Introduction
In recent years, the role of dietary fiber in promoting health and managing weight has gained considerable attention. Increasing evidence from long-term, prospective observational studies suggests that diets containing larger quantities of whole grains and dietary fiber are associated with a reduced risk of type 2 diabetes. While health authorities recommend increasing dietary fiber intake, actual consumption often falls short. This has led to interest in functional fiber preparations, like PolyGlycopleX (PGX), as a means to supplement dietary fiber intake. This article explores the research surrounding PGX, focusing on its impact on weight loss, glycemic control, and overall metabolic health.
Understanding Dietary Fiber and Its Benefits
Dietary fiber, particularly soluble fiber, plays a crucial role in regulating glucose and lipid metabolism. Higher intakes of cereal fiber have been shown to improve insulin sensitivity, while soluble fiber reduces postprandial glycaemia and serum lipids. These benefits have led health organizations to recommend a daily intake of at least 14 g of dietary fiber per 1000 kcal.
Despite widespread awareness of these benefits, most people consume only about half the recommended amount of dietary fiber. Supplementation with functional fiber preparations may be a viable option to bridge this gap. Soluble fibers that develop viscosity in solution appear to offer greater metabolic benefits, with higher viscosity correlating to greater improvements in glucose and lipid metabolism. However, the palatability and acceptability of functional fibers often decrease with increasing viscosity.
PolyGlycopleX (PGX): A Novel Functional Fiber
PolyGlycopleX (PGX) is a novel, highly viscous polysaccharide complex designed to overcome the limitations of traditional functional fibers. It is created through a proprietary process that induces strong interactions between different viscous fibers, resulting in a higher viscosity than any known individual polysaccharide. This allows for smaller doses to be used, potentially increasing acceptability while maintaining efficacy.
PGX is a soluble, highly viscous polysaccharide (functional fiber) that has demonstrated good tolerability in both animal and human studies. It is composed of 87.4% dietary fiber, with 81.8% being soluble. PGX is available in granular form, which can be dissolved in water or sprinkled on food, and in soft-gelatin capsules for easy consumption.
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PGX and Glycemic Control: Evidence from Clinical Trials
Several studies have investigated the effects of PGX on postprandial glycaemia. These studies have shown that PGX has clinically important, dose-related effects on both acute and delayed postprandial glycaemia.
Acute Effects on Glycemia
One study explored the dose-response relationship of PGX granules taken with a white bread meal. The highest dose (7.5 g) reduced the incremental area under the curve (iAUC) by 50%. The study showed a significant linear reduction of postprandial glycaemia with each additional gram of supplement, reducing iAUC by approximately 7%.
Another study examined the timing of a single dose of PGX (5 g) and the effectiveness of different forms (capsules vs. granules). The granular form significantly reduced glycaemia when consumed within 15 minutes of the start of a meal. The most effective reduction in iAUC occurred when the granules were consumed at the start of the meal (0 time), resulting in a 28% reduction. In contrast, PGX capsules did not produce acute lowering of glycaemia, regardless of timing.
Delayed "Second Meal" Effects
Another study determined whether there was a ‘second meal’ effect at breakfast following supplementation with capsule form in the previous evening meal. Doses of 3, 4.5 and 6 g (but not 1.5 g) reduced blood glucose iAUC relative to placebo. The greatest reduction was seen with the largest number of capsules. There was a significant dose-response effect at the second meal, indicating that each extra active capsule reduced the incremental AUC.
Comparison with Other Fiber Preparations
The magnitude of glycaemia reduction achieved with PGX appears comparable to or superior to other commercially available functional fibre preparations. For example, high viscosity guar gum can reduce glycaemia by up to 50% when mixed with a meal. However, guar gum is not effective when viscosity is low. Other fibers, such as psyllium and β-glucans, have shown smaller reductions in postprandial glycaemia compared to PGX.
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PGX and Weight Loss: Clinical Trial Results
Several studies have investigated the effects of PGX on weight loss and body composition.
Long-Term Weight Loss Study
A randomized, double-blind, parallel design study conducted over 52 weeks examined the effects of PGX on weight loss in overweight and obese individuals. Participants were instructed to take 5 g of supplement mixed with water before meals, three times daily. The study compared PGX to psyllium (PSY) and a control group receiving a placebo.
The results showed that weight and BMI were significantly lower in the PGX group at 12 months compared to baseline. Weight was significantly lower compared to the control group at 3 and 6 months in both the PGX and PSY groups, and at 12 months only in the PGX group. Body fat was also significantly lower in the PGX and PSY groups at 6 months, and at 12 months in both groups compared to the control.
The study concluded that PGX was better than PSY at maintaining dietary changes and weight loss over the 12-month intervention period, without changes to exercise. A simple strategy of PGX supplementation may offer an effective solution to long-term weight-loss and management without the need for other nutrient modification.
Impact on Appetite and Satiety
Another study investigated the effects of PGX on appetite and satiety in women consuming a low-calorie diet. Participants consumed a 1000-kcal per day diet for 3 days, supplemented with 5 g of PGX or placebo at each meal.
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The results showed that PGX consumption led to significantly lower mean area under the curve for hunger and prospective consumption. The study concluded that adding 5 g of PGX to meals during consumption of a low-calorie diet reduces subjective ratings of prospective consumption and increases feelings of satiety.
PGX and Metabolic Health: Additional Benefits
Beyond weight loss and glycemic control, PGX may offer other benefits for metabolic health.
Effects on Lipid Profile
One study found that PGX intake caused significant reductions in total and LDL cholesterol. This suggests that PGX may play a role in improving cardiovascular health.
Impact on Insulin Sensitivity
Animal studies have shown that PGX may improve insulin sensitivity. In Zucker diabetic rats, PGX supplementation was associated with lower serum insulin concentrations and improved insulin sensitivity scores.
Safety and Tolerability of PGX
PGX has been shown to be safe and well-tolerated in both animal and human studies. Genotoxicity studies have shown no mutagenic effects. While some individuals may experience mild to moderate gastrointestinal symptoms, PGX is generally well-tolerated.
PGX in Animal Models of Diabetes
Studies in Zucker diabetic rats (ZDFs) have explored the potential of PGX to prevent or inhibit the early development of metabolic syndrome. These studies have shown that PGX can slow the rate of weight gain, reduce food intake, and improve glycemic control in young ZDFs.
Effects on Body Weight and Food Intake
Rats fed a PGX-containing diet gained weight at a significantly slower rate than rats fed cellulose- or inulin-containing diets. Food intake was also significantly lower for PGX-treated animals.
Impact on Glycemic Control
Under non-fasted conditions, PGX-treated rats had lower blood glucose compared to rats in the other two groups. PGX supplementation also improved insulin sensitivity in these animals.
Limitations and Future Research
While the research on PGX is promising, it is important to acknowledge certain limitations. Some studies have small sample sizes and are funded by a single manufacturer. More research is needed to confirm the long-term effects of PGX on weight loss and metabolic health. Future studies should also explore the mechanisms by which PGX exerts its beneficial effects.