11/03/2026
đŹ đŠđČđčđČđ»đ¶đđș â đź đ°đčđźđżđ¶đłđ¶đ°đźđđ¶đŒđ»
~ (đ„đĄđđđŁ-đđŁđđĄđđšđ đ©đ§đđŁđšđĄđđ©đđ€đŁ đ€đ đżđ§ đđđĄđĄđ€đŁâđš đ§đđđđŁđ© đđ§đ©đđđĄđ - đŹđđ©đ đ đđđ© đ€đ đŸđđ§đ€đĄ-đđ§đđđŁđđĄđź đđ€đąđąđđŁđ©đđ§đź)
If anyone's read the recent article on selenium by Dr Eleanor Kellon, it may come as no surprise that weâve had a few messages about it!
Dr Kellon was responding to a piece published on the SanoAnimal website by Dr Christina Fritz, about discussions online about selenium forms in horse nutrition.
I can absolutely see why the article left some readers scratching their heads. Dr Kellon tends to write for readers who enjoy diving into more scientific detail, and when research papers are condensed into a short blog post, the science-overload result can sometimes feel⊠a little dense.
So what Iâve done here is attempt to unpack the discussion into clearer, plain-English terms, while also highlighting where the scientific disagreement actually lies between the Kellon view and the Fritz view. This post simply aims to:
âą acknowledge Dr Kellonâs point regarding toxicity studies
âą explain Dr Fritzâs perspective on selenium metabolism
âą and clarify why we formulate our EquiNatural mineral balancers the way we do.
Importantly, the Kellon/Fritz views are not actually as far apart as it might appear - theyâre simply emphasising đ±đ¶đłđłđČđżđČđ»đ đŻđ¶đŒđčđŒđŽđ¶đ°đźđč đ°đŒđ»đ°đČđżđ»đ.
I should also point out that both Dr Eleanor Kellon & Dr Christina Fritz are among the most scientifically rigorous and respected voices in the equine nutrition world, so when experts like this appear to disagree it can understandably leave horse owners feeling confused. So, I thought it might be helpful to translate the science into plain English, calm the concerns, and give a little clarity in the apparent confusion.
đđđ¶đżđđ â đđČđčđČđ»đ¶đđș đ¶đ đČđđđČđ»đđ¶đźđč
Selenium plays a critical role in antioxidant defence, immune function and muscle health. Horses have to obtain it from their diet because our UK soils are naturally low in selenium.
đđŠđČđ°đŒđ»đ± â đđ”đČđżđČ đźđżđČ đđđŒ đșđźđ¶đ» đłđŒđżđșđ đđđČđ± đ¶đ» đ»đđđżđ¶đđ¶đŒđ».
âą Organic selenium â usually selenium yeast containing selenomethionine
âą Inorganic selenium â usually sodium selenite or sodium selenate
Importantly, the words đŒđżđŽđźđ»đ¶đ° and đ¶đ»đŒđżđŽđźđ»đ¶đ° here refer to chemical structure, not to farming methods or âorganic foodâ. This often causes confusion - unless you're a chemist of course!
đđ§đ”đ¶đżđ± â selenium has a đđČđżđ đ»đźđżđżđŒđ đđźđłđČđđ đđ¶đ»đ±đŒđ between deficiency and excess.
So with all that laid out, let's get stuck in to the debate itself...
đȘđ”đźđ đđźđ đđ”đČ đ±đČđŻđźđđČ đźđŻđŒđđ?
Dr Kellonâs article was responding to a discussion from the SanoAnimal site suggesting that the organic 'chelated' selenium form đŽđŠđđŠđŻđ°đźđŠđ”đ©đȘđ°đŻđȘđŻđŠ might cause problems due to a so-called ârebound effectâ.
(đđŠđ§đŠđłđŽ đ”đ° đ”đ©đŠ đȘđ„đŠđą đ”đ©đąđ” đŽđŠđđŠđŻđȘđ¶đź đŽđ”đ°đłđŠđ„ đȘđŻ đŁđ°đ„đș đ±đłđ°đ”đŠđȘđŻđŽ đ€đ°đ¶đđ„ đđąđ”đŠđł đŁđŠ đłđŠđđŠđąđŽđŠđ„ đ„đ¶đłđȘđŻđš đŻđ°đłđźđąđ đ±đłđ°đ”đŠđȘđŻ đ”đ¶đłđŻđ°đ·đŠđł.)
Her first point was straightforward: she could not find any scientific studies demonstrating that such a rebound effect actually exists. In her view, the claim was not supported by the research literature.
She also reviewed some of the studies referenced in the SanoAnimal article. One claim was that đŽđ°đ„đȘđ¶đź đŽđŠđđŠđŻđȘđ”đŠ - the natural 'inorganic' form that we use in our EquiVita/VitaComplete balancers - is absorbed quickly but excreted quickly, while đŽđŠđđŠđŻđ°đźđŠđ”đ©đȘđ°đŻđȘđŻđŠ is absorbed more slowly.
However, when Dr Kellon looked at the research itself, the study suggested that both forms entered the bloodstream rapidly and behaved similarly once absorbed.
Another concern raised in the original article was that selenium from đŽđŠđđŠđŻđ°đźđŠđ”đ©đȘđ°đŻđȘđŻđŠ might accumulate excessively in the body. Dr Kellon examined the human-based study used to support that argument, and found that what the study actually showed was that when humans were supplemented with selenium:
âą blood selenium levels increased
âą but then stabilised after a period of time
This happens because the body increases urinary excretion as selenium intake rises. In other words, selenium levels do not keep rising indefinitely.
Dr Kellon also referenced laboratory 'LD' (lethal dose) toxicology studies comparing selenium forms. These studies examine extremely large experimental doses used to evaluate acute poisoning risk, rather than the tiny nutritional levels used in horse diets. At those very high experimental levels, inorganic selenium such as sodium selenite can show greater acute toxicity than selenium yeast.
However, itâs important to understand that đđ”đČ đđČđčđČđ»đ¶đđș đčđČđđČđčđ đđđČđ± đ¶đ» đŻđźđčđźđ»đ°đČđ± đ”đŒđżđđČ đ±đ¶đČđđ đźđżđČ đđđœđ¶đ°đźđčđčđ đ¶đ» đđ”đČ đżđČđŽđ¶đŒđ» đŒđł đŹ.đâđŹ.đŻđșđŽ đœđČđż đžđ¶đčđŒđŽđżđźđș đŒđł đłđČđČđ±, đđ”đČđżđČđźđ đđ”đČ đđâ
â đđŒđ
đ¶đ°đ¶đđ đđđđ±đ¶đČđ đ¶đ»đđŒđčđđČ đ©đđ€đȘđšđđŁđđš đŒđł đșđ¶đčđčđ¶đŽđżđźđșđ đœđČđż đžđ¶đčđŒđŽđżđźđș đŒđł đŻđŒđ±đđđČđ¶đŽđ”đ. In other words, we are talking about huge differences between laboratory poisoning studies and normal nutritional supplementation.
(đđ”âđŽ đąđđŽđ° đžđ°đłđ”đ© đŻđ°đ”đȘđŻđš đ”đ©đąđ” đ”đ©đŠđŽđŠ đ”đ°đčđȘđ€đȘđ”đș đ·đąđđ¶đŠđŽ đąđłđŠ đđđ đ„đŠđłđȘđ·đŠđ„ đ§đłđ°đź đŽđ”đ¶đ„đȘđŠđŽ đ°đŻ đ©đ°đłđŽđŠđŽ. đđ°đŽđ” đđâ
â đ”đ°đčđȘđ€đ°đđ°đšđș đ„đąđ”đą đ€đ°đźđŠđŽ đ§đłđ°đź đ©đȘđŽđ”đ°đłđȘđ€đąđ đđąđŁđ°đłđąđ”đ°đłđș đŽđ”đ¶đ„đȘđŠđŽ (1960'đŽ-1990'đŽ) đ¶đŽđȘđŻđš đŽđźđąđđ đąđŻđȘđźđąđđŽ đŽđ¶đ€đ© đąđŽ đłđ°đ„đŠđŻđ”đŽ, đžđȘđ”đ© đ”đ©đŠ đłđŠđŽđ¶đđ”đŽ đ”đ©đŠđŻ đ¶đŽđŠđ„ đŁđș đłđŠđšđ¶đđąđ”đ°đłđŽ đ”đ° đŽđŠđ” đ·đŠđłđș đ€đ°đŻđŽđŠđłđ·đąđ”đȘđ·đŠ đŽđąđ§đŠđ”đș đđȘđźđȘđ”đŽ đ§đ°đł đąđđ đŽđ±đŠđ€đȘđŠđŽ. đđŻ đ±đłđąđ€đ”đȘđ€đŠ, đ”đ©đŠ đŽđŠđđŠđŻđȘđ¶đź đđŠđ·đŠđđŽ đ¶đŽđŠđ„ đȘđŻ đ©đ°đłđŽđŠ đŻđ¶đ”đłđȘđ”đȘđ°đŻ đąđłđŠ đźđąđŻđș đ”đ©đ°đ¶đŽđąđŻđ„đŽ đ°đ§ đ”đȘđźđŠđŽ đđ°đžđŠđł đ”đ©đąđŻ đ”đ©đ°đŽđŠ đŠđčđ±đŠđłđȘđźđŠđŻđ”đąđ đ”đ°đčđȘđ€đȘđ”đș đ”đ©đłđŠđŽđ©đ°đđ„đŽ.)
đŠđŒ đđ”đČđżđČ đ±đŒđČđ đđ”đČ đđ°đ¶đČđ»đđ¶đłđ¶đ° đ±đ¶đđźđŽđżđČđČđșđČđ»đ đčđ¶đČ?
Interestingly, the debate between these two perspectives is not really about toxicity studies. It's about đ”đŒđ đđČđčđČđ»đ¶đđș đŻđČđ”đźđđČđ đșđČđđźđŻđŒđčđ¶đ°đźđčđčđ đ¶đ»đđ¶đ±đČ đđ”đČ đŻđŒđ±đ.
âą Dr Kellonâs discussion focuses mainly on toxicology data and blood selenium levels.
âą Dr Christina Fritz - who as you know Iâve personally studied with, and whose work many of us now also follow closely - focuses more on how selenium enters metabolic pathways and how it may be stored in tissues. Her concern with selenomethionine is based on its chemistry.
Reminder: đđŠđđŠđŻđ°đźđŠđ”đ©đȘđ°đŻđȘđŻđŠ is a chelated selenium compound that is chemically bound to the amino acid - and therefore structurally resembles, and behaves very similarly to - the amino acid đźđŠđ”đ©đȘđ°đŻđȘđŻđŠ, amino acids being protein building blocks. Because of this, the body may recognise it as a protein and incorporate it into body proteins - the so-called âTrojan horseâ mechanism - aka, sneaking in without an invitation, regardless of whether additional selenium is actually needed.
For this reason - and because EquiNatural is nothing if not natural - we avoid chelated sources of nutrients in our mineral balancers. In the case of selenium, we formulate with natural đŽđ°đ„đȘđ¶đź đŽđŠđđŠđŻđȘđ”đŠ, which enters the body through the normal selenium metabolic pathway where intake can be more tightly regulated.
In simple terms:
âą đđ°đ„đȘđ¶đź đŽđŠđđŠđŻđȘđ”đŠ â enters the body through the normal selenium metabolic pathway where its use and excretion can be regulated.
âą đđŠđđŠđŻđ°đźđŠđ”đ©đȘđ°đŻđȘđŻđŠ â can be incorporated into body proteins because it resembles an amino acid. This means selenium may be stored in tissues rather than immediately entering the bodyâs regulated selenium metabolism.
Overall, the concern here is not acute toxicity â đ¶đâđ đźđŻđŒđđ đ”đŒđ đđČđčđČđ»đ¶đđș đ¶đ đżđČđŽđđčđźđđČđ± đźđ»đ± đđđŒđżđČđ± đ¶đ» đđ”đČ đŻđŒđ±đ đŒđđČđż đđ¶đșđČ, particularly because selenium has a relatively narrow safety window between deficiency and excess.
đŠđŒ đđ”đ đ±đŒ đđ”đČđđČ đđđŒ đżđČđđœđČđ°đđČđ± â đđČđ đ±đ¶đłđłđČđżđČđ»đ - đČđ
đœđČđżđđ đżđČđźđ°đ” đ±đ¶đłđłđČđżđČđ»đ đ°đŒđ»đ°đčđđđ¶đŒđ»đ?
Because they are essentially asking different scientific questions.
âą Dr Kellon is primarily examining đđŒđ
đ¶đ°đŒđčđŒđŽđ đ±đźđđź đźđ»đ± đŻđčđŒđŒđ± đđČđčđČđ»đ¶đđș đčđČđđČđčs.
âą Dr Fritz is examining đșđČđđźđŻđŒđčđ¶đ° đżđČđŽđđčđźđđ¶đŒđ» đźđ»đ± đœđŒđđČđ»đđ¶đźđč đđ¶đđđđČ đđđŒđżđźđŽđČ.
And both perspectives are of course valuable pieces to the overall understanding of selenium metabolism.
đȘđ”đźđ đ±đŒđČđ đđ”đ¶đ đșđČđźđ» đłđŒđż đ”đŒđżđđČ đŒđđ»đČđżđ?
The most important point to understand is that selenium is essential, but must be provided in the correct amount.
And itâs important to remember that toxicity studies sometimes quoted online involve extremely high experimental doses that are many hundreds of times higher than the amounts used in balanced horse diets.
In our real-world feeding, the quantities used are tiny and carefully regulated.
đ§đŒ đ°đŒđ»đ°đčđđ±đČ
At EquiNatural we use natural đŽđ°đ„đȘđ¶đź đŽđŠđđŠđŻđȘđ”đŠ in our mineral balancers because it enters the normal selenium metabolic pathway where the body can regulate its absorption, utilisation and excretion.
Given seleniumâs narrow safety window, many nutritionists prefer this regulated pathway when designing balanced diets. In other words, the key factor with selenium is correct dosage, not simply the form used. đđ°đ„đȘđ¶đź đŽđŠđđŠđŻđȘđ”đŠ is a safe and well-established selenium source used widely in equine nutrition.
In short? This post is simply intended to explain the different metabolic pathways of selenium forms for horse owners. Both forms are used in equine nutrition, and correct dosage is the most important factor.
If you ever have questions about your horseâs mineral balance or selenium intake, our team is always very happy to help.
Carol & The EquiNatural Team
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