miércoles, 15 de junio de 2016

Alkalise or Alka-lies??

Here at Gabinete de Rueda-Bradley we are often asked what our opinion is on popular diets. By that we mean a diet that has appeared in the media offering to cure us of all our ills and is often endorsed by several celebrities. Usually the initial hype is quickly followed by cook books, apps and several supplements that we are encouraged to buy. While some diets can be dismissed immediately, (maple syrup diet anyone?) some do require a closer look.

One such diet is the alkaline diet (aka alkaline food, alkaline ash). It isn't particular new, we first came across it around 2010/11, but it is persistent and has the needed celebrity/health guru backing to be a popular choice for people. We wanted to take a closer look at the evidence for and against the diet and share our findings. 

The diet

The fundamental principle of the diet is balance! As we know the human body likes to be in a state of balance (homoeostasis), two obvious examples are temperature and blood sugar. The body has several mechanisms to keep both of these in check. The same can be said for pH, according to Greenopedia the body’s pH levels are the “key to life”1.

The pH scale is a measure of how acidic or basic (alkaline) something is, 0 - 6.9 is acidic 7 is neutral and 7.1 – 14 is alkaline. The pH of human blood is tightly controlled at a slightly alkaline range of 7.35 – 7.452. A point to remember here is be wary of people who claim the human body needs, or likes an alkaline state, while this is true for blood there is a wide range of pH throughout the body. Saliva for example is slightly acidic at 6.35-6.85. People who claim that the entire body needs to be alkaline misunderstand the concept. 

Now back to the diet, the idea behind the diet is that when we metabolise foods we are left with a residue (ash) that is either acidic or alkaline. The more foods you eat that leave an acidic residue the more acidic your blood becomes the more health problems you have. And so the opposite is said to be true if you eat more alkaline foods. Also, according to Greenopedia, when we don’t eat enough alkaline foods our body will pull magnesium, calcium and phosphorus from our bones, teeth and organs to bring our blood pH back into the desired range1. Not surprisingly advocates of the alkaline diet cite preserving bone health and preventing osteoporosis as key points of the diet. Other health claims range from improved immune health to a more eyebrow raising prevention of cancer. 


Foods are classified as either acid or alkaline forming based on their Potential Renal Acid Load (PRAL). This is a calculation put forward by Drs Remer & Manz3, basically the higher a food’s PRAL score the more acidic it is and in turn will lower the pH of the urine (notice we said urine and not blood). Followers of the alkaline diet are encouraged to eat an 80% - 20% split in favour of alkaline foods, or foods with a low or even negative PRAL score.

Followers of the diet are encouraged to eat lots of fruit and veg (organic if possible) and minimise sugar, grains, dairy, meat and fish. 

The evidence

As with most trendy diets you can find an overwhelming amount of supporting “evidence” on websites and social media. When visiting these websites, we found no references to clinical trials that support their claims, but we did see plenty of advertisements for books and supplements. we know, we were surprised too!! On a serious note anything that claims to fight something as serious as cancer but has no scientific evidence to back it up is at best irresponsible and at worst criminal. 

Diet and cancer

So starting with cancer “there is no scientific literature establishing the benefit of an alkaline diet for the prevention of cancer at this time”2. What is interesting though is that some (not all) chemotherapeutic agents function better under an alkaline environment. It has been suggested that using substances such as sodium bicarbonate may enhance treatment regimes2. One would assume that this works by increasing the body’s amount of bicarbonate, an abundant buffer found within the extra-cellular fluid. Those of us with a sports science background will be familiar with the potential unpleasant side effects associated with ingesting sodium bicarb. GI distress being the best way to put it. 

Diet and bone health

As mentioned before one of the key selling points of the alkaline diet is that by eating alkaline food your body will not have to take calcium from your bones in order to balance the pH of the blood. Early animal and human studies found that high protein diets resulted in an increase in urinary calcium loss. This was originally thought to reflect an increase in bone resorption (loss) possibly due to the body using calcium as a pH buffer4. However more recent studies have shown that the increased loss of calcium in the urine is partly due to an increase in efficiency of calcium absorption as opposed to increased bone loss2,4. In fact recent evidence has not only shown that a link between acid load and decreased bone health is not strong5 but adequate protein intake may actually be protective for bones2,4. The general consensus is that increasing fruit and veg intake is more important than limiting protein intake when it comes to bone health. 

pH of blood and urine

Although many of the advocates will refer to the pH of blood and urine as they were the same thing, this is not the case. As we know, the pH of our blood is kept tightly within a small range, if this were not this case there would be serious consequences, death obviously being the least favourable. The body has a number of tools to keep blood within its desired pH range including, several intracellular buffers (see our post on beta alanine), amino acids that can act as buffers, exhalation of carbon dioxide, and the kidney. These mechanisms act extremely quickly and can bring the blood back into the normal range within minutes6. The bottom line is that the food we eat has little or no effect on our blood pH2, it does however, have an effect on the pH of our urine which can vary widely from acidic to basic. Acidic urine is a completely normal process of the body although chronically acidic urine can increase risk of kidney stones2, following a balanced diet will prevent this. We may read that celebrities carry pH testing strips with them at all times to check “what state their body is in”, but all they are testing is the pH of their urine NOT the overall health of their body.

J3D3-CC BY-SA 3.0


While any diet that encourages us to eat fruit and vegetables and avoid process foods is certainly worth considering, the claims that alkalising the body will help us avoid osteoporosis and cancer are simply not backed up by any evidence. Alarm bells often ring when instead of references to clinical trial we are bombarded with adverts for books and supplements. We are also not convinced on the thought that limiting protein intake is beneficial to our health and in particular bone health. In fact, as mentioned before, recent evidence has shown that protein may have a protective effect for bone health. We certainly wouldn’t recommend this diet for elderly or athletic people.

In conclusion the health benefits associated with this diet have nothing to with pH and are most probably due to an increased intake of fruits and vegetables and an avoidance of processed foods.


  1. http://greenopedia.com/alkaline-diet- benefits/
  2. GK Schwalfenberg , Journal of Environmental and Public Health 2012, The Alkaline Diet: Is There Evidence That an Alkaline pH Diet Benefits Health?
  3.  Remer T1, Manz F. J Am Diet Assoc. 1995 Jul;95(7):791-7.Potential renal acid load of foods and its influence on urine pH.
  4. C Geissler & H Powers 2005,Human nutrition 11 th Edition. Elsevir
  5. Garcia AH, Franco OH, Voortman T, de Jonge EA, Gordillo NG, Jaddoe VW, Rivadeneira F, van den Hooven EH Am J Clin Nutr. 2015 Dec;102(6):1595-603. 2015. Dietary acid load in early life and bone health in childhood: the Generation R Study.
  6. GJ Tortora & S Reynolds Grabowski. 1996, Principles of anatomy & physiology 8th Edition. Harper Collins.

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