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Acid-Alkaline Balance

Human blood pH should be slightly alkaline, at about 7.35 to 7.45.  Metabolism of too much protein and sugar causes a buildup of acidity in the blood.  It shifts the tissues to slightly acidic composition, which has any number of biological consequences, especially for the ability of the red blood cells to pick up and transport oxygen to other cells.  It also causes a slight congealing, or thickening, of the blood, lymph, and interstitial fluids, which promotes congestion and slows down metabolic processes.  This has serious consequences for your immune system and leads to many diseases of the heart and circulatory system, such as arterial sclerosis and atherosclerosis[6]
With a correct blood pH, the body is said to be in homeostasis, or inner balance.

Acid-Alkaline Balance Act

Our blood pH is affected by what we eat.  If you eat high-acid food, it will lower your blood pH (more acidic) and vice versa.  Consequently, our body is constantly attempting to balance its pH. 
Research shows that a prolonged acidic environment can give rise to inflammation and cancer and can lead to premature aging from free radical damage.  For example, Norwegian scientists have confirmed that acidic pH can induce metastatic cancer growth of human melanoma cells.  At the same time, the body responds to the acidic environment by drawing out calcium and other minerals from the bones and connective tissues to buffer the acid.  The Women's Health Initiative found that over a 12-year period, women who consumed more than 95 grams of protein daily had a 20% greater chance of breaking a wrist than women who took in less than 68 grams a day[6].
Dr. Rau[6] has summarized the most common problems that result from long-term hyperacidity are:
  • Hypertension, or high blood pressure
  • Decrease in microcirculation, which leads to coronary heart diseases, arterial sclerosis, and memory problems
  • Degenerative joint diseases, such as osteoarthritis
  • Osteoporosis
  • Disc problems, which result in back pain
  • All kinds of cancer
  • Impaired glandular function
  • Stomach and intestinal problems
  • Insomnia
Hyperacidity in the blood also causes a host of problems in the organs and other tissues[6]:
 Kidney/Bladder     Cystitis, prostate enlargement, kidney stones, yeast infections in women
 Stomach Acid reflux, ulcers
 Skin Excess sweating, rashes, swelling, eczema
 Intestines     Colitis, bowel irregularity
 Lungs Asthma, recurrent bronchitis
 Joints Arthritis, myalgia
 Neurological System Depression, decreased alertness, fatigue
Our body has a number of mechanisms to keep the acid-alkaline balance[2]:
  • Through breathing, the cells exhale carbonic acid, which becomes carbon dioxide and is released through the lungs, lowering the body's acid load.
  • The movement of muscles creates lactic acid due to the breakdown of glycogen to produce energy, increasing acidity.
  • The kidneys regulate the acid-alkaline balance in the blood by excreting urine that is more acid or more alkaline according to what needs to be eliminated.[18-19]
  • Hydrochloric (HCl) acid is the only acid the body produces.  All other acids are by-products of metabolism and are eliminated as soon as possible[3].
  • If the blood becomes too acid, the bones releases calcium and other buffering minerals into the bloodstream through resorption to rebalance the pH[5].
Acid-Forming vs. Alkalizing Foods

The foods we eat contribute to either an acidic or an alkaline effect on the blood pH once they're metabolized[13].  Their effect depends on the residue they leave behind:  If they leave acids (carbonic, phosphoric, or sulfuric) they are acid-forming. If they leave buffering minerals (mostly calcium, iron, magnesium, potassium, and sodium), they are alkalizing.  The rule of thumb is that the more minerals (especially Calcium, Sodium, Potassium, Magnesium, Cobalt and Copper) there are in the food, the more alkalizing it is.

Proteins and carbohydrate foods are acid-forming foods, while fruit and most vegetables are alkaline-forming foods[1].  Note that lemons,  limes, and apple cider vinegar taste acidic, they actually create an alkaline condition in the body and help reduce body acids.  In [10], Jean has also summarized vinegar's benefits to include:
  • Vinegar packs potent glucose-lowering effects and reduces insulin resistance
    • Jennie Brand-Miller, PhD, a professor at the University of Sydney says that four teaspoons of vinegar in your salad dressing can lower blood sugar spikes from an average meal by 30%.  Putting vinegar on blood-sugar-hiking white potatoes can reduce surges by 25%.
  • Vinegar can curb appetite and food intake
    • At studies at Arizona State University, subjects who took 1 and 1/2 tablespoons of apple cider vinegar ate 200 fewer calories at the next meal.

In [2], Dr. Colbin has listed foods that of acid-forming and alkalizing:

Acid-Forming Foods
Alkalizing Foods
  • Alcohol
  • Sugar
  • Oils
  • Nuts
  • Seeds
  • Flour
  • Whole grains
  • Beans
  • Fish
  • Poultry
  • Meat
  • Eggs
  • Juices
  • Fruit
  • Green vegetables
  • Green beans
  • Potatoes (because they contain solanine, an alkaloid)
  • Seaweeds
  • Soy sauce
  • Miso
  • Salt
As Dr. Colbin[2] has pointed out, western people has consumed too much acid-forming foods including meat, sugar and flour.  This has significantly drained calcium and other minerals from the bones and caused osteoporosis.
Normal urinary pH levels range between 5.0 and a little over 8.0. This varies with the time of day, food consumption, age, and other factors[8].  In the book China Study, Dr. T. Colin Campbell showed that the levels of acids and calcium in the urine of middle-aged and elderly women was influenced by their diet.  Based on the effect of foods on urine pH, we can classify them into either acidic or alkaline as shown below. Positive numbers indicate that the food makes urine acidic.  Negative numbers indicate that the food makes urine alkaline.

Food Item
Effect on Urine (in milliequivalents (mEq)
Apricots, dried
Figs, dried
Plums, dried (prunes)
Chard, cooked
Sweet potato (baked with skin)
Potato (red with skin)
Turkey (no skin)
Oats (rolled, dry)
Spaghetti, whole wheat
Chicken (no skin)
Corn beef
Different Cheese
Egg noodle
Egg yolks

Note that there are discrepancies on which food items are acidic or alkaline based on the different sources I quote.  One source says that seeds and some whole grains such as millet, quinoa, and amaranth are alkaline foods while Dr. Colbin list them as acidic (as two groups--seeds and whole grains).  Another source says that dairy foods are acidic food while Dr. Colbin list them as buffers (or neutral) because they contain both calcium (which is alkalizing) and protein (which is acid-forming).  Finally, some say that caffeine and processed foods are also acid-forming.

No matter what, our goal is to eat low acid foods, particularly fruits and vegetables, helps create the ideal blood pH.  As said before, acidic foods exert pressure on our body's balancing systems as it strains to maintain pH neutrality.  The process of counterbalancing the acidity can deplete the body of alkaline minerals such as
potassium, magnesium, and calcium, making the person prone to chronic and degenerative disease.  Because of this strain, the body can suffer severe and prolonged damage, leading to an unhealthy condition that may go undetected for years.


  1. The Complete Idiot's Guide to Detoxing Your Body by Delia Quigley.
  2. The Whole-Food Guide to Strong Bones by Annemarie Colbin, Ph.D.
  3. Alkalize or Die by Dr. Theodore A. Baroody
  4. The China Study by Dr. T. Colin Campbell
  5. Building Strong Bones
  6. The Swiss Secret to Optimal Health by Thomas Rau, M.D.
  7. 如何延缓衰老,保持健康长寿 (in Chinese)
  8. Risk Factors of Kidney Stones
  9. The Acid Alkaline Balance Diet by Folicia Drury Kliment
  10. 100 Simple Things You can Do to Prevent Alzheimer's by Jean Carper
  11. Sugar: The Bitter Truth
  12. pH Balance (Acid-Alkaline balance)
  13. 食品影響酸鹼體質的學理、迷思、及與健康的關係 (in Chinese)
  14. 30 Amazing Uses and Healing Powers of Apple Cider Vinegar
  15. Can an alkaline diet help prevent cancer?
  16. Metabolic acidosis
  17. Alkalize Your Body and Fight Disease With These 10 Healing Foods
  18. Banerjee T, Crews DC, Wesson DE, et al.  Dietary acid load and chronic kidney disease among adults in the United States.  BMC Nephrol. 2014 Aug 24;15:137.
  19. van den Berg E, Hospers FA, Navis G, et al.  Dietary acid load and rapid progression to end-stage renal disease of diabetic nephropathy in Westernized South Asian people.  J Nephrol. 2011; 24(1):11-7.
  20. All Things Considered—Kidney DiseaseAll Things Considered—Kidney Disease (Travel to Health)