WHAT DOES CURRENT PEER-REVIEWED RESEARCH TELL US ABOUT HOW MUSHROOMS EFFECT CHOLESTEROL?
Cholesterol is extremely important for our survival. It is the building block of steroid hormones (e.g. testosterone and estrogen), bile acids, and vitamin D. It also controls cell membrane fluidity, aids in cell signaling and intracellular transport, and is a major component of myelin sheaths in the nervous system. Diet can influence cholesterol levels, but the majority is synthesized inside the body. Although all cholesterol is identical, it is transported by different protein-fat complexes called lipoproteins that differ in density. High-density lipoprotein (HDL) and low-density lipoprotein (LDL) are what many refer to as “good” and “bad” cholesterol, respectively. These are two of many types of lipoproteins that shuttle cholesterol throughout the body.
Very low-density lipoprotein (VLDL) is released by the liver to transport fats and cholesterol to different cells in the body. As VLDL particles deliver their fatty components to target cells, their protein to fat ratio increases and so does their density. The increase in density leads to their transformation to LDL. VLDL starts out like a heavyweight boxer who loses a few pounds to fight in a lower weight division, so although it is the same lipoprotein, VLDL loses mass to become LDL. The liver produces LDL receptors that bind to LDL particles and reintegrate their components to form bile acids or to package them into other lower density lipoproteins. HDL particles absorb cholesterol in the body and transport it to the ovaries, adrenal glands, testes, and liver. HDL is commonly thought of as “good” cholesterol because it functions to remove excess cholesterol in the bloodstream, including the plaque that contributes to atherosclerosis, the thickening of arterial walls that can lead to heart attack and stroke. LDL deposits the plaque, and HDL cleans up the mess.
High levels of cholesterol in the blood can accelerate the progression of cardiovascular disease (CVD) because a large majority of this cholesterol is typically found in LDL particles, which tend to accumulate on arterial walls. Individuals with high LDL and low HDL populations are thought to be at an increased risk of developing CVD because plaque is forming, and HDL is not available in large enough quantities to counteract this action. Picture a house full of five year olds and only one babysitter trying to clean up the constant accumulation of clutter. For some individuals, decreasing fat intake can stabilize cholesterol levels. However, dietary changes are often not enough because the body tightly regulates cholesterol levels and what is not introduced through diet will be accounted for by producing it inside the body. When cholesterol levels are too high and dietary changes have no significant effect, a doctor may prescribe medication to slow or stop the production of cholesterol inside the body.
Some species of fungi are known to have cholesterol-lowering properties. According to the Slovenian National Institute of Chemistry, oyster mushrooms contain the chemical lovastatin, a natural statin. Cholesterol is synthesized by a long progression of enzyme- mediated steps, and statins, like lovastatin, inhibit one of the enzymes at the start of the process to keep cholesterol from being produced. Shiitake mushrooms are known to contain eritadenine, which according to a study published in the Journal of Nutrition, also decreases cholesterol, although the mechanism is thought to be indirect.
Another potential benefit of mushrooms is that they contain large amounts of water-soluble fiber called beta-glucans. Bile acids are composed of cholesterol derivatives, and according to the Marion Bessin Liver Research Center, 95% of the bile secreted by the liver is reabsorbed in the intestine. Beta-glucans increase the viscosity of bile inside the intestines and decrease reabsorption of cholesterol derivatives. According to a study published in the Journal of Clinical Lipidology, supplementation of beta-glucans may not only increase the effectiveness of treatment with statins, but may also reduce the required dosage. Coupling beta-glucans with statin treatment creates a cholesterol-lowering scenario where cholesterol production is limited and increased amounts are excreted from the body. It is like unplugging the bathtub and not refilling it. Beta-glucans taken alone–without statins–have been known to increase HDL and decrease LDL, which can help lower the risk of atherosclerosis.
Lowering cholesterol is not for everybody. Keep in mind that cholesterol is necessary for bodily function, and we produce it for a reason. Consuming mushrooms may help lower LDL and increase HDL levels, and their use in conjunction with statins appears beneficial. Do not attempt to lower your cholesterol without consulting a physician first, and do not rely on mushrooms as the sole treatment. They may increase the effectiveness of statins, but this claim is not supported by the Food and Drug Administration.
Atherosclerosis: The thickening of arterial walls due to the deposition of cholesterol and other fatty particles. The progression of atherosclerosis can lead to heart attack and stroke.
Beta glucans: Long chains of glucose (sugar) units with a specific bond orientation. Beta-glucans range in molecular weight, length and have different branch points. Humans cannot synthesize beta-glucans.
Bile acids: Derivatives of cholesterol that are secreted by the liver. They allow us to absorb a number of vitamins and dietary fat. The majority of bile acids are reabsorbed in the ileum, but some are lost to excrement. One way of decreasing cholesterol levels is to decrease reabsorption of bile acids.
Cholesterol: A steroid alcohol–sterol. It serves many functions in the body and is necessary for our survival. It is not soluble in water and therefore must be transported through the blood inside of a lipoprotein complex.
Enzyme: A protein that catalyzes reactions by lowering the amount of energy needed for a reaction to occur. If the reactions that take place in our bodies were to be repeated in the laboratory without the use of enzymes, many of them would require extremely high heat–energy. Enzymes are very efficient, produce no waste, and keep us alive.
Eritadenine: A chemical isolated from shiitake mushrooms that is known to have cholesterol-lowering properties. The mechanism is thought to involve a change of liver cell-membrane metabolism and the ratio of different phospholipids.
High-Density Lipoprotein (HDL): A complex that transports cholesterol and fats: what many people refer to as “good” cholesterol. HDL is successful in withdrawing and stabilizing the plaque that accumulates in the arteries and is therefore effective at decreasing the risk of cardiovascular disease. High levels of HDL are desirable.
Intracellular Transport: The trafficking of nutrients inside of a cell. Just like the organs in our body, each cell has its own set of organelles that require different molecules to function properly.
Lipoprotein: A complex of fats and protein that is used to transport fats and cholesterol to target cells in the body. Lipoproteins differ in density and are named accordingly. All of the cholesterol in lipoproteins is identical.
Lovastatin: A type of statin typically found in oyster mushrooms. Statins like lovastatin block up the cholesterol synthetic pathway by inhibiting the enzyme HMG-CoA reductase. Statins occupy this enzyme and keep other molecules from interacting with the enzyme.
Low-Density Lipoprotein (LDL): A type of lipoprotein that transports cholesterol and fats to target cells. LDL is often called “bad” cholesterol because it is notorious for accumulating on arterial walls, which increases the risk of cardiovascular disease. Low LDL levels are desirable.
Membrane Fluidity: Is the viscosity or rigidity of a cell membrane. Cholesterol can pack into the membrane of cells to reduce fluidity. In this way, cholesterol can help control what enters the cell.
Statin: A molecule that inhibits the HMG-CoA reductase enzyme and ceases the biosynthesis of cholesterol in the body. Statins are marketed by pharmaceutical companies as an effective treatment to hypercholesterolemia–high cholesterol.
Steroid hormone: A steroid that functions as a hormone to help control important bodily functions. A few well-known steroid hormones include testosterone, estrogen, and cortisol.
Very-Low Density Lipoprotein (VLDL): A type of lipoprotein produced by the liver to transport cholesterol and fats to different cells in the body. As the contents are transferred to target cells, VLDL becomes more dense, and this form is called LDL.
Selected Research and Highlights
Theuwissen, E., & Mensink, R. (2008). Water-soluble dietary fibers and cardiovascular disease. Physiology & Behavior, 94(2), 285-292.
“Water-solubility and molecular weight of β-glucan may also influence its hypocholesterolemic effect. Indeed, it has been postulated that the viscosity of β-glucan in the intestinal tract, which is positively related to its solubility in water and molecular weight, is an important determinant of its LDL cholesterol-lowering effects. Highly water-soluble β-glucan, with moderate to high molecular weight, may reduce serum LDL cholesterol levels better than β-glucan with a low water-solubility and low molecular weight. This difference in effect is explained by the assumption that a higher intestinal viscosity lowers the reabsorption of bile acids, leading to an increased excretion of bile acids. Increased bile acid excretion promotes bile acid synthesis from cholesterol, which will increase LDL cholesterol uptake in the liver.”
Chen, J., & Huang, X. (2009). The effects of diets enriched in beta-glucans on blood lipoprotein concentrations. Journal of Clinical Lipidology, 3(3), 154-158.
“Beta-glucans increase bile acid secretion and increase cholesterol excretion, which can result in an increased requirement for cholesterol in the liver, which stimulates HMG-CoA reductase activity. It has been shown that in subjects who were administered beta-glucan that HMG-CoA reductase activity is 12% greater than for control subjects. Thus, it could be necessary to combine beta-glucans with the HMG-CoA reductase inhibitor, i.e., statins, to increase treatment efficiency.
Another advantage of combining beta-glucans and statins is to reduce the dose of statins to be used; thus, their side-effects can be decreased. A similar combination has also been proposed in the combination of berberine and statins. Statin does not decrease TG nor increase HDL-C, whereas beta-glucans have been shown to increase HDL-C, which can complement the hypocholesterolemia effect of statin. Plant sterols could also be used in combination with beta-glucans. It has been demonstrated that portfolio diet pattern that is rich in plant sterols, soy protein, and viscous fiber is as effective as statins in lowering cholesterol.”
Gunde-Cimerman, N., & Cimerman, A. (1995). Pleurotus fruiting bodies contain the inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase–lovastatin. Experimental Mycology, 19(1), 1-6.
“Pleurotus fruiting bodies contain the inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase-lovastatin. In the fruiting bodies of the fungus Pleurotus ostreatus, also called the oyster mushroom, we found a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase—lovastatin. The appearance of the inhibitor during the development of fruiting bodies was followed and lovastatin determined in the vegetative mycelium, in the primordia, as well as in different parts of sporocarps of different sizes.”
Sugiyama, K., Akachi, T., & Yamakawa, A. (1995). Hypocholesterolemic action of eritadenine is mediated by a modification of hepatic phospholipid metabolism in rats. Journal of Nutrition, 125(8), 2134-2144.
“The hypocholesterolemic action of eritadenine, a compound found in the mushroom Lentinus edodes, was investigated in relation to its influence on phospholipid metabolism in the liver of rats fed diets containing different amounts of choline chloride (0, 2 and 8 g/kg diet).”
“These observations suggest that the essential hypocholesterolemic action of eritadenine might be associated with a modification of hepatic phospholipid metabolism rather than with the PC deficiency, due to the inhibition of PE N-methylation.”
Wolkoff, A., & Cohen, D. (2003). Bile acid regulation of hepatic physiology: I. Hepatocyte transport of bile acids. American Journal of Physiology and Gastrointestinal Liver Physiology, 284(2), 175-179.
“Bile acids are cholesterol derivatives that serve as detergents in bile and the small intestine. Approximately 95% of bile acids secreted by hepatocytes into bile are absorbed from the distal ileum into the portal venous system.”
Yoon, K., Alam, N., Lee, J., Cho, H., Kim, H., Shim, M., et al. (2011). Antihyperlipidemic effect of dietary Lentinus edodes on plasma, feces and hepatic tissues in hypercholesterolemic rats. Mycobiology, 39(2), 96-102.
“Feeding mushroom increased total lipid and cholesterol excretion in feces. The plasma lipoprotein fraction, separated by agarose gel electrophoresis, indicated that L. edodes significantly reduced plasma β and pre-β-lipoprotein but increased α-lipoprotein. A histological study of hepatic cells by conventional hematoxylin-eosin and oil red-O staining showed normal findings for mushroom-fed hypercholesterolemic rats. These results suggest that shiitake mushrooms could be recommended as a natural cholesterol lowering substance in the diet.”
Schneider, I., Kressel, G., Meyer, A., Krings, U., Berger, R. G., & Hahn, A. (2011). Lipid lowering effects of oyster mushroom (Pleurotus ostreatus) in humans. Journal of Functional Foods, 3(1), 17-24.
“Consumption of oyster mushrooms lowers concentrations of triglycerides, cholesterol and oxidized LDL. Additionally, the HMG-CoA-reductase inhibitor mevinolin (lovastatin) was detected in oyster mushroom (Pleurotus ostreatus), which could lead to a lipid lowering effect. The beneficial effects of oyster mushroom on blood serum parameters may be attributed to the presence of linoleic acid, ergosterol and ergosta-derivatives which showed notable activity in oxygen radical absorbance capacity and cyclooxygenase inhibition assays in vitro.”
Guillamon, E., GarcÃa-Lafuente, A., Lozano, M., DÂ´Arrigo, M., Rostagno, M. A., Villares, A., et al. (2010). Edible mushrooms: role in the prevention of cardiovascular diseases. Fitoterapia, 81(7), 715-723.
“Mushroom intake clearly has a cholesterol-lowering effect or hypocholesterolemic effect by different mechanisms such as decreasing very-low-density lipoproteins, improving lipid metabolism, inhibiting of activity of HMG-CoA reductase, and consequently preventing the development of atherosclerosis. The antioxidant and anti-inflammatory compounds occurring on mushrooms also may contribute to reduce the atherosclerosis risk.”
Charach, G., Grosskopf, I., Rabinovich, A., Shochat, M., Weintraub, M., & Rabinovich, P. (2011). The association of bile acid excretion and atherosclerotic coronary artery disease. Therapeutic Advances in Gastroenterology, 4(2), 95-101.
“Excess cholesterol is usually eliminated from the body by conversion to bile acids excreted in feces as bile salts. The excretion of large amounts of bile protects against atherosclerosis, while diminished excretion may lead to coronary artery disease (CAD).”
 Gunde-Cimerman, N., & Cimerman, A. (1995). Pleurotus fruiting bodies contain the inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase–lovastatin. Experimental Mycology, 19(1), 1-6.
 Sugiyama, K., Akachi, T., & Yamakawa, A. (1995). Hypocholesterolemic action of eritadenine is mediated by a modification of hepatic phospholipid metabolism in rats.. Journal of Nutrition, 125(8), 2134-2144.
 Wolkoff, A., & Cohen, D. (2003). Bile acid regulation of hepatic physiology: I. Hepatocyte transport of bile acids. American Journal of Physiology and Gastrointestinal Liver Physiology, 284(2), 175-179.
 Chen, J., & Huang, X. (2009). The effects of diets enriched in beta-glucans on blood lipoprotein concentrations. Journal of Clinical Lipidology, 3(3), 154-158.