The question of whether beans are alkaline or acidic goes beyond a simple pH test. While a food’s intrinsic pH value can be easily determined, it does not tell the whole story of how that food affects the body. Most foods, including beans, have a pH below the neutral point of 7, yet they are often discussed in the context of an alkaline diet. The more complex and scientifically relevant answer lies in understanding the body’s metabolic response to food, which involves calculating the overall acid or alkaline load.
The Difference Between Food pH and Metabolic Acid Load
The acidity of a food item before consumption (its pH) is distinct from its effect on the body’s internal acid-base balance after digestion. For instance, acidic citrus fruits like lemons are considered alkalizing once metabolized. The body maintains a tightly regulated blood pH between 7.35 and 7.45, and diet does not significantly change this level in healthy individuals. The real measure of a food’s impact is its Potential Renal Acid Load (PRAL).
PRAL is a scientific metric that estimates the amount of acid or base the kidneys must manage after digestion. A positive PRAL score indicates a food is acid-forming, while a negative score indicates it is base-forming or alkalizing. This score is calculated based on the food’s nutrient profile, specifically the balance between acid-forming and base-forming components.
Minerals like potassium, magnesium, and calcium act as base-forming elements, contributing to a more negative PRAL score. Conversely, protein and phosphorus are the primary acid-forming components. The sulfur-containing amino acids in protein are metabolized, producing non-volatile acids that the kidneys must excrete. Therefore, a food’s final PRAL score depends on the ratio of its alkalizing minerals to its acid-forming protein and phosphorus content.
Determining the PRAL Value of Beans
Applying the PRAL metric reveals that beans are low-acid or slightly acid-forming foods, not truly alkaline-forming. This is primarily because beans contain a significant amount of protein, which contributes to a positive acid load. However, they also contain beneficial alkalizing minerals. The balance between these elements results in a PRAL score that is typically low and positive, meaning they are mildly acid-forming.
The exact PRAL value varies depending on the specific type of bean and its preparation. Cooked kidney beans, for example, have a very low positive PRAL score of approximately +0.7 per 100 grams, indicating a minimal acid load. Lentils (+3.5) and chickpeas (+2.5) are also slightly acid-forming. Pinto beans fall in a similar range at about +1.25.
The positive score for most beans is a direct result of their role as a plant-based source of protein, which raises the acid-forming component of the PRAL calculation. Some varieties, such as lima beans (+6.16) and certain white beans (+5.64), have slightly higher positive PRAL scores. However, the overall low positive score for legumes places them far closer to truly alkalizing foods like fruits and vegetables than to high-acid foods like meat or cheese.
Incorporating Beans into a pH-Balanced Diet
The slightly acid-forming nature of most beans does not diminish their value as a highly nutritious component of a pH-balanced eating plan. Given their low positive PRAL score, beans should be viewed as a neutral component in a diet focused on acid-base balance. The key to incorporating them effectively is through strategic pairing with foods that have a strong negative PRAL score.
By combining a portion of beans with a large quantity of highly alkalizing foods, such as green leafy vegetables, broccoli, or sweet potatoes, the overall meal’s acid load becomes negative. This balancing strategy ensures that the meal provides essential protein and fiber from the beans without significantly contributing to the body’s acid load. Focusing on overall dietary balance, rather than the PRAL of a single food item, is the practical approach for pH-focused eating.
Beans offer substantial nutritional benefits, including high levels of dietary fiber, B vitamins, and various minerals, regardless of their slight acid load. These qualities make them a healthful choice for anyone. Their high nutrient density and low-acid profile make them a versatile and valuable food for maintaining a well-rounded and pH-conscious diet.