The Alkaline Diet: Does Biochemistry Support the Fad?

07 Dec 2017 12:49 AM | Anonymous

Written by: Sara Scheler, RDN

The alkaline, or acid-ash diet, has been gaining traction as the new, “best” way to eat. Proponents of this diet claim that high acidity causes our bodies to steal minerals from our bones and organs. They

the advocate a decreased intake of minerals that create acidic ash, namely phosphate, chloride and sulfur, to restore our body’s pH back to its normal range. Foods are rated on a scale based on their Potential Renal Acid Load (PRAL), a calculation of the acidic ash they create when consumed (Cl + Po4 + SO4 – Na – K – Ca – Mg). High PRAL foods are to be avoided. Meat, fish, eggs, dairy, alcohol, wheat and yeast are the biggest offenders. Low PRAL foods are to be consumed daily—leafy greens, sea vegetables, some fruits, most vegetables and sprouted seeds. Neutral PRAL foods (fruits, nuts, some grains and legumes) are to be used occasionally in the diet (see Supplement 1).

These concepts are not new; H.C. Sherman created the first list of acidic and basic foods in 1912 when scientists began to investigate the functional properties of food8. Popularity of this diet has grown in recent years. As with most fad diets, there are numerous blogs devoted to the alkaline eating pattern. Some alkaline diet gurus, such as the Alkaline Sisters Julie and Yvonne, describe their results as dramatic weight reduction, relief from chronic back pain and total body healing2. Others claim the diet protects from sarcopenia, improves immune function, prevents cancer, increases vitamin absorption and combats mineral deficiency1. Chiropractic and clinical nutrition celebrity Dr. Josh Axe claims that chronic disease will not occur in bodies with balanced pH levels.

pH and Mineral Balance in a Healthy Human Body

Of course, these claims rest on the assumption that our body cannot regulate pH effectively on its own. In most cases, our renal and respiratory systems are proficient at maintaining healthy pH levels. If phosphate levels rise in the blood, bone resorption occurs. Osteoclasts break down bone and release calcium, which acts as a buffer to neutralize the phosphate. Alkaline diet followers maintain that this breakdown process depletes our bones of minerals and leads to osteoporosis. However, current medical research shows that this is not the case. In a meta-analysis of the alkaline diet, researchers concluded that the pH of urine was not related to an increase in bone damage or fractures4.

The alkaline diet also maintains that phosphate intake causes calcium excretion and subsequently osteoporosis. However, in all studies reviewed, phosphate intake was found to increase levels of bone calcium and increase acid excretion4. A meta-analysis of these studies concludes, “Dietary advice that dairy products, meats and grains are detrimental to bone health due to “acidic” phosphate content needs reassessment. There is no evidence that higher phosphate intakes are detrimental to bone health.”4 Neither dietary phosphate nor supplements reduced the amount of excreted calcium, as presumed by the alkaline diet4.

Dr. Axe claims that calcium in dairy products causes acidity and calcium loss, leading to osteoporosis1. Most practitioners in the medical and nutrition worlds know that dietary calcium has a protective effect against osteoporosis, and regular calcium intake is recommended for all individuals, especially children, adults and pregnant or nursing mothers5. The body regulates calcium absorption and excretion to prevent our bones from deteriorating. When calcium levels are low, the parathyroid hormone increases calcium excretion from bones, while also increasing calcium resorption and absorption to rebuild the bone structure. A healthy human body will regulate its own calcium levels, rather than steal from our bones as Dr. Axe suggests.

Some studies indicate that an acidic diet can increase urinary calcium excretion, however, researchers note that urinary excretion is not an effective measure of the body’s calcium status4. Urinary calcium does not provide a good picture of calcium balance because this mineral is absorbed, secreted and lost in various ways throughout the body4. Many studies that support the alkaline diet consider urinary calcium excretion as the only measurable aspect of acid balance, while studies that consider whole body calcium balance do not support the diet’s hypotheses4. The biochemistry behind the alkaline diet is based on limited studies that consider urinary calcium excretion as proof that an acidic diet causes osteoporosis. A meta-analysis of calcium balance studies found no connection between acidic food intake and calcium loss or osteoporosis, further squelching this diet’s credibility4.     

Practicality of the Alkaline Diet                                        

The alkaline diet may have minor benefits during anaerobic exercise. A study of 10 participants found that a low-acid diet increased anaerobic exercise performance, as compared to a high-acid diet3. Participants who consumed 6-8 cups of vegetables, four cups of fruit, and low-acid seeds and plant fats for four days performed 21% better on an anaerobic exercise test (running on a treadmill) than those who consumed large quantities of meat, dairy and grains for four days prior3. Participants who followed the low acid diet consumed 60 grams of protein per day, while the high-acid participants consumed 110 grams per day3. Current recommendations for endurance athletes are 1.2-1.7 grams of protein per kilogram of body weight per day (70-100 grams per day for someone of my size, for example). The low-acid diet in this study would not provide enough protein to maintain athletic performance and muscle structure. It would not provide enough calcium, either; the Academy of Nutrition and Dietetics recommends 1000mg of calcium per day for adults5. The low-acid diet in this trial provided just 556mg per day.

A sample from the Alkaline for Life® 30-day meal plan provides just 1280 calories, 67 grams of protein and 610mg calcium. Alkaline for Life® meal plans focus on balancing acidic and alkaline foods at each meal, so dairy, meat and eggs are allowed in small amounts. Even with this modified alkaline diet, the meal plans do not provide enough nutrients to maintain weight in any healthy adult, much less an athlete. It would be difficult to maintain micro and macronutrient requirements while adhering to an alkaline diet, and almost impossible if adhering to a strict alkaline diet and avoiding all animal-based proteins.

A strict alkaline diet is vegan by nature. Research indicates that vegan diets can cause nutrient deficiencies6. Recently, the German Nutrition Society published a position paper stating that a vegan diet is not suitable for children, adolescents, or pregnant or nursing women7. Researchers cited vitamin B12 as the most notable deficiency but Omega-3, vitamin D, riboflavin, protein and mineral deficiencies are also commonly seen with vegan diets7. The alkaline diet recommends avoidance of meats, grains and dairy products, all of which contain bone-protecting protein, calcium and vitamin D. Strict alkaline diet followers are certainly at risk for developing nutrient deficiencies.

Clinical Significance and Implications for Practice

The principles of the alkaline diet are used clinically in two ways. Sodium bicarbonate is used to correct blood imbalances and improve growth rates in children with metabolic acidosis, and the higher pH level that results from an alkaline diet can make some chemotherapeutic agents more effective4. For healthy individuals, however, an alkaline diet does not have the benefits that its followers proclaim. Though some studies suggest that a low-acid diet can moderately increase exercise endurance, the diet is low in calories, protein and calcium, expensive, time-consuming and impractical to maintain. Furthermore, a strict alkaline diet poses serious risks of vitamin and mineral deficiencies. The limited and inconsistent research that supports this diet is certainly not enough to warrant recommendation of its use. I would not recommend an alkaline diet, as it would be difficult to maintain any level of athletic performance and avoid deficiencies with a diet devoid of animal, egg and dairy-based proteins. A minor increase in performance, based off the small cohort and very short duration found in one study does not transcend the risks this diet poses to long-term health.

As with all fad diets, it is important to investigate the biochemistry behind its claims and evaluate whether or not diet’s suggestions align with physiological fact; in the case of the alkaline diet, they do not.

Supplement 1: Alkaline Food Chart. Source: Alkaline Sister (web)

Accessed September 2016 from: Alkaline Food Chart

 1 cup seasonal fruit salad
¼ cup organic, full-fat plain yogurt 1 tsp ground flax seeds
 1 poached or soft-boiled egg with sautéed spinach
 1 pear-size handful of toasted pumpkin seeds
 Apple, celery, and cucumber mixed green salad with Apple Cider Vinaigrette
 1 Bowl of tomato soup

Celery with 1 tsp almond butter

4 oz. oven-roasted salmon

 ½ baked sweet potato with butter and cinnamon

Beets and Greens

Works Cited

1.    Alkaline diet: the key to longevity and fighting chronic disease? Dr. Axe Web site.  Accessed August 29, 2016.

2.    Alkaline sister: my story. Alkaline Sister Web site. Published  2009. Accessed September 1, 2016.

3.    Caciano C, Inman C, Gockel-Blessing E, Weiss E. Effects of dietary acid load on exercise metabolism and anaerobic exercise performance. Journ. Sports Sci and Med. 2015; 14, 364-371.

4.    Fenton T, Lyon A, Eliasziw M, Tough S, Hanley D. Phosphate decreases urine calcium and increases calcium balance: a meta-analysis of the osteoporosis acid-ash diet hypothesis. Nutr Journ. 2009; 8-41.

5.    Mahan L, Escott-Stump S, Raymond J. Krause’s food and the nutrition care process. 13th ed. St. Louis, MO: Elsevier; 2012.

6.    Mądry E, Lisowska A,  Grebowiec P, Walkowiak J. The impact of vegan diet on B-12 status in healthy omnivores: a five-year prospective study. Acta. Sci. Pol. 2012; 209-213.

7.    Richter M, Boeing H, Grünewald-Funk D, Heseker H, Kroke A, Leschik-Bonnet E, Oberritter H, Strohm D, Watzl B for the German Nutrition Society (DGE) (2016) Vegan diet. Position of the German Nutrition Society (DGE). Ernahrungs Umschau 63(04): 92– 102.

8.    Sherman H, Gettler A. The balance of acid-forming and base-forming elements in foods and its relation to ammonia metabolism. Columbia University; 1912; 205. 

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