Alkaline diets are a group of diets based on the discredited notion that the body's pH balance (its relative acidity or alkalinity) can be affected by the dieter's choice of foods. Proponents of alkaline diets hold that eating meats, fish, dairy products, and other high-protein foods increases the body's acidity and thereby increases the risk of cancer, heart disease, bone loss, other chronic disorders, and low energy levels. Alkaline diets are also known as acid alkaline diets, alkaline acid diets, alkaline ash diets, and acid ash diets. The word ash in this context refers to the solid material left when a food is completely combusted in a bomb calorimeter, not to the ashes left by a wood or charcoal fire.
Although alkaline diets as a form of dietary therapy began in the twentieth century, the science underlying research into the body's pH balance began in nineteenth-century France. Claude Bernard (1813–78), an eminent physiologist, was interested in the role of the kidneys in regulating the acidity of body fluids. He discovered that changing laboratory rabbits from a plant-based to a meat-based diet increased the acidity of the animals' urine. The next step in research was taken by Pierre Marcellin Berthelot (1827–1907), a chemist who invented the bomb calorimeter in 1879 to measure the calorie content of foods. A bomb calorimeter consists of a chamber with pressurized oxygen suspended in a water bath. The food to be tested is placed in the chamber and ignited by an electric current. The pressurized oxygen ensures that the food is combusted rapidly and completely. The ash that remains can then be mixed with pure water and tested to determine its acidity or alkalinity. In 1912, two chemists at Columbia University published a paper in the Journal of Biological Chemistry in which they classified various foods as either alkaline or acidic according to the pH of the ash taken from the bomb calorimeter. They found that fruits and vegetables in general left alkaline ash whereas grains and meats generally left acidic ash.
The purpose of the 1912 paper was to measure the effect of foods with acidic ash on the acidity of urine, not to treat a hypothetical disease or encourage weight loss. Consequently, the effect of alkaline-ash foods in lowering the acidity of urine was studied as a possible way to prevent kidney stone formation and/or lower the risk of urinary tract infections. This was the original purpose of alkaline diets; however, they were rapidly superseded by drug therapy for kidney stones and UTIs because of the difficulty of making precise calculations of the effects of food on urinary pH. As of 2018, the level of detail and precision needed to make such calculations is still formidable, as samples of specific foods not only vary somewhat in their acidity, but humans also vary in their rate of absorption of the nutrients in food.
The third stage in the development of alkaline diets was an unwarranted assumption on the part of some alternative medicine practitioners that alkaline-ash foods can affect the pH of the body in general and blood in particular, not just the urine. This assumption is not supported by the actual mechanism of acid-base homeostasis, which maintains the pH of human blood as slightly alkaline within a narrow range between 7.35 and 7.45. Levels above 7.45 lead to a condition called alkalosis; levels below 7.45 lead to acidosis. Both are potentially serious conditions. In healthy humans, acid-base homeostasis is maintained by the respiratory system and the urinary system, neither of which is controlled by dietary intake.
Alkaline diets became a fad that spread beyond the alternative medicine community around 2010, when they attracted the attention of such celebrities as Gwyneth Paltrow, Victoria Beckham, and Sarah Ferguson, the former wife of Prince Andrew. These and other celebrity endorsements resulted in a stream of articles about alkaline diets in the mass media and online websites recommending such diets.
There is no single alkaline diet, which can be confusing to consumers. Some so-called alkaline diets are short-term cleansing diets based on fruit and vegetable juice, whereas others are longer-term plans in which dieters add a higher proportion of alkaline-ash foods to their eating plan. No standard has been established for the ratio of alkaline-ash to acidic-ash foods recommended by these diets. Although an 80/20 ratio is the figure most commonly given, some diets recommend a 60/40 ratio. Alkaline diets are essentially a matter of food selection rather than calorie counting or portion weighing.
Most alkaline diets divide foods into alkaline and acidic categories as follows:
Some versions of the alkaline diet have different lists of “forbidden” foods, though most include processed foods, caffeinated beverages, refined sugar, and alcohol as foods to be avoided.
Alkaline diets do not usually contain any recommendations about physical exercise. In addition, some websites that offer information about these diets also encourage viewers to purchase dietary supplements, books or online courses, and alkaline water or alkalineinfused foods. It is not necessary to use any of these items to follow an alkaline diet. Moreover, the U.S. Food and Drug Administration (FDA) has sent recall notices since the early 2000s to manufacturers whose alkaline water products were misbranded and has denied the health claims (specifically, that these products can prevent osteoporosis) of alkaline products distributed by other manufacturers. These health claims were based on a debate in the medical literature in the early 2000s about the possible role of alkaline water in preventing bone loss.
Despite the fact that consumption of alkaline-ash foods does not affect the pH of the blood or body tissues, alkaline diets have been recommended, primarily by naturopaths and other practitioners of alternative medicine, for a variety of reasons ranging from losing weight and slowing the aging process to preventing osteoporosis, kidney stones, cancer, headaches, and the common cold. Alkaline diets are also touted for boosting energy.
Most people who follow an alkaline diet will lose weight, at least initially, because the fruits and vegetables identified as alkaline contain less fat and fewer calories than the meats, grain products, and dairy products categorized as acidic. In addition, alkaline diets are compatible with vegetarian and vegan lifestyles. A third benefit is that alkaline diets are generally easier on the budget than food plans that allow meat, dairy products, and sweets.
Some people who have tried alkaline diets find them more effective than other weight loss diets in managing hunger because the permitted foods are relatively filling due to their bulk and fiber content, and no limits are set on portion size.
People diagnosed with cancer should consult their physician or a dietitian about their nutritional needs before starting any kind of diet.
People taking medications for osteoporosis, arthritis, urinary tract infections, kidney stones, headaches, or other conditions supposedly treated by alkaline diets should not stop taking their medications if they decide to try an alkaline diet.
People who follow an alkaline diet plan must be careful to obtain enough protein and calcium from the foods they do consume because many sources of protein and calcium allowed in moderation in other diets, such as lean meat or skim milk, are not allowed in alkaline diet plans.
Many people find alkaline diets difficult to follow not only because of the restricted number of foods permitted but also because these diets complicate eating out or sharing a household with family members who do not follow the diet. In addition, alkaline diets frequently add to the time and labor involved in food preparation because processed foods are not allowed.
Long-term use of an alkaline diet puts the dieter at risk of nutritional deficiencies resulting from low intake of calcium, protein, and essential fatty acids. In addition, people who stop the use of medications prescribed to treat such disorders as arthritis, cancer, diabetes, osteoporosis, or kidney stones because they believe that an alkaline diet is sufficient treatment for their condition are at risk of having their symptoms worsen.
Dieters who purchase alkaline water or other alkaline supplements to accompany the diet are at risk of being defrauded by manufacturers who misbrand their products or make unproven health claims. In addition, the FDA notes that some samples of socalled alkaline water have been found to be contaminated by salmonella and other bacteria.
People interested in an alkaline diet should be aware that medical and nutrition professionals as well as many naturopaths dismiss these diets as fad diets. It is significant that neither the Academy of Nutrition and Dietetics (AND) nor the National Center for Complementary and Integrative Health (NCCIH) even mentions alkaline diets on their websites. In regard to naturopathy, responsible practitioners point out that the theory underlying alkaline diets is contrary to everything known about the chemistry of the human body, even though the overall results of a diet high in fruits and vegetables and low in fats and refined sugar are beneficial in regard to weight loss and heart health. Alkaline diets also scored low on the U.S. News and World Report Health rating (2.4 out of a possible 5) because of their many arbitrary rules about food choices and because they have been poorly researched.
As of 2018, few mainstream clinical trials have been conducted of either alkaline diets or alkaline water and other dietary supplements. Four studies of alkaline water had been registered with the National Institutes of Health as of early 2018. One was a study of alkaline water as a sports beverage; another was looking at whether alkaline water reduces skin toxicity in women being treated with radiation therapy for breast cancer. The remaining two were studies of the effect of alkaline water on the pH of human urine.
See also Fad diets ; High-protein diet ; Juice fasts .
Domenig, Stephan, and Martyna Angell. The High Alkaline Smoothie Cleanse: Balance Your pH in 7 Days. New York: Countryman, 2016.
Trivieri, Larry, Jr., and Neil Raff. The Acid-Alkaline Lifestyle: The Complete Program for Better Health and Vitality. Garden City Park, NY: Square One, 2015.
Wilson, Laura. The Alkaline 5 Diet: Lose Weight, Heal Your Health Problems, and Feel Amazing! Carlsbad, CA: Hay House, 2015.
Fenton, Tanis R., and Tian Huang. “Systematic Review of the Association Between Dietary Acid Load, Alkaline Water, and Cancer.” BMJ Open 6, no. 6 (June 13, 2016): e010438.
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Sherman, H. C., and A. O. Gettler. “Acid- and Base-Forming Elements in Foods and Its Relation to Ammonia Metabolism.” Journal of Biological Chemistry 11 (1912): 323–38. http://www.jbc.org/content/11/4/323.full.pdf . This is a copy of the original article from which contemporary alkaline diets derive their measurements of the acid or alkaline ash content of foods.
Zalvan, Craig H., Shirley Hu, Barbara Greenberg, et al. “A Comparison of Alkaline Water and Mediterranean Diet vs. Proton Pump Inhibition for Treatment of Laryngopharyngeal Reflux.” JAMA Otolaryngology—Head and Neck Surgery 143, no. 10 (October 1, 2017): 1023–9.
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Schneeman, Barbara O. “Health Claims: Letter of Denial—Alkaline and Earth Alkaline Citrates Minimizing the Risk of Osteoporosis.” Food and Drug Administration (FDA). https://www.fda.gov/food/labelingnutrition/ucm121764.htm (accessed April 24, 2018).
U.S. News and World Report. “Acid Alkaline Diet.” Health.usnews.com . https://health.usnews.com/best-diet/acid-alkaline-diet (accessed April 24, 2018).
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Academy of Nutrition and Dietetics, 120 S. Riverside Plaza, Ste. 2190, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, firstname.lastname@example.org, http://www.eatright.org .
American Association of Naturopathic Physicians (AANP), 818 18th St. NW, Ste. 250, Washington, DC, 20006, (202) 237-8150, (866) 538-2267, Fax: (202) 237-8152, https://www.naturopathic.org .
American Cancer Society, 250 Williams St. NW, Atlanta, GA, 30303, (800) 227-2345, http://www.cancer.org .
National Center for Complementary and Integrative Health (NCCIH), 9000 Rockville Pike, NIH Campus, Bldg. 31, Bethesda, MD, 20892, (888) 644-3615, https://nccih.nih.gov/tools/emailnccih, https://nccih.nih.gov .
U.S. Food and Drug Administration (FDA), 10903 New Hampshire Ave., Silver Spring, MD, 20993, (888) 463-6332, https://www.fda.gov/AboutFDA/ContactFDA/default.htm, https://www.fda.gov .
Rebecca J. Frey, PhD