The Blood-Sugar-Lowering, Lipid-Lowering, Anti-Cancer and Anti-Pathogen Effects of Mulberry Leaves

The mulberry is the most common plant in China; in Chinese, sang (mulberry) is a household word. We even use "sang-ma" (mulberry and hemp) to stand for farming. Meng Haoran wrote: "Opening the window to face the garden and fields, raising the cup to talk of mulberry and hemp." Tao Yuanming's Returning to the Fields also has a line: "Dogs bark deep in the alley; roosters crow atop the mulberry tree."

Mulberry leaves can feed silkworms; for a silk-producing nation like ours, in ancient times nearly every household planted mulberry trees in front of and behind the house. So much so that we use "sang-zi" (mulberry and catalpa, catalpa being another common tree) to refer to one's hometown; the ancients often used "deep affection for one's mulberry and catalpa" to describe attachment to one's hometown.

Mulberry leaves are not only for feeding silkworms; they can also be used as medicine. China's first pharmacopoeia, the Shennong Bencao Jing, already included mulberry leaf, saying it can "remove cold and heat, and induce sweating." The most commonly used TCM formula for wind-heat cold in spring and summer, Sangju Yin (Mulberry and Chrysanthemum Drink), is composed of mulberry leaf, Juhua (chrysanthemum), Bohe (mint), Jiegeng (platycodon), etc. Most of the patent medicines we can buy today for wind-heat cold contain mulberry leaf.

Traditional TCM holds that mulberry leaf is bitter and sweet in taste, cold in nature, slightly toxic, and enters the lung and liver meridians; it is a hand- and foot-Yangming meridian herb. It has the effects of dispersing wind-heat, clearing the lung, and improving vision. It mainly treats wind-heat cold, the onset of wind-warmth, fever and headache, sweating with aversion to wind, cough with chest pain, or lung-dryness dry cough without phlegm, dry throat and thirst, wind-heat and liver-yang disturbance, and red swollen painful eyes. The Mingbie Bialu says the juice of mulberry leaf can also detoxify centipede poison; the Bencao Gangmu records that mulberry leaf can "treat consumptive-heat cough, brighten the eyes, and promote hair growth"; the Benjing Fengyuan records that mulberry leaf "taken long-term as honey pills with black sesame, keeps hair and beard from turning white and delays aging." Mulberry leaf combined with black sesame was an ancient formula for treating hair loss and premature graying.

Mulberry leaf is also an important herb for treating women's menopausal syndrome. Mulberry leaf has the effect of stabilizing nervous-system function; it can relieve emotional agitation in elderly menopausal women, and also has some effect on menopausal hyperhidrosis. The Zhongxing Xianfang records: "For incessant generalized sweating, pick fresh mulberry leaves while covered with dew, let dry, grind into powder; take two qian each time, mixed in rice water on an empty stomach." The effect of mulberry leaf on the nervous system is also reflected in its ability to treat numbness of hands and feet; the Jijiu Fang, for numbness of hands and feet with no feeling of pain or itch, uses mulberry leaves collected after frost, decocted and taken frequently.

Worth noting is that, in ancient times, mulberry leaves picked after frost were generally used medicinally, customarily called winter mulberry leaf. TCM holds that frost-bitten mulberry leaves have stronger heat-discharging and dryness-moistening functions. The dryness-moistening function of mulberry leaf has always been valued; the Bencao Congxin holds that mulberry leaf's main efficacy is "moistening dryness, cooling blood, and stopping bleeding." Modern pharmacological studies have found that mulberry leaf has a significant blood-sugar-lowering effect, with obvious relief of thirst in diabetic patients.

Animal experiments show that mulberry leaf has a hypoglycemic effect on alloxan-induced diabetes in rats and on hyperglycemia in mice caused by adrenaline, glucagon, or anti-insulin serum. Ecdysterone in mulberry leaf can promote the conversion of glucose to glycogen; the blood-sugar-lowering mechanism of mulberry leaf may be because certain amino acids it contains stimulate insulin secretion. As far as the author knows, a Sino-British biopharmaceutical company in Beijing has already developed a new diabetes drug from mulberry leaf extract and is conducting clinical trials.

Besides lowering blood sugar, mulberry leaf also has a significant blood-lipid-lowering effect. Mulberry leaf can inhibit the increase of serum lipids and the formation of atherosclerosis. Total flavonoids of mulberry leaf can lower blood viscosity and improve heart and liver function. Mulberry leaf has a diuretic effect, flushing excess water out of cells while clearing excess neutral fat and cholesterol from the blood. Total flavonoids of mulberry leaf can also prevent myocardial injury by increasing nitric oxide content, and enhance the body's anti-lipid-peroxidation and free-radical-scavenging ability. So the ancients' use of mulberry leaf as an anti-aging drug has some scientific basis.

Mulberry leaf also has antitumor effects. The flavonoid quercetin in mulberry leaf shows a significant inhibitory effect on the human promyelocytic leukemia cell line (HL-60) and can induce differentiation of the HL-60 line. The alkaloid component 1-deoxynojirimycin isolated from mulberry leaf has a strong antitumor effect, with an inhibition rate on tumor metastasis up to 80.5%; its anti-metastatic activity may be related to its anti-glycosidase and anti-beta-glucosidase activity.

Mulberry leaf also has an anti-pathogenic-microorganism effect, inhibiting many bacteria and viruses. Phenolic substances in mulberry leaf can destroy the integrity of cell walls and membranes, thereby inhibiting the growth of bacteria. The 1-deoxynojirimycin and its derivatives in mulberry leaf have significant reverse-transcriptase-virus activity, so they can inhibit viruses.

Mulberry leaf is also a specific remedy for elephantiasis of the lower extremities (edema of the lower limbs caused by obstruction of lymphatic return due to surgery or other causes, in which the overlying skin over time becomes as rough as an elephant's hide). Clinical reports show that, using 10% mulberry leaf injection intramuscularly, 5ml each time, 1–2 times daily, or 25%–50% solution 4ml once daily, 15–21 days as one course, with a second or third course after a 10-day interval if necessary, treating 512 patients with elephantiasis at various stages: marked effect accounted for 42.3%, and failure only 0.3%. Elephantiasis of the lower extremities is a common complication or surgical sequela in cancer patients; mulberry leaf can improve its symptoms, related to mulberry leaf's diuretic effect.

Mulberry leaf has very low toxicity; animal experiments show that intraperitoneal injection of mulberry leaf extract at 60 times the human dose for 21 consecutive days causes no damage to the liver, kidney or lung. At larger doses, it may cause degeneration and hemorrhage of the liver, kidney and lung. This shows that, at the conventional dose (6–30g per adult day), poisoning will not occur. Mulberry leaf poisoning is mainly due to overdose; overdose may cause nausea, vomiting, abdominal pain and distension, and even gastrointestinal bleeding with jam-like stool. A few people may also develop side effects such as rash, chest tightness, restlessness, cold limbs, lowered blood pressure, dehydration, shock, and even death.