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Fenufibers

Fenufibers , a registered trademark of Sabinsa Corporation, is the fiber-rich fraction obtained from Fenugreek seeds. Fenugreek (Trigonella foenum-graecum, Family: Leguminosae) is an annual herbaceous plant, 30 to 60 cm in height. The herb is native to North Africa and countries bordering the eastern Mediterranean and is widely cultivated in India. The seeds of Fenugreek have been used as a spice since ancient times and are commonly used as a condiment in Indian homes.

The medicinal uses of Fenugreek seeds have been known since ancient times. In the Greek and Latin pharmacopoeias, Fenugreek seeds are described as posessing antidiabetic properties. In recent times, several preclinical and clinical studies have confirmed the anti-diabetic action of Fenugreek seeds, particularly, the fiber-rich, defatted portion of the seeds. The hypocholesterolemic activity, a complication of diabetes, of the defatted portions of the seeds has also been demonstrated. In addition, fenugreek seeds are assumed to have nutritive and restorative properties and they also stimulate the digestive process.

Gel fiber present in Fenugreek seeds, reduces the rate of glucose absorption and may also delay gastric emptying, thereby preventing the rise in blood sugar levels following a meal. Several studies provide direct and indirect evidence that subjects become sensitive to insulin after adaptation to high fiber diets.

Chemistry of Fenugreek Seeds

The chemical composition of Fenugreek seeds and defatted Fenugreek seeds is given in Table 1. These seeds are a rich source of fiber and protein. The fiber may be further classed as gum (gel fiber) and neutral detergent fiber. The protein fraction contains the amino acid 4-hydroxyisoleucine, which has been proven to stimulate insulin production. Whole Fenugreek seeds also contain 4.8% saponins. Fenugreek seed saponins are of steroidal nature (type furostanol saponins) with diosgenin as the principal steroidal saponin.

Table 1: Proximate Composition (%) of Fenugreek Seeds

Component Whole Seeds Defatted Seeds
Moisture 9.0 9.0
Ash 3.0 3.5
Lipids 8.0 Negligible
Protein 26.0 28.3
Starch 6.0 6.5
Total Fiber 48.0 51.7
Gum 20.0 19.2
Neutral Detergent Fiber 28.0 32.5

Dietary Fiber and Its Role in Health

Dietary fiber consists of all palatable foods that are consumed by single-stomach animals (including humans) and that remain largely undigested upon reaching the large intestine. Many fibers, such as cellulose, hemicellulose, and pectin, are carbohydrates. Humans do not posess the enzyme necessary for splitting the bonds linking the individual fiber units.

Dietary fiber is the fiber that remains in the colon following digestion whereas crude fiber is the fiber that withstands laboratory analysis with dilute acids and alkalis. For every gram of crude fiber, there are roughly two to three grams of dietary fiber. Crude fiber is composed of cellulose, which is a complex molecule composed of glucose molecules. Related to cellulose is hemicellulose - one type of hemicellulose is pectin. Lignin , another form of crude fiber, is not a carbohydrate per se, but it is of plant origin and is also indigestible. Another fiber of importance is guar gum, which prevents the rapid uptake of glucose in the small intestine, slows gastric emptying, aids in blood sugar retention in diabetic patients and may also be effective in the treatment of hypercholesterolemia.

In Fenugreek seeds, the gum (gel fiber) fraction consists of galactomannan which is made up of galactose and mannose units. The gum also resembles guar gum in structure and is very viscous (15 centipoise) when dissoved in water. The neutral detergent fiber is made up of indigestible carbohydrates such as cellulose, hemicellulose and lignin. According to Ribes et al (1984), the defatted fraction of fenugreek seeds contains 50.2% fiber and consists of 17.7% gum, 22% hemicellulose, 8.3% cellulose and 2.2% lignin.

The digestibility of Fenufibers was compared to fiber-containing products, Wheat Chex, Metamucil, Oat Bran, and Wheat Bran. Fenufibers is similar to the commonly used fiber-containing products in terms of digestibility. Fenufibers was only 39% digested in 48 hours, with little change thereafter. (Sabinsa sponsored study performed at the University of Georgia, reported in : Al-Khaldi et al. (1999)). Low digestibility indicates better fiber functionality, with lower incidence of gastrointestinal disturbances such as bloating due to fermentation by gastrointestinal microflora.

Biological Properties of Fenufibers

Both pre-clinical and clinical studies performed in recent years have demonstrated that the antidiabetic action of Trigonella can be associated with the defatted fiber-rich seed material. Fenugreek seeds exert both hypoglycemic and hypolipidemic effects.

Pre-clinical Studies

A subfraction of the defatted seed material, rich in fibers (79.6%) and constituted by the testa and endosperm was shown to have potent hypoglycemic action. Chronic administration of this fraction for 21 days (with two daily meals and in conjunction with insulin therapy) in alloxan-induced diabetic dogs resulted in a decrease of hyperglycemia and glycosuria. Simultaneously, the high plasma glucagon and somatostatin levels were reduced with a decrease in the hyperglycemic response to oral glucose tolerance. In contrast, the subfraction ‘b’ constituted by the cotyledons and the axes and rich in saponins and proteins had no effect on hyperglycemia or pancreatic hormone levels when chronically administered to diabetic dog. It was thereby concluded that the anti-diabetic action of Fenugreek seeds is contained within the fiber-rich testa and endosperm (Ribes et al, 1986).

When streptozotocin diabetic rats were subjected to diets containing 20% fenugreek seeds for a period of ten weeks, there was no improvement in the diabetic state. However, diabetic animals pretreated for five weeks with fenugreek and followed by six weeks of feeding with the same diet, showed a general improvement in their clinical status. Hyperglycemia, and serum levels of free fatty acid levels, cholesterol and triglycerides were reduced (Amin Riyad).

In another study, the researchers examined the comparative hypocholesterolemic effect of various fractions of Fenugreek seed in rats fed a high cholesterol diet. Among the Fenugreek fractions, the alkaloid fraction and the lipid extract were found to have no hypocholesterolemic activity, while the defatted fractions, gum isolate and crude saponins showed hypocholesterolemic activity (Sharma et al, 1986). Additionally, substitution of the hypercholesterolemic diet with Fenugreek seeds significantly reduced elevated cholesterol levels without affecting triglyceride levels. The authors of this study concluded that Fenugreek seeds are effective in lowering elevated serum choleserol levels, as well as preventing a rise in serum cholesterol when fed along with a hypercholesterolemic diet. The mucilaginous component of Fenugreek seed fibers was most effective in lowering serum cholesterol. Since high cholesterol levels are known to be associated with diabetes, it was proposed that Fenugreek seeds or its defatted portion may be useful in the treatment of diabetes and the associated hypercholesterolemia.

Clinical studies:

A. Type I Diabetes Mellitus
Recent studies have proven the efficacy of fenugreek as a hypoglycemic agent in humans. In a double blind study, ten Type I diabetics were given 100 g/day, fenugreek seeds (powdered, defatted and debittered) with meals, for ten days. Fasting glucose levels decreased by 30%, glucose tolerance improved and sugar excretion dropped by 54%. (Figure 1). There was no corresponding increase in insulin levels. (Sharma, 1990)

fig1.gif (5822 bytes)
Figure 1

In this study, the hypocholesterolemic effect of the defatted portion of the seeds were also demonstrated. As compared to the control group, serum cholesterol, LDL and VLDL cholesterol and triglyceride levels were significantly reduced in the treated group.


Figure 2

B.Type II Diabetes Mellitus
Administration of 25g of defatted Fenugreek seed for a period of three weeks significantly improved the performance of Type II diabetic patients in the glucose tolerance test (Figure 3). In addition, the 24 hr urine sugar content and serum cholesterol levels were significantly reduced (P<0.05) following therapy. Some of the patients under treatment also reduced their insulin requirements from 56 units/day to 20 units/day.


Figure 3

Another study investigated the cholesterol lowering effect of fenugreek in patients with high cholesterol.
Methods: Patients were divided into 3 groups of 6.
Group I.- 50 g Placebo*
Group II.- 25 g Placebo* + 25 g Fenugreek powder
Group III.- 50 g Fenugreek powder

Blood samples were collected after overnight fasting on days 0, 10, and 20 during the test period and estimated for lipid profile.

(The Placebo powder was a mixture of rice powder & Bengal gram powder in equal measures.)

Groups II and Group III serum cholesterol, triglycerides, LDL and
VLDL significantly decreased compared to Group I. Serum HDL levels had a tendency to decrease on day 10 in Groups II and III, but they rose again to near normal levels on day 20.


Figure 4

The results of similar double blind studies on sixty Type II diabetics, treated with 25 g fenugreek seed powder per day, were equally promising in reducing serum cholesterol and triglyceride levels (Figure 5) (Sharma, 1996). This effect was sustained and lasting, and the inclusion of Fenugreek seed powder produced no undesirable side effects. Within the duration of this study, there were no new incidences of heart problems such as angina and myocardial infarction, and no increases in blood pressure were observed. It was therefore concluded that Fenugreek can be considered to be a potentially useful dietary supplement to prevent hyperlipidemia and atherosclerosis in Type II diabetic patients.


Figure 5

Mechanism of blood sugar lowering action of Fenufibers

A high-fiber diet is associated with the improved ability to handle blood sugar. In the presence of a high fiber diet, the cells are more sensitive to insulin and an increase in the number of insulin receptor sites occurs or alternatively, there is a stimulation of the cell’s ability to burn glucose.  Certain dietary fibers reduce the rate of food passage through the intestine and into the bloodstream, thereby helping to control the increase in postprandial blood sugar levels. High-fiber diets are associated with less glycosuria (sugar in urine), lower fasting blood sugar levels, and lower insulin requirements. Water-retaining fibers, especially the mucilaginous compounds, such as the gel fiber present in Fenugreek seeds, reduce the rate of glucose absorption and may also delay gastric emptying thereby preventing the rise in blood sugar levels following a meal. In addition to its hypoglycemic effects, the hypolipidemic effect of Fenugreek fibers have also been documented. Therefore, Fenugreek fibers have a dual role to play in the management of diabetes.

1. Hypoglycemic Effect

The gel fiber fraction of Fenugreek seeds are thought to be responsible for the hyoglycemic effect. In animal studies, Fenugreek fiber has been shown to delay the rate of gastric emptying and slow carbohydrate absorption. Based on the results of clinical studies, Sharma (1986) proposed that Fenugreek fiber enriched diets cause a delay in the absorption of carbohydrate from the diet, thereby reducing insulin requirements. Fenugreek affects blood glucose by reducing glucose uptake from the intestine. The delay in gastric emptying and carbohydrate absorption may be attributed to the gel fraction which increases the viscosity of the digesta.

It was speculated that the reduction in insulin requirement seen in some of the Type II diabetic patients may be due to the Fenugreek fibers improving peripheral insulin sensitivity. Frequently, in Type II patients, insulin secrection is normal or even higher than normal but the reduced number of insulin receptor sites on body cell membranes in these patients leads to insensitivity to insulin, i.e., the cells do not respond to insulin. It has been shown in the past that in the presence of a high fiber diet, an increase in the number of insulin receptor sites occurs and the cells become more sensitive to the action of insulin.

In the clinical studies, a reduction in urinary excretion of glucose was also observed, indicating greater retention of dietary carbohydrate in the body. As carbohydrate-rich diets are known to improve glucose tolerance, increased carbohydrate retention may be beneficial to diabetics (Sharma et al., 1990). Clinical studies also indicate that diabetics become sensitive to insulin after adaptation to high fiber diets (Reiser, 1979).

Hypocholesterolemic effect of fenugreek fiber:

It has been shown that the gel fraction of fenugreek fiber, contains galactomannans which increase the viscosity of the digesta thereby reducing serum cholesterol levels. This is achieved through the inhibition of cholesterol absorption from the small intestine and also the inhibition of bile acid reabsorption from the terminal ileum. If bile acids are excreted, the balance tilts towards their synthesis in the liver from cholesterol, thereby lowering serum cholesterol levels (Gee, et al. (1983). Other studies have shown that galactomannans influence gastrointestinal hormone secretions, thereby increasing the activity of a number of key enzymes in carbohydrate and lipid metabolism.

In addition to its high fiber content, Fenufiber also contains a biologically significant level of saponins. Saponins are known to have hypocholesterolemic effects. When saponins are ingested in isolated or food borne forms, they form large mixed micelles with bile salts and significantly reduce serum cholesterol, by increasing fecal excretion of bile salts, therby inhibiting cholesterol absorption.

References

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