There are more diet plans out there than anyone could count. The alkaline diet is one diet plan based entirely on an incorrect understanding of biology. The idea behind this diet is that certain foods help maintain your body in a non-acid state. Somehow this promotes weight loss and general well-being. If you've taken a chemistry class, you are probably scratching your head. The human body is maintained in a very slightly alkaline state. Let's examine what that means to figure out why this diet makes no sense.
pH is typically defined as the negative log of the hydronium ion concentration in a solution. Hydronium is produced whenever an Arrhenius acid is dissolved in water. "Arrhenius acid" is just the term for hydrogen-producing acids. Don't worry about that. It might be easier to imagine from a reaction standpoint. Take this, for example, sulfuric acid (H2SO4) dissolved in pure water (pH 7.00) will produce positively charged hydronium (H30) and negatively charged sulfate ions (SO4). It may be easier to imagine H2SO4 breaking apart into H2 and SO4. Free protons don't like to exist in water, so the hydrogen atoms react with the water to create hydronium. The hydronium concentration goes up, which, when you take the negative base10 logarithm of it, will give you a number lower than 7.00.
The pH scale goes from 0 to 14, with the low end indicating an acid and the high end showing a base (alkaline). In a system where the pH is 7, that means there is an equal concentration of hydronium and hydroxyl. Hydroxyl (OH) is just the opposite of hydronium. When you dissolve an Arrhenius base in water, it produces hydroxyl. Whenever hydroxyl and hydronium are combined, they form water through auto-ionization.
Ok, let's talk diet. These diets are based on the idea that they somehow alter your body chemistry to promote weight loss. There are only two ways that your blood pH can change. These methods of pH control are the respiratory and renal systems.
Your respiratory system modifies bicarbonate levels (a reactant in the chemical equation that produces carbonic acid) by increasing or decreasing CO2 uptake from the lungs. This is a quick process that is the primary moderator of blood pH.
Your renal system increases or decreases your kidneys' uptake of hydrogen and bicarbonate levels. This is a much more gradual process.
Guess what? These two systems nullify any impact your diet has on your blood pH.
How important is blood pH? As it turns out, pretty important. Enzymatic reactions in your body require an extremely tight control band for your blood pH (7.35-7.45). If you wander outside this band, denaturing enzymes and protein may occur, resulting in the malfunction of metabolic processes. This is about as severe as suffering from hypothermia regarding the chance of death. The homeostatic processes in your body aren't quite working anymore, which is very bad. The medical term for suffering from an incorrect blood pH is either acidosis/acidemia or alkalosis.
This next bit is from a reader, David Jack, MLT(ASCP).
Blood pH can not only be set out of whack due to respiratory or renal reasons. There are a few more reasons as well. Ketoacidosis manifestsÂ fairly often (especially diabetic ketoacidosis). Ketone bodies pumped out by the liver when the body is not utilizing glucose for energy pushes pH down. The body WILL begin to compensate either through the lung or kidneys (usually both in these cases), but neither is involved in the initial state response. Some drugs given through IV can also impact pH. Usually something like sodium bicarbonate will also be administered along with it as a buffer.
So no, most people's bodies are not out of pH balance, and those experiencing acidosis or alkalosis are probably in the hospital suffering from acidemia (low blood pH). You may feel nausea, numbness, muscle spasms, and hand tremors at low levels. At more severe levels, you will feel increasing dizziness, difficulty breathing, confusion, stupor, and eventually go into a coma.
How do you prevent this? Stay hydrated! Otherwise, you should never be concerned about this unless you suffer from particular respiratory or kidney diseases.