What is the pH Scale?
pH, or potential of hydrogen, is a logarithmic scale that measures the concentration of hydrogen ions in a solution. The scale ranges from 0 to 14. A pH of 7 is considered neutral. Solutions with a pH below 7 are acidic, with a lower number indicating greater acidity. Solutions with a pH above 7 are alkaline (or basic), with a higher number indicating greater alkalinity.
The Body's pH Regulation vs. Dietary pH
It's important to differentiate between the pH of the foods and drinks you consume and your body's internal pH. The human body has robust mechanisms, primarily involving the kidneys and lungs, to maintain a very tight blood pH range of 7.35 to 7.45. Consuming slightly acidic or alkaline foods and drinks does not significantly alter this blood pH. However, consuming highly acidic or alkaline substances can overwhelm these systems and cause serious, immediate harm.
Highly Acidic Substances (Low pH)
Consuming substances with a very low pH (typically below 2.5) is extremely dangerous due to their corrosive nature. This is far more extreme than typical acidic foods like lemon juice (pH 2-3) or soda (pH ~2.5).
Health risks of low pH consumption
- Internal Corrosive Damage: Strong acids can cause immediate and severe chemical burns to the mouth, esophagus, and stomach lining.
- Tooth Enamel Erosion: Regular consumption of even mildly acidic water (below 6.5) can erode tooth enamel over time, leading to sensitivity and cavities.
- Heavy Metal Leaching: Water with a pH of less than 6.5 is corrosive and can leach toxic heavy metals like lead, copper, and zinc from plumbing and pipes into the drinking water supply. These can cause heavy metal poisoning, with symptoms including nausea, vomiting, and organ damage.
- Gastrointestinal Issues: Prolonged intake of acidic water or substances can irritate the stomach lining, exacerbating symptoms for individuals with conditions like acid reflux.
Highly Alkaline Substances (High pH)
Conversely, substances with an extremely high pH (typically above 12.5) are also corrosive and hazardous to consume. While mildly alkaline water (pH 8-9) is generally considered safe and may offer benefits for some conditions, highly basic substances are a serious threat.
Health risks of high pH consumption
- Corrosive Burns: Similar to strong acids, strong bases (high pH) can cause severe caustic burns upon contact with skin and mucous membranes, including the digestive tract.
- Metabolic Alkalosis: Excessively high alkaline intake can lead to a condition called metabolic alkalosis, which can cause symptoms such as nausea, vomiting, muscle twitching, and confusion.
- Digestive Disruption: High alkalinity can interfere with the stomach's natural acidity, disrupting proper protein digestion and killing beneficial bacteria. This can also inhibit the function of pepsin, an enzyme crucial for digestion.
- Skin and Eye Irritation: The World Health Organization notes that water with a pH greater than 10 can cause irritation to the skin, eyes, and mucous membranes.
What pH Is Harmful to Consume? A Comparison
| Feature | Low pH (Extremely Acidic) | High pH (Extremely Alkaline) |
|---|---|---|
| Danger Zone | ≤ 2.0 (Corrosive) | ≥ 12.5 (Corrosive) |
| Mechanism of Injury | Chemical burns from excess hydrogen ions. | Caustic burns from excess hydroxide ions. |
| Immediate Symptoms | Severe burning in the mouth and throat, abdominal pain, tissue damage. | Severe burning, gastrointestinal distress, irritation to mucous membranes. |
| Chronic Effects (Water) | Dental erosion, leaching of heavy metals from pipes, digestive issues. | Bitter or soapy taste, scaling on pipes, interference with normal body functions. |
| Associated Health Risks | Heavy metal poisoning, worsened reflux, chronic irritation. | Metabolic alkalosis, digestive problems, nutrient malabsorption. |
Safe and Unsafe pH Levels in Context
While highly corrosive pH levels (<2 and >12.5) are unequivocally harmful to consume, most people encounter a far narrower range of pH in their daily lives. The primary risk from water and food sources comes from long-term, low-level exposure to contaminants rather than the pH itself. For instance, acidic tap water (<6.5) can cause harm indirectly by dissolving harmful metals from your plumbing. On the other end, excessively alkaline water (>8.5) may cause aesthetic issues but isn't necessarily acutely toxic; however, its long-term health effects are not fully understood.
To ensure your water is safe, it is crucial to follow the guidelines provided by health authorities. Regular testing of your water, especially from private wells, is recommended if you have concerns about its pH or potential contamination. If any unexpected symptoms arise after consuming a substance, medical guidance is essential.
Conclusion
The question of what pH is harmful to consume has a clear answer: any pH at the extreme ends of the scale is corrosive and acutely dangerous. While the human body can effectively regulate its internal balance, it is no match for strong acids (pH below 2) or strong bases (pH above 12.5). For everyday consumption, the EPA-recommended range for drinking water (pH 6.5–8.5) is a reliable standard for safety. Mildly acidic or alkaline foods are typically not a threat to overall systemic pH, though certain water conditions can pose secondary risks like heavy metal exposure. By understanding these distinctions and ensuring your water source is monitored, you can make informed decisions to protect your health.
