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.
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.