I compiled this information a few years ago; to my knowledge it is still current. I hope it helps.
Garlic has mild-moderate cholesterol lowering effects
Hypercholesterolemia: (Dyslipidemia; Hyperlipidemia) “is elevation of plasma cholesterol and/or [triglycerides] TGs or a low [high-density lipoprotein] HDL level that contributes to the development of atherosclerosis. Causes may be primary (genetic) or secondary. Diagnosis is by measuring plasma levels of total cholesterol, TGs, and individual lipoproteins” (Merck Manual, 2005).
In addition to the commonly prescribed pharmaceuticals for hypercholesterolemia, standard recommendations by the American Heart Association for treatment or prevention include:
- eat foods low in cholesterol and saturated fat
- maintain a healthy weight
- exercise regularly
Herbal Statins: work as HMG-CoA Reductase Inhibitors, blocking the main pathway where cholesterol is made. An example is red yeast rice (Monascus purpureus). Originally red yeast rice was used to develop the pharmaceutical lovastatin, and has the same efficacy, side effects, and potential interactions as lovastatin (Neafsey, 2004). Between 16 to 31% reduction of total serum cholesterol was observed in four randomized clinical trials (Coon & Ernst, 2003). See safety concerns below.
Fiber: on a basic level works similarly to bile acid sequestrants by binding to bile and increasing elimination of bile through the large intestine, thus increasing the need for the liver to make more bile from cholesterol. Examples include psyllium seed husks (Plantago psyllium), flaxseed (Linum usitatissimum), and oat bran (Avena sativa). Each of these herbs has additional health benefits, which may or may not lower cholesterol through other mechanisms (Petchetti, Frishman, Petrillo, & Raju, 2007; Reyna-Villasmil, Bermudez-Pirela, Mengual-Moreno, et al, 2007; Pellizzon, Billheimer, Bloedon, et al, 2007).
Working differently than fiber, the saponins in fenugreek seeds (Trigonella foenum-graecum) also increase total bile output by the increased conversion of cholesterol to bile acids by the liver (Stark & Madar, 1993; Sauvaire, Ribes, Baccou, et al, 1991; Valette, Sauvaire, Baccou, et al, 1984). Of five trials on fenugreek seeds, four of which are considered to have poor methodological quality, reductions of total serum cholesterol was between 15 and 33% (Coon & Ernst, 2003).
Among many other herbs used to support healthy blood lipid levels, two possibly effective herbs are artichoke leaf extract (Cynara scolymus) and garlic (Allium sativum). A review of studies on artichoke’s affect on lipid levels shows a mild lowering effect (Pittler, Thompson, & Ernst, 2002). In a large trial, 18.5% reduction of total serum cholesterol levels was observed (Coon & Ernst, 2003). Artichoke extracts have been shown to produce various pharmacological effects, such as the inhibition of cholesterol biosynthesis and of LDL oxidation (Lupattelli, Marchesi, Lombardini, et al., 2004). A recent single-blind study of garlic tablets in 150 hyperlipidemic patients has shown a significant favorable effect on cholesterol, LDL-cholesterol, and HDL-cholesterol (Kojuri, Vosoughi, Akrami, 2007). However, a comparative study of the effects of raw garlic, garlic powder, and aged garlic on LDL-cholesterol levels showed no significant effect from any of the three forms of garlic (Gardner, Lawson, Block, et al, 2007). A meta-analysis of garlic’s lipid-lowering effects shows that garlic is superior to placebo; however, garlic affects on cholesterol do not appear robust. Garlic does show a deceleration of atherosclerotic plaque formation, giving reason to use garlic in cases of atherosclerosis, or as a preventative measure (Stevinson, Pittler & Ernst, 2000). The mechanism of the supposed effects of garlic on cholesterol levels is unknown.
Safety Concerns/ Herb-Drug Interactions
Due to the association of hypercholesterolemia and heart disease, it is important to note the precautions that need to be taken with people on other heart medications, especially those with a narrow therapeutic window. As red yeast rice (Monascus purpureus) works by the same mechanism as pharmaceutical statins, the same caution applies. “Statins that are metabolized by CYP3A4 compete with other drugs for the CYP3A4 enzyme. CYP3A4 activates the antiplatelet drug, clopidogrel. Atorvastatin (and, presumably lovastatin in red yeast rice) interferes with clopidogrel activation and reduces its ability to inhibit platelet aggregation” (Neafsey, 2004). Furthermore, lovastatin has resulted in increased INR by inhibiting warfarin metabolism and displacement of warfarin from plasma proteins. Presumably lovastatin may increase digoxin concentrations by as much as 20% by increasing absorption via a drug transporter protein in the small intestines called P-glycoprotein (Neafsey, 2004).
Though rare at standard doses (1 in 10,000), dangerous side effects of statin drugs can occur on muscle such as myopathy and rhabdomyolysis. Adverse effects, though unusual, may occur on the liver, in increasing levels of transaminases. Statins are not clearly associated with increased risk of liver disease (Armitage, 2007). Consumers of red yeast rice, however, need to be aware of any muscle aches or unusual lethargy, and report symptoms to their primary care practitioner. A recent clinical trial with patients with myopathic symptoms tested whether supplementation with coenzyme Q10, which is essential for mitochondrial energy production, would reduce muscle pain, due to the fact that the manufacture of coQ10 is blocked by statins. Indeed, muscle pain was reduced in 40% of the patients after supplementation compared with vitamin E (Caso, Kelly, McNurlan & Lawson, 2007). Therefore, supplementation with coenzyme Q10 would be beneficial for consumers of red yeast rice. Other adverse events reported from taking red yeast rice include: stomachache, heartburn, dizziness, and flatulence (Coon & Ernst, 2003).
Of the five fenugreek trials on 140 participants, mild gastrointestinal symptoms were reported. None were severe enough to warrant discontinuance. Though studies of fenugreek leaves do not show as significant a reduction in total serum cholesterol, a 14% reduction in serum potassium was noted in healthy subjects after a single dose of the extract made from fenugreek leaves (Coon & Ernst, 2003).
A review of garlic’s lipid-lowering effect in clinical trials showed few differences with placebo in recorded adverse events. The most common complaint was gastrointestinal symptoms, besides garlic breath and body odor (Stevinson, Pittler & Ernst, 2000). Due to the limited number and nature of reports of excessive blood-thinning caused by garlic, true risks and assessment of an interaction between garlic and warfarin is difficult to make (Vaes & Chyka, 2000). In a double-blind, randomized, placebo-controlled pilot study of 48 patients, concomitant use of aged garlic extract (AGE) and anticoagulant therapy (warfarin) showed no evidence of increased hemorrhage in either the placebo or the AGE group (Macan, Uykimpang, Alconcel, et al., 2006).
A PubMed search of adverse effects of fiber revealed nothing significant. Psyllium seed husks appear to be well-tolerated and cost-effective (Petchetti, Frishman, Petrillo,& Raju, 2007). Oats are commonly listed on the foods-to-avoid list for gluten intolerance and may need to be avoided in gluten-sensitive people. The only recommendation is for the consumer to take fiber with plenty of water, and away from medications and other supplements.
American Heart Association. (2007). Hypercholesterolemia: Assessment of current dietary habits and formulating recommended changes. Retrieved on June 15, 2007, from http://www.americanheart.org/presenter.jhtml?identifier=712
Armitage, J. (2007). The safety of statins in clinical practice. Lancet
Caso, G., Kelly, P., McNurlan, M.A., & Lawson, W.E. (2007). Effect of coenzyme Q10 on myopathic symptoms in patients treated with statins. American Journal of Cardiology, 99(10), 1409-12.
Coon, J.S.T. & Ernst, E. (2003). Herbs for serum cholesterol reduction: A systematic review. Journal of Family Practice, 52(6), 468-78.
Drug Digest. (2007). Hypercholesterolemia. Retrieved on June 15, 2007, from https://www.drugdigest.org/DD/HC/Treatment/0,4047,15,00.html
Gardner, C.D., Lawson, L.D., Block, E., Chatterjee, L.M., Kiazand, A., Balise, R.R., & Kraemer, H.C. (2007). Effect of raw garlic vs commercial garlic supplements on plasma lipid concentrations in adults with moderate hypercholesterolemia: A randomized clinical trial. Archives of Internal Medicine, 26(167), 346-53.
Kojuri, J. Vosoughi, A.R., Akrami, M., (2007). Effects of anethum graveolens and garlic on lipid profile in hyperlipidemic patients. Lipids in Health and Disease, 1(6), 5.
Lupattelli, G., Marchesi, S., Lombardini, R., Roscini, A.R., Trinca, F., et al (2004). Artichoke juice improves endothelial function in hyperlipidemia. Life Sciences, 76(7), 775-82.
Macan, H., Uykimpang, R., Alconcel, M., Takasu, J., Razon, R., Amagase, H., & Niihara, Y. (2006). Aged garlic extract may be safe for patients on warfarin therapy. The Journal of Nutrition, 136(3 Suppl), 793S-795S.
Merck Manuals Online Medical Library, The. (2005). Dyslipidemia. Retrieved on June 17, 2007, from http://www.merck.com/mmpe/sec12/ch159/ch159b.html?qt=hypercholesterolemi a&alt=sh#S12_CH159_T003
Neafsey, P. (2004). Self-medication practices that alter the efficacy of selected cardiac medications. OVID, 22(2), 88-98.
Pellizzon, M.A., Billheimer, J.T., Bloedon, L.T., Szapary, P.O. & Rader, D.J. (2007). Flaxseed reduces plasma cholesterol levels in hypercholesterolemic mouse models. Journal of American College Nutrition, 26(1), 66-75.
Petchetti, L., Frishman, W.H., Petrillo, R., & Raju, K. (2007). Nutriceuticals in cardiovascular disease: Psyllium. Cardiology Review, 15(3), 116-22.
Pittler, M.H., Thompson, C.O., & Ernst, E. (2002). Artichoke leaf extract for treating hypercholsterolaemia. Cochrane Database Systematic Reviews (Online), (3), CD: 003335.
Reyna-Villasmil, N., Bermudez-Pirela, V., Mengual-Moreno, E., Arias, N., Cano-Ponce, C., et al. (2007). Oat-derived beta-glucan significantly improves HDLC and diminishes LDLC and non-HDL cholesterol in overweight individuals with mild hypercholesterolemia. American Journal of Therapeutics, 14(2), 203-12.
Sauvaire, Y., Ribes, G., Baccou, J.C., & Loubatieeres-Mariani, M.M. (1991). Implication of steroid saponins and sapogenins in the hypocholesterolemic effect of fenugreek. Lipids, 26(3), 191-7.
Stark, A. & Madar, Z. (1993). The effect of an ethanol extract derived from fenugreek (Trigonella foenum-graecum) on bile acid absorption and cholesterol levels in rats. British Journal of Nutrition, 69, 277-287.
Stevinson, C., Pittler, M.H., & Ernst, E. (2000). Garlic for treating hypercholesterolemia. Annals of Internal Medicine, 133, 420-9.
Vaes, L.P. & Chyka, P.A. (2000). Interactions of warfarin with garlic, ginger, ginkgo or ginseng: Nature of the evidence. The Annals of Pharmacotherapy, 34(12), 1478-82.
Valette, G., Sauvaire, Y., Baccou, J.C., & Ribes, G. (1984). Hypocholesterolaemic effect of fenugreek seeds in dogs. Atherosclerosis, 50(1), 105-11.