Madness in blaming acidogenic food

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

The pH of different items (Illustration: Edward Stevens)

The pH of different items (Illustration: Edward Stevens)

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

Diet and diabetes studied in 10,000 women (Photo: The Advocacy Project)

Diet and diabetes studied in 60,000 women (Photo: The Advocacy Project)

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.

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The dark force in gaining weight

A variety of microbes colonise the gastrointestinal system

A variety of microbes colonise the gastrointestinal system

You better know your Smithiis from your Bacteroidetes and Firmicutes or you might start gaining weight. I guess this statement will require quite a lot of explanation. Can I just assume that you know that you carry a lot of microorganisms in your gastrointestinal system? As a matter of fact the number of microbes easily outnumber your own cells. It is believed that the gut microflora contains somewhere around one million million cells (trillion if you are American or billion if you are continental European, confusing I know but big numbers anyway) and weighs between 1 to 2 kilograms. It consists of around 500 different types of microorganisms, many we have not been able to grow outside the gut.

Just so you know, we are born with a sterile gut but very quickly pick up the crucial microorganisms. Within days bugs have colonised the colon in particular with the initial composition dependent on the birth method and food delivery method (natural birth or cesarian section, breast or bottle to be precise).

Why do we carry so many bugs?

The fact that we quickly colonise the colon with beneficial bugs is very important. We actually will live in a symbiotic relationship with our friendly bugs, that is we are mutually beneficial to each other. Our friends fulfil a host of useful functions, including digestion of left-over energy in food, stimulating cell growth, hindering the growth of harmful microorganisms, training the immune system to respond only to disease causing bacteria, and defending against some diseases. Without gut microflora, the human body would be unable to use some of the undigested carbohydrates we consume. However, because some types of gut flora have enzymes that human cells lack they can break down left-over polysaccharides. These include certain starches, fibre, oligosaccharides and sugars that the body failed to digest and absorb.

The bacteria ferment the left-over carbohydrates into short chain fatty acids including acetic acid, propionic acid and butyric acid. These materials provide a major source of useful energy and nutrients for humans. The bugs also help the body to absorb essential dietary minerals such as calcium, magnesium and iron. Evidence also indicates that bacteria enhance the absorption and storage of lipids and produce and then facilitate absorption of necessary vitamins like vitamin K.

This is all good to an extent, because we don’t want to waste food. And we would without the gut microflora. It has been shown in laboratory experiments that animals raised in a sterile environment and lacking gut flora need to eat 30% more calories just to remain the same weight as their normal counterparts. Unfortunately, the gut flora is in a constant state of change and the important balance between microbes can be disturbed. An excess of some of the bugs can make digestion too efficient, and in here lies the problem.

The problem bug

In 2009, a large human study concerning obesity and gut flora was conducted. It was found that obesity disorders could be the result of an imbalance in the gut flora, which could have serious consequences such as cardiovascular disease, type-2 diabetes, and colon cancer. However, a recent study by a different group took the science one step further finding that overweight people may be more likely to harbour a certain type of intestinal microbe. This microbe may contribute to weight gain by helping other organisms to digest certain nutrients, making even more calories available.

The dark force that seems to cause weight gain is called Methanobrevibacter smithii (the Smithii from the initial sentence). The more M. smithii bugs you have, the more you are likely to weigh. As is implied by the name of the organism it produces methane when digesting food. A way of detecting the presence of the organism is to test the amount of methane and hydrogen in the breath – elevated levels indicate the presence of the bug. The scientists found that people with the highest readings on the breath test were more likely to be heavier and have more body fat, and they suspect that M. smithii may be at least partly responsible for their obesity.

This type of organism may have been useful thousands of years ago, when people ate more roughage and needed all the help they could get to squeeze every last calorie out of their food. But modern diets are much richer and the need less. It thus seems that our external environment is changing faster than our internal environment can cope.

As a curiosity M. smithii was also found in higher numbers in anorexic patients. On the surface this seems to be an anomaly. However, it is believed that this may be due to an adaptive attempt by the gut microflora towards optimal use of the low caloric diet of anorexic patients.

A possible future solution

A future pill might help weight loss (Photo: fantasyhealthball)

A future pill might help weight loss (Photo: fantasyhealthball)

Question is should we just accept our fate and let the bugs grow as they want? Maybe not since scientists are trying to figure out if it would be possible to help people lose weight by selectively killing off the guilty bug. They are fully aware that to just kill gut bacteria in general could be a disaster. Studies have already shown that taking antibiotics can alter the balance of microbes in a bad way, causing stomach upset, possibly allowing deadly infections to take hold and, perhaps, even allowing a takeover by the obesity-generating bugs. However, a future selective pill targeting our Smithii might be a possibility for losing weight.

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