The Use of Psyllium for Insulin Resistance

In the horse world, psyllium is the product of choice to prevent sand colic, but little else in known about its usefulness. However, in human nutrition circles, researchers are finding more and more uses for this innocuous seed coat. Most notably, the use of psyllium (common in products like Metamucil) is now often recommended for patients with diabetes because it moderates glucose response and insulin release. It is even recommended as a preventive for humans at risk of developing diabetes. Will psyllium find its way into equine diets because of these same properties? Because the focus of psyllium use in horses centers around its use in sand colic, little is known about its effect on insulin sensitivity.

Psyllium is the seed husk of the Plantago ovata plant and is known for its ability to absorb water rapidly and form a gelatinous substance of glycosides and musilages, known in human nutrition as soluble fiber. The husk is 70% soluble fiber, which can increase tenfold in bulk with addition of water. Most commonly it is sold ground to a near powder and is the ingredient that adds the fiber to some of the high-fiber cereals, breads, and snack bars.

The gel-forming property of psyllium has other uses. For humans, psyllium is recommended for several problems: relief of both diarrhea and constipation, hemorrhoids, diabetes, heart disease, high blood pressure, high cholesterol, inflammatory bowel disease, irritable bowel syndrome, and obesity (reducing hunger cravings). The hydrophilic property and gel formation as well as high dietary fiber content make it an attractive food ingredient.

How psyllium can help with constipation (draws water into the bowel), diarrhea (absorbs excess water in the bowel), and hemorrhoids (softens stool) is obvious, but the exact mechanism of how psyllium affects glucose and insulin is not completely understood. It is thought that psyllium might decrease blood glucose by decreasing the absorption of glucose from food. Whether this is from increasing the rate of transit of the food through the intestinal tract or from affecting the pH of the digesta because it leaves the acidic environment of the stomach more rapidly, which in turns changes the ability of the digestive enzymes to digest starch, needs further investigation. Researchers have found that psyllium can make dietary fat more difficult to digest and can increase the amount of fat lost in the stool when taken in combination with dietary fats such as soybean oil or coconut oil in humans. This effect on fat has never been looked at in horses; however, researchers at Montana State University performed preliminary studies on the effect of psyllium on glucose and insulin in horses.

Given the recent research highlighting the influence of abnormal responses to glucose and insulin from the diet in metabolically challenged horses, like those with equine metabolic syndrome, if there is a feed ingredient that could moderate the glucose response to a meal, it would be incredibly useful in preventing devastating diseases like laminitis. Psyllium appears to be a promising product that may decrease glucose response to a meal and may have a role in treating insulin resistance if it proves effective in horses.

Researchers at Montana State University performed a series of three experiments on the use of psyllium and its effect on the metabolic factors that play into equine metabolic syndrome. They used eight Quarter Horses in the first and 16 in the second and third studies. All of the horses were of normal body condition between 4.5 and 6 (on a scale of 1-9) and ranged in age from 7 to 16 years old. Horses were fed mixed-grass hay at 1.5% of body weight and a commercial whole-grain feed at 0.5% body weight.

In the first study, horses were fed 90 g of psyllium per day (the recommended amount for sand clearance) in the feed for 60 days, and researchers looked at changes in glucose, insulin, leptin, neck circumference, and tailhead fatness. They did not find any differences between before and after in this study in any of the parameters except an increase in neck circumference with the psyllium supplementation, which they could not explain. The reason they may have not had any significant results with this study was because of too much individual variation within the small number of horses. In the follow-up study, researchers used twice as many horses.

In the second study, horses were fed 90, 120, or 250 g of psyllium per day to see what level of supplementation was needed to be effective and to document change after 60 days of supplementation. This was a simpler study because researchers did not look at as many parameters, focusing instead on glucose and insulin. At the end of the 60-day supplementation period, the horses were fasted for 12 hours and then fed a concentrate meal. Blood samples were taken every 30 minutes for the following 6.5 hours. In this study, researchers found that the horses all responded similarly regardless of level of intake of psyllium. They found a lower peak glucose response and average glucose and insulin values in the horses with psyllium supplementation. There was no difference in the insulin peak value or the other parameters such as area under the curve and time to peak.

In the third study, researchers used an intravenous glucose infusion to further investigate the effect of psyllium on glucose and insulin dynamics. This study took place immediately following the second study. First, the horses were fasted 12 hours, then given an intravenous dose of glucose, followed by 30-minute interval sampling of blood for glucose and insulin levels for 240 minutes. In this part of the study, peak glucose response to the glucose infusion was lower than the control. There were no differences seen in insulin or glucose with the other parameters from this test.

Although the results of this study were not overwhelmingly positive for insulin, what researchers found appears to offer a glimmer of hope to owners of insulin-resistant horses. However, while researchers were successful at lowering the glucose and insulin response in these Quarter Horses, they were clinically normal and of normal weight. Even though the use of psyllium is becoming widely recommended by veterinarians, there has not been any published research on the effect of psyllium in obese horses or those diagnosed with insulin resistance. Further, it is not known whether repeated use of psyllium will cause it to lose effectiveness due to potential digestion. While psyllium is a soluble fiber that is indigestible in humans, with the versatile microbial population found in the digestive tract of the horse, there may be an adaptation to the psyllium that will eventually lead to a population of microbes that can digest it.

If the option to try this product is taken, there are a few things to keep in mind when dealing with psyllium. Be sure to store any psyllium product away from moisture because of its high water-loving property. It is best not to let the psyllium get wet until just before feeding because the gelatinous mass that forms can be difficult to swallow. Try not to breathe in the powder when adding it to feed because especially the ground product can cause some severe allergic reactions if inhaled.

Here’s another article on Equinews.com about this topic: Can Psyllium Influence Blood Glucose Level?