Chelated minerals are also known as organic minerals.
In the petfood industry, inorganic forms of essential trace
minerals such as iron, zinc, copper, manganese, iodine and
selenium have been the staple. In recent years, though,
chelated forms of these minerals have found their way into a
number of petfoods. The questions are whether they provide
additional benefit to the dog or cat and if they have a place
What are they?
These so-called chelated trace minerals, also known
colloquially as organic trace minerals, are purported to be
nutritionally superior to the inorganic sources. What makes
them different is their ligand. A ligand is an atom or molecule
that forms a coordination complex with a central atom or ion.
In this case, the ion is the mineral and the ligand is the
compound to which it is bound. In their native form, most trace
mineral ions are bound to an inorganic anion like an oxide,
sulfate or chloride. But for chelated trace minerals, they are
bound in a coordinate covalent bond (chelated) to a
carbon-containing organic compound like a polysaccharide, short
chain fatty acid, protein or amino acid. They are generally
synthesized in very strong acid-base reactions under extremes
in heat and pressure.
The rationale for adding chelated trace minerals to the diet
is to improve mineral availability and animal health. Because
of its bond to an organic ligand, the mineral is supposedly
more bioavailable. There are a couple of prominent theories as
to why this would be; they each focus on the mechanism for
uptake of the mineral in the intestine, as either dissociated
or intact. Both theories seem to ignore the notion that mineral
absorption and utilization are under endocrine control and (or)
the animal's mineral status.
One theory suggests the chelated mineral is more available
because it breaks apart into its ionic form to facilitate
effective absorption. To do so requires a gut pH near the
molecule's pKa (the pH at which ½ the molecule is in the ionic
form). The other hypothesis is that the mineral-ligand complex
is absorbed intact like a peptide. This theory requires the
mineral chelate be taken up by peptide transporters in the gut
and it assumes that there is a benefit in efficiency and
utilization from pre-formed chelates for cellular
Each theory has been supported with research using model
molecules and each has data to support an increased ionic and
(or) chelated mineral measured in the circulation. But, does
this increase make any difference? Perhaps some. The use of
organic trace minerals has been shown to improve markers of
hair "health" in dogs and improve puppy litter size. Beyond
this, the data in dogs and cats is fairly limited.
Since mineral utilization depends on mineral status, more
mineral in the diet doesn't necessarily mean more mineral
utilized. For livestock diets in which the emphasis is on cost
containment and where mineral fortification may be skirting
minimum requirements, a consistent response might be detectable
when a more bioavailable form of mineral is provided. However,
in petfood applications in which the recommended allowances
provide a buffer over minimal needs, and the amount supplied in
the food is typically twice the recommended allowance,
providing a small increment of a more bioavailable mineral may
not necessarily improve the animal's mineral status.
There is a broad array of these chelated trace minerals (or
metals) from which to choose. According to the American
Association of Feed Control Officials, one can use a metal
amino acid complex, metal specific amino acid complex, metal
amino acid chelate, metal polysaccharide complex, metal
propionate or metal proteinate.
Regardless of which type, they are most commonly
merchandised in 50 lb. bags or drums either as the individual
trace minerals, e.g., zinc methionine, or blended into a
premix. They are commonly free-flowing with a granular to
powder consistency and come in a multitude of colors like blue,
black, pink, green and white depending on their own particular
chemistry. Even though chelated trace minerals often have a
distinctive color of their own, they are not likely to be seen
in the finished petfood due to their small inclusion level.
On the other hand, trace minerals can lead to discoloration
or spotting in some higher moisture foods (such as canned
petfoods). We are also instructed to separate minerals and
vitamins to reduce fat soluble vitamin losses in premixes. In
both circumstances, the issue is oxidation in which transition
metals such as iron and copper are involved. Chelated trace
minerals have been proposed as a possible solution to these
issues. The over-simplistic premise is that since these
minerals are bound, they may be less reactive.
But this is an incorrect assumption. Rather, it depends on
the redox potential of the molecule (its ability to reduce or
oxidize), which is influenced by the ligand. A more neutral
salt of the metal will be less oxidative in a petfood,
regardless of whether it is chelated. Some of the chelated
trace minerals, such as a metal-proteinate, are more neutral
and so are less likely to be involved in this oxidation
The benefits of chelated trace minerals are increased
bioavailability of 5-15% and the resolution of some
discoloration issues resulting from oxidation. However, they
are one-half to one-third the concentration of inorganic trace
minerals, and can be more than five times the cost per unit
mineral. So the case for their use in petfoods is not
overwhelming. Despite this, some petfood companies promote the
inclusion of chelated trace minerals individually or in
combination with inorganic sources as insurance against the
unexpected times when absorption or utilization may be
impaired. Under extremes in performance or stress there may be
need for the additional level of nutritional support. So they
may impart some small benefit to the pet and possibly peace of
mind to the pet owner.
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