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Alkaline vs Acidic
In chemistry, alkaline refers to something with a high pH (>7), while acidic refers to a substance with a low pH (<7).

The terms “alkaline” and “acidic” are fundamental concepts in chemistry and play a significant role in various scientific disciplines, including biology and nutrition. These terms relate to the pH scale, which measures the acidity or alkalinity of substances. Here is a closer look at what alkaline and acidic mean, their relationship to the pH scale, examples of alkaline and acidic substances, and how the body maintains its pH balance.

Alkaline vs Acidic

pH Scale: The pH scale is a way of telling how alkaline or acidic an aqueous (water-based) solution is. The pH scale is a logarithmic scale that ranges from 0 to 14, with 7 being neutral. A pH value less than 7 indicates acidity, while a pH greater than 7 signifies alkalinity. This scale quantifies the concentration of hydrogen ions (H+) in a solution, with lower pH values indicating higher H+ concentrations (more acidic) and higher pH values indicating lower H+ concentrations (more alkaline).

Acidic Materials: Examples of acidic materials (acids) include lemon juice (pH 2), vinegar (pH 3), and battery acid (pH 1). Wine, coffee, acid rain, and milk are also acidic. These substances have high concentrations of hydrogen ions, making them sour or corrosive in nature.

Neutral Materials: Pure water is neutral, with a pH of 7. It has an equal balance of hydrogen ions (H+) and hydroxide ions (OH–), resulting in a neutral taste and properties.

Alkaline Materials: Alkaline materials are also known as basic substances or bases. They include substances baking soda (pH 9), milk of magnesia (pH 10), and household ammonia (pH 12). These materials have lower concentrations of hydrogen ions and tend to feel slippery or soapy.

Alkaline vs Acidic Substances in the Human Body

The human body is a complex system that relies on maintaining a precise pH balance to function optimally. Different parts of the body have varying pH levels:

  1. Stomach: The stomach has a highly acidic environment with a pH ranging from 1.5 to 3.5. This acidity is crucial for digesting food and killing harmful bacteria.
  2. Blood: Blood is slightly alkaline, with a pH range of 7.35 to 7.45. Homeostasis, the body’s self-regulating mechanism, tightly controls blood pH to ensure metabolic processes occur efficiently.
  3. Urine: Urine pH varies but is typically slightly acidic, around 6.0. It changes due to diet, hydration, and other factors.
  4. Skin: The skin’s pH is slightly acidic, around 5.5. The low pH helps protect against harmful microorganisms and maintains the skin barrier.
  5. Small Intestine: The small intestine’s pH becomes more alkaline (around pH 8) as it receives partially digested food from the stomach. This neutralizes stomach acid and creates an environment that maximizes nutrient absorption.

Homeostasis and pH Regulation

Homeostasis is the body’s ability to maintain a stable internal environment. In the case of pH regulation, the body employs various mechanisms to ensure blood pH stays within the narrow range necessary for survival. So, acidic parts like the stomach and skin surface remain acidic, while alkaline regions like blood and the small intestine remain alkaline. These mechanisms involve the respiratory and renal systems, which control the elimination of excess acid or base from the body.

Alkaline vs Acidic – The Alkaline Diet Debate

The alkaline diet is a nutritional trend based on the idea that consuming more alkaline-forming foods and fewer acidic foods can improve health and prevent diseases. A food is alkaline even if it starts out acidic (e.g., lemon juice) if it yields alkaline earth elements (such as magnesium and calcium) or basic ions upon digestion. Sugar, starches, and high-protein foods, on the other hand, are considered acid-forming. While proponents of the alkaline diet claim it balances pH levels in the body, there is limited scientific evidence supporting these claims. The human body tightly regulates its pH, and dietary changes alone rarely impact blood pH. However, the diet’s emphasis on consuming fruits, vegetables, and whole foods has health benefits due to their nutrient-rich nature.

References

  • Boron, Walter, F.; Boulpaep, Emile L. (2012). “Acid-Base Physiology.” Medical Physiology: A Cellular And Molecular Approach (2nd ed.). Elsevier Health Sciences. Saunders. .ISBN 9781455711819.
  • Chung, L.H.M. (1997). “Characteristics of Alkali.” Integrated Chemistry Today. ISBN 9789623722520.
  • Covington, A. K.; Bates, R. G.; Durst, R. A. (1985). “Definitions of pH scales, standard reference values, measurement of pH, and related terminology.” Pure Appl. Chem. 57 (3): 531–542. doi:10.1351/pac198557030531
  • Otoxby, D. W.; Gillis, H. P.; Butler, L. J. (2015). Principles of Modern Chemistry (8th ed.). Brooks Cole. ISBN 978-1305079113.