Yes, a lemon will assist you to alkalize, but don't think that a lemon is alkaline, or that all of its juice is alkaline. 

It is true that if you plunge a pH meter into a lemon it will read as acid. But once you have consumed (burnt up/converted to energy/metabolised) a lemon, what is left in your body is alkaline.

It is this 'ash' that is left over from all of our foods that determines our acid/alkaline balance, not the pH of the food we are about to consume. This is known as the 'ash' of a food.

After food has been completely burned up and converted to energy, the leftover minerals are what makes up our mineral reserves and therefore our pH or acid/alkaline balance.

Many other factors affect our pH balance, including pollution, stress and our own body's metabolic wastes.

We are not "what we eat". We are what is left over after we eat.