Low blood sugar, or hypoglycemia, is caused by not eating enough or eating the wrong foods and can cause headaches. This is why people get headaches when they are hungry. The pain comes from the low blood sugar stimulating the nerve pathways, but the specific mechanics aren't clear. Low blood sugar also can make migraines that already exist more painful.
The body's blood sugar depends on glucose levels. Glucose comes from eating carbohydrates such as potatoes, fruit and bread. When it enters the bloodstream, glucose provides energy to the cells. The glucose that isn't needed right away is converted to a form called glycogen and is stored in the liver and muscle cells. If a person isn't eating, the blood sugar begins to drop and the body converts the glycogen back to glucose. The glucose released raises the blood sugar back to a normal level.
The best way to control blood sugar is to eat regular meals. The types of food eaten are also key. When a person eats sugary food on an empty stomach, the blood sugar goes up. But it also raises the insulin levels in the body. The insulin helps the glucose enter the cells, which causes the blood sugar to drop, often to a level that's too low.
Eating a combination of complex carbohydrates (like whole grains, beans and peas) and protein is the best way to keep the blood sugar steady and avoid headaches. Complex carbohydrates break down into glucose faster than simple carbohydrates. Eating foods high in fiber also helps stabilize blood sugar, as does including healthy fats (from nuts or olive oil, for example) in the diet. These fats are digested more slowly than carbohydrates and protein. In addition to helping keep the blood sugar even, they may make headaches less painful.
Eating foods rich in magnesium (spinach, beans, nuts, and seeds) and riboflavin (leafy greens, dairy products, lean meat, enriched breads and cereals) may stop headaches or make them milder.
Eating more often also can help stabilize blood sugar. Some nutritionists recommend eating six small meals a day instead of three large ones. Keeping snacks handy for when a person has gone too long without food also helps. Skipping breakfast often leads to low blood sugar. The body needs fuel after eight hours of rest. The body also needs fuel after exercise, because the blood sugar drops while exercising. It helps to eat a high-carbohydrate snack before vigorous exercise.
Caffeine doesn't usually have a big effect on blood sugar, especially if it's just a couple cups of coffee a day. But taking in large amounts of caffeine, especially over a short period, can interfere with keeping blood sugar stable.