in all times and places, some basic concepts can be isolated. One central tenet is that "medicine and food share a common origin", and that food materials can therefore be used to prevent or treat medical disorders. Like medicinal drugs, food items are classified as "heating" () or "cooling" (). In popular understanding, "heating" food is typically "high-calorie, subjected to high heat in cooking, spicy or bitter, or 'hot' in color (red, orange)", and includes red meat, innards, baked and deep-fried goods, and alcohol. They are to be avoided in the summer and can be used to treat "cold" illnesses like excessive pallor, watery feces, fatigue, chills, and low body temperature caused by a number of possible causes, including anemia. Green vegetables are the most typical "cooling" or "cold" food, which is "low-calorie, watery, soothing or sour in taste, or 'cool' in color (whitish, green)". They are recommended for "hot" conditions: rashes, dryness or redness of skin, heartburns, and other "symptoms similar to those of a burn", but also sore throat, swollen gums, and constipation. In more systematic understandings, each medicine or food item has one of five flavors: sour, sweet, bitter, pungent (or "acrid"), and salty. Besides describing the taste of food, each of these "flavors" purportedly has specific effects on particular viscera. The sour flavor, for instance, has "constriction and emollient effects" and "can emolliate the liver and control diarrhea and perspiration", whereas "bitter" food can "purge the heart 'fire', reduce excessive fluids, induce diarrhea, and reinforce the heart 'Yin'". Scientific assessments There are few studies in English on the scientific validity of these beliefs and practices. A few studies conducted in China suggest that a diet designed according to the precepts of Chinese food therapy may help control blood pressure, but these studies are based on different diagnostic categories than those of evidence-based medicine ("Yin deficiency" instead of hypertension), and on chiefly qualitative and conceptual evidence rather than on modern randomized controlled trials. Consequently, the claims of efficacy are weaker in scientific evidence than those based on mixed nutritious foods and demonstrated to have health effects by extensive clinical research, such as the DASH diet or Mediterranean diet. Other examples Qiu Li Gao is a pear syrup or paste used to treat lung ailments. See also Bencao Gangmu, a materia medica compiled by Li Shizhen during the Ming dynasty. Ch'ang Ming, a series of dietary and lifestyle