4 Sneaky Reasons Cutting Out Sugar Can Cause Headaches

People often cut sugar out of their diet to lose weight, manage diabetes or simply improve the quality of their food and beverage choices. Regardless of the reason, giving up sugar can be a real challenge.

While swapping some of your favorite sugary foods and drinks for more healthful choices, you could experience an unwanted side effect: Headaches. While there's some suspicion that cutting back on sugar can lead to headaches and other withdrawal-like symptoms, it's most likely something else going on that's indirectly related.

The American Heart Association recommends that only 6 percent of your daily calories come from added sugars. So on a 2,000-calorie diet, you should aim for no more than 30 grams of added sugar per day. For context, one 16-ounce soda has almost 50 grams of added sugars, so you can see how easy it is to go over the recommended sugar intake.

Too much added sugar can lead to an increased risk of inflammation, high blood pressure, weight gain, diabetes and liver disease, per Harvard Health Publishing. It's also been associated with depression and anxiety, per an August 2019 report in ‌Neuroscience & Biobehavioral Reviews‌.

Given all the health problems related to eating too much sugar, you would expect to feel amazing after cutting it out. Unfortunately, a common complaint of cutting out sugar is increased headaches — at least temporarily.

Here are some of the top reasons you might experience headaches after cutting sugar out of your diet and some steps to prevent it from happening to you.

Soda, energy drinks and specialty coffee and tea drinks are common culprits of added sugar, making up almost 50 percent of the average sources of added sugars, per Harvard Health Publishing. Along with sugar, they also often have substantial amounts of caffeine.

If you're cutting out drinks with sugar ‌and‌ caffeine, your headache could be a symptom of caffeine withdrawal.

Researchers found that headaches occur in as many as 50 percent of people who routinely drink caffeine and then stop, according to a September 2022 ‌StatPearls‌ report. Headaches and other withdrawal symptoms can start as quickly as 12 to 24 hours after your last dose of caffeine and can last an average of 2 to 9 days.

In the brain, caffeine helps constrict blood vessels, which makes it helpful in treating and even preventing headaches. The mechanism behind this involves caffeine's ability to block the uptake of adenosine, a chemical that causes blood vessels to dilate. If you habitually drink caffeine and then abruptly stop, the sudden increase in blood flow can lead to headaches, according to the Mayo Clinic.

So, cutting out sugary coffee drinks decreases your overall caffeine intake and can trigger the onset of headaches.

If cutting out sugar also means you're on a low-carb diet or eating fewer calories overall, then not getting enough carbohydrates or calories (not just sugar) could trigger headaches.

While sugar is a simple carbohydrate associated with many health conditions, complex carbohydrates such as fruits, vegetables, beans and whole grains are health-promoting, even though they also break down to sugar in the body.

Headaches are a common side effect of low-carb and low-calorie diets, per the Cleveland Clinic. Consider this the culprit if your head hurts after drinking just a protein shake for breakfast, eating just a small salad for lunch or going too long in between meals.

Hypoglycemia, or low blood sugar, can also cause headaches, blurry vision, trembling, sweating and other symptoms, per the Centers for Disease Control and Prevention (CDC). Hypoglycemia is usually associated with diabetes, but it can also be caused by a lack of food from dieting, accidentally going too long between meals or fasting for health or religious reasons.

If your sugar restriction has led you to drink more diet beverages, this could potentially explain your headaches, although research has yet to prove a strong relationship between the two. There's speculation that a small portion of the population is sensitive to aspartame, a non-calorie sweetener found in anything from sugar-free beverages to gum, ketchup and salad dressings.

While case studies and a notable small human study have found a connection between reduced headaches in children after quitting aspartame-containing products, per a March 2017 study in ‌Nutrition and Health,‌ many of the research studies that have been completed are small and inconclusive.

"When sugar is eaten, the chemical dopamine that's responsible for making you feel pleasure is released," says New Jersey-based registered dietitian Christa Brown, RDN, LD.

In addition to making you feel good, dopamine dilates blood vessels in the brain and throughout the body. The sudden removal of sugar and drop in dopamine can cause blood vessels to quickly tighten, reducing blood flow to the brain and resulting in a headache, Brown explains.

Research on sugar withdrawal symptoms has primarily been completed on animals, where symptoms such as teeth chattering, tremors, head shakes and aggression occurred with sugar deprivation following a high-sugar diet, per a July 2016 review in the ‌European Journal of Nutrition‌. At this point, there is not enough human data to support that headaches are linked to cutting sugar out of the diet.

Drastically making changes to your diet might seem like a good idea, but when it comes to cutting out sugar, slow and steady may be the best approach. Remove sugar slowly from your diet until you've reached the point where you're comfortable to give your body time to adjust, Brown suggests.

Consider the other potential causes of headaches and try not to change too much at once. Instead of swapping all of your caffeinated sugary drinks for water, choose low-sugar options that still have caffeine until and if you're ready to cut down on caffeine.

Make sure to replace those sugary drinks and food with other fluids and energy sources to avoid hunger headaches and dehydration. Replace pastries, candies and other sweet foods with plenty of complex carbohydrates, lean protein and healthy fats, and be sure to eat at regular intervals throughout the day.

Headaches have many causes, and cutting out sugar is an unlikely reason for this symptom. While caffeine withdrawal, undereating, certain food sensitivities or even dehydration and stress can lead to headaches, sometimes this indicates a more serious medical problem.

Contact your doctor if you experience any of these symptoms along with your headache or if your headache is severe and not able to be controlled by over-the-counter medications, per the Mayo Clinic:

• Slurred speech
• Vision problems
• Confusion or loss of memory
• Difficulty moving your limbs
• Nausea or vomiting
• Stiff neck or fever
• Trouble seeing, speaking or moving