‘Alkalising the body’ is probably too broad brush for us to develop the understanding of this area.  There are different key systems and parts of the body that require different pH levels.   We probably want to achieve a higher acidic pH on our skin and within our urinary system to balance bacteria, and within our GI tract to break down protein, but within the liver / gall bladder and pancreatic fluids we would hope for a higher alkaline pH to stabilise the amount of stomach acids with digestion. 

In the last 200 years alone, the changes to our diet have caused a net acid load, such changes as increased sodium intake and depleting levels of potassium, magnesium and zinc are particularly common.  

While a low-carb high, protein diet would probably change very little in the blood chemistry, the urinary chemistry would almost certainly be affected and by incorporating alkalising foods and drink in to our diet we can help to offset the increased acid load. 

It’s worth mentioning that food groups can be compartmentalised in to categories of PRAL’s (Potential Renal Acid loads), this gives an indication of how much acid load we may have to handle.  Calcium helps to buffer a net acid load but in the case with repeated daily high acid loads, we risk depletion of calcium which has its own issues.  

Do consider that if you are on a high protein diet for sporting / professional purposes but also happens to be combined with high acid renal load this may decrease bone density over time.  In this case, it is very prudent to take a look at the PRAL group for the foods you consume and consider taking measures to buffer by using foods / drinks or supplements that are alkali rich.