Understanding the Body's pH Balance
The idea that diet can significantly alter the body's overall pH, particularly in the blood, is a persistent myth. In a healthy individual, the pH of the blood is kept in a remarkably tight range of 7.35 to 7.45. Any major deviation from this range is indicative of a serious medical condition (acidosis or alkalosis) and can be life-threatening. The body achieves this stability through two primary regulatory systems:
- Respiratory System: The lungs control the amount of carbon dioxide in the blood. Since carbon dioxide forms carbonic acid, changes in breathing rate can rapidly adjust blood pH.
- Renal System: The kidneys filter out excess acids and bases, excreting them in the urine. This is the mechanism by which dietary choices can affect urine pH, but not blood pH.
The Potential Renal Acid Load (PRAL)
The concept that foods can be 'acid-forming' or 'alkaline-forming' is based on the Potential Renal Acid Load (PRAL) score, which estimates the amount of acid the body's kidneys must excrete after a food has been metabolized. Foods with a positive PRAL contribute to a higher acid load, while those with a negative PRAL have an alkaline-forming effect. The misconception is that this acid load directly affects blood pH, when in fact, the kidneys simply process the load and excrete it in the urine.
Foods That Contribute to a Positive Acid Load (Higher PRAL)
Consuming a diet high in foods with a positive PRAL is the key to understanding what to eat to lower pH, specifically the pH of your urine. These are the foods that, after digestion, leave an acidic residue for the kidneys to handle.
- High-Protein Foods: Meat, poultry, fish, and eggs are significant contributors to a high acid load. The metabolism of sulfur-containing amino acids within proteins leads to the production of sulfuric acid.
- Grains: Whole grains, such as wheat, rice, and oats, are also acid-forming. This is due to their phosphorus and sulfur content.
- Dairy: Certain dairy products, especially hard cheeses, contribute to a positive PRAL.
- Processed Foods and Drinks: Sodas and other sweetened beverages are highly acid-forming due to phosphoric acid. Processed foods, which are often high in sugar and refined flours, also increase the acid load.
Comparing Acid-Forming and Alkaline-Forming Foods
The following table illustrates the typical PRAL effect of different food types based on their metabolic residue. While the foods with a positive PRAL answer the question of what to eat to lower pH, it's critical to note that many of these are essential parts of a healthy diet, and the focus should be on balance rather than elimination.
| Food Category | PRAL Effect | Examples of High-PRAL Foods (Lowering Urine pH) | Examples of Low/Negative-PRAL Foods (Raising Urine pH) |
|---|---|---|---|
| Protein | Positive | Red meat, poultry, fish, eggs | Tofu, tempeh, most plant proteins |
| Grains | Positive | Wheat, refined pasta, white rice | Quinoa, buckwheat, amaranth |
| Dairy | Positive | Hard cheese | Milk (neutral-forming), most plant-based milks |
| Fruits & Vegetables | Negative | Cranberries (exception) | Most fruits (including citrus) and vegetables |
| Fats & Sugars | Neutral/Variable | Sugars, trans fats | Natural fats like olive oil, avocado oil |
Medical Context: When pH Matters
While a healthy person’s diet won't affect their blood pH, diet modification to influence urine pH is a medically recognized strategy for specific conditions.
- Kidney Stones: In cases of uric acid kidney stones, a physician may recommend a diet lower in acid-forming foods to raise urine pH and help dissolve or prevent the stones. Conversely, if oxalate stones are a concern, other dietary interventions are needed.
- GERD (Gastroesophageal Reflux Disease): People with GERD often find relief by avoiding naturally acidic foods, such as citrus fruits and tomatoes, which can trigger symptoms.
- Kidney Disease: For individuals with chronic kidney disease, a diet lower in acid-forming animal protein may be recommended to reduce the acid load on the already-compromised kidneys.
Conclusion
For a healthy person, the body's internal pH is not a concern, and diet does not impact it significantly. The idea of eating what to eat to lower pH is scientifically misguided if referring to blood pH. However, dietary choices do influence the acid load handled by the kidneys and can alter urine pH. For those with specific medical conditions, like certain kidney stones, a doctor-supervised dietary approach might focus on managing urine pH, not changing overall body acidity. Ultimately, the health benefits often attributed to alkaline diets—increased intake of fruits, vegetables, and whole foods—are due to better overall nutrition, not pH manipulation. Adopting a balanced diet rich in whole foods, regardless of PRAL, is the best path to overall health.
This article is for informational purposes only and is not medical advice. Consult with a healthcare professional before making significant changes to your diet, especially if you have a pre-existing medical condition.
