does lemon or lime reduce acidity
Lemon juice is less acidic than the gastric acid -- primarily Hydrochloric acid -- already present in the body. Gastric acid has a pH of between 1-2. Lemon juice has a pH of 2-3. That will dilute (i.e., lower the acidity) of stomach acid, but that acid will be neutralized in the small intestine by the presence of and production of bicarbonates. There is no significant effect on the body's acidity from consuming lemon juice.
Because foods are not known to alter the pH of your blood or body, lemons won't acidify you either. Drinking lemon juice with water may increase the acid level of your urine, however, which is a sign that your kidneys are doing their job -- ridding you of excess acid.