Normal Blood pH: How Your Body Maintains It

Okay, so let’s look back at Monday’s post on Acidosis and Alkalosis. In my haste to go sit on the beach and stare at the ocean, I gave short shrift to covering how the body actually maintains normal blood pH.

Normal Blood pH

So to quickly recap, the body works hard to maintain a normal blood pH between 7.35 and 7.45, a fairly tight range. And pretty much nothing you do, at least in terms of food, is going to change that. So you can’t really “acidify” or “alkalize” your body. Your body requires a rather tight pH in the blood (and equally tight, though different pH in other systems) in order for your bodily functions to proceed as normal.

If you were to “acidify” or “alkalize” your blood, you’d quickly run into some serious issues, regardless of which way you took it.Basically, the foods you eat are digested and broken down into their components. These metabolites exhibit an acid, base, or neutral pH to the body. When you add them all up, you get the net-acid or net-base load of the overall diet. And then the body has to deal with this acidity or alkalinity to make sure the body stays at the proper pH in all of its various systems, particularly the blood.

Effects On Urine

One of the ways that the body deals with excess acid or base is to pass it off to the urine for excretion. According to this study:

In conclusion, a more alkaline diet, higher fruit and vegetable and lower meat intake were related to more alkaline urine with a magnitude similar to intervention studies. As urine pH relates to dietary acid-base load its use to monitor change in consumption of fruit and vegetables, in individuals, warrants further investigation.

But here’s an interesting observation from Dr. Jarvis, author of Folk Medicine:

By keeping logs, he was able to show that ill health went along with the alkaline urine, while good health went along with acidic.

An interesting observation indeed and, to be fair, I really have no idea what to make of it. Just throwing it out there for discussion. It makes sense though, since urine is typically acidic (5-6 pH).

Effects On CO₂ Exhalation

Unbeknowst to me (but knownst to others…name it!), Yael Grauer recently wrote a similar article over at The Performance Menu looking at this exact same issue.

Great minds…She pointed out that the body maintains proper pH in the blood by breathing out either more or less CO₂, depending on whether the blood is too acidic or too alkaline. Basically, when your blood is too acidic, your breathing increases to release more CO₂. Think about when you exercise…breathing increases due to increased acidity in the blood from the cells doing their thing as much or more than the need for oxygen.

Effects On Bones

Another claim is that the body buffers acidity largely by pulling from its largest reserve of alkaline material – calcium from the bones. Well, Yael’s article pushed me to go out to Pubmed and look for some work by Jane Kerstetter. According to Kerstetter,

We conclude that in rats, as in humans, acute increases in protein intake result in hypercalciuria due to augmented intestinal Ca absorption. BBMV Ca uptake studies suggest that higher protein intake improves Ca absorption, at least in part, by increasing transcellular Ca uptake.

But, it’s not quite so simple. That study shows that meat protein increases calcium uptake from the intestines. That’s not necessarily true of all protein though. In fact, (vegetarians take note) Kerstetter showed that soy protein is detrimental to calcium uptake:

These data indicate that when soy protein is substituted for meat protein, there is an acute decline in dietary calcium bioavailability.

Here is one more from Kerstetter regarding high-protein (which says “high acid” to me) diets and bone health:

The high-protein diet caused a significant reduction in the fraction of urinary calcium of bone origin and a nonsignificant trend toward a reduction in the rate of bone turnover. There were no protein-induced effects on net bone balance. These data directly demonstrate that, at least in the short term, high-protein diets are not detrimental to bone.

Of course, if you aren’t taking in enough calcium, perhaps this is an issue. Perhaps not. I’m guessing that, once again, the body is far smarter than we give it credit for. Maybe the increase in osteoporosis isn’t necessarily due to “an acidic diet,” but the particular types of acidic foods we eat, namely:

• the “healthy” soy protein to replace meat – see above
• lots of grains – contain phytic acid that binds with calcium
• high salt intake – may also bind with calcium
• sugar – depletes vitamins and minerals and has been shown (in rats) to throw off calcium/phosphorus balance

There’s also the severely detrimental effects on bone health of low vitamin D and low magnesium intake, both just as important as calcium for building bone.

It All Adds Up To…

Something I’m still not concerned about. If you’re not eating much in the way of grains, you can likely eat your meat and eat plenty of fruits and vegetables with impunity. You don’t need to calculate acid and base loads like John Berardi mentions in his article Covering Your Nutritional Bases.

As I said in my last article, this is mainly just “eat your vegetables” and anti-meat repackaged, because the people that are talking about it are usually promoting high whole grain diets, another acidic food.

As Yael said:

Don’t worry about meat robbing calcium from your bones. You’ll excrete calcium if your urine is more acidic (with hydrogen ions being secreted to balance the acid load), but your body will be getting it from elsewhere. And even though your urine can become more or less acidic, your blood is going to stay the same. Though eating vegetables is generally a good idea for a variety of reasons, it’s not because minerals are being robbed from the bones. And since it appears that half of the hunter-gatherer diets had high acid-load diets, and none of our caveman buddies had modern diseases, I wouldn’t lose sleep over the possibility.

We really can’t take things out of context, especially when talking about a highly complex biological machine like the human (or any mammalian) body, and expect to be able to distill things down to some excessively simple talking point. If you’re concerned, eat more plant matter. But I maintain that meat, fruit, vegetables, properly-prepared beans and non-glutinous grains (like rice), and some dairy are highly unlikely to harm you or your bones, especially if you’re active (which stimulates bone growth) and you have adequate intake of magnesium and a good vitamin D status.

Any additional thoughts on this matter? Anyone have additional supportive or conflicting evidence that I missed?