>> Jan 14, 2010
Alkaline or “low acid” diets seem to be popping up everywhere lately. The premise behind them is that the western diet is too high in acidic foods, which can cause everything from decreasing fat loss to increasing your risk of cancer.
What is “pH”?
“Physiological pH” is the level of acidity in the body. The human body is really good at controlling pH levels, because they are so critical - every cell in our bodies depend on it! pH must remain neutral in order for our bodies to function properly. When your pH shifts a little, your body will make adjustments to correct it. It does this through changing breathing rates (which adjusts CO2 levels), using up excess hydrogen (acidic) ions, and excreting or holding onto acidic substances via the kidneys.
The “Alkaline Diet” or “Acid-Ash hypothesis” are theories that the western diet is high in acidic foods, which alters the pH in our bodies and is not corrected properly by the mechanisms listed above. In order to correct the pH, our internal reserves are used to neutralize the acids, mining our bones, joints and vital organs of precious elements. Over time, they say, this leads to disease. The "acid-ash" idea is the theory that acids in the diet, such as phosphate, lead to more acid ion loss through urine, taking calcium with it, which leads to de-mineralization of bone and may result in osteoporosis. Wow! Sounds horrible!
So what are “acidic” foods? Animal protein, sugar, caffeine, and processed foods to name a few. Cutting out these foods and following the “Alkaline Diet” leaves you with the components of any typical “healthy” diet. The fact that eating a diet higher in fruits and vegetables, lower in fat and higher in fibre is good for us is not news, and this part of the diet is fine. However, the alkaline diet also promotes exclusion of many foods with well-known health benefits, such as fats and oils (essential fatty acids), beans and legumes (phytonutrients, fibre), and some fruits (antioxidants, vitamins, fibre).
What the facts say...
This alkaline diet is based on a theory. There is a significant lack of studies looking at pH in the human body. Most studies regarding the alkaline diet have been done in test tubes and animals, neither of which are necessarily applicable to humans. I was able to find 2 studies and 2 articles on the subject, and here’s the low down...
I found two studies looking pH. The first was a massive review (which examined 30 other studies) looking at calcium balance with acid (from phosphate) intake. They found that the amount of calcium excreted through the urine was actually less when subjects were given more phosphate, regardless of how much calcium they were taking in, or how acidic the phosphate was. Basically, it disproves the acid ash theory and, in fact, calcium retention actually increased with phosphate supplementation.
The second study I found looked at acid-base load of the diet and urinary pH. (put in links to studies). This study measured urine pH in relation to how acidic the diet was. They found that a diet higher in fruits and vegetables, and lower in meats, lead to a more alkaline pH, at least in the urine. But the question is - does the pH of our urine accurately represent the rest of the body? That seems to be unclear and could throw this study out the window. And even with a slightly alkaline or acidic pH, we don’t know what the exact effects on health would be, if any.
I did find 2 articles (not studies) from MD's whose personal opinion it is that there is some basis to this diet. For people who propose this diet, the theories are still just that, theories. But the advice from these people is familiar - more fruit, veggies, fiber! I had to laugh when I read the advice from one of the advocates of this diet, advising people to "fill half their plate with vegetables" at meals... exactly what dietitians are advising! The theory may be new, but the recommendations are not groundbreaking.
The reasons to eat less protein and more fruits and vegetables are plenty, but currently, the acid-alkaline basis isn't a strong one. We already know that the western diet isn't a particularly healthy one for a myriad of reasons, and the chronic disease epidemic is evidence of that. We need to focus on eating healthier... period. "Acidic" foods just happen to be those that are also high in preservatives, chemicals, salt, sugar, etc... Foods that we already KNOW are bad for us and contribute to cardiovascular disease, high blood pressure, diabetes, and so on. At this point, what ever gets people eating their fruits and veggies is a good thing. Don't bother getting too caught up in what fruits and veggies are less acidic - JUST EAT THEM!