A diet popularized in the early 2010s by celebrities like Victoria Beckham and Gwyneth Paltrow is re-emerging in scientific research with potential health benefits that may rival those of weight-loss medications. The concept, often referred to as the alkaline diet, is now being studied through the lens of potential renal acid load (PRAL), a more measurable scientific concept.
Initially, the alkaline diet, which gained widespread attention in 2013, divided foods into those considered 'acid-producing' and 'alkaline-producing.' Advocates claimed that consuming acidic foods—such as meat, dairy, eggs, and processed items—disrupted the body's natural pH balance, leading to issues like fatigue, muscle pain, and even chronic diseases. Conversely, alkaline foods like fruits, vegetables, nuts, and whole grains were said to restore balance and slow aging. However, the original claims faced significant skepticism from medical experts who refuted the idea that diet could alter blood pH or prevent diseases like cancer. The diet's originator, Robert Young, was later imprisoned for practicing medicine without a license.
Modern Scientific Approach: PRAL and Health Outcomes
More recent research is examining the diet's principles through the concept of potential renal acid load (PRAL). PRAL estimates the amount of acid the kidneys must process after food metabolism, with acid generated from nutrients like protein and phosphorus. Foods with a negative PRAL, such as fruits, vegetables, and legumes, are considered alkalizing, while those with a positive PRAL, like meat and refined grains, are acid-forming.
Researchers now theorize that a sustained higher acid load on the body over time, rather than a direct pH change, may contribute to chronic diseases. Studies suggest that a diet low in acid-producing foods may reduce the risk of conditions including osteoporosis, type 2 diabetes, and kidney disease.
Clinical Study Findings
A study led by Dr. Hana Kahleova, an endocrinologist, and researchers from the University of Utah and George Washington University, compared a low-fat vegan diet rich in alkaline foods with the Mediterranean diet. In the trial, 62 overweight adults followed both diets for four months each, without calorie restrictions. Participants on the alkaline-focused vegan diet lost an average of 13.2 pounds over 16 weeks, whereas the Mediterranean diet showed no significant weight loss. Dr. Kahleova stated that participants on the vegan diet experienced not only weight loss but also improvements in blood pressure, insulin sensitivity, and blood lipids, while gaining muscle.
This effect is potentially linked to stress hormones. According to Dr. Kahleova, consuming more acid-producing foods may trigger the release of cortisol, a stress hormone linked to altered metabolism, increased appetite, and greater fat storage. A diet higher in alkaline foods could reduce stress hormone release, making weight loss easier.
Expert Perspectives and Caveats
However, some experts caution that the weight-loss benefits may be overstated. Dr. Susan Lanham-New, Professor of Human Nutrition at the University of Surrey, suggested that the weight loss observed in the trial might be partly due to participants on the vegan diet simply consuming fewer calories. Despite this, Dr. Kahleova maintains that higher consumption of alkalizing foods was linked to greater weight loss, even when calorie intake was considered.
Further research has linked a high dietary acid load to increased risks of conditions such as low-grade metabolic acidosis, inflammation, impaired kidney function, arterial thickening associated with heart disease, and osteoporosis. While the concept of dietary acid load is considered promising for health outcomes, more research is needed.
Registered nutritional therapist Grace Kingswell noted that while adopting a vegan diet often leads to immediate health improvements due to increased fruit and vegetable intake and reduced processed foods, long-term adherence can pose a risk of nutrient deficiencies, particularly in protein, unless carefully managed. She emphasized that reducing dietary acid load does not necessitate an extreme approach, but rather a shift towards more alkalizing foods.