Antitumor, Anti-Ulcer and Anti-Atherosclerotic Effects of Oyster Shell
Oyster is a delicious seafood, and oyster shell is also a commonly used traditional Chinese medicine (TCM). Although the medicinal material is called oyster, it is actually the shell of the oyster. In the current TCM market, oyster shell mainly comes from the shells of Crassostrea rivularis, Crassostrea gigas and Crassostrea talienwhanensis, all animals of the Ostreidae, genus Crassostrea.Oyster shell was recorded in the Shennong Bencao Jing (Shennong Classic of Materia Medica), the earliest TCM materia medica. It states that oyster shell is salty in flavor and neutral in nature; it chiefly treats cold and fever from cold damage, intermittent fever with chilly sweating, fright and anger, relieves spasmodic tension and scrofulous ulcers, and treats red and white vaginal discharge in women. Long-term use strengthens the bones and sinews, dispels evil influences, and prolongs life.The Shennong Bencao Jing claims that long-term use of oyster shell prolongs life, but in practice while oyster meat can be eaten regularly, oyster shell should not be taken over a long period, because its main component is calcium carbonate; prolonged or heavy use easily causes constipation and indigestion.Oyster shell contains over 90% calcium carbonate, along with calcium sulfate and calcium phosphate. It also contains small amounts of magnesium, sodium, strontium, iron, aluminum and silicon, and trace amounts of titanium, manganese, barium, copper, zinc, potassium, phosphorus and nickel. In addition it contains protein, and its hydrolysate yields more than ten amino acids including aspartic acid, glycine and glutamic acid.The oyster shell sold in TCM markets is divided into raw oyster shell (sheng muli) and calcined oyster shell (duan muli). Calcined oyster shell is made by taking raw oyster shell, removing impurities, and roasting it over a fire until it turns grayish-white (the furnace temperature must reach about 900 degrees Celsius, with a calcination time of about one hour). After calcination, the protein is no longer present, but trace element content increases; calcium carbonate also decomposes into calcium oxide during calcination. Therefore raw and calcined oyster shell do not have identical effects.Calcined oyster shell tends toward astringency and securing, and toward neutralizing acid and relieving pain. It chiefly treats spontaneous sweating, night sweating, seminal emission, metrorrhagia and vaginal discharge. Calcined oyster shell is a TCM herb with a very strong anti-ulcer effect, with an effective rate against ulcers reaching 94.8%, while raw oyster shell anti-ulcer effective rate is far lower. Calcined oyster shell reduces gastric juice secretion, lowers pH and reduces pepsin activity in experimental animals. Therefore it can be used for stomach pain caused by excess stomach acid.Raw oyster shell, by contrast, tends toward heavy settling to calm the spirit, leveling the liver and subduing yang, softening hard masses and dissipating nodules, and nourishing yin with astringency.Raw oyster shell is an important herb in TCM treatment of neoplastic diseases. The famous antitumor formula Xiaoluo Wan (scrophularia, fritillary and raw oyster shell) contains raw oyster shell. TCM uses oyster shell to treat various cancers, including thyroid tumor, lymphoma, breast cancer, gastric cancer, liver cancer, intestinal cancer, lung cancer and nervous system tumors.TCM holds that raw oyster shell softens hard masses and dissipates nodules. Modern pharmacology shows that oyster extract has a marked inhibitory effect on the human colon cancer LoVo cell line and on mouse liver cancer. It can also enhance host immune function, especially the activity of natural killer (NK) cells; oyster shell can inhibit tumor growth by strengthening the host immune system. In addition, oyster natural active peptide (BPO) can effectively inhibit proliferation of gastric cancer BGC-823 cells and induce apoptosis of cancer cells at the G1 phase.Raw oyster shell is also an important herb in TCM treatment of hypertension and atherosclerosis; TCM summarizes this effect as leveling the liver, subduing yang, and heavily settling to calm the spirit. Dizziness, tinnitus, insomnia, palpitations and convulsions caused by hypertension and atherosclerosis respond well to raw oyster shell. Guizhi Jia Longgu Muli Tang and Chaihu Jia Longgu Muli Tang are famous formulas commonly used in TCM to treat cardiovascular and nervous system diseases.Animal experiments show that after intragastric administration of oyster extract at 10 g/kg for 8 consecutive weeks in quail, the degree of atherosclerotic plaque formation in the aorta and coronary artery intima was markedly reduced, and plasma total cholesterol, triglycerides, LDL-cholesterol and apolipoprotein B levels were also significantly lowered. Studies have found that oyster short peptides have strong angiotensin-converting enzyme (ACE) inhibitory activity. Using the patent medicine Jinmuli Capsule to treat hyperlipidemia markedly lowers cholesterol and triglyceride levels in patients, with significant therapeutic effect.The COVID-19 virus mainly binds to the human angiotensin-converting enzyme 2 (ACE2) receptor. After COVID-19 infection, many people develop atherosclerotic plaques in the aorta and coronary arteries, leading to the three highs: hyperlipidemia, hyperglycemia and hypertension. By pharmacological inference, oyster shell should have some therapeutic effect on long COVID.The glutathione contained in oyster also protects the liver. In modern medicine, glutathione is a principal drug for treating drug-induced liver injury, alcoholic liver disease and liver injury caused by hepatitis virus. Therefore, when oyster extract is used to treat patients, it also has a certain liver-protective effect. Patients eating fresh oyster meat can also achieve liver protection, anti-aging and anti-fatigue effects. Oyster extract also has a certain blood-sugar-lowering effect.TCM holds that raw oyster shell also nourishes yin, astringes the intestines and clears heat. Yijia Jian (One-Jia Decoction) in the Wenbing Tiaobian (Systematized Identification of Warm Diseases) uses only raw oyster shell to treat warm disease after purgation, when yin is damaged and there is loose stool with a rapid pulse. This formula uses only 60 g (two ancient liang) of raw oyster shell, ground fine and decocted in water (1.5 liters of water boiled down to about 500 ml). This formula both stops diarrhea and clears heat.