Almost like the mythological chimera, they can have some unique properties, including an ability to transport minerals more easily across the gut wall. But how many of these properties are myths and how many are real?
First, some background: chelates (pronounced “kee-lates”) are organic compounds containing minerals bonded in a carefully designed molecular lattice. (Organic compounds are molecules that contain carbon.) The word chelate comes from the ancient Greek term “chelé,,” which refers to the claw of a lobster. It’s rather fanciful, but some chemist must have thought that trapping a mineral atom inside a molecule resembles a lobster grabbing its prey with its large claw.
Maybe that chemist had a cousin who was a lobster fisherman. In any case, I like to think that a chelate resembles a fullback in American football – hugging the football tightly with his arms, leaning forward, shoulders hunched, smashing through the opposing line for a few more yards.
Which minerals? There are quite a few chelated mineral products commercially available for livestock, but the most common minerals are zinc, copper, manganese, selenium, iron and cobalt – sometimes molybdenum, potassium and calcium. For human use, I’ve also seen some chelated products containing boron, chromium and vanadium, which is rather strange since humans do not have established nutritional requirements for boron, chromium or vanadium.
The main characteristic of mineral chelates is that they act differently in the gastrointestinal (GI) tract than the inorganic forms of the mineral, especially for the trace minerals. Normally, livestock mineral supplements are composed of “inorganic” molecules – compounds like zinc sulfate, cupric oxide and manganese sulfate. But when these same minerals are bonded in chelates, they are more stable in the GI tract.
Chelated minerals can pass through the rumen without interference from rumen microbes or other inhibitory substances that can reduce absorption into the blood. Inorganic minerals can also stick (“adsorb” with a “d”) onto undigested plant fiber and get excreted in the manure, but chelated minerals do not. The bottom line, depending on a lot of factors, can be an increased efficiency of absorption of those mineral atoms across the gut wall.
Various forms
Chelates come in many forms. The feed industry, which is very concerned about precision and legal issues, defines four types of organic molecules with mineral chelating characteristics: metal amino acid complexes, metal amino acid chelates, metal proteinates and metal polysaccharide complexes.
The first three bond minerals to amino acids; the last one bonds minerals to carbohydrates. Typical products are things like zinc methionine, zinc lysine complex, copper proteinate and calcium glucoheptonate. These four definitions are actually very narrow.
In a broader sense, some other organic compounds effectively act like mineral chelates. For example, iodine is usually fed as inorganic iodates or iodides, but it can also be fed as EDDI (ethylenediamine dihydriodide). In this form, iodine moves through the rumen untouched and is absorbed from the GI tract via a different pathway than the inorganic forms. EDDI is also metabolized in the body differently than the iodates.
Similarly, we routinely add selenium to mineral mixtures as sodium selenate or sodium selenite, but when selenium occurs as an integral part of an amino acid like selenomethionine, its absorption pathway is much different than the inorganic forms. Also, once in the body, the selenomethionine is incorporated directly into proteins because it’s an amino acid. When those proteins are eventually broken down, the selenium is released. In effect, the organic amino acids of selenium are long-acting, slow-release compounds.
Claims
There are lots of marketing claims for chelated minerals. The most common is an increased efficiency of mineral absorption into the blood and also increased dependability of that absorption since the absorption of chelated minerals is not affected by as many inhibitory factors as the inorganic forms. And that results in more mineral atoms crossing into the blood and therefore more atoms available to meet nutritional requirements.
This can be particularly important for high-producing animals that sometimes have higher mineral requirements. It also implies that less minerals may be needed in the feed to meet the requirements, although that is usually not a problem if the trace mineral intake is constant and sufficient.
A typical claim about chelated minerals is improved animal performance: growth rate, milk production, reproduction, etc. The logic is that increased mineral absorption provides more minerals for the animal, which then boosts performance.
Other claims involve better immune responses and therefore better health, particularly for animals under stress. There is actually a technical metabolic basis for this. Some trace minerals are known to be involved in the immune system, particularly zinc, iron, copper and selenium.
These minerals are components of various enzymes of the immune system, including enzymes that repair oxidative damage to cell membranes. The hypothesis is that providing more of these minerals can help reduce oxidative damage to critical cells of the immune system, like white blood cells, and thus improve the animal’s ability to fight off infections and diseases.
Separating fact from fiction
But does real-world data support these claims? Yes and no. As we’ve noted, there are many types of mineral chelates – different minerals, different molecular forms, different types of bonds. There is also a vast spectrum of feeding situations to test with different livestock species and different levels of minerals in the diet. There are also different things to measure.
Weight gains and milk production are relatively easy to measure; reduced oxidative damage and improved immune function are not. Basically, there is an almost infinite universe of situations. And in that universe, some experiments have indeed shown improvements in performance and health, but some have not.
We should keep in mind that even under the best situations, an animal will only benefit from extra minerals if it needs them. If an animal is already obtaining enough minerals in its diet, then increasing the efficiency of absorption of those minerals probably won’t have any effect. Which can explain some of the experimental results in the literature.
So what’s a person to do? Read. Investigate. University and government research trials can be very useful. Documents from feed companies, of course, paint their products in the best light.
But have you heard of Google? It’s the latest thing, and I understand that sometimes it gives good results. (Facebook and Twitter are somewhat less dependable for scientific information.) Seriously, the internet opens a wealth of information, but the internet is a buyer-beware world. You need to characterize the details carefully and have trust in the authors.
Not just for rations
Interestingly, chelates are not limited to livestock nutrition. Farmers use chelated fertilizers as sources of trace minerals (called “micronutrients” in the agronomic vernacular), especially in high-value crops, lawns and greenhouses. Chelated fertilizers are often applied as foliar applications to avoid loss of these minerals in the soil. Also, as any internet search will turn up, chelated minerals are found in human nutrition and medicine, for many reasons beyond the scope of this article.
But the concept of capturing minerals in chelates is also found in literature, even in the 19th century. Lewis Carroll was far ahead of his time when he wrote the poem “Jabberwocky”:
“Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious Bandersnatch!”
Claws, indeed. He was, of course, thinking of different ways of using mineral chelates. 
ILLUSTRATION: Illustration by Kristen Phillips.
Woody Lane, Ph.D., is a livestock nutritionist and forage specialist in Roseburg, Oregon. He operates an independent consulting business and teaches workshops across the U.S. and Canada. His book, From The Feed Trough: Essays and Insights on Livestock Nutrition in a Complex World, is available through Woody Lane.
