There has been a lot of recent focus on the suggested health benefits of alkaline foods, such as new products like alkaline water or certain fruits and vegetables, including spinach, tomatoes and lemon. These foods are claimed to provide a variety of health benefits include reducing inflammation, helping with weight management and reducing the risk for chronic diseases like diabetes and hypertension. But is there any science to back up the hype?
First, let’s review what alkaline means: on the pH scale, a substance that has a pH higher than 7 is basic or alkaline and accepts hydrogen ions (H+), while an acid has a pH less than 7 and can donate H+. For reference, the pH of tap water is right around neutral (7), whereas the pH of blood is slightly basic, between 7.3 and 7.4.
The thinking is that by replacing certain “acidic” foods, such as alcohol, grains and refined carbs, with alkaline foods, the body will function better. In reality, consuming “acidic” or “alkaline” foods has little impact on the body’s pH. That’s because if there are pH changes in the body, the body responds with a rapid metabolic response. And because the pH scale is logarithmic, even a small change in pH, such as 7.3 to 7.4, would have major effects. But, both the lungs and kidneys help bring the pH back to a normal level. For example, if the blood becomes acidic, the lungs will excrete more CO2 and the kidneys will reabsorb more bicarbonate. Both mechanisms are imperceptible and help raise the pH back up.
Furthermore, once any food or drink enters the stomach, the very acidic environment (around a pH of 2) makes reaping the suggested benefits of alkaline foods very unlikely. To date, the scientific evidence does not support the health benefits of alkaline foods.
- Fenton TR, Huang T. Systematic review of the association between dietary acid load, alkaline water and cancer. BMJ Open, 2016;6:e010438. doi: 10.1136/bmjopen-2015-010438
Baum, I. The Truth About the Alkaline Diet. Huffington Post. June 29, 2017. Available at: https://www.huffingtonpost.com/entry/the-truth-about-the-alkaline-diet_us_59550cb3e4b0326c0a8d0e34.