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The effects of psyllium on lipoproteins in type II diabetic patients

Abstract

We examined the effects of 2 months of psyllium treatment in optimizing metabolic control and lipoprotein profile, and its postprandial effects on lipids in type II diabetes. We recruited 40 type II diabetic patients who were on sulfonylureas and a controlled diet, sequentially assigning them to psyllium treatment (G1) or to a control group (G2) treated with dietary measures alone. After 2 months of treatment, body mass index, waist circumference, HbA1c (hemoglobin A1c) and fasting plasma glucose levels had significantly decreased in both groups. There were no postprandial differences in the lipoprotein profile between the two groups. Triglycerides were significantly lower in G1, but not in G2. Our study contributes toward elucidating the effects of psyllium on serum lipids, and suggests that psyllium treatment may help in reducing triglycerides (a known risk factor for cardiovascular disease) in type II diabetic patients.

Introduction

In addition to pharmacological treatments, dietary measures (in particular, the use of fibers) have recently become important in the treatment of diabetes. Soluble fibers render food absorption slower, and their mass effect accelerates the passage of food through the intestinal tract. There are different opinions in the literature regarding this issue; however, some authors say that a diet rich in fiber could optimize metabolic control (Sierra et al., 2002), whereas others believe that fiber alone is unable to achieve this effect (Jarjis et al., 1984).

The second important issue concerns the use of fiber for reducing cholesterol. Several, but not all, studies (Neal and Balm, 1990; Van Rosendaal et al., 2004) have found that psyllium supplementation significantly lowered total and low-density lipoprotein (LDL) cholesterol concentrations in individuals with hypercholesterolemia (Anderson et al., 2000) and in type II diabetic patients (Rodriguez-Moran et al., 1998; Sierra et al., 2002). Further research is needed to clarify the effects of psyllium on serum lipids.

This study examined the effects of a 2-month psyllium treatment in optimizing metabolic control and lipoprotein profile, and its postprandial effects on lipids, in type II diabetic patients.

Patients and methods

A total of 40 type II diabetic patients were recruited for the study. All patients required treatment with sulfonylureas and a controlled diet. None were taking any drugs that directly affected lipoproteins. These patients had no history of gastrointestinal and other major diseases.

Their daily energy intake during the study was 1800 Kcal and consisted of carbohydrates (52%), lipids (30%), proteins (18%) and fiber (26 g). Patients were sequentially assigned either to treatment with psyllium 3.5 g (one dose of sugar-free Agiofibre, Plantago ovata, Madaus SA, Barcelona, Spain), thrice a day, before breakfast, lunch and dinner (G1), or to a control group (G2) treated with the prescribed diet alone. Patients treated with psyllium were instructed to mix each sachet of fiber in 250 ml of water, followed by 50 ml water to rinse the glass and to drink the mixture before each meal.

All patients were followed up for 8 weeks. At baseline (T0), and again at the end of the study (T1), they were tested for body weight, body mass index, waist circumference, blood pressure, glycemia, HbA1c (hemoglobin A1c), lipids and lipoproteins. At T0 and T1, all patients in both groups were given a test meal consisting of yogurt (200 g) and two packets of wholemeal crackers (40 g of carbohydrates), to which patients in G1 added 3.5 g of psyllium. Levels of total cholesterol, high-density lipoprotein cholesterol and triglycerides were measured in all patients immediately before (fasting levels) and 120 min (T120) after the test meal.

Glycemia and glycated hemoglobin were tested in the central laboratory at the Padova General Hospital to standardize the results for all patients. Venous glycemia was measured using the glucose–oxidase method and HbA1c by high-performance liquid chromatography (Jaynes et al., 1985). Cholesterol and triglycerides were measured using the enzymatic method (Wahlefeld, 1976). High-density lipoprotein cholesterol was assayed after precipitating lipoproteins containing apoB (apolipoprotein B) with polyanions (Lipid Research Clinics Program, 1982). LDL cholesterol was calculated using the Friedewald formula, except in cases for whom triglycerides were higher than 300 mg/dl (Friedewald et al., 1972). The study protocol was approved by the local ethics committee. Written informed consent was obtained from all participants before they joined the study.

Statistical analyses

The SPSS software, 16.0 (Chicago, IL, USA) was used for the statistical analyses. Data were expressed as mean±s.d. Student's t-test for paired data was used to compare the data obtained at baseline and at the end of the study, and before and after the test meal, within each group of patients. The t-test for unpaired data was used to assess differences between the two groups. A value of P<0.05 was considered significant.

Results

On the basis of reports obtained from our patients, psyllium treatment was readily acceptable and well tolerated as a supplement to a standard diet for diabetes. No adverse events were recorded.

The treatment and control groups, G1 and G2, did not differ significantly at baseline in terms of age, body weight, body mass index, waist circumference, blood pressure, glyco-metabolic parameters or lipoproteins (Table 1). No significant differences were observed between the two groups with regard to sulfonylurea dosage and daily intake.

Table 1 Anthropometric and glyco-metabolic parameters in both groups before (T0) and after 8 weeks of psyllium treatment (T1)

After 8 weeks of psyllium treatment, body mass index, waist circumference, HbA1c and fasting plasma glucose levels were significantly lower in both groups, whereas blood pressure was significantly lower in G1, but not in G2 (Table 1).

As for lipoprotein profile, triglycerides were significantly lower after 8 weeks of psyllium treatment in G1, whereas no such reduction was seen in G2 (Table 2).

Table 2 Total, HDL, LDL cholesterol and triglycerides in patients treated with psyllium (G1) and controls (G2) at baseline (T0) and at the end of the study (T1), that is, before the first (T0) and second meals (T1), and after the first and second test meals (T120)

The test meal assessment showed no differences between the two groups; after the meal, total and LDL cholesterol decreased significantly, whereas triglycerides increased significantly and high-density lipoprotein cholesterol remained the same (Table 2).

Discussion

The palatability of psyllium fiber makes it acceptable and easier to eat than vegetables with an equivalent fiber content in the diet. Psyllium could be useful in improving compliance in patients who are prescribed the ingestion of large amounts of fibers.

The improvement in glyco-metabolic parameters noted in both our groups probably relates to a good compliance with the diet because of all patients frequently attending the dietetic clinic (twice in 8 weeks).

An earlier study (Clark et al., 2006) using a test meal found no evidence of any postprandial improvement in free fatty acids with psyllium treatment, but provided no data on lipoproteins. In our study, psyllium did not seem to reduce postprandial cholesterol and triglyceride levels.

A meta-analysis conducted on eight studies showed that psyllium ingestion improved cholesterol and total cholesterol LDL levels in patients who were on a low-fat diet (Anderson et al., 2000). Another study (Neal and Balm, 1990) found a significant reduction in total cholesterol and LDL cholesterol in men, but not in women. Most of the studies on this issue were carried out on hypercholesterolemic patients and this could explain their results. Our patients were all normocholesterolemic and this might have influenced our findings. In fact, we recorded a mild decrease in total and LDL cholesterol after 2 months in both our treatment group and in our control group, with no significant difference between the two. On the other hand, triglycerides were only significantly lower in G1, after 8 weeks of psyllium treatment. Further studies are required in type II diabetic patients to confirm these findings, which might mean that psyllium treatment has different effects on different populations and different individuals; hence, it would need to be tailored (Sierra et al., 2002). It would seem to be necessary to continue the treatment for at least 2 months to obtain effective results.

Our study helps to document the effects of psyllium on serum lipids in different groups of individuals and suggests that psyllium may be useful in reducing triglycerides (a known risk factor for cardiovascular disease) in patients with type II diabetes.

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Correspondence to G Sartore.

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Sartore, G., Reitano, R., Barison, A. et al. The effects of psyllium on lipoproteins in type II diabetic patients. Eur J Clin Nutr 63, 1269–1271 (2009). https://doi.org/10.1038/ejcn.2009.60

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Keywords

  • type 2 diabetes
  • lipoproteins
  • psyllium
  • dietary fiber

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