Are Alkaline Diet Claims About Cancer and Other Health Benefits True?

Posted by Eric Troy on 20 Jul 2015 18:36

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There are many books and websites that promote so-called alkaline diets, or that advise that you must somehow balance your intake of "acid" and "alkaline" foods to ensure good health. It is even suggested that such a diet will treat or prevent cancer. Some websites also claim you can test your pH so that you can then adjust it to a proper level via the foods you eat. Is it true?

What is pH, Acid, and Alkaline?

Acidic solutions are solutions that have a low pH, and basic (or base) solutions have a high pH. This has to do with the number of hydrogen ions the solution contains. Learn more about acids, bases, and the pH scale. A pH of 7 is considered neutral, neither acidic nor basic. A pH of less than 7 is considered acidic, and a pH of more than 7 is considered alkaline, or basic.

What is the pH of Your Body?

The fluids of your body, of course, have a pH as well. The pH of blood is between 7.35 and 7.45 (approx. 7.4), just slightly alkaline. This slightly alkaline condition is necessary for the cells of your body to carry out their functions. The pH of your blood must be maintained very precisely by your body, as even slight alterations can cause you to become very ill, or even to die.

For example, if your blood pH were to shift only a little lower than 7.35, you'd begin to have symptoms, and if it went much lower, you would be in grave danger. Conditions of low pH are called acidosis. Conditions of high pH are called alkalosis. The symptoms of each depend on the causes, which are generally separated into two categories, metabolic, and respiratory. Although it is possible for either condition to occur in anyone given the right circumstances, they are most commonly seen in very ill or hospitalized people.

acid versus alkaline foods or healthy foods
acid versus alkaline foods or healthy foods

Do the Foods You Eat Affect Your pH?

As you are probably beginning to understand, there is little to no chance that the pH of your blood is abnormal at present. Also, if the food you ate significantly affected the acid-base balance of your body, surely, you would have a hard time continuing to function, let alone to survive. Fortunately, the body, under normal circumstances, is very good at maintaining its proper pH. When substances are present that can shift the balance, your body uses very swift mechanisms to deal with them, such as through your respiration, and your kidneys. The first line of defense, however, is the body's chemical buffer systems, such as the phosphate buffer, protein buffers, and bicarbonate buffer.

Are Foods Really "Acid" or "Alkaline?"

The foods you eat do not affect the pH of your blood, but it is true that they can be considered alkaline or acidic. This does not depend on how acidic the foods are, but rather on the "ash" they leave behind once they are metabolized. Foods higher in alkaline minerals like calcium, magnesium and potassium are alkaline forming and foods higher in phosphate and sulfur are acid forming. Therefore, orange juice, even though it is acidic, is actually alkaline in its effect.

Although plants are generally more alkaline to the body than meats, which are acidic, you can eat a very large amount of either acidic or alkaline foods, and the body's buffer systems will ensure that the pH of your blood remains within a constant narrow range.

Such a highly acid or highly alkaline meal, however, can affect the pH of your urine. This may be a cause for some of the confusion. The pH of your urine, though, does not reflect the pH of your blood. What it does reflect, however, is your kidney's doing their job to maintain the proper pH in your body.

Despite all this, many claims are made as to the amazing positive effects of alkaline, or alkaline-acid diets. Many of these claims center on the diet's effect on your body's pH. Although shifting to a primarily plant-based diet is not generally a bad idea for your health, if it is taken too far, such as cutting out all fats and oils, and limiting protein intake, nutrient deficiencies in essential fatty acids and protein can result. The people that recommend these diets usually try to convince us that we must eat a certain way to maintain the body's equilibrium, despite the fact that there is no scientific support for the claim.

Monitoring Your pH

Books promoting a so-called Alkaline Diet even stress the importance of monitoring our pH, and that we must labor to "hit our pH target" as if we aren't already within this target. To monitor our pH, we are told to use pH test strips to test our urine or saliva. As we have seen, the pH of your urine is no indication of the pH of your blood! Furthermore, the pH of your saliva will tend to be more acidic than the pH of your urine, which will be very erratic depending on the foods you eat throughout the day. It may be just this variability that convinces people that they are positively affecting their health. They can see the effects of what they eat, and they imagine that they are controlling the pH and "hitting their target." Some books claim that the pH of blood is 7.5, which actually the average pH of urine, rather than the actual blood pH of 7.4. It is probably not hard to guess why they would make this slight error. Ironically, the changing pH of your urine with the foods you eat is one indication of your body maintaining its proper pH!

Do Alkaline Diets Prevent or Treat Cancer?

Although there are some possible health benefits to shifting to a more "alkaline" diet, medical science is unsure about most of them, and they are severely overstated by alkaline diet proponents. Other claims made are downright absurd. A very popular claim is that an alkaline diet will decrease your risk of cancer since if your blood becomes too acidic, cancer cells will thrive, whereas they cannot live in an alkaline environment. As Oliver Childs says in his article, 10 Persistent Cancer Myths Debunked, "This is biological nonsense. True, cancer cells can’t live in an overly alkaline environment, but neither can any of the other cells in your body."4

Primarily plant-based diets may have preventative benefits for certain types of cancer, such as colon cancer, but the evidence is far from clear. Even if it is true, it has nothing to do with the diet's effect on your acid-base balance. Other benefits of a diet high in fruits and vegetables may be true as well, but not for the reasons suggested by alkaline diet proponents. Many of the books and articles are written by lay-persons who are simply copying information they have found on sensationalist websites. These people have absolutely no understanding of how the human body works, even though such information is readily available to anyone who cares to look for it. Extreme versions of these diets usually include supplements and such innovations as "alkaline water," with hefty price-tags that benefit the diet promoter's bank account more than they benefit your health. You will probably be encouraged to purchase pH testing strips, as well.


Your body maintains a constant blood pH of around 7.4. The foods you eat have no effect on this pH, and if it is disrupted, it is because of serious illnesses or severe conditions that rarely occur. The pH of your urine changes based on the foods you eat throughout the day. This pH is evidence of your body's maintenance of its steady pH, and does not indicate your blood's pH. The claims made by proponents of alkaline or acid-alkaline balancing diets are without scientific support and are contrary to how the body actually works. Moderate versions of these diets, so long as they ensure adequate nutritional intake, may be quite healthy, but not for the reasons stated by their proponents. Extreme versions can be very difficult, expensive, and may negatively affect your health.

1. Kovács, Lajos, Dezső Csupor, Gábor Lente, Tamás Gunda, and Katalin Ősz. 100 Chemical Myths: Misconceptions, Misunderstandings, Explanations. Springer. 2014.
2. TannerThies, Roger, and Kirk W. Barron. Physiology. New York: Springer-Verlag, 1995.
3. Rosdahl, Caroline Bunker., and Mary T. Kowalski. Textbook of Basic Nursing</i>. Philadelphia: Lippincott Williams &amp; Wilkins, 2008.
4. Childs, Oliver. "Don’t Believe the Hype – 10 Persistent Cancer Myths Debunked." Cancer Research UK. Cancer Research UK, 24 Mar. 2014. Web. 20 July 2015

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