pH Regulation, Dietary Influences, and Health Evidence
Maintaining the body’s acid-base balance is an important aspect of metabolic health. There could be a small change in body fluid pH that can affect cellular functions, enzymatic reactions and overall homeostasis. Body fluid indicates the concentration of hydrogen ions (H+), which is generated from different metabolic processes. Organic acids, including β-hydroxybutyric acid and lactic acid, are generated in tissues such as the liver, adipose tissue, and skeletal muscle. These acids separate into protons and conjugate bases, and that leads to acidification of intracellular and extracellular environments. The human body uses many buffering systems and transport mechanisms.
The major contributions of the buffering system involve the proton-proton binding, bicarbonate stems and phosphoric acid buffering, and this stabilises pH by neutralising excess protons. Cells use special transporters for moving extra protons out of the cell into the space around them, including monocarboxylate transporter MCTs and Na+/H+ exchangers NHEs. These procedures allow the cells to keep the cells of internal pH at a normal level around 7.03-7.46, and that is crucial for healthy metabolism. Therefore, when cells are affected by too much acid, the problem arises with the transporter, and normally, the fluid around the cells becomes more acidic.
According to experts, a drop in interstitial fluid pH, the fluid between cells, may contribute to metabolic problems, for example, in insulin resistance, obesity and type 2 diabetes. Furthermore, food can improve proton transport and also support metabolic health (Aoi et al., 2020).
Understanding pH
Alkaline acid has to do with pH. It is considered acidic when pH is low (between 0 and 6), and high in pH scale (from 8 to 14) is considered alkaline, and 7 is considered neutral. Understanding food better shows that some foods contain alkaline and others are acidic. For example, citrus fruits such as lemon, grapefruit, and oranges are acidic foods. The acidic food we consume over time can change the pH level in our blood. The reaction occurs continuously through our breath, with a chemical signal, through the brain, and the kidneys work hard to regulate pH through large and small adjustments (Henry, 2019). According to studies, the more you consume acidic food, the harder your body will work, and this can have long-term effects.
The concept of Alkaline and Acid comes from human practice. The meaning of acid comes from the Latin word acere, which means sour. Acid tests have a sour taste, observed from foods like sour milk, lemon juice, and vinegar. The word Alkaline is an Arabic word al-qily, which refers to burnt plant ashes. The terms acids and bases began in 1776 with Antonio Lavoisier. In 1838, Justus von Liebig declared acids as substances that contain hydrogen. Later, Sørensen, a Danish scientist, introduced the concept of pH at the Carlsberg Laboratory, updated in 1924 based on modern electrochemical methods.
Ancient Indian texts like Hatha Yoga Pradipika, Shiv Samhita, and Gheranda Samhita studied food effects on the body and classified it as sattvic (pure), rajasic (stimulating), and tamasic (heavy/impure). Charak (~200 AD) in Charak Samhita classified foods as light or heavy; light foods were recommended for good health. E.V. McCollum (Johns Hopkins) recommended more alkaline-forming foods like vegetables, grains, milk, fruits, butter, and cheese. Blood pH should be between 7.35 and 7.45. Small pH changes affect organisms, like oceans dropping from 8.2 to 8.1 due to CO₂, harming coral reefs. Soil pH 6–7 provides optimal nutrients; extremes lead to nutrient imbalances.
As we age, kidney function declines, and modern diets can lead to metabolic acidosis. Blood pH below 7.35 indicates acidosis; above is alkalosis. Most enzymes function within a specific pH range; deviations can impair their activity (N Suthar, 2024).
Research Evidence on Urine pH and Bone Health
Modern diets may cause slightly acidic urine (~pH 6). Some promote alkaline diets to sell products claiming balance of acid and base levels. Acid load can be measured by urine pH or calculating total acid excretion, including sulfates, chlorides, phosphates, minus minerals like magnesium, calcium, potassium, and sodium. Traditional urine pH measurements may be inaccurate due to bacterial changes.
Better measurements consider post-digestion urine, reflecting actual diet. Lab tests analyzed urine for pH, creatinine, calcium, phosphate, and other ions. Results show low urine pH or high acid levels do not increase osteoporosis risk. A single urine test cannot indicate long-term diet effects. More research is needed to assess diet effects on bone health and the validity of alkaline diets (Fenton et al., 2010).
Acid Ash Hypothesis and Bone Strength
The acid ash hypothesis claims high-protein diets harm bones due to acid load. Excess acid is neutralized by bicarbonate from bone minerals, possibly weakening bones over time. Some studies suggested acid-forming foods (dairy, grains) increase urinary calcium and bone calcium depletion. However, reviews questioned this, considering biochemical mechanisms, protein influence, phosphate, calcium balance, and validity of the theory. Evidence is weak on dietary acid load causing osteoarthritis.
A systematic review analyzed whether high acid diets contribute to osteoporosis, reviewing human interventional studies, long-term observations, and lab studies. Researchers examined whether reducing dietary acid load could reduce risk or slow osteoporosis progression (Fenton et al., 2011).
Meta-Analysis of pH Methods
Experts explored calcium excretion, acid load, and bone health through meta-analyses of RCTs and RCOs. When no meta-analyses existed, individual studies were reviewed. Another meta-analysis examined effects of alkaline treatments or low acid diets on bone resorption markers (serum CTX, deoxypyridinoline crosslinks, urinary N telopeptide) using standardised mean differences with Cochrane RevMan5. Random effect models were applied if heterogeneity p-value was 0.05–0.5. Sensitivity analysis excluded urine CTX due to biological fluctuations. Lab studies on bone mineral loss at different pH levels assessed acid impact on bone health within normal physiological pH (Fenton et al., 2011).
Food and pH Balance
Food does not change blood pH directly; the body manages acidity and minerals. Below is a guide to alkaline and acidic foods:
Low Acidic / Alkaline Foods
- Yoghurt and fermented foods
- Black tea
- Butter in moderation
- Brown rice and beans
- Natural honey (unprocessed)
Middle or Moderate Acidic Foods
- Tuna, Salmon, Tilapia, Mackerel
- Whole wheat and rye bread
- Cottage Cheese, hard Cheese, Cream cheese
- Ketchup, Mustard, Mayonnaise
- Olives, Garlic, Pomegranates
- Pistachios, Eggs, Corn
Highly Acidic Foods
- Chocolate, ice cream, milkshakes
- Soda, liquor, beer
- White sugar and pastries
- Espresso and strong coffee
- Cheese
- Pork (bacon, chops, ribs)
- Beef
Practical Tips for Getting Started
- Gradually replace processed foods with vegetables, fruits, and whole grains.
- Limit sugary drinks; opt for water or herbal teas.
- Balance meals: include a grain, vegetables, and plant-based protein.
- Experiment with alkaline-friendly recipes like quinoa salads or brown rice bowls.
Frequently Asked Questions (FAQs)
Further Reading & Internal Links
Explore related guides: Asthma and Macrobiotics, What is Healthy Food?, Foods to Avoid for Asthma.
Medical Disclaimer
I am not a medical professional. This article is for informational and educational purposes only. Please consult your doctor or a qualified healthcare professional before making changes to your diet, exercise, or lifestyle.
External Reading & Resources
- Dietary Acid-Base Balance and Bone Health – NCBI
- Alkaline Diet: What It Is, Benefits, and Risks – Healthline
- Foods That Affect Your pH Levels – Medical News Today
- Body Fluid pH Regulation and Metabolism – ScienceDirect
- Nutrition for Bone Health – NIH Osteoporosis and Related Bone Diseases
- Effect of Acid-Base Diet on Urinary pH and Bone Health – NCBI
- Alkaline Diets and Health – British Nutrition Foundation
References
- Aoi, W. et al. (2020) ‘Body Fluid pH Balance in Metabolic Health and Possible Benefits of Dietary Alkaline Foods’, eFood, 1(1), pp. 12–23. Available at: https://doi.org/10.2991/efood.k.190924.001
- Fenton, T.R. et al. (2010) ‘Low urine pH and acid excretion do not predict bone fractures or the loss of bone mineral density: a prospective cohort study’, BMC Musculoskeletal Disorders, 11(1), p. 88. Available at: https://doi.org/10.1186/1471-2474-11-88
- Fenton, T.R. et al. (2011) ‘Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill’s epidemiologic criteria for causality’, Nutrition Journal, 10(1), p. 41. Available at: https://doi.org/10.1186/1475-2891-10-41
- Henry, B. (2019) 30 Day Alkaline Diet Challenge.
- N Suthar, N. (2024) ‘ALKALINE DIET AND HEALTH-A BRIEF REVIEW’.
