What is ADHD?
Attention deficit/hyperactivity disorder, or ADHD, affects about 4% of children and about 2% of adults. ADHD is a complex condition and poorly named, because it is not really an attention deficit—but rather an inability to regulate attention. People with ADHD have trouble directing attention to what’s most important and sustaining that attention for as long as required. This can cause all kinds of problems in school, at home, on the road, at work, and in relationships.
I would estimate that about a quarter of my students at Harvard University and Smith College present with a chief complaint of “difficulty concentrating.” When I worked at the Hallowell Center, which specializes in the treatment of people with attention-related disorders, 100% of clients came to me because of problems with focus and productivity. Nearly every psychiatric diagnosis—depression, anxiety, bipolar disorder, schizophrenia, substance abuse, and PTSD, just to name a few—can affect the ability to concentrate. Even common issues like stress or lack of sleep can impair attention. Therefore, the majority of people who have attention problems do not turn out to have ADHD after all, which is why a skilled psychiatric evaluation is so important in determining the underlying problem. Whether you are interested in treating ADHD with diet or simply improving your concentration, it is important to understand how diet affects attention regulation.
The chemistry of concentration
We psychiatrists are fond of saying that ADHD is caused by a chemical imbalance in the brain, and that medicines can help to correct the imbalance. There are at least two brain chemicals (or neurotransmitters) that seem to be involved in ADHD: dopamine and norepinephrine. These are tiny messengers that send signals from one brain cell to the next. If levels of dopamine or norepinephrine are too low, or if the system that processes these neurotransmitters is not functioning properly, a stimulant medication (like Ritalin or Adderall) might help by forcing brain cells to release higher amounts of these chemicals. But what causes the chemical imbalance in the first place? Why are the levels of these chemicals too low? And where do these chemicals come from?
Brain chemicals come from food.
After all, where else could they possibly come from? This seems so obvious, but many doctors don’t think about the connection. We are trained to think about which medications might correct the imbalance, not what causes it in the first place. So which foods does your body need to make these important chemicals?
Dopamine and norepinephrine are made from protein.
The body breaks down proteins in foods like fish, chicken, and beef into amino acids, and one of these amino acids is called tyrosine. The body then uses special chemical reactions to turn tyrosine into the dopamine and norepinephrine brain cells need to communicate with each other:
TYROSINE → DOPAMINE → NOREPINEPHRINE
Therefore, those not getting enough protein (especially at breakfast), may have difficulty concentrating. For more information about proteins and amino acids, including daily requirements and best food sources, see my Protein page.
The brain is mostly made of fat.
Yes, even yours. :) About 2/3 of the brain is made of fat, and about 20% of that fat should consist of omega-3 fatty acids. Omega-3 fatty acids keep cell membranes flexible and healthy. Without these special polyunsaturated fats, brain cells become stiff and can’t communicate with each other easily. So even if there is plenty of dopamine and norepinephrine around, brain cells may not be able to pass these chemicals back and forth properly if the right fats aren’t built in to their membranes.
The brain is picky about omega-3s
There are 3 types of omega-3 fatty acids: ALA, DHA, and EPA. The brain’s favorite omega-3 fatty acid is called DHA. ALA is found in both plant and animal foods. Popular vegetarian sources of ALA include flaxseed, walnuts, and chia seeds. ALA is often called the “parent” omega-3 because of this pathway:
ALA → EPA → DHA
Looking at this pathway you might think that if you eat enough ALA, you’re all set. But here’s the problem—the body has a very hard time converting ALA to EPA and DHA, so about 95% of it remains stuck in the form of ALA. However, we convert EPA to DHA very easily. This means that in order to be sure our brain gets enough DHA, we need to eat EPA and DHA themselves. Plant foods do not contain any EPA or DHA. EPA and DHA are hard to find in the typical American diet because the best sources are wild animal foods, such as cold-water, fatty fish (like salmon and mackerel), and naturally-raised animals, such as grass-fed cows and pasture-raised chickens. This is why public health officials sometimes recommend omega-3 supplements. These supplements are typically in the form of fish oil, but there are also new vegan-friendly supplements available which are made from algae.
Omega-3s and ADHD
There have been many studies of omega-3 fatty acids in the treatment of ADHD, but most have shown no benefit or only modest improvement compared to medications. However, many experts seem to agree with this conclusion, quoted from a 2011 (Bloch) review:
“Based on the currently available evidence, using omega-3 fatty acid supplementation in lieu of traditional pharmacologic treatments is not recommended in children with significant ADHD symptoms. However, given the evidence of modest efficacy of omega-3 fatty acid supplementation and its relatively benign side-effect profile, omega-3 fatty acid supplementation, particularly with higher doses of EPA, is a reasonable treatment strategy as augmentation to traditional pharmacotherapy or for those families reticent to use psychopharmacologic agents.”
The bottom line is that medications seemed to work much better than omega-3 supplements. In the studies that did show a modest benefit from omega-3s, the doses of EPA that seemed to work best were between 300 and 600 mg per day. But wait . . . doesn’t the brain prefer DHA? Yes. Even though the brain loves and needs lots of DHA to work properly, researchers find that EPA supplements seem to work much better than DHA supplements. As these were short-term studies, the thinking is that EPA works better because of its fast-acting anti-inflammatory properties.
Is your brain unbalanced?
There’s another kind of essential polyunsaturated fatty acid we need to take into consideration: omega-6. Theoretically, if you eat too much omega-6 it is harder for the omega-3s to work properly because they compete with each other. Many scientists believe that these two types of polyunsaturated fats—the omega-3s and the omega-6s—need to be in balance for our brains and bodies to function at their best. Omega-6 fatty acids are found in a wide variety of plant and animal foods, but certain kinds of plant foods are extremely high in omega-6. Animal fats contain on average 10-20% omega-6, whereas vegetable oils, such as soybean, corn, peanut, and sunflower oils, contain 50-80% omega-6. The average American eats a diet that is far too high in omega-6 and far too low in omega-3. Would the omega-3 ADHD studies have been more impressive if the people in the experiments were also asked to reduce the amount of omega-6 they were eating? Hard to say . . .
For more information about omega-3 fatty acids, the difference between EPA and other omega-3s, best food sources, and how to improve your omega-3 balance, please see my Fats page.
Minerals are mandatory: iron and zinc
Iron is the most prevalent mineral in the body. When we think of iron, we usually think about its role in our red blood cells where it functions to carry oxygen from the lungs out to all of our cells. We don’t usually think of it as a brain mineral, but remember our neurotransmitter pathway from the top of this article? The first step on the road from tyrosine to dopamine and norepinephrine requires an enzyme called tyrosine hydroxylase, and this enzyme needs iron in order to do its job. Iron is also important in regulating dopamine function. Therefore, iron deficiency, which is relatively common, can impair concentration.
The second most common mineral in the body is zinc. Brain cells that release dopamine out into the synapse (space between cells where communication occurs) vacuum it back up using a dopamine transporter. This crucial transporter is regulated by zinc. Zinc binds to the dopamine transporter and slows it down, allowing dopamine to remain active in the synapse for a longer period of time before being pulled back into the cell to be recycled. It is essentially a natural dopamine reuptake inhibitor. Interestingly, this is also one of the ways in which stimulant medications work to improve dopamine activity.
There have been two clinical trials of zinc supplements in the treatment of ADHD, both of which noted some benefit. An Iranian study found that Ritalin + (15 mg of elemental) zinc given for six weeks worked twice as well as Ritalin + a sugar pill. A Turkish study found that (40 mg of elemental) zinc given for 12 weeks worked twice as well as a sugar pill.
Zinc and iron supplements can be hard to stomach. Zinc frequently causes nausea, and iron supplements can cause constipation and other gastrointestinal problems. Are there alternatives to supplements for people who have mineral deficiencies? What is causing these deficiencies in the first place? Are there dietary changes we can make that can improve our mineral status?
Plant foods are very low in zinc, whereas animal foods are excellent sources of zinc.
While both plant and animal foods contain iron, the type of iron found in animal foods (called heme iron) is 8 times more bioavailable (useful) to us than the type found in plant foods.
Seed foods (which include grains, beans, and nuts) contain phytic acid, which interferes with our ability to absorb essential minerals. For more information, including a surprising study illustrating the degree that phytic acid interferes in zinc absorption, see my “Micronutrients and Mental Health” article.
Some plant foods contain tannins, which interfere with iron absorption. For more information, please see my Fruits page.
Tips for treating ADHD with diet
- Be sure to eat some protein at breakfast
- Include foods rich in omega-3 fatty acids in your diet (healthy animal foods), or take a daily supplement containing at least 300 mg of EPA
- Reduce omega-6 intake by minimizing vegetable oils, nuts, and seeds
- Improve mineral absorption by reducing phytic acid intake (minimize grains, beans, nuts and seeds)
- If you have iron deficiency, increase meat intake and reduce phytic acid intake (grains, beans, nuts, and seeds) and/or take a heme iron supplement.
- Improve zinc status by reducing phytic acid intake (minimize grains, beans, nuts, and seeds), and including animal foods in your diet. Zinc supplements may also be helpful.
- If you eat a vegan or vegetarian diet, please see my see my “Micronutrients and Mental Health” article for information about how to optimize your mineral status.
So, paying more attention to the quality of your diet just might help you pay more attention to . . . everything.
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Bilici M et al. Double-blind, placebo-controlled study of zinc sulfate in the treatment of attention deficit hyperactivity disorder. Prog Neuropsychopharmacol Biol Psychiatry. 2004;28:181-190.
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