The other day I was in a health food store and overheard the shop clerk selling a customer a type of supplement that contains nutrients extracted from green plants like chlorella and spirulina. She told the customer to put this powdered supplement into her smoothies and by drinking it, with other fruits and vegetables, she will “alkalise” her body. She told the customer that alkalising her body is desirable because acidity in the body leads to poor health and disease.
The reason why she said this is because there is this idea going around that the food we eat can effect the pH of our blood and extracellular fluid. An acidic state in the body leads to disease and a more alkaline state prevents disease.
Acidic foods are things such as animal products, dairy and grains. Alkalising foods are things like fruits and vegetables. What makes a food acidic or alkaline is determined by the chemical structure of nutrients in a particular food group and how it is metabolised in the body.
It has been thought that you could test the pH of the body through testing the urine. Depending on what you eat does have an effect on your urine pH, so if you have meat your urine is more likely to be acidic compared to having a green smoothie.
However, the pH of your urine has nothing to do with pH of your blood and body. The pH of blood and extracellular fluid is tightly regulated by the kidneys through various mechanisms (sodium, potassium etc.). The pH of the blood will only change to an acidic pH in serious disease such as end stage kidney failure, when the kidney can’t regulate acid/-base balance anymore. The pH of our blood is tightly regulated between a neutral 7.35-7.45. Any variations in pH above or below these numbers can lead to coma and death. Therefore, what you eat has little effect on the pH of your blood as it is so tightly regulated. If your blood pH was to be affected by what you ate, you would not survive very long.
Despite all of this, certain foods we eat leave an acidic or alkaline “ash” after they are metabolized and this can be seen in the urine, which is why the pH of our urine changes depending on what we eat. So if you have a green smoothie for breakfast it is likely your urine would be an alkaline pH, as opposed to if you ate a steak, it is likely your urine pH would be acidic.
Eating an acidic diet has been linked to cancer, osteoporosis, muscle wasting and other chronic diseases. Is this true?
Lets look at each one individually.
Osteoporosis and muscle wasting.
Some studies show that a higher acid diet often increases the excretion of calcium in the urine. Some researchers assumed that this extra calcium was coming from bone. The idea behind the excess calcium in the urine was that in order to keep blood pH constant, the body pulls minerals and other nutrients like phosphorus from our bones and muscle, in order to neutralise any excess acid that is produced from our diet.
Therefore, an overall acid-forming diet (such as the typical Western diet) can cause bone demineralisation, muscle wasting and osteoporosis. However, this is not correct, as it is the kidneys, not the bone or muscle, which produce buffers to keep the blood pH neutral. This hypothesis is also a common reason as to why some people say that high animal protein diets cause bone demineralisation, however it is actually quite the opposite. While it is true that the body will pull calcium from bone to maintain blood levels of calcium as calcium is vital for nervous system and muscle function, calcium is not used to maintain blood pH. The body will pull calcium from bone at the expense of bone health because calcium levels in the blood keep us alive, however it doesn’t do this to maintain blood pH
High animal protein diets are associated with increased bone mass and increased muscle mass. These diets also increase calcium absorption in the gut, which most studies don’t measure. Although there is calcium excretion via the urine, there is more that is absorbed in the gut.
Overall, most of the evidence doesn’t support the idea that a high acid forming diet leads to osteoporosis or muscle wasting. It doesn’t make sense physiologically and well-designed studies do not support it.
It is said that cancer grows better in an acidic environment; therefore eating a high acid diet can lead to cancer. First of all, as I mentioned before, your diet does not influence the pH of your blood. And even if it did, it turns out that cancer creates its own acidic environment. It’s not the acidic environment that causes the cancer; it’s the cancer that causes the acidic environment. Furthermore, cancer is capable of growing in an alkaline environment as well.
Acidic diets may be associated with certain chronic diseases, however correlation does not mean causation. This is because eating lots of processed and refined foods is acidic, and we know that eating lots of processed foods can lead to chronic health issues. This is why an association can be drawn. However, an acidic diet based around whole, unprocessed foods will be unlikely to cause health issues.
If you switch to a more alkaline diet from a highly refined and processed food diet, it is likely you will feel better. This has nothing to do with pH balance in the body. Eating more fresh, unprocessed produce is always going to make you feel healthier, especially when it displaces nutrient poor processed foods.
The goal is to eat a well balanced diet with a variety of animal based and plant based foods that are minimally processed. Check out this post, to get an idea of what a balanced diet may look like.