Simply put, the North American diet is very acidic. From most proteins to many dairy products (especially cheese) to most grains, we take in far more dietary acids than we do bases. And this imbalance between acid and base can cause some serious long-term health and physique problems.
You see, when a food is ingested, digested, and absorbed, each component of that food will present itself to the kidneys as either an acid-forming compound or a base-forming one. And when the sum total of all the acid producing and the base producing micro and macronutrients is tabulated (at the end of a meal or at the end of a day), we're left with a calculated acid-base load. If the diet provides more acidic components, it will obviously manifest as a net-acid load on the body. And if it provides more basic components, it will obviously manifest as a net-base load on the body.
Since I already noted that a net acid load is bad, let’s discuss why.
Every cell of the body functions optimally within a certain pH range (pH is a measure of the acidity or alkalinity of the body). In different cells, this optimal range is different, however, the net pH of the body has to remain tightly regulated. One common problem with most industrialized societies is that our diets produce what's called a "low grade chronic metabolic acidosis." In other words, the PRAL (potential renal acid load – a measure of the amount of acid being introduced through the diet) of our diets is high and this means that we're chronically in a state of high acidity.
While there are a number of disease states that induce severe metabolic acidosis, we're talking a sub-clinical rise in acidity here. Therefore, your doc probably won't notice the problem. But that doesn't mean that you're in the clear. Your cells will recognize the problem.
So what's wrong with this low-grade chronic metabolic acidosis?
Well, since the body must, at all costs, operate at a stable pH, any dietary acid load has to be neutralized by one of a number of homeostatic base-producing mechanisms. So, although the pH of the body is maintained and your doctor visits turn out fine, many cells of the body will suffer. Here are some of the most severe consequences of your body's attempt to maintain a constant pH in the face of an acidic environment:
• Hypercalciuria (high concentrations of calcium in the urine). Since calcium is a strong base and bone contains the body's largest calcium store, metabolic acidosis causes a release in calcium from bone. As a result, osteoclastic (bone degrading) activity increases and osteoblastic (bone building) activity decreases. The net result of these changes is that bone is lost in order to neutralize the acidic environment of the body. The calcium that was stored in the bone is then lost in the urine along with the acid it was mobilized to neutralize. This creates a negative calcium balance (more calcium is lost from the body than is consumed) and bones get weak. (2,3,4,6)
• Negative nitrogen balance (high concentrations of nitrogen in urine). Glutamine is responsible for binding hydrogen ions to form ammonium. Since hydrogen ions are acidic, glutamine acts much like calcium to neutralize the body's acidosis. Since skeletal muscle contains the body's largest glutamine store, metabolic acidosis causes muscle breakdown to liberate glutamine from the muscle. The amino acids from this muscle breakdown are then excreted, causing a net loss of muscle protein. (2,7)
In addition to bone and muscle loss, other consequences of acidosis include:
• Decreased IGF1 activity (4)
• GH resistance (4)
• Mild hypothyroidism (4)
• Hypercortisolemia (4,5)
Interestingly, low-grade metabolic acidosis seems to worsen with age. Many have speculated that this is due to an age-related decline in kidney function (and acid excretion). Of course, osteoporosis and muscle wasting are unfortunate consequences of aging. While it's too early to tell, perhaps some of the bone and muscle loss evident as individuals get older is a result of diet-induced acidosis. This means that employing a few simple acid-base strategies may help slow osteoporosis and sarcopoenia.
So the big question is this – who’s at risk?
Recently, Sebastian and colleagues compared the pre-agricultural diet of our ancestors to the modern North American diet. After evaluating the two diets for what they call NEAP (net endogenous acid production) — essentially the same measure as the PRAL above — a -88mEq/day acid load characterized the pre-agricultural diet while the modern diet was characterized by a +48mEq/day acid load. What this means is that our ancestors evolved eating a diet that was very alkaline/basic and therefore very low acid. However, modern people are eating a diet that is high in acid, and therefore very different from what we evolved to eat. As a result, our modern diet is responsible for what the authors have called a "life-long, low grade pathogenically significant systemic acidosis."
How have we gotten so far off track? Well, the shift from net base producing foods to net acid producing foods comes mostly as a result of displacing the high bicarbonate-yielding plants and fruits in the diet with high acid grains. In addition, most of our modern energy dense, nutrient poor selections are also acid forming. Finally, high protein animal foods tend to be acid producing as well.
If you're now wondering how your diet stacks up, check out the online acid-base forum here: http://www.acid-base.de/. There you’ll be able to calculate your PRAL and determine how much of an acid or base load your body is under. Further, if you’re ingesting too many dietary acids, as most North Americans are, here’s what you can do:
• Add more vegetables - regardless of the final tally. Everyone can always benefit from more vegetables in the diet. Many bone specialists are now recognizing that the most effective way to improve bone health is to eat lots of fruits and vegetables. Vegetables, in addition to all of their other benefits, are powerful acid-neutralizers.
• If you're eating a big meal that's going to be a net acid producer (such as one that contains a large amount of protein and/or grains) and don't want to add more basic foods, consider adding a small amount of glutamine to this meal. Exogenous glutamine supplementation has been shown to neutralize acidosis.
• A cheaper alternative to glutamine supplementation is either sodium or potassium bicarbonate supplementation. You can add sodium bicarbonate (in the form of baking soda) to your beverages including your protein shakes, which probably are a bit on the acidic side (see milk above). A small 2-5g dose of baking soda would be sufficient to neutralize the shake. An alternative to baking soda is alka-seltzer.
• Adding sodium to foods can increase the base potential and reduce the acidity of the meal although a high salt diet isn’t necessarily recommended.
Although few individuals in the exercise nutrition world are discussing this issue, it remains an important one. Employing a few simple strategies to neutralize your high-acid diet may mean the difference between chronic low-grade acidosis — and the associated muscle wasting, bone loss, and altered hormonal profile — and a healthy, alkaline diet. So make sure you’re dietary acids are covered!
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