If you've ever had a headache after eating a sweet treat, you may have blamed the sugar. It's true that sugar can cause headaches, but the actual cause of a sugar headache is not too much sugar — it's not enough sugar, essentially a crash of your blood sugar level.
Simply put, your brain needs a constant supply of sugar for energy, and you can get a headache if the level falls too low, known as hypoglycemia.
Too Much Sugar Can Cause Low Sugar
When you eat carbohydrates, your body converts the carbs to glucose, which is the medical term for sugar. Glucose travels through your body to be used as energy.
"High glucose itself is not the problem," says Michael Doerrler, DO, assistant professor of neurology and a headache specialist at Loyola University Medical Center in Chicago. "When you load up on sugar, your body produces more insulin to use up the sugar. Your blood sugar can drop rapidly. This is called reactive hypoglycemia."
As he explains, "anything that upsets the delicate balance of the brain can trigger a headache and other low-sugar symptoms."
Low sugar can cause a migraine headache, and it also may be why some people with migraines crave sugar just before or during a migraine attack, according to The Migraine Trust. Migraine headache symptoms include intense and throbbing pain on one side of the head along with nausea and vomiting, according to Harvard Medical School.
For people who don't get migraines, a low-blood-sugar headache can cause a dull, throbbing headache on both sides of the head over the temples, according to the National Headache Foundation.
Postprandial syndrome is another term used to describe low blood sugar after eating, according to University of Wisconsin Hospitals. Symptoms of both postprandial and reactive hypoglycemia start within four hours after a high-sugar meal. Along with headache, other symptoms can include sweating, weakness, nausea, moodiness, confusion and craving for sweets.
Sugar Headache and Hunger Headache
Reactive hypoglycemia is not the only sugar-related cause of headaches. Another type of low-sugar headache is what's sometimes called a hunger headache, according to the National Headache Foundation. Your blood sugar can fall if you go too long between meals, exercise without eating or put yourself on too strict of a diet. Sleeping too late in the morning can also make you go too long between meals.
The type of carbs you eat is also important, the foundation notes. Simple carbs are foods or drinks with added sugar, as well as foods like baked goods and white bread or pasta. These foods are loaded with carbs that are easy and quick to absorb. That can lead to a rush of glucose, followed by a surge in insulin and a headache.
Complex carbs are fruits, vegetables and whole grains. These more natural foods are digested more slowly and may help you avoid the high glucose surge and headaches.
How to Avoid Sugar Highs and Lows
"There is no special diet for headaches," Dr. Doerrler says. "You need a balanced diet. Avoid simple carbs and get some calories from fats and proteins along with vegetable, fruits and whole grains."
- Don't skip meals.
- If you are dieting, lose weight slowly. Avoid crash diets.
- Eat smaller more frequent meals instead of a few big meals.
- Don't exercise on an empty stomach.
- Avoid drinking alcohol on an empty stomach.
- If you feel a hunger headache coming on, have a small sugar snack, followed by a nourishing, well-balanced meal.
If you have frequent headaches and other symptoms of hypoglycemia, talk to your doctor. You can also get some advice on how to balance your diet and choose healthy carbs.