Before I begin his article, I want to admit that I was slightly hesitant to write about this topic as I know it divides people’s opinions. I don’t seek to be controversial or knock other people down but in the name of health, I feel it’s only right to set the record straight on certain nutrition facts. It’s slightly cringeworthy when I see social media posts about how certain diets can cause or cure x, y or z disease.
Some health conditions linked to food or diet are very legitimate such as non-coeliac gluten intolerance or intermittent fasting. They have substantiated research and data to back them up.
One of the most common nutrition myths I see is the acid-alkaline hypothesis or ‘alkaline diet’. I want to discuss here the reasons why the health claims for an alkaline diet are not valid and why you don’t need to be concerned about eating ‘acid forming’ foods or going on an alkaline diet.
The rationale behind the ‘acid-alkaline’ belief is as follows: acid ash is produced by meat, poultry, cheese, fish, eggs and grains. Alkaline ash is produced by fruits and vegetables, except cranberries, prunes and plums. Pure fats, sugars and starches are neutral as they don't contain protein, sulphur or minerals. I repeat, sugar is NOT acid forming! That doesn’t mean it’s ok to guzzle down a tub of Haribo, but I’m just setting the record straight as almost always sugar is listed as ‘acidic’.
Proponents of the alkaline diet believe eating a net gain of alkaline ash producing foods vs acid ash producing foods will lead to good health and prevent disease. Their initial test to prove this theory is to take a urine pH strip and measure urine a few of hours after having a green smoothie vs a chicken sandwich. The green smoothie will create a more alkaline pH on the urine test strip while the sandwich produces an acidic urine pH. Therefore, the theory is this equates to a more alkaline environment in the body. This is fundamentally flawed as I will go on to explain.
Before I continue, it's important to note that the pH value varies greatly within the body. Some parts are acidic, others are alkaline. There is no overall level. The stomach is loaded with hydrochloric acid, giving it a pH value between 2 and 3.5 (highly acidic). This is necessary to break down food so guzzling down that alkaline water isn’t the best idea if you actually want to digest your food! On the other hand, human blood is always slightly alkaline, with a pH between 7.35 and 7.45.
The obvious problem with the alkaline diet theory, is that the function of the kidneys’ is completely ignored. Our kidneys are fundamental to removing acids and regulating body pH. It's one of their main roles. The kidneys produce bicarbonate ions that neutralise acids in the blood, a sustainable process which enables the body to tightly regulate blood pH (1)
The blood pH value falling out of the normal range is very serious and can be fatal if untreated. However, this only happens during certain disease states like diabetes (acute acidosis) or kidney failure, and has absolutely nothing to do with the foods you eat from day to day (2)
Our respiratory system is also involved in controlling blood pH. When bicarbonate ions from the kidneys bind to acids in the blood, they form carbon dioxide (which we breathe out) and water (which we pee out).
Acid forming foods cause Osteoporosis by leaching calcium and minerals from our bones to neutralise excess acid from our diet… or so the theory goes.
The alkaline diet originated from theories related to osteoporosis research, however, most proponents of the diet maintain the incorrect belief that certain foods can affect the acidity (pH) of the body and can therefore be used to treat or prevent diseases such as cancer and osteoporosis.
Recent systemic reviews have been published which have methodically analysed the weight of available scientific evidence, and have found no significant evidence to support the acid-ash hypothesis regarding prevention of osteoporosis (3,4) In fact, high protein diets (acid forming) are linked with healthier bones (5, 6)
Cancer cannot survive in an alkaline environment; therefore an alkaline diet must be beneficial in treating cancer or preventing it. Well no, not really. As highlighted already, the pH of the blood cannot be modified by diet so adopting an alkaline diet is not likely to make any impact on cancer cells. Also, while tumours grow faster in acidic environments, the tumours create this acidity themselves. This is due to differences in the way that tumours create energy and use oxygen compared with healthy tissue (7). Cancer is a complex process initiated by mitochondrial dysfunction caused by DNA mutations, and has nothing to do with the acidity of your diet.
Having said all the above, I believe it’s in our best interest to have a good mix of nutrient-dense, alkaline and acid-forming foods; ideally, you want to eat more alkaline-forming foods than acid-forming foods to have the net acid and alkaline-forming effects of your diet match the slightly alkaline pH of your blood. This takes the burden off the body’s energy reserves leaving more energy for enjoyable tasks like exercise and learning. If you’re eating a balanced diet consisting of real unprocessed food this should happen quite easily.
There are certainly benefits to consuming alkaline foods and limiting processed foods which have nothing to do with pH. There are specific phytonutrients in fruit and vegetables that simply can’t be found in other types of foods. Anyone switching to an alkaline diet would significantly reduce their consumption of grains, which for some people may result in health improvements especially if they have blood sugar issues or a gluten intolerance.
My advice… don’t waste your money on "alkaline water" and other marketing gimmicks. Unless you have a medical condition such as chronic kidney disease, you can enjoy eating a balanced diet of unprocessed alkaline and acid foods without any concern.