An “alkaline state” refers to a condition where the body’s fluids, particularly blood, have a pH level above 7.0. pH measures acidity or basicity: below 7.0 is acidic, 7.0 is neutral, and above 7.0 is alkaline. The human body maintains a remarkably narrow blood pH range, typically between 7.35 and 7.45, to ensure proper biological function. This balance is continuously regulated by internal mechanisms.
The Body’s pH Balance
The body possesses robust systems to maintain a stable internal environment, a process known as homeostasis. Blood pH is meticulously regulated by buffering systems that absorb or release hydrogen ions, preventing significant shifts in acidity or alkalinity. The bicarbonate buffer system, a primary example, uses carbonic acid and bicarbonate ions to neutralize excess acids or bases, quickly responding to metabolic changes and ensuring pH stability.
Lungs and kidneys play roles in maintaining this balance. Lungs regulate carbon dioxide levels, influencing blood pH; increased breathing expels more CO2, making blood less acidic. Kidneys excrete excess acids or bases and reabsorb bicarbonate, tuning the body’s pH. When these systems are overwhelmed, severe imbalances can occur: acidosis refers to a blood pH below 7.35, while alkalosis indicates a blood pH above 7.45, both can be life-threatening.
The Alkaline Diet Concept
The “alkaline diet” is an eating plan based on the premise that certain foods can alter the body’s pH to be more alkaline. Proponents suggest an alkaline body environment benefits health and prevents various diseases. Foods are categorized as “acid-forming” or “alkaline-forming” based on the theoretical pH of their ash residue after digestion, not their initial pH.
Foods promoted on an alkaline diet include most fruits and vegetables, legumes, nuts, and seeds, considered alkaline-forming. Conversely, foods like meat, poultry, fish, dairy products, eggs, grains, and processed foods are discouraged as acid-forming. Health claims range from improving bone health and energy to preventing chronic diseases like cancer. These claims suggest an acidic environment promotes disease, while an alkaline one protects.
Scientific Understanding vs. Diet Claims
While the alkaline diet emphasizes the consumption of many healthy foods, its core premise regarding blood pH alteration through diet lacks scientific support. The body’s homeostatic mechanisms, involving the lungs, kidneys, and buffer systems, resist changes to blood pH. While foods can influence urine pH as kidneys adjust acid excretion, this does not reflect a change in regulated blood pH or other internal tissues.
Maintaining a stable blood pH is important for the functioning of enzymes and proteins, which are sensitive to pH changes and can denature if the environment becomes too acidic or alkaline. For example, the idea that an alkaline diet can prevent or cure cancer lacks scientific evidence; cancer cells thrive in various pH environments, and their growth is not solely dependent on external pH manipulation. Similarly, claims about improved bone health are unsubstantiated; the body does not leach calcium from bones to neutralize dietary acids. Health benefits observed from an “alkaline diet” are likely due to increased intake of nutrient-dense fruits, vegetables, and whole foods, and reduced processed foods and saturated fats, rather than direct changes in body pH.