be an advantage for cold food processing. To further increase
the solubility and ease of dispersion, companies such as Jungbunzlauer
have developed several types of particularly fine (micronized) TCC grades.
However, the high solubility of calcium salts, such as calcium lactate
or calcium gluconate, can also lead to adverse effects. Due to the fact
that with high-soluble salts, more free calcium ions are in solution
and available for reaction than with TCC, complications in the form
of calcium sediments can develop with time. This is the case if components
(e.g. free protein, tartrate or phosphate) that give insoluble salts
with calcium are present in the product. Thus, although it is possible
to add more calcium lactate than TCC to beverages, higher amounts of
calcium in the product might be difficult to achieve without control
of pH and addition of chelating agents, such as potassium citrate.
Taste and mouthfeel. Generally, high levels of calcium, particularly
insoluble forms such as carbonates and phosphates, tend to produce a
chalky mouthfeel and may promote astringency or bitter taste in the
finished product. Calcium lactate may impart some bitter notes at high
concentrations. Calcium carbonate comes across as soapy or lemony and
has the disadvantage of developing CO2 in the stomach. Calcium phosphate
has a bland flavor, but imparts a gritty mouthfeel. TCC, calcium lactate
gluconate and calcium gluconate are considered to be the most neutral
Since the particle size and solubility are linked with mouthfeel properties,
companies have developed micronized grades that provide a neutral taste
profile in final applications with excellent dispersion characteristics.
Calcium content. Inorganic salts, such
as carbonates and phosphates, contain more calcium than the organic
salts, but their application in foods and beverages remains limited
due to their poor solubility and their influence on taste in the final
application. However, organic calcium salts remain an option, with TCC
showing by far the highest calcium content (21%), compared to calcium
lactate (13%), calcium lactate gluconate (10% to 13%) and calcium gluconate
Economic considerations. Among the organic salts with better solubility
and more neutral taste profiles, TCC clearly stands out as the most
economic option for calcium addition, especially when the price per
gram of calcium added is calculated for the product to be fortified.
Bioavailability. Any nutrient’s effectiveness
depends on its bioavailability, which means how well the human body
absorbs and utilizes it. On average, only about 10% to 30% of calcium
is absorbed from a mixed diet by healthy adults, according to the National
Research Council’s “Recommended Dietary Allowances: 10th edition.
A Report of the Subcommittee on the Tenth Edition of the RDA.”
Several different factors influence this level, including which type
of salt provides the calcium.
Various scientific studies have shown that organic calcium salts outperform
inorganic calcium sources, such as calcium carbonate and calcium phosphate,
with regard to their relative bioavailability. Accordingly, the United
States National Institutes of Health has recommended calcium citrate
for supplementation, especially for older individuals where absorbability
can be a limiting factor due to reduced gastric-acid production. Recently,
researchers at the University of Texas, Austin, conducted a meta-analysis
of calcium bioavailability, which evaluated studies on the bioavailability
of two of the most common forms of calcium supplements, TCC and calcium
carbonate. Over 90% of the studies reviewed showed greater absorption
of calcium from TCC than calcium carbonate by an average of 22% to 27%.
Similarly, calcium phosphate also has been shown in scientific studies
to display lower bioavailability than TCC. Furthermore, it is not considered
to be an appropriate ingredient for calcium fortification due to the
undesired characteristics of the phosphate anion. Intake of phosphate
is reported to exceed adult RDAs in practically 100% of the population.
Therefore, further addition of phosphate to food should be avoided in
order to gain a higher calcium-to-phosphorus ratio, which is considered
favorable for sufficient calcium absorption.
In comparison with the other common organic salts, TCC showed similar
bioavailability in various studies, even though significant solubility
differences exist among organic calcium salts in plain water. It is
concluded that these differences have no effect on absorbability in
acidic environments such as the gastric acid in the human stomach. Studies
with healthy male volunteers revealed that, compared to calcium lactogluconate/carbonate
and calcium phosphate, oral administration of TCC induced the highest
serum calcium and greatest reduction in parathyroid hormone, conditions
most favorable for building bone mass or minimizing resorption.
Furthermore, TCC displays specific advantages from the nutritional/
pharmacological point of view. Scientific studies showed that contrary
to other calcium salts, TCC does not promote, but rather inhibits, the
formation of kidney and urinary duct stones by providing beneficial
citrate for renal excretion. Additionally, TCC was reported to exhibit
only low effects on the absorption on nutritional minerals whereas alternative
calcium sources significantly interfered with iron.
The use of TCC is particularly recommended for acidic applications,
such as juices and fruit preparations, but also in various dairy products,
such as yogurt and cheese. Due to its outstanding biocompatibility and
long history of safe use in critical dietetic products and over-the-counter
products, it is also the calcium source of choice for baby food as well
as dietary supplements.
Citrate in Fortified-Food Applications
By Gerhard Gerstner, Ph.D.
Gerhard Gerstner, Ph.D. has been Technical Service
Manager for Special Salts at Jungbunzlauer Ladenburg GmbH since 2000.
Gerstner focuses on nutritional salts of calcium and potassium that are
produced for the pharmaceutical and food industries in a dedicated facility.