Eating sugary food can have an immediate, cascading impact on your health. It affects almost every part of your body, including your brain. So if sweet snacks and carb-heavy meals seem to make your head hurt, it’s probably not just your imagination: sugar really can lead to headaches.
The good news is that it’s relatively easy to reduce blood sugar spikes and headaches if you follow some simple guidelines. We’ll delve into that shortly—but first, let’s explore why these headaches happen.
“Like a finely tuned engine that runs on high-octane fuel, your brain has an exquisitely sensitive relationship with glucose. Small fluctuations can cause big problems.”
Why does sugar cause headaches?
Your brain runs on glucose—the simple form of sugar that circulates in your bloodstream and serves as a primary energy source for all of your cells. Even though the brain makes up just two percent of a typical adult’s body weight, it uses about 20% of the total glucose. Brains are energy-hungry organs.
And like a finely tuned engine that runs on high-octane fuel, your brain has an exquisitely sensitive relationship with glucose. Small fluctuations can cause big problems. As one group of researchers puts it, the “tight regulation of glucose metabolism is critical for brain physiology,” and the disruption of this metabolism is linked to many brain disorders, including brain fog, cognitive decline, and Alzheimer’s disease.
But why, exactly, do blood sugar fluctuations cause headaches? We don’t know. Commonplace headaches (sometimes called Tension-Type Headaches, or TTH) remain mysterious. Their relationship with blood sugar has not been studied in depth—but the mechanisms behind these headaches may offer some clues.
During a tension-type headache, it’s believed that pain receptors in the head, neck, and face—peripheral nociceptors—become overexcited and pain pathways become dysregulated. We experience this as pain. It can result from physical or mental strain such as muscle tension, poor posture, or cognitive exertion.
Among people with frequent tension headaches, an effect called central sensitization may also take hold. This means some of the nerves involved (such as the trigeminal nerve) require less and less stimulation to activate, while their message to the brain becomes more and more extreme. That may explain why people with TTH are more sensitive to physical touch as well as electrical and thermal stimulation in some studies.
Again, it’s unclear why blood sugar fluctuations would cause this dysfunction, but hypoglycemia may play a key role. Hypoglycemia—aka low blood sugar—can be caused by skipping meals and exercise, which are known headaches triggers. It can also be caused by eating sugary foods, which leads to a blood sugar spike followed by a crash. (More on this shortly.) When your blood sugar plummets into hypoglycemic territory, your brain may perceive a potential threat or even sustain damage from lack of glucose. This may cascade into a tension-type headache.
For headache researchers, this relationship raises an intriguing possibility: You may be able to prevent headaches by stabilizing your blood sugar levels to minimize glycemic variability.
What is glycemic variability?
Your blood sugar (i.e., your glycemic level) naturally rises and falls over the day. This change is called your “glycemic variability,” and it’s a normal part of a healthy metabolism.
High glycemic variability means a big gap between your blood sugar’s tallest spike and its lowest dip. To avoid headaches (and other health problems), we want to lessen that variability, meaning we cut down the peaks and raise the valleys. Your daily blood sugar levels should look more like a rolling country road and less like a terrifying roller coaster.
Many different factors influence your glycemic levels, including exercise, sleep, and stress. But one of the biggest levers is diet. Sugary and carb-heavy foods are digested quickly and easily, dumping a massive load of glucose into your bloodstream. Your body then releases a large amount of insulin, the hormone that helps move glucose into cells, to bring the blood sugar down. But this flood of insulin can have an over-correcting effect and lead to a blood sugar crash when the glucose is depleted.
Headaches are just one of many problems this cycle can cause. High glycemic variability is also a risk factor for heart disease and diabetes, as well as neuroinflammation, cognitive dysfunction, and stroke. These are good reasons to minimize your glycemic variability and maintain steady blood sugar levels.
Can sugar cause migraines?
Migraines are not regular headaches. Everyday headaches, sometimes called tension-type headaches, usually occur as a mild to moderate ache on both sides of the head. On the other hand, migraines tend to cause severe throbbing pain, typically occur on one side of the head, and are often accompanied by nausea, visual symptoms, and sensitivity to light and noise. While tension-type headaches are unpleasant, migraine headaches can be debilitating.
But despite their differences, migraines—like tension-type headaches—can be caused by eating sugary foods. Low-blood-sugar episodes (e.g., from skipping a meal or the crash after a carb-heavy meal) are an established migraine trigger. In fact, migraines are linked not just with blood sugar fluctuations but with poor metabolic health generally.
During a typical migraine, specific brain regions become overexcited, blood vessels in the head dilate, neuropeptides are released, and the trigeminal nerve is activated. But how exactly these events are linked—and why they’re triggered by glycemic variability—is still being studied.
Some researchers have suggested that insulin causes migraines directly because people with migraines tend to have higher insulin levels. Others have argued that migraines and metabolic illness may be caused by a third variable like oxidative stress (chemical wear-and-tear) or deficiencies in certain micronutrients (e.g., riboflavin and ALA). And still, other research has identified nitric oxide (an essential regulator of nerve activity and blood flow) as a possible migraine culprit linked to metabolic health.
Research in this area continues, but if you’re trying to avoid migraines, there is promising evidence that stabilizing your blood sugar is part of an effective strategy.
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How to avoid sugar-induced headaches
If you’re trying to prevent blood glucose headaches, a little effort can go a long way. You’ll just need to experiment conscientiously, learn about your unique metabolism, and work closely with your doctor when making any significant changes.
Generally speaking, strategies to minimize blood sugar spikes (and their attendant headaches) fall under four broad categories: diet, exercise, sleep, and stress. Let’s dig into each of these in turn.
- Diet is perhaps the most significant and most rapid influence on your glycemic levels. As we’ve discussed, certain foods spike your blood glucose almost immediately. That includes sweeteners like sugar, corn syrup, fruit juice, and honey. It also includes refined grains like pasta, white bread, white rice, and some vegetables like potatoes and sweet corn. Our goal is to avoid these foods when possible. When you do eat refined grains or potatoes, some research shows that eating your protein and veggies first, followed by the carbohydrate, may help stabilize blood sugar.
It’s also important to check ingredient labels for sources of hidden sugar. An astonishing number of processed foods contain sweeteners, including salad dressing, ketchup, yogurt, breakfast cereal, and premade pasta sauce. And don’t forget about beverages like sweetened coffee drinks, soda, and cocktails.
So what should you eat? Whole, unprocessed plant foods are high in fiber and have a low glycemic index (the speed at which the body absorbs the food’s glucose). The presence of fiber in your gut slows down digestion and turns a meal into a slow-burning energy release. Cruciferous vegetables (e.g., broccoli, kale, cauliflower), legumes (e.g., beans and lentils), nuts and seeds, and many fresh fruits are all gentle on your blood sugar and minimize glycemic variability.
Please note that these are only rough guidelines. One large study found that people have very different glycemic responses to identical meals, which means that dietary advice should only be taken as a starting place.
- Exercise can also help you limit glycemic variability—but it does so by different means. When you exercise, your muscles consume more energy. This burns off blood glucose immediately, lowering your blood sugar and reducing the need for insulin. Even a post-meal walk can help lower the glucose spike from a meal.
Exercise also increases your body’s sensitivity to insulin, a cornerstone of metabolic health. One small study (11 subjects) found that a single workout session improves insulin sensitivity among overweight people the very next day. Better insulin sensitivity means your body uses sugar more effectively, protecting you from extreme glycemic highs and lows.
Reaping these benefits doesn’t take a huge commitment. Just 30 minutes of daily exercise three times per week for eight weeks produced significant metabolic health gains in one study.
- Sleep. A large body of research has shown that curtailing your sleep—and possibly just interrupting it—has a severe negative impact on your metabolic health. That means you use glucose less effectively, need more insulin to process your meals, and are more likely to develop dysfunction.
Practice good sleep hygiene by keeping your bedroom cool, dark, and quiet. Follow a similar wake-sleep schedule every day, and avoid screens for several hours before bedtime. Try to limit your total caffeine intake, and avoid it entirely after noon.
If you can, aim for 7-8 hours of sleep every night. According to one study, people who fall in this range are the least likely to develop Type 2 diabetes.
- Stress. Stressed people tend to crave sugary foods and overeat. Stress also causes elevated blood glucose levels, diminishing insulin sensitivity over time. In other words, managing your daily stress levels is crucial to managing your blood sugar.
Spending just 20 minutes in nature can significantly lower your stress level, and people who spend more time in green spaces have lower levels of Type 2 diabetes. Research also shows that people who meditate twice weekly for at least 6 months have lower blood sugar levels at baseline and after meals. Meanwhile, daily deep breathing exercises (when combined with other treatments) may yield similar benefits.
Eating sugary meals may cause headaches by driving a blood sugar spike that’s often followed by a crash. This cycle of glycemic variability may trigger both regular, tension-type headaches and migraines.
Fortunately, positive changes are easy to make and can quickly impact your risk. Eating for stable blood sugar may help you avoid glucose-triggered headaches. Lowering your stress levels, improving your sleep, and getting moderate exercise may also be helpful. And in the long run, there’s promising evidence that these lifestyle changes will benefit your overall health.