The optimum pH levels of the human body vary depending on the specific body part, states the Journal of Environmental and Public Health. For example, the stomach has a very acidic pH range of 1.35 to 3.5, while the bile has an alkaline pH range of 7.6 to 8.8.
The optimum pH level of the blood is 7.35 to 7.45, which is slightly alkaline, mentions WebMD. The blood remains at that pH level regardless of whether a person eats alkaline or acidic foods. However, the urine is affected by the variety of food that a person eats, so its pH level ranges from acidic to alkaline.