12/01/21 - Dr. Giulia Vincenzo


Now let us talk about a slightly more discussed topic, especially after the post lockdown burden: diets. The market (not surprisingly I use this term) of diets has never flourished so much, precisely because it wants to propose easy, miraculous (and drastic) solutions to drop that handful of kg that people just cannot seem to get rid of. One of these is the Alkaline or Acid-Base diet (also called “the alkaline miracle”) which, in addition to not being personalised, and this is a necessary condition for every diet, is unbalanced, and completely lacks scientific basis. Let us see why.

Let us start with the basics: a substance is acidic or basic if, when dissolved in water, it releases or binds hydrogen ions. The acidity value of a substance is called pH and is measured on a logarithmic scale ranging from 0 (maximum acidity) to 14 (maximum basicity).

The physiological pH of our body is very close to neutrality, and the range considered compatible with life is between 7.38 and 7.42 (we will see the difference between the two numbers elsewhere). What really matters, is knowing that the body works well at that value, and a healthy person corresponds to an organism that works well. In fact, this value corresponds to a whole series of very fine body balances and functions such as the folding of proteins which determines their specific function (whether they are hormones, antibody, signal molecules, structural molecules and so on).
In fact, millennia of evolution have endowed us with a long and very fine series of pH control mechanisms (especially blood pH). Remember when I said that it is a logarithmic scale? It means that very small variations correspond to enormous effects and therefore it is good that the body never deviates too much from that perfect number.

The famous alkaline diet, also called acid-base, was invented by a certain Robert Young (naturopath who graduated from an unrecognised online university, then accused of abusive practice and fraud) and is based on a true assumption: the body pH is an important value for health (metabolic acidosis is a serious pathology), it is less true that this can be modified with food, so this dietary proposal lacks scientific foundation.

Perhaps not everyone knows that our stomach from the point of view of acidity is an extremely inhospitable environment with its pH of 1.5-2! For comparison, lemon juice is about 2.5, like that of the more famous Cola. Yes, the one with which you remove the rust from the bolts. At these pH values ​​not even our own enzymes work and, indeed, one of the reasons why it is and must be so low, is precisely to chemically demolish everything that we cannot break up with chewing.

In short: our stomach does not consider how acidic what we eat is, meanwhile it acidifies it even more! Obviously, this is all the more valid for alkaline substances.

The same thing, but on the contrary, happens in the intestine. In fact, after the chemical digestion, it is necessary that the enzymes start working again and therefore it is essential that what we have ingested is brought back to a physiological pH value (or almost). It is at this point that the bile intervenes, which brings everything back to a value of about 7.5-8, effectively neutralising anything that entered our mouth, regardless of its initial pH.

To be able to move forward, it is necessary to adopt the concept of PRAL. Literally translatable as “renal acid loading potential”, PRAL is a scientifically validated method used to calculate the chemical balance of the acidifying and alkalising molecules of a food. The PRAL concept estimates the ability of a food to interact with human blood and vary it.

But then, it is true that food can change the pH of the blood … and what do the kidneys have to do with it? Stay calm! From a practical point of view, all those foods with negative PRAL (e.g. vegetables and fruits) are potentially alkalising towards the blood and, vice versa, those with positive PRAL (e.g. meat, milk derivatives, fish and yolk egg) are potentially acidifying. The key lies in the word “potentially”.

Yes, because we talked about pH control systems, also called “buffer systems” and one of them passes right through the kidneys. When the “acidifying” or “alkalising” substances present in food pass the stomach, they are immediately directed towards the most direct elimination route (e.g. kidneys and lungs). If a food changes blood pH considerably, it means that one or more of these buffer systems has become ineffective and, as a result, it may be a good time to start worrying. To say how important that aforementioned range is, blood itself has its own buffer systems! No! Because, if this has not been understood, i.e. too much above or below 7.4 is not that you feel a little better or worse … you just die!

Yet those who follow the alkaline diet are often better off… Having ascertained that those who follow the alkaline diet tend to change only the pH of their urine, it is not surprising that blood tests tend to improve.

As in all scams, in fact, even in this case, a high-sounding name only serves to mask a series of rules of good food conduct. Those who follow the acid-base diet eat more fruit and vegetables, consequently they are more hydrated, eat more fibre and complex carbohydrates, reduce red meat and other sources of saturated fat, abolish alcohol and simple sugars, ingest vitamins, minerals and antioxidants … The bottom line is not that the so-called acid-base diet is “wrong”, it is that in most cases our everyday diet is completely unbalanced!!!

A varied diet balances itself and what remains to be done, our body does very well, all by itself, regardless of the name we give or the pseudoscientific mechanism with which we justify the way we eat.

Dr Giulia Vincenzo, Freelance Nutritionist Biologist and lecturer at the II level Master in Dietetics and Nutrition at the Catholic University of the Sacred Heart in Rome and Master in Food Behaviour at the Nicolò Cusano University.

Consultant of, and Radio Lattemiele, author for Il Pensiero Scientifico Editore and the Universe Publishing Company, member of the scientific committee of the Peristorie per Strade Onlus project and collaborating partner of the association of psychologists and nutritionists MInD-MettersiInDiscussione.