A reader left a comment on the Lacto-fermented Beverages post I did last week asking, "The article says how much acid is in kombucha, then says it helps to alkalize blood and tissues. This sounds contradictory. Is there an explanation?" An excellent question, and, as I often do with excellent questions, I decided to answer it in a blog so that everyone could benefit from the response.
Some of you may remember the term pH from high school science class, but for those of you who don't, here's a quick explanation - the pH scale is a measurement of how acidic or alkaline (basic) something is. It's actually a measure of hydrogen ion activity, but we'll keep it simple here and just say it measures acidity, or lack thereof. The scale runs from 0 to 14; 0 being extremely acidic, 14 being extremely basic and 7 being neutral. A lemon is acidic whereas baking soda is basic. Simple enough.
Just like your body needs to maintain a consistent temperature, it needs to maintain a consistent pH. Different parts of the body have different ideal pH levels and changes in those levels can have fairly drastic results depending on the system. A change in the pH of the colon can lead to an infestation of harmful bacteria, whereas a severe change in blood pH can lead to death. "Chronic low-grade metabolic acidosis" can lead to a greater risk of developing osteoporosis, muscle weakness, heart disease, diabetes, kidney disease, and other health problems. In fact, tumor growth thrives in an acidic environment but slows in one that is alkaline.
And how do we maintain the pH of the body? One important way is through diet. Different foods have different net effects on the pH of the body. A simple rule of thumb would be that acid yielding foods deplete minerals whereas mineral-rich foods have alkalizing effect. When the kidneys detect a low pH they respond by buffering the fluids of the body, releasing mineral stores. Calcium and magnesium are released from the bones and muscle tissue is broken down to produce ammonia to reestablish alkalinity. It's easy to see why chronic low grade acidosis can lead to muscle weakness or osteoporosis.
Now, don't go rummaging through your kitchen cupboards, throwing out all your lemons, grapefruits and vinegar just yet. It's important to note that just because a food is acidic on the palette doesn't mean it has an acidifying effect on the body. Lemons are a perfect example - while they are quite tart and acidic, lemons are actually loaded with minerals and have a net alkalizing effect when you eat them.
In general, high protein foods like meat and dairy, high in amino acids that make up proteins, will have an acidifying effect on the body. Fruits and vegetables, on the other hand, have an alkalizing effect. But the distinction isn't always that straight forward. Grains and legumes, which have decent mineral content, are generally acidifying. Similarly milk, which we all know is loaded with calcium, has a net acidifying effect. (Isn't it ironic that milk is sold with the promise of giving healthy bones and teeth due to its calcium content, yet it's actually using up mineral stores).
Before you start to worry that this acid/alkaline thing might be too tricky to figure out, check out this handy-dandy chart I found online for you. It gives a fairly comprehensive list of acidifying versus alkalizing foods. (Note that I'm not endorsing the program they're selling on this page, I just like the chart). You may find other charts online or in books, and that's fine. Different charts may disagree on some of the nitty-gritty points but the general principles will likely be in agreement. (For example, some will say that organic eggs are actually alkalizing, where as others don't differentiate and say all eggs are acidifying. The same distinction is sometimes made for raw milk, which some report to be alkalizing).
Researchers agree that the Standard North American Diet is extremely acidic, favouring meats, grains (particularly white flour), dairy and sugar while drifting away from fruits and vegetables, the use of sea weed, traditional bone broths and unrefined sea salt (all mineral rich and alkalizing). For this reason, we could all stand to get a little more alkalizing foods into our diet. As if we needed another reason to eat those fruits and veggies! But don't get too carried away - you will always have some acidifying foods in your diet and this is as it should be. Balance between the acidifying and the alkalizing foods is the key.
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