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An Honest Look at Baking Soda For Horses With PSSM: 3 Pros, and Potential Cons?

PSSM horses, electrolyte imbalances, big head syndrome in horses, and baking soda for horses
PSSM horses, electrolyte imbalances, big head syndrome in horses, and baking soda for horses
PSSM horses with electrolyte imbalances: big head syndrome, and baking soda for horses, sodium bicarbonate for horses

Sodium Bicarbonate for Horses: Pros

Baking Soda for horses: let’s start with the reason I feed baking soda to my PSSM horse. Baking soda, or sodium bicarbonate, is an alkalizing agent. It’s been said to help RER horses by preventing tie ups, and as an alkalizing agent may prevent ulcers by buffering acid. There’s also potential that it can help neutralize lactic acid production in the muscles (note that PSSM is not an issue of lactic acid, but every little bit helps with these horses!).

Whether these claim are true or not is for someone above my pay grade – the only thing I know is that, for quite a number of years, baking soda was a huge part of keeping my PSSM horse healthy, stopping his bloody urine issues, and giving him back his exercise tolerance.

Sounds great, right? Well, let’s lay some foundation for the potential cons of using oral sodium bicarbonate for horses on a daily basis:

Electrolyte Disturbance Possibilities Specific to PSSM:

Big Head Syndrome in horses: It’s generally believed that there is enough calcium in the equine diet.  I, too, have believed that for a number of years, though my horse may have been exhibiting mild calcium deficiency signs (hypocalcemia) since I got him nine years ago (though he had no physical signs of horse big head syndrome in the first couple of years). 

I’ve gone into some of the signs and symptoms he’s exhibited in other electrolyte posts, but let’s take a closer look at the potential causes of calcium deficiency, acidosis and alkalosis issues, and the possible effects of baking soda for horses (sodium bicarbonate) specific to PSSM horses and possibly related to big head syndrome in horses.

Hypocalcemic Tetany – Defined as an acute depletion of serum ionized (free/unbound) calcium.  Signs mimic exertional rhabdomyolysis and muscle disorders.  Causes include:

  • grazing lush pastures (similar to a PSSM1 episode?)
  • prolonged physical activity
  • low serum chloride (hypochloremia) causing metabolic alkalosis
    • causes calcium to bind to albumin
      • results in decreased free/usable serum ionized calcium
  • stress-induced (PSSM episode? Shedding stress?) high corticosteroid levels
    • corticosteroids inhibit vitamin D activity
      • causes decreased absorption of calcium through intestines
      • causes mobilization of skeletal calcium (resorption) 1

Signs of low calcium mimic muscle disorder symptoms – so how do you know whether your horse is having a PSSM episode or a mild low-grade calcium deficiency?

How metabolic pH can affect calcium and bones, and how baking soda and other alkalizing agents may affect calcium uptake, binding, and excretion:

Acid base disorders are pathologic changes in arterial (blood) pH and carbon dioxide partial pressure (Pco2), and in serum bicarbonate (HCO3) 2.  High protein diets (listed in reference #3 as 14.5%) can cause metabolic acidosis (serum pH < 7.35) and accelerate bone resorption by increasing urinary calcium excretion by up to 74% – the most likely source of the excess excreted calcium is from bone resorption 3,4

It is believed that an alkaline diet inhibits bone resorption, but metabolic alkalosis (serum pH > 7.45) can cause calcium to bind to albumin thus making the free ionized body calcium unavailable for normal processes 5,6.  This could potentially lead to bone loss due to low ionized calcium.  Basically, anything other than neutral  pH could affect the bones and other processes/systems (including the Central Nervous System)!

PSSM horses are already prone to metabolic acidosis due to rhabdomyolysis episodes – and there is evidence that a high protein PSSM2 diet could potentially increase acidity as well.  Baking soda can combat the acidic properties of a high protein diet, stressed kidneys, or a muscle episode 7,8.  The question is, can too much baking soda cause alkalosis, causing calcium to bind to albumin, thus making the benefits of non-resorption moot due to calcium being bound to albumin (and therefore unavailable for bodily processes)? 

Both high potassium (high protein feeds are usually very high potassium) and bone resorption can also put the body in an acidic state 2 – is this why PSSM can turn into a vicious cycle?  Once the system turns acidic, do these issues compound and keep pushing the body into an acidic state, not allowing it to return to neutral?  HCO3 (sodium bicarbonate) is consistently and repeatedly used up due to metabolic acidosis, potentially keeping the bicarb from returning the body to a neutral pH:

Increased anion gap is most commonly caused by metabolic acidosis in which negatively charged acids—mostly ketones, lactate, sulfates, or metabolites of methanol, ethylene glycol, or salicylate—consume (are buffered by) HCO3. Other causes of increased anion gap include hyperalbuminemia [an increased concentration of albumin in the blood – the same protein that binds to calcium in alkalosis. Typically, hyperalbuminemia is due to abrupt dehydration.  Albumin – a simple form of protein that is soluble in water and coagulable by heat, such as that found in egg white, milk, and (in particular) blood serum.]  and uremia (increased anions) and hypocalcemia or hypomagnesemia (decreased cations).” 2

According to this research hypocalcemia (low serum calcium), which is caused by acidosis, can also cause metabolic acidosis – the start of the vicious cycle.  PSSM horses are notoriously high users of magnesium raising the risk for hypomagnesemia, so here’s another trigger for acidosis. 

Combine the fact that bicarb, the main bodily component to balance acidity levels in the body is being consumed and this can be the cause of the “crash” that many horses, including mine, experience with PSSM, and why they don’t seem to come out of this crash with management sometimes – especially since management can also induce an acidic state (high protein diets)! 

However, PSSM1 horses aren’t safe, as they also mention ketones overusing bicarb.  PSSM1 management is replacing NSCs with fat to get the horse working off fat for energy rather than sugars.  Here’s a description of ketones from WebMD:

“Ketones are chemicals your liver makes. You produce them when you don’t have enough insulin in your body to turn sugar (or glucose) into energy. You need another source, so your body uses fat instead. Your liver turns this fat into ketones, a type of acid, and sends them into your bloodstream. Your muscles and other tissues can then use them for fuel.

Not only is PSSM2 management acidic, but it appears that PSSM1 management may be acidic as well!

More on Electrolytes, PSSM, and Rhabdomyolysis Episodes:

“Rhabdomyolysis is a rupture (lysis) of skeletal muscles due to drugs, toxins, inherited disorders, infections, trauma and compression. Lysis of muscle cells releases toxic intracellular components in the systemic circulation which leads to electrolyte disturbances, hypovolemia, metabolic acidocis, coagulation defects and acute renal failure due to myoglobin.” 9

Now that we’ve seen that the rupture of skeletal muscles due to a PSSM episode causes “electrolyte disturbances” let’s take another look at electrolytes:

“Rhabdomyolysis can also cause abnormality of electrolytes in the blood. Because of muscle injury, the contents of the muscle cells can be released into the blood causing high levels of potassium (hyperkalemia) and phosphorus (hyperphosphatemia).” 10

It’s fairly well recognized that muscle contraction and relaxation depends on two major electrolytes – calcium to contract, and magnesium to relax – which is one of the big reasons for magnesium supplementation with PSSM horses; we supplement magnesium in order to (among other things) help the chronically contracted muscles to relax.  (After more research I question this theory as a whole!)

However, my research is proving that things are far more complex – high potassium can stop the relaxation of muscles and inhibit calcium uptake; and low calcium can cause increased muscular tension, mimicking low magnesium! (see my high potassium and low calcium symptoms list for more). 

Most of us in the horse world know the dangers of too much phosphorous or an unbalanced calcium:phosphorous ratio as horse big head syndrome, which we usually recognize as facial swellings; but painful movement and lameness also accompany this disorder, which can mimic PSSM.  For an early case of horse big head syndrome I don’t have to look any further than my backyard – here’s the main reason I put Jax on a calcium supplement this year:

Baking soda for horses: swellings on the bridge of Jax’s nose – an early indications of big head syndrome

While this is not a full-blown case, coupled with high potassium symptoms and other electrolyte research I’ve been doing, this was enough to set me straight!  While I was recognizing the high potassium symptoms for the past year or two, I wasn’t recognizing the unbalanced calcium:phosphorous ratio (though his diet was balanced, something in his system was causing a major imbalance!)

This swelling has come up each spring for the past 2-3 years along with high potassium symptoms, but the swelling was milder in past years.  This year it was obvious and was getting worse as we were entering the spring months. One thing I’ve learned in this is that big head syndrome in horses isn’t an overnight process – it’s far more insidious than that…

Note: At the time of these swellings, I was giving a daily supplement of baking soda for my horse.

“Secondary hyperparathyroidism occurs when calcium is wasted and phosphorus is in excess. If this occurs via dietary imbalance, it is termed nutritional hyperparathyroidism. In instances of renal failure [PSSM stresses the renal system], the increased blood P due to decreased renal clearance results in increased PTH secretion. In extreme cases, big head syndrome in horses, or fibrous osteodystrophy can develop. In less severe cases, horses may present with indeterminate lameness and stiffness.” 11  [emphasis mine]

“When calcium is wasted” – possibly due to the binding of free ionized calcium (alkalosis) or excess calcium excretion (acidosis)?  So hyperparathyrodism, or big head syndrome, is another real risk with PSSM along with joint and other bone issues?  I don’t think it’s a coincidence that a lot of PSSM horses end up with arthritis – not only are they moving in a compensatory manner that stresses joints, but there’s real potential that the bones and joints aren’t receiving the minerals they need. 

I need to do more research here, but I believe the most important thing to take from this is that a balance is needed.  PSSM alone is a major push towards acidemia, and finding ways to balance that without going overboard are needed.

I believe a balance is possible, even for PSSM horses, through diet by supplementing alkaline substances including baking soda for horses prone to acidemia. Other alkaline substances include herbs (including parsley which is helpful for kidney issues), MSM (sulfur-containing compounds are alkaline), apple cider vinegar (an acid that turns alkaline once digested), certain minerals like calcium carbonate or magnesium oxide, and grass hay. 

Alfalfa, soy, and grains are all acid forming (alfalfa and soy due to high protein?), and have caused issues for Jax (except for 1-2 tbsp of rolled oats on occasion – those seem to help rather than hinder, possibly due to their gut-helping volative fatty acid known as butyrate).

Sodium Bicarbonate for Horses: Too Much Of A Good Thing?

I believe I may have raised my horse’s calcium needs by over-supplementing baking soda, and possibly magnesium these past couple of years, but I don’t think fully removing baking soda is the answer.  Gut supplements and herbs/forage that support the natural, healthy gut bacteria (Google EquiBiome for more on this), supporting the kidneys, and keeping PSSM horses as healthy and episode-free as possible can help with acidosis, but some need a little more help, and I think baking soda and other alkaline foods and supplements can be huge for those horses. When used as needed for that individual, it shouldn’t pose a big head syndrome or hyperparathyroid risk. 

The drastic increase in exercise tolerance and overall health that occurred with my horse after adding baking soda was amazing, but in mid-2019 I think his need went down as his symptomatic state decreased.  As with everything, these horses never stay the same, and management is always shifting (at least it is for mine).  So find your perfect diet but realize things will shift and change, and tweaking may be a forever thing with these guys.  To everyone fighting this battle, good luck with your horses!

References on Using Baking Soda for Horses and Big Head Syndrome:

  1. Hypocalcemic Tetany in Horses
  2. Acid Base Disorders – Merck Manuals
  3. Dietary protein influences acid-base responses to repeated sprints
  4. Acid diets increase bone resorption
  5. Calcium overview (humans)
  6. pH effects on calcium and magnesium
  7. Grocery store baking soda. A source of sodium bicarbonate in the management of chronic metabolic acidosis.
  8. Sodium Bicarbonate Therapy in Patients with Metabolic Acidosis – Metabolic acidosis is a common acid-base disorder and its management should be directed by the current guidelines of therapy. The utility of sodium bicarbonate replacement in conditions associated with loss of sodium bicarbonate is widely accepted, such as renal proximal tubular acidosis and diarrhea, for in these disorders the loss of sodium bicarbonate contributes to generation of the acidosis. However, evidence of more favorable clinical outcomes associated with the use of symptomatic therapy with sodium bicarbonate in order to increase plasma pH in most acute conditions featuring metabolic acidosis is not definitive in humans. Available evidence suggests that the severity of metabolic acidosis in these conditions reflects the gravity of the underlying illness rather than being itself a contributor to mortality. Sodium bicarbonate administration usually, although not always, corrects the acidosis, rising serum bicarbonate concentration, serum pH, and the partial pressure of carbon dioxide, but evidence for clinical benefit derived from this effect is not conclusive. Therapy of such situations should be focused on the cause of the acidosis. On the other hand, management of chronic conditions leading to metabolic acidosis, such as kidney disease, may be challenging. Nonetheless, evidence for a net beneficial effect of symptomatic sodium bicarbonate administration to correct the acidosis in this condition is not compelling and further studies are needed to establish its therapeutic value [13, 37, 40, 64]. Recent studies have suggested that metabolic acidosis might contribute to worsening kidney disease and sodium bicarbonate supplementation has been proposed as a renoprotective strategy. However, limitations of these studies prevent reaching definite conclusions and further investigations are required in order to ensure the validity of this therapeutic approach [79].
  9. Rhabdomyolysis Updated
  10. Rhabdomyolysis
  11. Recognizing and treating disorders of calcium metabolism in horses
  12. FROM THE FIRST PIC – Hyperchloremic acidosis –

Keywords – big head syndrome in horses, PSSM, baking soda for horses, electrolyte imbalances in horses

4 thoughts on “An Honest Look at Baking Soda For Horses With PSSM: 3 Pros, and Potential Cons?

  1. Very interesting on Hypocalcimia I had a 7 month old weanling come in very poor. Her blood work confirmed Hypocalcimia. She was shedding calcium in her urine( urine was white) Also a heart murmur. I monitor her calcium levels by monitoring her heart. Murmur add calcium. No murmur she is fine!!!

  2. Thanks for commenting! Jax's urine was white for a time as well, before I got his management lined out. I'm finding an irregularity in his heart rhythm when his electrolytes get out of whack now, so I appreciate you sharing your experience!

  3. I just came across this article about baking soda. I have a newly diagnosed pssm1 horse. And I am searching for a great diet for him. I am interested to know what supplements have worked best for these horses. Thank you for the information

    1. I’m sorry to hear you have a positive horse, but, according to Dr. Valberg around 90% of these horses can be managed with correct diet and exercise, so don’t lose heart! All of these horses are different – different environments, metabolisms, allergies/sensitivities, etc – so there isn’t a “one size fits all” with diet and supplements. That said, I have a couple of posts that talk about the specific effects of many supplements and what has worked for my horse that you may find of interest:
      Jax’s PSSM Diet and the Solutions to Stop Symptoms pages are especially useful. Take a look at the Dietary Management tab for all of my tested feeds and supplements for more.

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