Sugar headaches

There are several different reactions that happen in the body when you consume carbs that can result in headaches. The most common one goes something like this (for refined carbs or sugars): when the carbs first hit your body (starting even with a sweet taste), it causes insulin to be released, in preparation for the upcoming glucose load. As you continue to eat, your blood sugar and insulin levels go up together for a while. The insulin works to move the glucose out of the blood into cells to be used or into storage (fat).

[[MORE]]However, because high-GI foods like sugar and refined carbs cause such a rapid increase in blood glucose (BG), the amount of insulin released can be more than the body really needs. As a result, your BG levels can over-correct, and you can end up hypoglycemic. It is that state of having a low BG that then causes headaches in some people (often along with sudden fatigue). Somewhat paradoxically, the high BG levels that hit before the insulin fully takes effect can also cause headaches in some people. You can get a hint as to which one is affecting you by the time interval between when you eat and when it hits, since BG tends to peak about a half hour or less after you eat, where the low might be two hours or so afterwards.

What happened for me when I first switched to Paleo is that my baseline insulin levels dropped as a result of not consuming carbs, but my body retained insulin sensitivity. That meant that if I did try to eat carbs, I would often over-correct to the low side. However, after maybe six months or so, I became more insulin resistant; the over-corrections to the low side stopped and my baseline BG level increased slightly. From what I've heard, this seems to be a common pattern.

Another sugar-related cause of headaches can be candida overgrowth. Consuming sugar feeds the yeast, which then give off a burst of toxins, which causes a headache. Fortunately, the Paleo diet is also basically an anti-Candida diet, so I would expect that effect to fade over time as well. Candida seems to respond equally badly to low-GI carbs (like berries) that don't produce the big spikes that sugar or refined carbs do.