Muscle stress

Stress Impact on Horses and How Magnesium Can Help

Stress is both an angel and a demon: On the one hand, it pushes us forward to adapt, achieve and strengthen muscles, and on the other hand it can kill us prematurely. Building strength rather than wearing out is dependent on ability to recover from stress: And the quality of recovery is dependent on magnesium status.  Low magnesium causes acute stress responses, inflammation, acidosis and metabolic syndrome.  The body can literally break down with premature ageing as a result of chronic magnesium deficiency.

Magnesium deficiency can result from a number of causes:  Stress in excess causes increased loss of magnesium, insufficient magnesium in diet, exposure to toxic chemicals, and sometimes there are genetic causes for excessive magnesium loss.  If your horse is acting up and easily spooked, if their body is bracing or they are experiencing pain or hoof sensitivity, chances are they have magnesium deficiency and would benefit greatly from adding natural magnesium chloride salt flakes to daily feeds. 

Horses evolved from small mammals whose survival depended on their ability to flee from predators. Their first instinct when frightened is to escape. If running is not possible, the horse resorts to biting, kicking, striking or rearing to protect itself. Many of the horse’s natural behaviour patterns, such as herd-formation and social facilitation of activities, are directly related to their being a prey species. This means they are easily spooked and subject to stress – especially if they don’t get enough attention and feel lonely. They are intensely social creatures, relying on relationships to give them confidence and the ability to relax and rest.

Other sources of horse stress to be aware of are inclement weather, travelling, performance, bullying by horses or humans, not being able to graze, chemicals and nutrient deficient food, and isolation (no equine companionship). Unrelenting stress can cause colic, irritability and even deteriorate into diseases of diabetes and laminitis (hoof disease). Horses have a sensitive digestive system which is easily disrupted by stress.

Take care to ensure they are not exposed to pesticides on their grazing pastures and in their drinking water from dams and waterways. Grains can also cause acidosis because they share the same acidic by-product as sugar in metabolism – especially in the absence of sufficient magnesium and acid-buffering antioxidants.

A vital key to making sure that stresses are beneficial and not detrimental is to maintain an appropriate balance between tension and relaxation. If you keep pushing and stressing muscles, ligaments and joints without appropriate recovery time they can get injured and inflamed. It can lead to Repetitive Stress Injury, acidification and tissue breakdown, as detoxification pathways start to fail.  Dietary magnesium supplementation is a great way to enhance recovery after stress by calming inflammation[1, 2], supporting detoxification enzymes and protein synthesis to re-build tissue cells[3].

When animals are tensed and in the ‘fight or flight’ mode it is called the ‘sympathetic mode’.  This is when the blood rushes to extremities ready for quick-twitch muscle firing to escape danger or to fight the predator. During this phase the digestive system stops, as does the cellular detox and cell-building systems. When the danger is gone, the horse relaxes back into the ‘parasympathetic mode’ (sometimes called grazing or ‘rest and digest’ mode) – where digestion and the other systems return to normal.

If a horse is constantly in a stressed sympathetic mode the body cannot adequately digest foods and extract nutrients.

Muscles Need a Lot of Magnesium and Water

For muscles to have a good tone with strength and flexibility they need to be ‘trained’ with exercise, but also provided with sufficient recovery nutrients like magnesium.  Magnesium is essential for protein synthesis, including enzymes, collagen and elastin.   These help keep muscles flexible and stretchy.

Magnesium chloride attracts water and helps hold it inside the cell in the structure of the cytoplasm.  Magnesium and water keep us younger, more flexible and ‘juicier’ longer!  They are essential for cell membrane integrity and electrolyte charge [4, 5].  If magnesium drops too low the cell wall depolarises (drops in charge) and therefore becomes looser, allowing escape of valuable hydration and potassium ions, as well as too much ingress of calcium ions (which contract).  If you lose too much magnesium and potassium your heart muscle can cramp in cardiac arrest.


The loss of magnesium and hydration is what leads to the crumpling and squeezing effect of the cramp, as calcium moves in to contract the muscle fibres. Yes, we do need the calcium to contract, but magnesium performs the relaxation phase via its control of the calcium channels.  With chronic magnesium deficiency over time, muscles, ligaments and joints get dehydrated, stiffer and more calcified – or older, harder and crunchier faster!

Both horses and humans alike are more likely to be magnesium-deficient than calcium-deficient these days.  For many years we have been sold the myth that we are calcium-deficient and that we need to add a lot more calcium to diet to make strong bones.  This promotion actually gained ground way back in the 60’s via the dairy industry wanting to improve the sales of milk products.  Since then the idea has also moved into the horse industry.

However there is a real danger in getting too much calcium.  As magnesium gets too low, calcium becomes a tough bully and suppresses the work of magnesium.  Here is the conclusion of a significant horse study which shows the impact of excess calcium (hypercalcemia) in upsetting electrolyte balance:

“Hypercalcemia resulted in hypomagnesemia, hypokalemia, and hyperphosphatemia; increased urinary excretion of calcium, magnesium, potassium, sodium, phosphate, and chloride; and induced diuresis. This study has clinical implications because hypercalcemia and excessive administration of calcium have the potential to increase urinary excretion of electrolytes, especially iMg, and induce volume depletion.” [6]

The fact is that we (humans and horses) can get plenty of calcium from diet rich in vegetables and green plants. Adding calcium or vitamin D supplements can overload our system with excess calcium which suppresses magnesium. What makes bones stronger is more magnesium, phosphate and other trace minerals collectively. Calcium on its own is like chalk.  It may harden structures, but is brittle and can break easily.  It’s the magnesium that supports collagen and elastin structures, as well as cell hydration to help absorb shock so we can bounce back.

Therefore, take care to make sure the diet is correctly balanced without overload of calcium and including sufficient magnesium.  Pasture grasses after a lot of rain tend to be very lush and ‘tasty’ for horses.  However, as magnesium is highly water soluble, it is easily washed away from surface soils, making the ratio of sugars in the grasses too high.  A high calcium, high sugar and low magnesium diet leads to diabetes and laminitis.  Adding some natural magnesium chloride flakes to feeds can help to counter-balance the effects of the sugars.

Confinement and Lack of Exercise Causes Stress

Playful exercise helps move and circulate the lymphatic system to eliminate wastes. This is particularly important for horses. Lack of exercise can also cause severe stress because the body can’t get enough oxygenation for cell respiration.  Metabolism can then switch from aerobic to anaerobic which results in high acidic waste products, not to mention less efficiency of energy output.

Horses love to run or walk long distances. For thousands of years they have served humans well as modes of transport. Today they are more prone to stress from confinement and lack of exercise. This leads to build-up of toxic waste products. The hoof wall acts like a pressure container for filling and emptying of lymphatic initial vessels via the ground contact and suspension of the moving foot.

If movement is restricted it can cause problems for the lymphatic system such as ‘filled legs’/’stocking up’, which may eventually lead to lymphangitis.  When excessive fluids build up the body is usually in a state of drought and is trying to hold back more water to dilute the toxic accumulation in tissue cells. Lack of movement, too much restriction, low magnesium and dehydration all combine to exacerbate this problem.

Stable and exercise bandages, steel horse shoes and lack of regular or correct trimming of hooves (maximum 4 weeks) have been shown to adversely affect the blood and lymphatic circulations of the leg, leading to less oxygen and nutrient delivery to extremities. See Dr Professor Bowkers research at and

Sugar Metabolism, pH and Acidosis

The evolution of the horse was from alpine regions with an abundance of magnesium chloride and trace minerals from glacial waters. The plant food they ate was high in minerals and low in sugars. These plant foods also carried an abundance of beneficial bacteria to assist digestion and produce essential fatty acids. Their natural diet was very nutrient-dense with an abundance of magnesium and other trace minerals.

Modern horses are mostly confined to fenced paddocks and back yards that do not have access to the same abundant natural sources of magnesium. As magnesium gets lower, sugar sensitivity, acidity, inflammation and agitation increases. Conversely, as magnesium levels are increased in cells the sugar sensitivity, bad temperament and acidification settles down again. It’s like a see-saw effect. Magnesium is vital in energy metabolism because it is used by the mitochondria to co-factor with ATP (adenosine triphosphate) – the energy currency of the cell. A deficiency leads to metabolic syndrome.

The mitochondrial bio-electrical system drives enzyme reactions in the body which are catalysts for all cell functions. Electrical energy is the life force, with magnesium at the crux of the energy process in all organisms.  Magnesium is at the centre of the chlorophyll molecule and essential for photosynthesis in plants (conversion of light energy to stored starches).   It is essential to help the haemoglobin carry oxygen in animal blood. Oxygen is vital for cell metabolism.  Low magnesium can manifest with symptoms of anaemia and chronic fatigue, hypothyroid conditions and diabetes[5].

It takes 28 magnesium molecules to metabolise one sucrose molecule into energy, and 56 magnesium molecules to metabolise one fructose molecule. Consumption of sugars therefore gobbles up a lot of magnesium in metabolism and can quickly lead to magnesium deficiency and dehydration.  Why dehydration?  Because low magnesium causes cell membranes to lose water. Water comes out and calcium moves in to tighten and harden.

As you consume more sugar, which depletes magnesium, the electrical system starts to splutter and falter like an ill-tuned car engine. It also causes involuntary muscle spasms or hypertension as the smooth walls of the vascular system contract and increase pressure. It can also lead to hyperactivity and bad temper.

The body starts to panic because of dehydration, with extra adrenaline being released for action. Screaming for water and minerals as a result of the sugar assault and consequent acid by-products, the body desperately looks to re-establish pH balance.

The Best Magnesium Supplement and Horse Calmer

The best way to help make a smiling horse no stresshorse calmer, returning to equilibrium and relaxed ‘grazing mode’, is to supply adequate hydration and the right nutrition. The most bio-available form of magnesium is the salt form called magnesium chloride hexahydrate (magnesium flakes) dehydrated from natural sea water.

Chloride is abundant in cells and the body is hungry for it.  Inside cells the most abundant ions are chloride, potassium and magnesium. To get access to intracellular spaces the magnesium ion needs to be joined to chloride, which then becomes fully water soluble, ionised and bio-available.  Magnesium chloride, once dissolved, is already in the right form for cell uptake without further digestion required.  This is also why it can be absorbed transdermally.

Make sure to use ‘food grade’ for feeds, as most magnesium chlorides are industrial grade with contaminants from agricultural or mining runoff, ocean pollutants or population waste sources. Food grade magnesium chloride flakes are usually from remote alpine regions, naturally dehydrated with the sodium removed, and retaining about two percent other trace minerals, without mercury or lead contamination.

Magnesium sulphate (Epsom salts) has also been used as a feed supplement, but sulphates tend to break membrane barriers and over time this form of magnesium can be too irritating for the gut lining, causing rapid expulsion of the magnesium sulphate via the digestive system.

Magnesium oxide is much harder to absorb due to its insolubility.  Studies have shown bioavailability is only about 4% [7]. It also has a higher tendency to cause stool scouring.  Many horse owners that have tried this supplement on their horses note that they have to add too much to the feeds to get any effect.  This amount makes the feeds taste bad for the horse.

Magnesium chloride flakes can be added in smaller quantity (half to one cup per day) for a noticeable benefit, are more hydrating, easier on the digestive system – and more palatable for the horse.

Calm the Horse: Get Better Performance

Not only is it more common for performance horses to suffer from stress and therefore lose excessive amounts of magnesium due to training and travelling, but the difference and improvement to performance with magnesium chloride supplementation is quite remarkable.  Even race horses have demonstrated rapid improvement in muscle recovery during agistment between races.  Dressage riders have also noted calmer and more controllable horses when their magnesium needs are fully met.

Stomach Ulcers?

If the horse has acidosis and/or stomach ulcers these issues will need to be met via dietary changes with possibly some toxin binders and bicarbonate of soda treatment before oral magnesium chloride supplementation.  While waiting for the gut to heal you can use magnesium chloride soaked in a bandage or towel and applied over the rump and muscle area to absorb and induce muscle relaxation.  Horses can also absorb magnesium ions via skin like humans, which soothes muscle tension and enhances healing.

FOOTNOTE:  As with any changes to a horse’s diet, introduce new elements like magnesium chloride in small increments for the first month.

By Sandy Sanderson B.A., Uni NSW.  ©2016-2018
Sandy Sanderson is the founder and CEO of Elektra Life Pty Ltd since 2008, which supplies food grade magnesium chloride to the human and horse markets via the brands ‘Elektra Magnesium’ and ‘Magnesium4horses’. Prior to that she nearly lost her life with severe heart arrhythmia caused by magnesium deficiency, but was able to fully recover by adding magnesium chloride to her daily lifestyle routine.  She now writes articles and presents seminars to help educate the public about the benefits of magnesium chloride for humans and horses. and


  1. Malpuech-Brugère, C., et al., Inflammatory response following acute magnesium deficiency in the rat. Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease, 2000. 1501(2): p. 91-98.
  2. Maier, J.A.M., et al., Low magnesium promotes endothelial cell dysfunction: implications for atherosclerosis, inflammation and thrombosis. Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease, 2004. 1689(1): p. 13-21.
  3. Senni, K., A. Foucault-Bertaud, and G. Godeau, Magnesium and connective tissue. Magnes Res, 2003. 16(1): p. 70-4.
  4. Martin-Molina, A., C. Rodriguez-Beas, and J. Faraudo, Effect of calcium and magnesium on phosphatidylserine membranes: experiments and all-atomic simulations. Biophys J, 2012. 102(9): p. 2095-103.
  5. Seelig, M.S., Magnesium Deficiency in the Pathogenesis of Disease. 1980: Springer US.
  6. Toribio, R.E., et al., Effects of hypercalcemia on serum concentrations of magnesium, potassium, and phosphate and urinary excretion of electrolytes in horses. Am J Vet Res, 2007. 68(5): p. 543-54.
  7. Firoz, M. and M. Graber, Bioavailability of US commercial magnesium preparations. Magnes Res, 2001. 14(4): p. 257-62.

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