Does sugar cause ADHD symptoms?

While many parents suspect that sugar plays a role in their children’s behavioral patterns, short-term studies conducted in the 1980’s and 1990’s were not able to show a connection between sugar and hyperactivity or attention problems.

These studies compared the effects of sugar (sucrose) to artificial sweeteners (aspartame/Nutrasweet® or saccharin/Sweet ’n Low®) on children over a period of days to a few weeks. However, the problem is this: researchers did not remove other high glycemic index and refined carbohydrates from children’s diets, only sugar. There are many foods which rapidly break down into simple sugars in the body, such as flour, corn starch, white potato, and fruit juice. Therefore there was still a significant amount of sugar in the diets of all of the children in these studies:

“In addition to the drink, each child was served either (1) one slice of white toasted bread spread with 1½ pats of butter on days that the sugar sweetened drink was served on (2) two slices of white toasted bread spread with 3 pats of butter on days that either placebo drink was served. The amount of carbohydrate and fat contained in the toast and butter, in addition to the drink, provided an approximately equal amount of calories each testing day. All children were offered an identical lunch of French fried potatoes prior to the last testing session.”

Can you believe it? A breakfast of white bread and a lunch of French fries? This diet consisted almost entirely of high glycemic index refined carbohydrate and fat, and almost no protein. So, all we really know is that removing sugar from a junky diet and replacing it with artificial sweeteners does not make ADHD symptoms better. We do not know if adding sugar to a healthy diet can cause ADHD symptoms, or whether removing all refined carbohydrates from the diet could reduce ADHD symptoms. In 1995, a comprehensive analysis of all sugar studies to date concluded that there was no evidence that sugar caused ADHD (although the authors acknowledged there weren’t enough studies to be certain). This influential JAMA paper seemed to close the case, because no studies of sugar and ADHD have been conducted since.

This is your brain on sugar

In a Yale study of healthy children without ADHD, blood levels of glucose and a variety of hormones and neurotransmitters were measured before and after a sugary drink (decaffeinated cola sweetened with glucose; equivalent to two 12-oz cans of Coca-Cola). These children were compared to a control group of children drinking a diet cola. In the sweet cola group, the expected spike and drop in blood sugar occurred: blood sugar rose from a fasting level of 83, to a peak of 135 after the cola, then to a valley of 61 about 4 hours after drinking the cola (values are in mg/dl). When blood sugar bottomed out, blood levels of epinephrine (aka adrenaline, our fight or flight hormone) skyrocketed to 5 times higher than they had been before the cola. When this occurred, the children felt panicky—shaky and weak with a pounding heart.

adrenaline spikes 400% four hours after drinking a sugar drink

These are the symptoms we typically associate with “hypoglycemia”, but they are actually due to the surge of fight or flight hormone produced by the body in reaction to falling blood sugar, not due to the low blood sugar itself. For more information, including a graph of sugar and adrenaline levels, please see my Psychology Today post "Stabilize Your Mood with Food."

These same researchers also studied the electrical activity of the brains of children as their blood sugar dropped. They found that problems with brain activity could be seen as soon as the blood sugar dropped to below 75 mg/dl, getting worse as it fell even lower.

Sleep, sugar and ADHD

An interesting Australian study examined the diets and sleep patterns of children with ADHD who were not taking medications. Children with high-sugar diets were more likely to have disrupted sleep, most commonly breathing problems and night sweats. Association does not equal causation but, given what we know about sugar and panic symptoms, this connection would make sense.

There's something about the Western diet

A large epidemiological study out of Australia  (where would we be without our forward-thinking mates from down-under?) found that teenagers who reported eating a “Western” diet were more than twice as likely to have ADHD than teens who reported eating a “healthy” diet.

High total fat Low total fat
High saturated fat Low saturated fat
High refined sugars/grains Low refined sugar
High sodium Lower sodium
Low omega-3 High omega-3
Low fiber High fiber
Low folate High folate

Foods Eaten (in order of frequency)

Take-out foods Vegetables
Sweets Fruits
Refined grains Legumes
Red meat Whole grains
Processed meat Fish
French fries/potato chips Soups
Cakes/cookies Meat dishes
White potato Mineral water
Sauces/dressings Low-fat dairy
Full-fat dairy Eggs
Poultry Juices
Soups Nuts
Fish (battered/fried)  
Added sugar  

This was an observational study and cannot prove cause and effect. There is no way to know whether the Western diet may make ADHD more likely or whether ADHD makes it more likely that a teen will gravitate towards the Western diet (i.e. impulsive teens may make poorer dietary choices). We have no way of knowing which aspects of the Western diet may be causing trouble here—fat? Sugar? Refined grains?

Does chronic sugar consumption eventually lead to ADHD?

A group of scientists at the University of Colorado thinks that eating sugar on a regular basis may cause long-term problems for the brain that can’t be corrected simply by removing sugar from the diet in short-term studies. Theoretically it is possible that the chronic use of sugar could cause changes in brain chemistry that may eventually lead to ADHD, but there have not yet been any studies exploring this question. Here is their reasoning:

  1. Sugar is a powerful trigger for dopamine release in the brain (dopamine is one of the brain chemicals thought to be involved in ADHD). Eating sugar floods brain cells with dopamine, which feels good, because dopamine is our pleasure/reward neurotransmitter. Channeling Homer Simpson: “Mmmmmm  . . . Donut . . . ”
  2. The brain tries to bring dopamine activity back to normal by reducing the number of dopamine receptors, so it will then take even more sugar to produce the same effect (tolerance). “Mmmm . . . two donuts . . . ”
  3. If a person keeps eating sugar, there may be times when brain cells run low on dopamine from being stimulated so frequently. Low dopamine activity is one of the possible causes of ADHD symptoms. This vicious cycle may also lead to binge eating and sugar addiction. “Donut . . . donut . . . donut . . . donut . . . Marge, we’re out of donuts!”

ADHD and obesity

Children with ADHD are about twice as likely to be overweight or obese and vice versa. Is there something about ADHD that causes overeating or obesity? Is there something about obesity that causes ADHD? Or does it go both ways? In a large German epidemiological study:

“children with ADHD more often endorsed ‘‘lost control over eating’’ and ‘‘food dominates life’’ than their peers without ADHD” (regardless of body weight).

There is a strong connection between the consumption of high glycemic index and refined carbohydrates and the obesity epidemic. However, because we do not yet have any studies of refined carbohydrate and ADHD, we do not yet know if refined carbohydrate may be one of the bridges connecting ADHD and obesity.

What about low-carb diets for ADHD?

Unfortunately, there have not yet been any studies of low-carbohydrate diets in people with ADHD. However, one study of the ketogenic diet (a special low-carbohydrate diet) on children’s behavior found small but significant improvements in attention and social problems compared to children eating a regular diet. These were children with seizure disorders, not ADHD. [The differences in behavior were not due to the fact that these children had many fewer seizures than the children eating a regular diet.]

The bottom line about sugar

Studies of sugar itself, compared to artificial sweeteners, have not found a connection between sugar and ADHD. However, wondering whether sugar per se is a culprit in ADHD may not be the right question to ask. Since sugar and other refined and high glycemic index carbohydrates behave the same way in the body, it would make more sense to ask whether refined carbs, as a food group, increase risk for ADHD, and as of today there are no studies exploring this possibility.

However, here’s what we do know:

  • Refined carbs such as sugar put the brain and body on a hormonal roller coaster that can cause panic symptoms and brain dysfunction.
  • Diets high in refined carbs increase risk for insulin resistance, high insulin levels, diabetes, heart disease, and obesity.
  • Insulin can reduce dopamine levels in the brain.

It is hard to know what all of this means for people with ADHD. However, it would make sense for everyone, including those with ADHD, to stay off of this hormonal roller coaster as much as possible.

It all starts with breakfast

Refined carbohydrates include sugar, honey, all kinds of flour, maple syrup, corn syrup and even fruit juice (here is a list of refined carbs). In fact, the typical “healthy American breakfast” tends to be the meal that is highest in refined carbs and lowest in protein—waffles, muffins, toast, instant oatmeal, cereals, bagels, orange juice, etc. Making changes to breakfast is the most important place to start for families, but most children eat far too much sugar all day long.

Contrary to popular belief, fruit juice, chocolate milk, granola bars, sweetened cereals, home-made desserts, whole-grain muffins, and fruit juice-based candies are not healthy foods for children. All of these foods are very high in sugars, which are strongly associated with high insulin levels and inflammation throughout the body. This is not the kind of inflammation you can see with the naked eye; it can only be detected by special blood tests in research labs. Over time, this microscopic inflammation can be very damaging to all of the organs of the body, including the brain.

For more information about carbohydrates and health, check out my carbohydrates page, or take my carbohydrate sensitivity quiz to find out how carbohydrate-sensitive you are.

For further reading, I suggest my post, "Attention! Is Your Diet Causing ADHD?" and "Food Sensitivities and ADHD."

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