Here we go again, you do think that some myths proven wrong would disappear. But not so. This time it is a dubious epidemiological study (yes I know I have a bias against spurious epidemiological results) that is claiming a relationship between acidifying foods and diabetes without a believable mechanistic theory to explain the results.
Let’s start from the beginning to better understand why the researchers even thought about testing the influence of so called acid producing foods on the development of type 2 diabetes.
Body regulation of pH
In the early 20th century nutritionists coined the term acidic and alkaline diets describing a group of foods that was supposed to be able to affect the pH of bodily fluids like blood and urine. As I am sure you know acidity-alkalinity is expressed on a pH scale with 7 as neutral between the two. A pH of 0 is completely acidic, and a pH of 14 completely alkaline. Blood happens to be slightly alkaline, with pH maintained in a very close range of between 7.35 and 7.45. The theory of the alkaline diet proposed that eating certain foods would help maintain the body’s ideal pH balance to improve overall health. But we now know that the body maintains its pH balance regardless of diet. This is very important and thus precise regulatory mechanisms make sure there are no deviations.
But pH is not constant across the body. On the contrary, the stomach has a pH ranging from 1.35-3.5. It must be acidic to aid in digestion. Urine can also be acidic and this is the one area in which the diet may affect the pH level. The role of the diet and its influence on the acidity of urine has been studied for decades. Urine excretion is actually a clever way of balancing our overall body pH.
Diet will not influence blood pH
Next we should look at the purported acidic and alkaline diets. And this is not as easy as it sounds. You would think that the acid in foods like lemons, grapefruit and even tomatoes would cause the trouble, but this is not the case. Instead, it is claimed that meat, fish, poultry, dairy products, processed foods, white sugar, white flour, alcohol and caffeine produce acid in the body after they’ve been digested. On the contrary, the alkaline diet is mostly vegetarian. In addition to fresh vegetables and some fresh fruits, alkaline-promoting foods include soy products and some nuts, grains, and legumes.
There’s no doubt that replacing sausages and potato chips with fruits and vegetables is good for you. But this has nothing to do with the alkalinity of the diet, rather basic facts about nutrition and physiology. No matter what we eat, the pH of our blood is going to stay the same.
The term “alkaline diet” has been used by alternative medicine practitioners, with the proposal that such diets treat or prevent cancer, heart disease, low energy levels as well as other illnesses. These claims are not supported by medical evidence and make assumptions about how alkaline diets function, contrary to current understandings of human physiology. The “acid diet” has also been considered a risk factor for osteoporosis, though more recently, the available weight of scientific evidence does not support this hypothesis.
The new epidemiological results
Now researchers propose that an acidic diet may be associated with up to a 56% increased risk of type 2 diabetes. They followed more than 60,000 women over 14 years in order to assess whether dietary acid load impacted later risk of type 2 diabetes. At the beginning of the study the women had to complete a food frequency questionnaire. From the collected dietary data they calculated a potential renal acid load at that time and then followed the women for 14 years recording new cases of diabetes. Assuming that their diets stayed the same over that long time span, they concluded that dietary acid load 14 years ago was linked to increases in the incidence of type 2 diabetes.
While there have been recent improvements in recognising different variables that can affect acid excretion in urine, the level of detail needed to predict the urinary pH based on diet is still daunting. Precise calculations require very detailed knowledge of the nutritional components of every meal as well as the rate of absorption of nutrients, which can vary substantially from individual to individual, making effective estimation of potential renal acid load very difficult.
Although the research team attempted to adjust for confounding factors, there could be many other reasons for their findings. Intake of various macronutrients and food categories were very different across the diet groupings. The high acid group consumed the least magnesium and magnesium has previously been inversely linked to type 2 diabetes. The high acid group consumed the fewest vegetables. Although the evidence is somewhat unclear, vegetable intake is usually associated with a reduced risk of type 2 diabetes, particularly root vegetables and leafy greens. Coffee is one of those consumables that everyone knows is bad for you but which is actually linked to a number of health benefits, including a reduced risk of type 2 diabetes. The high acid group consumed the least coffee. We could go on and on.
The myth exposed
That diets high in acid producing elements will lead the body in general to become acidic and foster disease goes against “everything we know about the chemistry of the human body” and has been called a “myth” in a statement by the American Institute for Cancer Research. Unlike the pH level in the urine, a selectively alkaline diet has not been shown to cause a sustained change in blood pH levels, nor to provide the clinical benefits claimed by its proponents. Because of the body’s natural regulatory mechanisms, which do not require a special diet to work, eating an alkaline diet can, at most, change the blood pH minimally and transiently.
What you eat can have a profound affect on your health, but the acidity or alkalinity of foods is not important. As has been stated in another blog, eat your vegetables and fruits. Get your micronutrients and plant polyphenols. Drink your coffee. Try not to eat so much food that you gain weight and overload your cells’ ability to handle the energy. Exercise consistently and intelligently. And you will be fine without worrying about acid producing food.
- The Alkaline Diet: Fact or Fad? (deakinnutrition.wordpress.com)
- Study is the first to show higher dietary acid load increases risk of diabetes (eurekalert.org)
- Increased Diabetes Risk for Women Who Eat High Acidic Foods (medindia.net)
- High acidic diet increases diabetes risk in women (indiavision.com)
- Meat’s Acidity Linked To Diabetes Risk In Women: Can Fruits And Veggies Lower The Risk? (medicaldaily.com)
- pH Balance. Does it matter if my foods are alkaline? (ewehmer.wordpress.com)