“Say goodbye to low energy, poor digestion, extra pounds, aches and pains, and disease.”
“Restore your health by creating balance in your diet that will give you the energy of a child again.”
“Boost your alkalinity and lose weight fast.” (www.acidalkalinediet.com)
Here’s yet another diet with a villain (acidic foods) and a hero (alkaline foods) promising spectacular results. While perhaps not as trendy as “going keto,” the alkaline-ash diet still possesses a bit of cachet, helped along by celebrity endorsements from Victoria Beckham, Gwyneth Paltrow, Jennifer Aniston, Jared Leto and others. Sure, the Hollywood crowd looks good, but do they know anything about acid-base balance? A recent Amazon search on the topic revealed 20 pages of titles—alkaline diet books for beginners, for women, for children, for people with cancer, osteoporosis, and inflammation. Seems there’s a pH miracle cure for all comers. But where’s the evidence?
To glean why it’s impossible to “alkalize” the blood through food requires a basic understanding of chemisry and human physiology. Put simply, an acid is a molecule capable of either donating a positively charged hydrogen ion, or accepting negatively charged electrons. A base (alkali) is a molecule capable of doing the opposite. The stronger the acid, the stronger the tendency to relinquish protons and accept electrons. The pH (potential Hydrogen) of a solution is a measure of its hydrogen ion concentration, expressed logarithmically on a scale from 1 to 14, where 7 is neutral. Solutions with a pH of less than 7 are termed “acidic,” while those with a pH greater than 7 are “alkaline.” Blood is slightly alkaline at a pH of 7.4. Although blood pH is considered normal between a range of 7.35-7.45, in practice, the pH rarely varies by more than 0.02 units in either direction. The reason the pH varies so little is that even small perturbations are poorly tolerated. If the blood pH rises just to 8, or drops to just 6.8, proteins denature, enzymes no longer function, and death ensues. The body has a very strong, vested interest in keeping a tight rein on pH. By way of comparison, symptomatic heart failure doesn’t occur until the heart has lost more than a third of its pumping capacity, removal of a lung is hardly noticed, and kidneys will continue to produce normal quantities of urine until the loss of more than 85% of their filtering capacity, but just a 10% rise or decline in blood pH is fatal.
This doesn’t mean that the pH need be 7.4 everywhere in the body. For instance, the lining of the stomach is quite acidic with a pH between 1.5-3.5. Here, acid jump-starts digestion by unraveling highly structured protein molecules and activating digestive enzymes to further break down proteins into their basic amino acid components. A thick protective mucus prevents the acid from harming the stomach. (This mucus is not found in the esophagus which is why gastroesophageal reflux is so painful). But when it comes to blood, only a pH very close to 7.4 will do.
The body keeps pH in check through a tightly regulated set of buffering systems. Buffers are defined as solutions that resist changes in pH. Boring science alert: The blood pH can be calculated as follows:
While it’s not pertinent to understand the particulars of the equation, what matters is to recognize that anything raising the concentration of bicarbonate (HCO3) results in an increase in pH. Similarly, anything lowering the carbon dioxide level (pCO2) will also raise the pH. Reversing the particulars achieves the opposite effect.
The three organ systems that work to maintain acid-base balance in the body are the kidneys, the lungs, and the blood. The enzyme carbonic anhydrase catalyzes the conversion of carbon dioxide to bicarbonate. The reaction can proceed in either direction depending on circumstance. When confronted with an acid load, the kidney excretes the excess in the form of acidic ammonium ions (NH4), while also shifting the carbonic anhydrase reaction rightward to form additional bicarbonate that acts as a base. Both of these effects serve to normalize pH through the elimination and neutralization of acid. The opposite occurs when the kidney faces an alkaline challenge. So while the urine pH reflects the net acid or alkali load confronting the kidney, it does not reflect the blood pH which remains constant. Alkaline diet proponents who recommend performing urine pH testing to measure the diet’s success are wasting their time and yours.
What if the kidneys become overwhelmed? No worries, the lungs are quite capable of helping. Although we think of the lungs primarily as an oxygen bellows, an equally important function is to expel carbon dioxide. When confronted with excess acid, the body responds by increasing the rate and depth of breathing, resulting in enhanced carbon dioxide elimination. Remember that lowering the carbon dioxide (CO2) level raises the pH, thereby provided a protective compensatory mechanism to deal with acid loads. All this works in reverse when the body is confronted with excess alkali, in which case slow shallow breathing serves to lower pH.
In addition to the kidneys and lungs, the hemoglobin inside our red blood cells offers additional buffering capacity as do the phosphate salts and proteins contained in our blood. The net effect of these buffering systems is so powerful that an individual would have to drink 1,300 ml of hydrochloric acid (0.05 molar) to drop their pH from 7.35 to 7. It is literally impossible to alter the blood pH through diet, no matter how many grains, meats, and carbonated beverages you consume. I have been working in ERs for more than 30 years and have never encountered a blood pH lower than 7.35, or higher than 7.45, in the absence of severe pathology. Not. Even. Once.
And this brings me to the patently false claim that alkaline diets can prevent or cure cancer. First, some background: Back in the 1920s, Otto Warburg first observed that cancer cells take up huge amounts of glucose relative to surrounding cells. Normally, glucose is metabolized to pyruvic acid within the cytoplasm, then converted to acetyl-CoA to enter the Krebs cycle within mitochondria, producing enormous amounts of energy. This process is known as oxidative phosphorylation. During times of oxygen deprivation (like sprinting at maximum speed) pyruvate is converted, not to acetyl-Co A, but to lactic acid through a non-oxygen-dependent pathway known as fermentation. This proceeds faster than oxidative phosphorylation, but is far less energy efficient. Cancer cells, for reasons still not entirely elucidated, ferment a substantial amount of glucose to lactic acid rather than proceeding through normal oxygen-dependent pathways. Part of the reason for this is because tumors can—and often do—outgrow their blood supply. The resulting oxygen deficiency drives fermentation, but even when provided with adequate oxygen, cancer cells still produce more lactic acid than normal cells. This accumulation of lactic acid, in turn, results in an acidic pH environment. The enhanced glucose utilization and lactic acid production by cancer cells is now known as the “Warburg Effect.” Warburg concluded (incorrectly) that cancer was a disease of mitochondria. Others mistook cause for effect and attributed cancer formation to the acid environment that frequently accompanies its growth. But acid doesn’t cause cancer, it’s the result of it.
Thus, there are several good reasons why eating an alkaline diet doesn’t cure cancer:
- Acid is the result of cancer, not the cause of it. Neutralizing it after the fact doesn’t help.
- Even if acid did cause cancer, eating an alkaline diet wouldn’t help because it doesn’t alter the blood pH.
- Finally, if it were possible to alkalinize the blood sufficiently to kill cancer cells, this would also kill healthy cells.
There is no wiggle room. The notion of alkalinizing the blood to cure cancer is quackery.
The other major claim of alkaline diet proponents is that the diet prevents osteoporosis. Once again, there is a bit of science but no data. The supposition is that Western diets high in acidic foods like grains and meats, and carbonated beverages deplete the body’s bone calcium stores, as calcium phosphate and calcium carbonate are mobilized from bone to buffer the excess acid. And it’s true that high acid diets do lead to increased urinary calcium loss, but there is no data to support the notion that this, in turn, leads to osteoporosis. Why doesn’t it? Because the body has counter-regulatory mechanisms to balance the loss, primarily mediated by vitamin D. If the body loses more calcium through the urine, it responds by absorbing more dietary calcium in the intestine. An acid diet leads to osteoporosis only if combined with dietary deficiencies of vitamin D and calcium. A 2009, meta-analysis of 12 studies looking at this issue concluded: “There is no evidence from superior quality balance studies that increasing the diet acid load promotes skeletal bone mineral loss or osteoporosis.” Acidic diets do not cause osteoporosis, and alkaline diets do not prevent it.
Still, proponents remain unconvinced, arguing that the diet lowers the risk of diabetes, cancer, hypertension, heart disease and stroke, even citing studies to “prove” it. The results of the studies do demonstrate an association. Unfortunately, the association likely has no causal relationship to the outcomes being measured. For example, if you follow a population of beer drinkers, you’ll likely find a higher incidence of cancer. You might then be tempted to conclude that beer causes cancer, but in this case, you’d be wrong because beer drinkers are also more likely to be smokers, and the data linking smoking to cancer is incontrovertible. When proponents of alkaline diets claim that the health benefits observed are due to the alkalinity of food, they are likely suffering from a similar attribution bias.
Where did this notion of “acidic” and “alkaline” foods come from in the first place? It dates back to 1864, when Marcellin Berthelot first began experimenting with his bomb calorimeter, essentially an explosive device containing a pressurized oxygen canister sitting inside a sealed water vat. Igniting the bomb results in a violent explosion that instantly incinerates the bomb’s contents. The energy from the explosion, transmitted in the form of heat to the surrounding water, may then be calculated based on the temperature change of the water bath (where it takes 1 calorie to raise the temperature of 1 ml of water by 1 degree Celsius). In addition to calculating the calorie content of food, Berthelot observed that incinerated foods leave behind an ash. Sometimes the ash is acidic, sometimes alkaline. By measuring the pH of the ash and knowing the original amount of the food in the bomb, a rough idea of its acid content can be determined. Incinerated meats, nuts, and grains leave behind an acidic ash, while vegetables and fruits leave an alkaline ash. If you’re bored, check out some of the alkaline-ash diet websites and see how many of them still report that eating alkaline foods results in an “alkaline ash residue” inside the body, as if the process of digestion is the same as incinerating foods inside a metallic calorimeter bomb. These folks really need to get a better hobby.
In general, foods high in chloride, phosphorous, sulfates and organic anions are more likely to be acidic. Examples include meats, cheeses, nuts, and grains. Alternatively, foods high in mineral cations like magnesium, calcium, and potassium are more alkaline. These include primarily fruits and vegetables. A scoring system based on the protein and mineral content of foods is often used to gauge their acid content. Known as the PRAL score (Potential Renal Acid Load), foods with negative numbers are considered alkaline (and therefore healthy), and those with positive scores acidic (and therefore unhealthy). In research settings, an even simpler scoring system based on just the dietary protein and potassium intake, called the NEAP score (Net Endogenous Acid Production), is often used as an indirect measure of dietary acid load. While some studies have noted an increased risk of diabetes and hypertension associated with high PRAL and NEAP scores, the problem lies in establishing cause and effect. For example, since these scores are based largely on dietary protein intake, it follows that people with high dietary PRAL and NEAP scores consume more meat (and consequently more animal fat) than those with low scores. So is the acidity or the fat the culprit? From these studies it’s impossible to know, but there’s far more data linking high animal fat and protein intake to poor health outcomes than there is linking dietary acid, especially given that dietary acid has no clinical effect on blood pH. I’m not saying that alkaline diets are unhealthy. In fact, just the opposite—they’re quite healthy, but not for reasons having anything to do with acid-base balance. The diets work because they restrict processed foods, saturated fat, salt, and animal protein. Alkaline diets are nothing but vegan diets without the nuts, but you’d have to be nuts to believe the hype.
Finally, a note on alkaline water. Distilled water has a neutral pH of 7, while most tap waters fall between 6.5-8 depending on local mineral content. Alkaline water is generally either spring water with a high mineral content (i.e. “hard” water), or water whose pH has been enhanced through an artificial ionization process. In either case, the pH of these waters generally runs between 8-10. There is zero scientific data to support their use. The placebo effect reigns. You obtain all the minerals you need from food. Water is for hydrating. Please also note that the laws of chemistry still apply, meaning that the hydrochloric acid naturally residing in the stomach will immediately neutralize any and all alkali in the water you drink. Your blood pH won’t budge, but your wallet will feel instantly lighter. Save the environment from unnecessary plastic, and just say “no.”
Bottom Line: It is impossible to alkalinize the blood through food. Alkaline diets do not cure cancer or prevent osteoporosis. They are healthy in the sense that they are fruit- and vegetable-based with a healthy blend of salts (high potassium, low sodium). Alkaline water is devoid of any health benefit above that of regular tap water.
- Gary Schwalfenberg, “The Alkaline Diet: Is There Evidence That an Alkaline pH Diet Benefits Health?” J Environ Pub Health 2012: doi:10.1155/2012/727630.
- Tanis Fenton and Tian Huang, “Systematic Review of the Association Between Dietary Acid Load, Alkaline Water and Cancer,” BMJ Open 2016; 6: e010438.
- Tanis Fenton et al, “Causal Assessment of Dietary Acid Load and Bone Disease: A Systematic Review and Meta-Analysis Applying Hill’s Epidemiologic Criteria for Causality,” Nutr J 2011; 10: 41.
- Tanis Fenton et al, “Phosphorous Decreases Urine Calcium and Increases Calcium Balance: A Meta-Analysis of the Osteoporosis Acid-Ash Diet Hypothesis,” Nutr J 2009; 8: doi: 10.1186/1475-2891-8-41.
- Shamina Akter et al, “High Dietary Acid is Associated with Insulin Resistance: The Furukawa Nutrition and Health Study,” Clin Nutr 2016; 35: 453-59.
- Guy Fagherazzi et al, “Dietary Acid Load and Risk of Type-2 Diabetes Mellitus: The E3N-EPIC Cohort Study,” Diabetologia 2014; 57: 313-20.
- Luxia Zhang et al, “Diet-Dependent Net Acid Load and Risk of Incidental Hypertension in United States Women,” Hypertension 2009; 54: 751-55.
- Marielle Engberink et al, “Dietary Acid Load and Risk of Hypertension: The Rotterdam Study,” Am J Clin Nutr 2012; 95: 1438-44.
- Han et al, “Association Between Dietary Acd Load and the Risk of Cardiovascular Disease: Nationwide Surveys (KNHANES 2008-2011),” Cardiovasc Diabetol 2016; 15 (1): 122.