Thursday, January 01, 1998

Electrolytes - Calcium Lactate in Perform`N Win - Michael I. Lindinger, Ph.D

Regarding: Calcium Lactate in Perform`N Win (PNW)

It has come to our attention that there has been concern expressed by an individual(s) that the Perform`N Win electrolyte product contains calcium lactate. We would like to address these concerns.

First, the amount of calcium in the solution when PNW is formulated according to package directions is 1.9 mmol/L, equal to that found in blood plasma.

Second, the calcium in PNW is complexed with various monovalent anions of which lactate may be a small part -- we cannot detect lactate in our assays of PNW solutions, which means that lactate is in concentrations less than 0.2 mmol/L (only 1/5 that found in blood in resting horses).

Third, some correct information regarding calcium and calcium salts: Calcium must be supplied in the form of a calcium salt. Calcium carbonate is a cheap source of calcium and therefore is widely used as a calcium supplement, but is less well absorbed than salts formed with monovalent anions such as citrate, malate, lactate, formate, gluconate and chloride. All of these show a higher bioavailability in humans and ruminants than calcium from calcium carbonate. The above forms of calcium are available as supplements. Calcium supplements in the form of calcium citrate/malate, calcium citrate, calcium gluconate or calcium lactate are commonly prescribed in oral doses of 500 to 1000 mg per day in humans, and higher amounts have prescribed for specific situations. Calcium is absorbed more efficiently when in a free ionic form (i.e., dissolved, as it is when you mix PNW with water). Therefore the calcium in PNW is a readily absorbed, highly available form of calcium.

Calcium is absorbed by the small intestine. The absorption of calcium can be increased when there is a need for more calcium in the body. Calcium is included in electrolyte supplements for exercising horses due to the loss of calcium, along with sodium, potassium and chloride in the sweat.

There is a common misconception that lactate is the "culprit" blamed for fatigue in the horse and has frequently been blamed for horses tying up. In anaerobic exercise, very high concentrations (greater than 10 mmol/L) lactate and its associated ion H+ inhibit glycolysis and may contribute to muscle fatigue, as do the diminishing stores of glycogen in the muscle. However, in race horses it is not uncommon for very high levels of lactate to be detected in the blood of the horse following intense exercise. If lactate were a problem, then the horses that had the highest lactate levels would be the ones having the most trouble. In fact, often the winner of the race was the one with the highest lactate levels and the horse suffers no apparent problems.

The reason for this is simple. Lactate is a breakdown product of anaerobic glycolysis. When the muscle demands large amounts of energy in a hurry, the glycogen in the muscle (or glucose in the blood) is broken down without using oxygen to contribute to the increased energy demand. As lactate accumulates in the muscles it is released into the blood, and blood concentrations of lactate increase.

More important to the current issue, though, is that lactate is a very good metabolic substrate in resting horses and humans and is in fact preferred over glucose by skeletal muscle to provide energy to the cells. Lactate is also more readily utilizable than glucose by muscle cells (including heart muscle). All glucose that is taken up by cells must first be broken down to lactate before the glucose carbons can be utilized in cellular metabolism. Lactate is one of the most readily absorbed and utilized energy sources by the body. For evidence, just look at the horse or human or greyhound recovering from high intensity exercise - lactates initially high at the end of the exercise are rapidly lowered after a short period of recovery - much faster than if a similar amount of glucose had been administered into the blood.

Also, lactate generated in exercising muscle is a gluconeogenic precursor in the liver and in muscle recovering from exercise, i.e., converted by liver and recovering muscle cells to make glucose (liver) or glycogen (muscle). Liver glucose can then be released to the blood for more energy (for all you biochemical junkies, this is called the Cori Cycle). The production of glucose from glycogenolysis in the liver and from peripheral precursors (i.e., lactate, glycerol, amino acids) can play an important role when dietary glucose is not readily available. In the post-prandial state (after a meal) much of the dietary glucose bypasses the liver and is metabolized by the tissues such as the skeletal muscle. The lactate recycles back to the liver where it is converted to glycogen for storage in the liver. Lactate production by some tissues is a normal state for the animal.

The lactate in PNW is barely detectable by a Nova Statprofile 9 ion analyzer. Of 25 electrolyte products analyzed, 9 have trace or measurable amounts of lactate (<2 mmole/L). Two products tested had levels in the range of 4 to 7 mmole/L! Some of these products with much higher levels of lactate have been in use for years. Several horses that have been a part of our total sample group of over 300 horses have used these products with no noticeable problems attributable to the lactate in the electrolyte product.

In the resting horse, lactate levels are generally 1-2 mmoles/L. In trials where 8 L of PNW (ie, 8 oz at once) is administered to horses, there is no detectable increase in blood lactates following ingestion (unpublished data). This is because the lactate is absorbed through the small intestine and can be used by the intestinal cells as a form of energy. Any lactate passing into the bloodstream would also be quickly metabolized as a source of fuel. During exercise, several researchers have suggested that lactate may be an important oxidizable substrate during exercise. A trained (i.e., well-conditioned physically) horse can use the lactate efficiently as an energy source. In fact, there are reports of human athletes ingesting lactate as an ergogenic aid (performance enhancing substance).

Michael I. Lindinger, Ph.D., Dept. of Human Biology & Nutritional Sciences
University of Guelph, Guelph, ON Canada N1G 2W1
Phone: 1 519 824 4120 ext. 3752
FAX: 1 519 763 5902

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