Disclaimer: if you are experiencing dizziness or vertigo, contact your health care provider! Come back after you're feeling better.
As I mentioned in part 3 of the low carb diet series, during the first month of keto-adaptation I experienced some dehydration and cramping, which are typical symptoms if you do not sufficiently increase both fluid and salt comsumption to compensate for the extra water and sodium excreted by the kidneys when in nutritional ketosis. Other symptoms, which I also experienced to some extent, include dizziness, weakness, fatigue, headaches, and hypotension (low blood pressure). All these are exacerbated by physical exertion or heat stress. I was unaware of the heat aspect, and as a result ended up feeling like I was on the verge of heat stroke a couple of times during those first 4 weeks (July-August 2012).
The Art and Science of Low Carbohydrate Living explains how sodium depletion can lead to reduction of plasma volume, and eventually to potassium excretion (transcription found on this low carb forum):
At some point, when confronted with this low sodium intake plus carbohydrate restriction, most peopleís defense mechanisms canít maintain normal mineral balances. So the bodyís next level of defense is for the adrenal gland to secrete the hormone aldosterone, which makes kidney tubular cells excrete potassium in order to conserve sodium. That is, the body wastes some of its intracellula potassium in order to cling to whatever sodium it can. However unless there is copious potassium coming in from the diet, this excess urinary potassium comes from the bodyís potassium pool inside cells. Two things then happen. First, nerve and muscle cells donít work well, leading to cardiac dysrhythmias and muscle cramps. Second, because potassium is an obligate component of lean tissue, the body starts losing muscle even if thereís plenty of protein in the diet.
Recently, I experienced some vertigo after starting a strength training program. I was also feeling dehydrated, so my first instinct was to up my fluid and sodium intake. However, after a few days, it was clear that sodium depletion wasn't the problem (and in retrospect it doesn't really make sense that it would be).
My friend, Ted, from kendo mentioned seeing a program on Japanese television demonstrating physical therapy to cure the type of vertigo involving grains of "sand" in the inner ear. I could not believe my problem was this type of vertigo, since the only new thing in my life was the strength training (and it was a very moderate program at that). However, applying google-fu, I eventually found the following:
Remember my disclaimer!