In a nutshell, here’s the controversy: your blood maintains its pH regardless of what you eat, according to what we know of physiology.

This is true.  Our bodies are designed to compensate quite well.

But at the same time, certain foods tax the blood buffering system more than others.  This is also true.

So, alkaline diets – are they all hype, or is there any science behind them?

To answer this, here’s a crash course in acid/base chemistry: 

  • An acid is any substance that can lose a proton (or a hydrogen ion: H+).
  • A base (alkaline substance) can accept a proton.  A good example is hydroxide (OH-).
  • That’s why water is considered to be “neutral” (pH 7.0) – water is H2O, and when it dissociates, it forms both H+ and OH–, in a one to one ratio.

Crash course in pH physiology: 

  • Our blood naturally maintains a pH between 7.35 and 7.45 – ideally about 7.40, so slightly alkaline.  If the pH drops below 6.8 or rises above 7.8, we’re in big trouble.
  • So to prevent either of those extremes, your blood has a buffer system in place to absorb the excess.  (Think of a buffer like the bumper on your car – it keeps the initial impact of an accident from crumpling the whole thing like an accordion.)  This main buffer system involves bicarbonate (HCO3–), which can accept a proton (that’s why bicarbonate is considered alkaline).
  • Bicarbonate is also stored in your bones, though, complexed with calcium and sodium (Ca+ and Na+).  Phosphate (PO4–) can also function as a buffer, and it too is stored in your bones, complexed with calcium.  So in order to release these buffers, your bone minerals have to break down as well.  (Remember that, it’ll come up again.)

How your buffer systems get activated:

Your tissues use oxygen to convert chemical energy (glucose) into mechanical energy.  Ever had your muscles burn after a particular intense workout?  That means your muscles created lactic acid (which increases H+ in the tissue, along with CO2 in exchange for oxygen).

Some foods also have an acidic effect on the body, which is what this article is all about.  Also – as your tissues release protons to the blood stream, they have to make an exchange, for electrolytes like sodium and potassium (Na+ and K+).  So these are inversely related.  (My guess is, that is why foods high in electrolytes have a more alkaline effect on the body – but I don’t know this for sure.)

Where buffering happens:

Ultimately your kidneys are responsible for removing the excess proton buildup from your blood and reabsorbing bicarbonate ions.  (Because the buck stops with your kidneys, too, an acidic diet is correlated with a higher incidence of kidney stones.)

Your lungs can also get rid of excess acid through exhaling CO2 (which functions as an acid in the blood, since as CO2 goes up, bicarbonate goes down).

Finally, your bones can bear up to 40% of the burden of an acute acid load on the blood.  Even a week of an acidic diet is enough to decrease concentration of bone minerals from the surface of the bones.

So which foods are acidic, and which are alkaline?

Foods with an acidic effect on the body buffering systems include beef, ice cream, canned fruits, peanuts, bacon, tuna, corn, sugar, vinegar, corn syrup, cereals, mustard, mayo, corn tortillas, milk, sardines, soft drinks, artificial sweeteners, and ketchup.

I’m not against the unprocessed things on this list – just make sure you diet doesn’t consist of nothing but.

Foods with an alkalinizing effect include alfalfa, celery, barley grass, peppers, beet greens, broccoli, cabbage, mustard greens, chard greens, collard greens, chlorella, onions, cucumber, spinach, spirulina, garlic, green beans, dandelions, lettuce, kohlrabi, kale, pumpkin, wheat grass, sprouts, watercress, and wild greens.

So what should you do with this information?

First, be thankful for your blood buffering systems.  They’re pretty neat, and you’d die without them (no matter how you eat).

Also, to keep from overtaxing them and suffering long-term effects,

  1. Eat your vegetables, especially the green ones.  
  2. Avoid your white carbs, sugars, sodas, and processed foods.  
  3. Exercise – this will activate your lungs’ buffering system, oxygenating your body and releasing excess CO2.