We continue answering questions about diet and cancer myths from our chat last month.
Question from Kathy:
Does eating an “alkalizing” diet help prevent cancer? I’ve never read a medical study that says this is the case, but boy, there are a lot of books touting eating foods that “alkalize” the body. Is there merit to this, or is it just the fact that most “alkalizing” foods happen to be vegetables that this way of eating may help prevent cancer?
A quick search on Google for “alkaline diet” or “pH diet”* results in hundreds of thousands of hits, so yes, it is very popular. Food is considered alkaline or acid based on laboratory combustion of the food.**
It’s based on the claim that cancer cells thrive in an acidic environment and can’t survive in alkaline surroundings, so an “alkalizing diet” would promote a more alkaline environment in the body. There are problems with this claim.
1. The studies finding that cancer cells thrive in an acidic environment were done in a laboratory setting. It would be nearly impossible to alter the cell environment to create a less-acidic environment in our bodies. For example, the stomach is very acidic for proper digestion, so we wouldn’t want it more alkaline.
2. Our acid-base balance is well regulated – blood pH is tightly controlled normally by the body between 7.35 and 7.45. If it becomes too acid or alkaline, that could be life threatening and it is typically an indication of a serious health problem, not the underlying cause.
Generally, vegetables, fruits and seeds are considered to be alkaline and meats, beans, nuts and grains are acid. So, as you say, the diet would be rich in vegetables and fruit and lower in meat. This is similar to AICR’s diet recommendations for lowering cancer risk – a mostly plant-based diet, limiting red meat to no more than 18 oz. per week, and avoiding processed meat.
However, some very healthy foods are listed as “acidic” such as whole grains, beans and even some vegetables such as carrots. So keep it simple and follow AICR’s New American Plate to lower cancer risk simply by filling at least 2/3 of your plate with vegetables, fruits and whole grains, and 1/3 or less with meat, poultry and fish.
There are many claims about this diet including weight loss, more energy and solutions to other common problems, but according to the American Dietetic Association, “large, well-designed clinical trials on the effectiveness of the many claims made for the alkaline diet are lacking.”
Just a note: the pH of urine can be changed somewhat by diet because the kidney is key in maintaining the proper body pH. Some proponents of this diet encourage checking your urine pH to see if your diet is alkaline or acid. Keep in mind that an increase in acid or alkaline in the urine reflects the fact that the kidney is doing its job. A change in urine status does not indicate a change in “overall body pH.”
*pH is a measure of acidity/alkalinity on a scale of 1-14. Seven is neutral, with anything above that alkaline and anything below that acid.
**Alkaline-ash foods or Acid-ash foods: This is based on the ash that remains after the combustion of foods under laboratory conditions.