Cholesterol- and Glucose-Lowering Effects of Fenugreek

By Susan T. Marcolina, MD, FACP

The role of diet has long been recognized as the cornerstone of therapy for the treatment of both diabetes and hypercholesterolemia, well-known risk factors for coronary artery disease, the leading cause of death worldwide in both men and women. Recent studies have elucidated the benefits of dietary fiber in both of these chronic medical conditions.1 Pereira et al showed that for each 10 g/d of dietary fiber consumption, there was a 14% lower risk of coronary disease events and a 27% risk reduction of fatal coronary events.2 The seeds of the herb fenugreek, Trigonella foenum graecum L., a condiment regularly used in East Indian, Mediterranean, and African cuisines, are a rich source of fiber and as such may be a useful adjunct in dietary management of these conditions.

Botanical Characteristics

Fenugreek is an annual leguminous plant extensively grown in India, Egypt, and Middle Eastern and Mediterranean countries. Its leaves are generally used as vegetables while its seeds, which mature in long pods, are ground and used as culinary condiments and for medicinal uses.3,4

Fenugreek is one of the oldest medicinal plants. In ancient Egypt, fenugreek was used in embalming processes, for incense, and as a supplement added to wheat and corn flour for bread-making. The first recorded use of fenugreek in the Ebers papyri, which have been dated to 1500 BCE, was for labor induction during childbirth. Latin and Greek pharmacopoeias describe the antidiabetic effects of fenugreek seeds.5,6

Widespread medicinal use has been somewhat limited by the pungent odor and bitter taste attributed to the presence of sotolone, a volatile chemical concentrated in the testa, the hard outer coat of the seed. As a result, solvent or physical extraction methods to isolate the biologically active compounds in a debittered, defatted product have been developed to mitigate this feature.5

Chemical Composition

Table 1 gives the nutritional composition of fenugreek seeds compared to other legumes.7 The dietary fiber of fenugreek seeds is dispersed throughout the seed coat and the endosperm (nutritive tissue of the plant seed). Analyses of fenugreek seed samples grown throughout the world have shown that dietary fiber constitutes up to 48% of the dry weight.8,9 Chemical analysis of the fiber content of fenugreek revealed high concentrations of hydrocolloids or water-soluble gums called galactomannans, which have a unique structure of mannose and galactose monomers grafted in a 1:1 ratio. This accounts for its high water solubility in comparison to the galactomannans contained in other legumes.10

Table 1
Comparative nutritional composition* of several legumes7

Mechanism of Action

The glucose-lowering effects of fenugreek have been attributed to several mechanisms. Sauvaire et al showed in vitro that the amino acid, 4-hydroxyisoleucine, unique to the Trigonella species, increased glucose-induced insulin release in human and rat pancreatic islet cells.11 Amin et al demonstrated in human studies that fenugreek’s hypoglycemic effects were due to stimulation of glucose-dependent insulin secretion from pancreatic beta cells, as well as by inhibition of the activities of alpha amylase and sucrase, intestinal enzymes involved in carbohydrate digestion.12 The viscous galactomannan gel fraction of fenugreek appears to be an effective hypoglycemic agent and significantly inhibited glucose absorption from perfused rat small intestine by decreasing digestate transit time. These soluble dietary fibers are active in both ground whole seeds and as a purified galactomannan isolate.13,14 In addition, this gel fraction inhibits cholesterol absorption from the small intestine and bile acid resorption from the terminal ileum, thus increasing bile acid excretion. Fenugreek also contains saponins which, when ingested, form micellar complexes with bile salts, thereby minimizing their absorption and increasing fecal excretion.6

Pre-Clinical Animal Studies

Madar and Shomer isolated galactomannan from fenugreek seeds and demonstrated that this fraction decreased digestion and absorption of starch and uptake of bile salts by the rat intestinal mucosa.10 Similarly, Evans et al found that addition of fenugreek galactomannans, in contrast to guar gum and locust bean gum galactomannans, to the diet of rats lowered liver and plasma cholesterol levels and the rate of hepatic cholesterol synthesis.13 Ribes et al demonstrated that the galactomannan extract from fenugreek seeds decreased hyperglycemia and glucosuria in alloxan-induced diabetic dogs.15 Stark showed that defatted fenugreek seeds, a gum isolate rich in dietary fibers, and a crude saponin extract each decreased cholesterol levels in rats to the same extent as did whole ground fenugreek seeds.16

Human Studies—Antidiabetic Effects

Gupta et al conducted a randomized, controlled, double-blind trial to evaluate the effect of fenugreek seeds on glycemic control in 25 patients with newly diagnosed Type 2 diabetes.17 The patients received either 1 g daily of debittered fenugreek seeds or dietary discretion and exercise for two months. After the study period, although mean fasting glucose levels and mean glucose tolerance test values were reduced in both groups, there were no significant intergroup differences. Despite the fact that study design and methods were not well described, it suggested that both fenugreek and diet/exercise improve glycemic control.

Two randomized, controlled, crossover studies in patients with Type 2 diabetes were conducted by Sharma and Raghuram.18 Fifteen patients in the first study had their diabetic drugs decreased 20% and were stabilized on diet and medication for a week prior to beginning the study. Seven of the 15 subjects ate meals with 100 g of defatted fenugreek seed powder divided into two equal daily doses for 10 days. They then crossed over to no fenugreek supplementation without a washout for the next 10 days. The other eight patients did the converse.

The second study had a similar design but only five patients participated, three of them receiving the fenugreek supplementation first. Significant improvements in mean fasting blood glucose levels, oral glucose tolerance tests, and 24-hour urinary glucose excretion were seen in the fenugreek-treated patients. In addition, these patients reported improvements in polyuria and polydipsia symptoms.

Human Studies— Hypocholesterolemic Effects

Sharma et al conducted a study of 10 healthy, non-obese subjects with serum cholesterol levels above 240 mg/dL.19 Each subject was assigned to receive a control diet and an experimental diet, which was supplemented with defatted fenugreek seed powder over two successive time periods, each lasting 20 days. During the experimental period, 100 g of defatted fenugreek powder was divided into two equal parts and incorporated into chapatti (unleavened bread) for lunch and dinner. For the control period, the chapatti contained no fenugreek. Both diets were isocaloric and nutritionally similar except for the higher dietary fiber content of the experimental group. Physical activity was stable during the study. After ingestion of the fenugreek diet, eight of the 10 subjects experienced a 25% reduction in serum cholesterol. The fenugreek significantly reduced the LDL and VLDL fractions without altering the HDL levels. After 20 days of the control diet, the serum cholesterol and triglyceride levels were unchanged from baseline.

Sharma et al performed a long-term study of 60 diabetic patients, 40 of whom were taking one or more antidiabetic medications.20 Each subject was initially placed on a control diet for seven days, followed by placement on an experimental diet for 24 weeks. During this experimental diet, 25 g of the fenugreek seed powder was divided into two equal parts and consumed in soup 15 minutes prior to lunch and dinner. Blood tests were drawn at the end of the control period and at weeks 4, 8, 12, and 24 of the experimental period. After 24 weeks of fenugreek, the mean total cholesterol level decreased 14% from baseline, a highly statistically significant result (P < 0.001). The decrease was primarily in LDL, triglyceride, and VLDL fractions, with HDL levels showing a small increase that was not statistically significant.

Dosage

Fenugreek seeds, called methi, can be obtained in markets that sell East Indian foods. One tablespoon is approximately 6 g of seed. It can be ground into powder and incorporated into breads, curry dishes, and other foods to augment their nutritional value. The typical intake range for diabetes or cholesterol lowering is 5-30 g of the powdered seeds with each meal.21 The German E Commission monograph recommends a daily intake of 6 g. Due to the bitter taste of the fenugreek seeds, debittered seeds or encapsulated extract products are preferred.4

The galactomannan extracts, which contain the active principals, can be taken in lower doses than the seeds. One such product, FenuLife, manufactured by Acatris, Inc., is a patented dietary source of odorless galactomannan fiber extract from fenugreek. It is standardized to contain at least 85% total fiber, 75% of which is the soluble galactomannan hydrocolloid. Table 2 lists some products on the market which contain this extract.22

Table 2
Products containing standardized fenugreek galactomannan extract

Adverse Effects

Ingestion of more than 100 g of fenugreek seeds daily can cause intestinal cramping, diarrhea, and nausea. Study patients taking fenugreek initially reported mild gastrointestinal complaints consisting of diarrhea and excess flatus, which resolved within 3-4 days.23

Fenugreek should not be used in pregnant females because it causes uterine tonic activity and can be an abortifacient.5 It is folklore practice, however, to use fenugreek to augment lactation in nursing women. Schanler et al support the use of fenugreek for this purpose in the medical literature.24

Korman described a case of pseudo maple syrup urine disease (MSUD) in a healthy full-term male infant, secondary to fenugreek ingestion by his mother in the form of a spicy paste called "hilbe" during the early hours of labor. The infant was noted to have the characteristic urinary odor several hours after birth. However, clinical examination was normal and plasma amino acid analysis revealed normal levels of branched chain amino acids without detection of alloisoleucine, a derivative of isoleucine, which is elevated specifically in MSUD.5

Patients on anticoagulants should avoid taking fenugreek as it contains coumarin-like substances that may potentiate their effects.25 Patients on oral hypoglycemics or insulin should have blood sugars closely monitored as fenugreek can significantly potentiate their glucose-lowering effects.

Patients with a documented peanut allergy should not take fenugreek due to the possibility of cross reactivity. Rare allergic reactions to fenugreek have been described and those patients who experienced such a reaction should avoid its use.26

Conclusion

Legumes are functional foods that promote good health because they are low in sodium and an excellent source of low-glycemic carbohydrate, dietary fiber, protein, and minerals. Animal and human clinical research thus far suggests fenugreek has the potential to be a useful dietary intervention. However, more studies involving larger numbers of patients with fenugreek products standardized to specific galactomannan content must be performed to strengthen the evidence for its utility as a routine dietary intervention. Its use is contraindicated in persons who are pregnant, have a documented peanut allergy, or are taking anticoagulant medicines. Blood sugars should be carefully monitored in patients on insulin or oral hypoglycemics.

Recommendation

Fenugreek in various forms, including whole ground seeds, defatted seed powder, and standardized galactomannan extracts, can be safely consumed in divided daily doses of 5-30 g to achieve glucose and cholesterol lowering. Fenugreek is an inexpensive, low-risk, food-based addition to the dietary armamentarium that may be useful for certain patients with diabetes and hypercholesterolemia.

Dr. Marcolina is a board-certified internist and geriatrician in Issaquah, WA.

References

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19. Sharma RD, et al. Hypolipidemic effect of fenugreek seeds. A clinical study. Phytotherapy Res 1991;5:145-147.

20. Sharma RD, et al. Hypolipidaemic effect of fenugreek seeds: A chronic study in non-insulin dependent diabetic patients. Phytotherapy Res 1996;10:332-334.

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23. Sharma RD, et al. Toxicological evaluation of fenugreek seeds: A long term feeding experiment in diabetic patients. Phytotherapy Res 1996;10:519-520.

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25. Miller LG, Murray WJ, eds. Herbal Medicinals: A Clinician’s Guide. New York: Pharmaceutical Products Press; 1999:313-315.

26. Ohnuma N, et al. Anaphylaxis to curry powder. Allergy 1998;53:452-454.