the PH of food

my chemical teacher told us:it can help us to keep fit with the PH,like do sports.
It is well known, food may divide into alkalinity food and the acidicfood two big kinds, the people eat food to have acid and alkali foodto match can maintain in vivo blood sour alkalinity are the PH valuebalances. The so-called acidity and alkalinity food, by no meansdistinguish by the feeling in the mouth or the sense of taste, aftermainly is looked food the chemical element which is contained by theorganism absorption oxidation takes the distinction the basis.Generally contains the nitrogen, the sulfur, the phosphorus and so onthe nonmetallic element more is acidic food, but contains isalkalinity food which metallic element and so on sodium, potassium,calcium, magnesium are more. The flavor acid is acidic food by nomeans, for instance the vinegar is sour, fruit and so on citrusreticulata, plum, apricot also is sour, but they not only are notacidic food, just the opposite, actually is typical alkalinity food.Also like grain, candy, cakes and pastries, fish, pork and otheranimal meats and so on, then is not alkalinity food, all belongs toacidic food.
For example，The banana origins southeast Asia, namely area Southeast Asia,Malaysia and China. China's Yunnan, Guangdong, Hainan, Fujian andTibet's southeast area discovered has the wild banana thedistribution. The banana is in the world one of most ancientcultivation fruit trees, far in 3,000 more than ~ 4,000 years ago hadbeen discovered and Greece had the writing in more than 4,000 yearsago the record. At present the banana rapidly has developed in worldeach place, mainly distributes south the thing two hemispheres thenorth latitude 30° tropics subtropics area, minority distribution innorth latitude 30° outside. The world cultivation banana's countryand the area reach 120, host production area for south centralAmericas and Asia.