Micronutrient Status of Overweight and Obese People After 3 Months of PolyGlycopleX (PGX®) or Psyllium Supplementation: A Randomized Controlled Trial | BMC Nutrition


Over the years, research has consistently shown that a higher dietary fiber intake is correlated with a reduced risk of several chronic diseases, including cardiovascular disease (CVD), cancer, type 2 diabetes, and obesity. . [11]. The health benefits provided by a higher intake of dietary fiber are thought to occur via the following mechanisms: delaying glucose absorption; increased satiety and satiety effect which can reduce food intake and promote weight loss; gut microbe-induced production of short-chain fatty acids, which have immunomodulatory and anti-inflammatory properties; trapping of bile acids and carcinogens; and an increased intake of biologically active compounds, such as phytochemicals and antioxidants [28, 29]. However, it remains unclear how higher fiber intake via supplementation affects micronutrient absorption in the gastrointestinal tract, particularly in overweight and obese people. Therefore, the aim of this study was to determine whether 3-month supplementation with psyllium or PGX® fiber affects the micronutrient status of overweight and obese adults.

Current literature, although limited, suggests that high fiber intake may inhibit or promote bioavailability depending on the nutrient, the absorption mechanism involved, and the composition of the food matrix as a whole. [30]. Factors affecting the bioavailability of vitamins or minerals include how they are absorbed, excreted, stored/distributed; whether sequestered by fat or dispersed in tissues, metabolic processes (catabolic, possibly oxidative losses), increased physiological requirements, or lower absolute total food intake [31, 32]. This may help explain the variability that can occur in serum micronutrient levels. The habitual diet of overweight and obese people is often considered energy-dense and nutrient-poor, so maintaining nutritional sufficiency can potentially be compromised. An emerging theory suggests that nutritional deficiency states in obese people are not more prevalent, as they may naturally consume more food to compensate for the poor nutritional quality of their diet in order to achieve sufficiency. However, due to the satiating effects of fiber, if a therapeutic dose is consumed, less food intake may occur. Therefore, nutrient intake and nutritional status may be affected in the long term, if malabsorption due to the combined effects of obesity on bioavailability and poor diet is already in effect.

This study examined the micronutrients present in serum samples and self-reported food intake data of overweight and obese people at baseline and 3 months after consuming 15g daily of a control supplement (rice flour) , psyllium or PGX® fiber. According to serum values ​​(Table 1 and Table 2), there were no differences between groups in micronutrient status compared to control, both at baseline and after 3 months of fiber supplementation. Self-reported food intake using 3-day food diaries (Table 1) showed that the baseline value for zinc was significantly different in the PGX® group compared to the control group. As this is a reference value, its significance is likely unrelated to increased dietary fiber and could be explained by simple misreporting or poor zinc status in overweight and obese people. [33, 34]. All other micronutrients for self-reported food intake data at baseline showed no significant differences from control at baseline. p

There was no significant difference between the groups in serum micronutrient levels after 3 months of fiber supplementation (Table 2), but there was a notable increase or decrease for some key micronutrients from baseline to 3 months (within groups) (Table 1 and Table 2). Folate, sodium, and potassium all showed changes from baseline, although they were not significant at pp

Although these results may reflect differences or changes in dietary intake (respectively), they may potentially be the result of inaccurate self-reporting. [33]. It is well known that overweight and obese participants frequently underreport food intake in self-reported food diaries. [35], therefore, these results may be due to simple misreporting of the 3-day food diaries completed by the participants, as opposed to any real change. Another possibility of data on reduced nutrient intake after 3 months of dietary fiber supplementation of 15 g per day is due to the satiating effect of dietary fiber. Participants physically consumed less food because they were simply not as hungry, which means that overall recorded dietary intake of macro and micronutrients was reduced. This theory was supported by the significant reductions in energy, fat, carbohydrate, and protein and the significant increase in daily fiber intake in the self-recorded dietary macronutrient intake after fiber supplementation. 3 months (Table 4).

The fact that there were no differences between the groups in serum micronutrients after three months of PGX® or psyllium fiber supplementation is a positive result for the present study. Dietary fiber supplementation is increasingly recognized as an adjunct to weight management programs for overweight and obese people, and potentially complements many existing weight loss programs. However, as with any new treatment, it is essential to eliminate the negative effects that a new method or product may have on patients’ health, in this case their micronutrient status. Recent research promotes the safety and efficacy of the new fiber supplement PGX®, as well as positive effects on metabolic syndrome (MS) and associated risk factors such as cardiovascular disease, blood pressure and blood lipids [13, 27]. However, the effect of PGX® or psyllium fiber on micronutrient status, when used as part of weight loss treatment in overweight and obese people, has not been well reported. studied to date. The micronutrients examined in this study play an essential role in the regulation of biochemical pathways associated with metabolism. Because obesity is a complex and multi-faceted disease, daily intake of 15 g of additional dietary fiber to aid weight loss needed to be ruled out as a possible confounder to achieve a better health outcome for this subpopulation. .

Strengths and limitations

This study is unique in that there has been very little research examining the micronutrient status of overweight and obese people taking high doses of fiber to help with weight loss. Although much remains to be learned about how fiber and micronutrients interact in the digestive system, the results of this study add to the body of knowledge in this area.

One of the limitations of this study was the time frame examined (baseline 3 months only). It is possible that, although no significant difference was found in micronutrient status after 3 months of high fiber supplementation (15g per day), longer term fiber treatment or higher fiber dosages high produced different results. It would be desirable for any future studies in this field to be carried out over a period of more than 3 months as well as to vary the dosage of the dietary fiber supplement. A second limitation of this study was the use of self-reported dietary intakes. With all self-reported nutrition data, potential bias is introduced as overweight and obese populations are most likely to under-report their dietary intake [36]. Although food diaries are a useful tool in examining food intake in weight management trials, fluctuations in folate, zinc, magnesium, sodium, and vitamin C data found in this study may not represent changes in food intake, but rather inconsistent food consumption reports. Third, the fiber dosage itself must be considered. Participants consumed an additional 15 g of fiber each day in supplement form before breakfast, lunch and dinner. If this amount of fiber were to increase in an attempt to maximize or encourage additional weight loss, it could produce more significant effects on serum micronutrient status. Another point to consider for any future study is whether significant results or differences between fiber groups between baseline and 3 months are due to increased PGX® or Psyllium fiber supplementation and not a possible weightloss. A high dietary fiber content promotes satiety, so participants physically consumed less food and fewer kilojoules. Over a longer period, this may have led to greater differences in serum micronutrients. Another limitation was the lack of intention-to-treat analysis, as excluding dropouts from the study may have introduced bias.


As high fiber diets have been associated with deficiencies of calcium, iron, trace metals and certain vitamins in previous studies, it is important to update the body of knowledge to determine possible implications for health of therapeutic doses of fiber. If fiber is to be recommended as a potential adjunct to weight loss treatments for overweight and obese people, it is important to identify all possible limiting factors. The results of this research trial provide further evidence of the physiological and biochemical effects of high intakes (15 g per day) of psyllium or PGX® fiber supplements on the micronutrient status of an overweight or obese individual.


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