Before I was vegan I went on an alkaline diet to improve my pH and it helped greatly. I measured my pH before the diet and for a year after. I used litmus paper to test my urine and saliva. An alkaline diet is a lot like a plant based diet, except you allow yourself one or two non-ideal items a day. Foods to totally avoid we’re animal products, margarine, alcohol, soda water, coffee, black tea, soy sauce, vinegar, sugar, corn syrup, white flour, and processed foods. I would pick one or two small servings a day from this list: Whole grain flour/bread, corn chips, rice, oil, fruit juice, peanuts, pistachios, cashews. Totally acceptable foods are: fruits, vegetables, beans, almonds, dark chocolate, smoothies, and herbal tea. It’s about reducing the amount of stomach acid needed to digest your food. The less processed the food, the easier on our digestive system. Optimizing protein is also key because it is takes more acid to process. I spent that first year tracking my protein to make sure I was not over consuming it but also getting enough. There was a clear relationship between my daily diet and the pH of my fluids. Blood is the only bodily fluids that stays constant; everything else ranges based on diet and exercise. As long as I’ve been alkaline I haven’t had a cold/flu. When our pH is low our fluids slowly erode our tissue, like vinegar marinating a steak.
Your body maintains a very strict pH at all times. If it were to veer even slightly off and not right itself, you would die. That’s just basic physiology. That being said, you can certainly have other levels in your body that are off (blood levels of vitamins or minerals or electrolytes, etc.) that could contribute to not feeling optimal.