People who are actively concerned about their health have been making lifestyle changes, including decreasing or eliminating their consumption of cholesterol-rich foods, but information about nutritional factors that affect cholesterol levels is obscure to many. Understanding the role of cholesterol in fat assimilation is the key to understanding recent research.
Physiological roles of cholesterol
Cholesterol, a steroid alcohol, is synthesized in most body tissues and is an important structural element of all cell membranes. It emulsifies fats, thereby enabling their digestion and assimilation.
Cholesterol is a major component of bile, a fluid secreted by the liver that emulsifies crude fats in the small intestine so that they can be broken down into fatty acids, glycerol, and triglycerides (all known as lipids) to be absorbed into the bloodstream. The blood that drains the small intestine passes through the liver, where cholesterol forms water-soluble complexes called lipoproteins, with the lipids and proteins in the blood.
Tests of total serum cholesterol (TSC) are conducted after a fast of at least twelve hours. As the fast progresses, lipids are absorbed from the blood, and the proportion of cholesterol and protein in the lipoproteins being formed in the liver becomes increasingly great. What begins as predominantly very-low-density lipoproteins (VLDL) gives way first to low-density lipoproteins (LDL) and eventually to high-density lipoproteins (HDL). In a TSC test, a predominance of HDL in the blood indicates relatively efficient fat metabolism whereas a large proportion of LDL, VLDL, or free triglycerides indicates inefficient fat metabolism.
Herbs that improve lipid profiles
Garlic (Allium sativum)
Five studies of patients with high TSC levels (more than 200 mg/dL) showed that eating about half a clove of garlic per day can decrease TSC levels by about 9% (1).
Forty-two volunteers with elevated TSC levels received either 900 mg/day of a dried garlic preparation or a placebo. After twelve weeks, TSC dropped by 6% and LDL by 11% in the first group. The placebo group showed no change in either TSC or LDL (2).
Two hundred sixty-one patients with elevated TSC and/or triglycerides randomly received either 800 mg/day of garlic powder or a placebo. After sixteen weeks, mean TSC levels in the experimental group decreased by 12% and mean triglyceride levels by 17%. Patients with initial TSC levels of 250 to 300 mg/dL showed the greatest improvement (3).
Psyllium (Plantago psyllium or P. ovata)
An eight-week trial (preceded by a baseline period) was conducted with 118 people twenty-one to seventy years old who had TSC levels of 220 mg/dL or above. Thirty-seven participants followed a high-fat diet, and eighty-one followed a low-fat diet. Either 5.1 g of psyllium or a placebo was administered randomly to all participants twice a day. Psyllium recipients in the high-fat diet group decreased TSC and LDL levels by 5.8% and 7.2%, respectively; in the low-fat diet group, respective reductions were 4.2% and 6.4% (6).
Fenugreek (Trigonella foenum-graecum)
When patients with elevated TSC levels ingested an experimental daily diet containing 100 g of debittered, powdered fenugreek seeds for twenty days, TSC decreased by 24%, LDL and VLDL by 32%, and triglycerides by 37% without significant reduction in HDL (4).
Administration of defatted fenugreek seed, in daily doses of 1.5 to 2 g/kg, to both normal and diabetic dogs reduced blood levels during fasting and after meals of TSC and triglycerides while increasing HDL levels (5).
(1) Warshafsky, S., R. S. Kamer, and S. L. Sivak. Ann. Intern. Med. 1993, 119: 599-605.
(2) Jain, A. K., et al. Am. J. Med. 1993, 94: 632-635.
(3) Mader, F. H. Arzneim. Forsch. 1990, 40: 1111-1116.
(4) Sharma, R. D., et al. Phytother. Res. 1991, 5(3):145-147.
(5) Ribes, G., et al. Proc. Soc. Exp. Biol. Med. 1986, 182(2):159-166.
(6) Sprecher, D. L., et al. Ann. Intern. Med. 1993, 119(7):545-554.
Ginkgo: Circulatory Therapy
The ginkgo tree (Ginkgo biloba) has been in existence for some 200 million years. Ginkgo became extinct over much of its range during the most recent ice age, but in China it survived and gradually spread to other parts of Asia. It was introduced in 1784 to North America, where it is now widely grown as an ornamental tree, popular because of its high tolerance to salt, heat, a wide range of soil pH, and air pollution, and because of its resistance to pests and disease.
The ginkgo tree was mentioned in ancient Chinese herbals and in fifteenth- and sixteenth-century pharmaceutical books as an external treatment for skin and head sores and freckles and as an internal treatment for diarrhea. Traditional Chinese medicine has also used ginkgo leaves internally for brain medicine, filariasis, and frostbite.
Ginkgo preparations include dried leaf, tinctures, homeopathic preparations, and various leaf extracts. Ginkgo leaf extract is used clinically in Europe to treat poor circulation, heart disease, and conditions that involve oxygen metabolism in the blood (1,2). Clinical use in modern China includes treatment of angina pectoris, bronchitis, and elevated cholesterol.
Active constituents of ginkgo leaf extract include bioflavonoids, flavones, and organic acids. Current pharmacological and clinical research is focused on ginkgo lactones. Nearly all recent research has tested a standardized extract called GBE (or EGb).
The effects of GBE center on improving blood circulation and the absorption and metabolism of oxygen. The extract has also been shown to scavenge or suppress formation of free radicals as effectively as or more effectively than uric acid.
A sampling of clinical studies
Clinical studies suggest that the standardized extract may be useful in treating a number of conditions common in elderly people, such as short-term memory loss. A review of twenty clinical studies (2), most of which used a GBE dosage of 120 mg/day, indicated that many elderly patients, especially those suffereing from vascular disorders, dementias, or decreased intellectual function associated with depression, could benefit from GBE.
Another clinical review (3) summarized the results of ten controlled trials of GBE in treating cerebral insufficiency as evidenced by absentmindedness, confusion, difficulty of concentration/memory, decreased physical performance, tiredness/ lack of energy, anxiety, depression, dizziness, headache, and tinnitus. The effectiveness of ginkgo extract in increasing blood flow in the capillaries and decreasing blood clotting was demonstrated. Ginkgo extracts apparently improve oxygen metabolism in the brain and protect the brain against damage from oxygen deficiency.
Future ginkgo research will examine the activity of individual chemical components, especially the ginkgolides, which are considered pharmacologically and clinically distinct from GBE. These bitter diterpenes, found in the leaves and roots, were first isolated in 1932. Japanese researchers elucidated and named their chemical structure in 1966 (4). Ginkgolide B, considered the most active of the four main ginkgolides, was first synthesized in 1988 (5).
The broad-spectrum therapeutic potential of ginkgolides stems from their effects on enzyme systems and ion pressure gradients (6). All selectively counteract platelet aggregation, thus reducing the risk of arterial deposits and clotting (7).
A 1989 study showed that Ginkgolide B was as effective as conventional pharmaceuticals in preventing ventricular fibrillation, ventricular tachycardia, and negative preventricular beats caused by oxygen deprivation of the heart (8).
A review of twenty clinical studies using GBE revealed no deleterious side effects except minor temporary gastric disturbances and, rarely, headache, dizziness, and vertigo (2). Another review of all clinical ginkgo research to date has revealed neither serious side effects nor drug interactions (3).
(1) Drieu, K. In Agnoli, A., et al. (eds.). Effects of Ginkgo biloba Extract on Organic Cerebral Impairment. London: John Libbey Eurotext, 1985.
(2) Warburton, D. M. In Fünfgeld, E. W. (ed.). Rökan [Ginkgo biloba]: Recent Results in Pharmacology and Clinic. Berlin: Springer-Verlag, 1988.
(3) Kleijnen, J., and P. Knipschild. Ginkgo biloba. The Lancet 1992, 340(7): 1136-1139.
(4) Nakanishi, K. In Braquet, P. (ed.). Ginkgolides: Chemistry, Biology, Pharmacology, and Clinical Perspectives. I. Barcelona, Spain: J. R. Prous, 1988.
(5) Boralle, N., P. Braquet, and O. R. Gottlieb. In Braquet, P. (ed.). Ginkgolides: Chemistry, Biology, Pharmacology, and Clinical Perspectives. I. Barcelona, Spain: J. R. Prous, 1988.
(6) Michel, P. F., and D. Hosford. In Braquet, P. (ed.). Ginkgolides: Chemistry, Biology, Pharmacology, and Clinical Perspectives. I. Barcelona, Spain: J. R. Prous, 1988.
(7) Braquet, P. Blood Vessels. 1985, 16:559-572.
(8) Koltai, M., et al. Euro. J. Pharm. 1989, 164:293-302.
Aloe Wards Off X-Rays
Japanese researchers report that pressed leaf extracts of candelabra aloe (Aloe arborescens), a relative of the familiar house plant A. vera, protect the skin against radiation damage from X-rays. Levels of protection provided by injecting different fractions of the extract varied: the whole centrifuged aloe extract gave 60% protection, a purified fraction provided 98% protection, but aloin, the laxative component of the extract, increased radiation damage by 160%. Aloe appears to provide protection through its activity as an antioxidant and free-radical scavenger (1).
Astragalus for the Liver
Astragalus (Astragalus membranaceus) is a popular Chinese spleen tonic, and scientific evidence confirms its immunity-enhancing effects. Chinese research has focused on the role of astragalus in liver protection and on its clinical application against chronic hepatitis. A 1986 study demonstrated that astragalus protects animal livers against damage from carbon tetrachloride (2).
A 1990 study found that astragalus protects against damage from stilbenemide, an anticancer compound that is s known liver toxin. In animals receiving stilbenemide alone, there was a marked increase in liver enzyme activity (toxicity) over that of an untreated control group and visible liver damage. In animals receiving stilbenemide and astragalus, liver enzyme activity was not significantly different from that of controls, and visible changes in the liver were less than those seen in the animals receiving only stilbenemide (3).
Medicinal Use of Black Pepper
Researchers from the University of Wales have demonstrated that guinea cubeb (Piper guineense), a West African species of black pepper, protects mice against epileptiform seizures for as long as 24 hours after injection of a water extract of the plant. Complete protection was demonstrated for 6 hours after administration of the extract. After 18 hours, protection was measured at 58%. Guinea cubeb fruits are a popular Nigerian condiment. Nigerian healers use the plant to treat epilepsy. The plant is also used for the treatment of coughs, colds, intestinal disorders, and infections. Its fruits contain many of the compounds found in black pepper (P. nigrum) and also in kava (P. methysticum).
The effect of phenobarbitone, a common Western anticonvulsant drug, has been shown to last only 1 to 2 hours, and the risks of toxicity, depression, and other side effects are significant. Guinea cubeb pepper extract produced neither significant depression of the central nervous system nor toxicity (4).
The alkaloid berberine, which occurs in high concentrations in barberry (Berberis spp.) and goldenseal (Hydrastis canadensis), was up to 99.97% effective against replication of various type A and B influenza viruses in laboratory experiments (6).
Cancer Inhibition with Tea
The effects of black and green tea on tumor cells are being studied at New Jersey Medical School, the State University of New Jersey, and Rutgers University. It was previously shown that polyphenols in green tea can block the action of some mutagens and inhibit certain chemical-induced cancers, and the antioxidant properties of those polyphenols are well established. In a recent study, extracts of both black and green tea inhibited up to 43% the ability of leukemia and hepatoma (liver tumor) cells to synthesize DNA (7).
Fenugreek for Diabetes
Seeds of fenugreek (Trigonella foenum-graecum) were the subject of an Indian clinical study involving ten insulin-dependent diabetics ranging in age from twelve to thirty-seven years. Some patients had been insulin-dependent diabetics for as long as fifteen years. Patients were maintained on a dose of insulin that was too low to maintain the blood sugar at normal level. Each patient ate 100 g of debittered, powdered fenugreek seeds for ten days and a placebo for ten days. The diet of the control group was identical to that of the experimental group except for the seeds and placebos.
The fenugreek diet reduced twenty-four-hour urinary sugar excretion by 54%, and glucose tolerance was improved. Levels of serum insulin in the control and experimental groups were similar, but blood glucose levels were significantly lower in the experimental group, suggesting that fenugreek increased sensitivity to insulin. Improvements may result from fenugreek’s rich (51.7%) fiber content, which resembles that of guar gum in chemical structure and viscosity (8).
Anti-Aging Effects of Soybeans
A phospholipid paste prepared from soybeans has been shown to retard two measures of aging in both guinea pigs and humans. When administered orally at 10 to 20 g/day for two months, the paste retarded aging of red blood cell membranes, had a similar effect on the membranes of heart muscle, and reduced fat levels in the blood. (9)
(1) Sato, Y., et al. Yakugaku zasshi 1990, 110(11):876-884.
(2) Jiang, J.-W., and Q.-S. Xiao. Handbook of Planta Medica. Beijing: People’s Health Publishers, 1986, 127-128.
(3) Zhang, Z.-L., Q.-Z. Wen, and C.-X. Liu. J. Ethnopharm. 1990, 30(2):145- 149.
(4) Abila, B., A. Richens, and J. A. Davies. J. Ethnopharm. 1993, 39:113-117.
(5) Biochem. Biophys. Res. Commun. 1990. 172(1):149-153.
(6) Lesnau, A., et al. Pharmazie 1990, 45(8):638-639.
(7) Lea, M., et al. Cancer Lett. 1993, 68: 231-236.
(8) Eur. J. Clin. Nutr. 1990, 44:301-306.
(9) Li, I., Q. Sun, and F. Li. Shongguo Zhongyao Zazhi 1990, 15(12):749-750.
Steven Foster is an herbalist, author, researcher, and consultant who is associate editor of HerbalGram magazine.