BY UMA NAIDOO, MD

Sanjay, a thirty-year-old computer programmer, was referred to me because of debilitating worry and panic attacks.

He was constantly getting into trouble at work. He had missed several deadlines, and when he was asked about his performance, he was too terrified to say that he was struggling mentally.

As a result, he often skipped work entirely, but of course his absenteeism just made the situation worse. His team leaders chalked his issues up to laziness and questioned his ability to perform his duties. He found himself at risk of losing his job.

Despite his best efforts, Sanjay still found himself procrastinating whenever he had a task to complete. As I talked to him about his problems with work and life, I began to suspect that Sanjay was suffering from attention deficit hyperactivity disorder (ADHD).

In fact, as we delved into his history, it seemed likely that he had been suffering from symptoms of the condition since high school, but his teachers and peers had written off his struggles as stubbornness, insubordination, or worse, lack of intelligence.

After making several key changes to his diet and daily habits, Sanjay experienced a remarkable turnaround. He stopped drinking alcohol impulsively, felt less depressed and anxious, and the world started to feel manageable again. He began eating whole foods in place of highly processed snacks, fast food, and sugary drinks. He could focus on tasks at work and became a valuable member of the team. Most of all, he was relieved that people no longer thought of him as “dumb.”

Although ADHD may be addressed through a variety of approaches, it is often highly resistant to treatment. For this reason, dietary interventions can play a significant role in supporting focus and well being, especially when combined with other healthy habits such as behavioral therapy, mindfulness, and regular exercise.

ADHD & Your Gut

When you have ADHD, the connections between different brain regions are disrupted, specifically between the prefrontal cortex—the “thinking” brain—and the striatum, the part of the brain that deals with reward behaviors. Additionally, your brain chemistry is affected, particularly your levels of dopamine, the brain’s “reward” chemical, and noradrenaline, a fight-or-flight hormone.

Although medications used to improve ADHD symptoms can increase the levels of dopamine and noradrenaline, we are learning that treating ADHD isn’t as simple as boosting the levels of these chemicals, as other brain chemicals such as gamma-aminobutyric acid and serotonin are also involved. While a full explanation of how brain chemistry impacts ADHD is beyond the scope of our conversation, it’s clear that attention is regulated by a delicate balance of factors.

So, if ADHD is caused by chemical imbalances in your brain, what role does your gut play? Larger molecules such as dopamine and noradrenaline cannot cross the blood-brain barrier, which means that they are confined solely to your brain. But they are made of precursor molecules—building blocks—that can. And where are these precursor molecules made? You guessed it: the gut.

Gut bacteria play an important role in ADHD, synthesizing many of these chemical precursors. Different bacterial species in the gut produce different chemicals, which means that if gut bacteria change, the brain’s chemical stability can be upset. And as we’ve seen with other conditions, a reduction in the diversity of gut bacteria can be particularly problematic.

In 2017, cognitive neuroscientist Esther Aarts, PhD, and her colleagues examined the differences in the microbiome between patients with ADHD and healthy individuals. Compared to controls, people with ADHD had more bacteria that made phenylalanine, a building block necessary for dopamine and noradrenaline synthesis.

The investigators then looked at how the brains of each group responded to reward. Decreased anticipation of brain reward is a hallmark of ADHD—in other words, studies show that people with ADHD aren’t motivated as strongly by incentives to behave in a certain way. Sure enough, the researchers found that the ADHD subjects showed less brain activation in response to being rewarded.

Furthermore, the less their brains responded to the reward, the more phenylalanine-producing bacteria were present in their guts. The researchers concluded that ADHD subjects had to make more bacteria that produce phenylalanine to compensate for how their brains responded.

That’s a highly simplified view of how chemical and bacterial mechanisms interact, but it gives you an idea of the important scientific research being done with respect to ADHD. In fact, even in this major study, the investigators recognized that the only sure conclusion they could draw was simply that gut “disturbances” correlate with brain “disturbances.”

Foods that Worsen ADHD–Gluten

There is a well-established link between ADHD and gluten intolerance or celiac disease. In 2006, Helmut Niederhofer, MD, PhD, a child psychiatrist and director of the Department of Child Psychiatry at Rodewisch Psychiatric Hospital in Germany, and Klaus Pittschieler, MD, a pediatric neurologist in Bolzano, Italy, assessed a sample of individuals to explore the connection between ADHD and celiac disease.

The participants’ ADHD symptoms were measured before starting a glutenfree diet and again after six months. The study found that individuals with celiac disease were more likely to have ADHD, and that a glutenfree diet led to symptom improvement over the six-month period.

You don’t have to have celiac disease to be sensitive to gluten. This condition is called nonceliac gluten sensitivity. While the association between non-celiac gluten sensitivity and ADHD is by no means conclusive, various studies point to a connection between the two. In some instances, gluten sensitivity may cause neurologic and psychiatric symptoms without any corresponding digestive symptoms. People typically associate gluten sensitivity with digestive issues, so in the absence of upset stomach or bowel symptoms, gluten isn’t on the radar as a factor that can worsen ADHD.

The exact reason that gluten sensitivity and brain dysfunction are connected is not fully understood. In 2005, Päivi A Pynnönen, MD, PhD, a Finnish pediatrician and researcher specializing in pediatric gastroenterology and celiac disease, and her colleagues assessed adolescents with celiac disease and behavioral problems. They found that adolescent celiac disease patients had significantly lower tryptophan concentrations in their blood.

Three months after patients started a gluten-free diet, the researchers found a significant decrease in patients’ psychiatric symptoms compared to their baseline condition, coinciding with significantly decreased celiac disease activity and prolactic levels and with a significant increase in L-tyrosine, L-tryptophan, and other amino acids known to be precursors of brain chemicals such as serotonin.

The authors concluded that it was possible that behavioral problems, such as those that occur with ADHD, may in part be due to certain important precursor amino acids not being available until people stopped eating gluten. In certain individuals, gluten-free diets can help the body increase levels of the precursors to make serotonin, which is one neurotransmitter involved in ADHD.

Dairy

Eating a lot of dairy means you eat a lot of casein, which may worsen ADHD. Casein is the main protein found in dairy products such as milk, cheese, yogurt, and ice cream, but it can be a factor even in foods that are thought of as dairy substitutes, like nondairy creamer and margarine.

Not all casein is the same. The main form is called beta-casein, of which there are two major types, A1 and A2. Most regular milk contains both types, but research suggests that A1 proteins may be harmful to the gut in ways that A2 proteins are not.

In 2016, a team led by Chinese medical researcher and professor Sun Jianqin, MD, PhD, studied forty-five participants who consumed milk containing both A1 and A2 milk proteins, and then milk containing only A2 protein.

The researchers found that when subjects drank milk containing A1 protein, they had more gastrointestinal inflammation, their thinking was slower, and they made more errors on an information processing test. It was as if the A1 protein muddied their thinking, something that ADHD patients can ill afford. The study even suggested that lactose intolerance may be caused by sensitivity to A1 caseins rather than lactose itself.

Although more research is under way about whether A1 milk causes any adverse effects except occasional digestive problems, it’s clear that sufferers of ADHD should be cautious about the kind of casein they consume.

Food Colorings, Additives, & the Few Foods Diet

The earliest research linking diet to ADHD dates back more than forty years, when pediatric allergist Benjamin Feingold, MD, proposed that artificial food additives—such as IS A2 RIGHT FOR YOU? colorings and flavorings—and naturally occurring salicylates could contribute to hyperactivity and inattention in children.

Salicylates are chemicals found naturally in some fruits, vegetables, coffee, tea, nuts, spices, and honey. They are synthesized for use in medications like aspirin, Pepto-Bismol, and other products.

In 1976, Feingold formulated a diet that eliminated food additives and salicylates, which would come to be known as the Feingold diet. Some people refer to it as the Kaiser Permanente diet. It was popular in its early days, though the effects were poorly understood. The studies by Dr. Feingold were followed by other studies investigating the effects of eliminating artificial food coloring and eventually led to a diet eliminating many foods and additives called the few foods diet.

This diet is essentially an elimination diet, a category of diets pioneered in 1926 by food allergy specialist Albert Rowe and still in use today. In this approach, you remove one potentially offending food at a time and carefully record any changes in symptoms, before adding foods back in one at a time.

In 1983, a meta-analysis found that the effect of the Feingold diet on ADHD was actually quite weak, casting doubt on the efficacy of elimination diets in improving ADHD in general. However, in 2004, another meta-analysis of only the higher quality studies demonstrated that eliminating food colorings seemed to make a difference in parents’ observations of children with ADHD, but not in teachers’ or other caretakers’ observations.

A 2012 meta-analysis by Joel Nigg, PhD, and a 2017 meta-analysis by Lidy Pelsser, PhD, demonstrated that a restriction diet that eliminated food-coloring additives benefitted some children with ADHD, determining that between ten and thirty percent of people with ADHD would likely respond.

While none of the elimination diets are ironclad ways to eradicate ADHD, they are still worth considering if symptoms don’t respond to less drastic dietary measures.

Foods for Focus

Preliminary research indicates that certain foods may improve the symptoms of ADHD. Before diving into specific nutrients, it’s worth noting that research has shown that overall diet intervention has been effective at staving off ADHD—in other words, it’s important to eat healthily over a broad spectrum of food. For example, several studies have shown that ADHD responds well to the Mediterranean eating pattern.

In 2017, Alejandra Rios-Hernandez and her colleagues studied 120 children and adolescents and found that those who did not stick to the Mediterranean diet were more likely to have ADHD. Other studies have confirmed that low adherence to the Mediterranean diet is associated with ADHD.

Beyond the Mediterranean diet, there are several specific foods and nutrients that can help fight ADHD.

Breakfast

In 2017, David O Kennedy, PhD, and his colleagues explored what morning nutrients could be helpful for ADHD sufferers. They compared the cognition of ninety-five people after they ate a non-commercial nutrient-enriched breakfast bar made for this study (containing alpha-linolenic acid, L-tyrosine, L-theanine, vitamins, minerals, and 21.5 mg of caffeine) versus a control bar for fifty-six days.

Then they examined how cognitive function differed before eating the bars and at 40 and 160 minutes after eating the bars. They found that in all tests, people who ate the nutrient-enriched bars were more alert and attentive, and they could process information more rapidly.

It’s unclear which specific nutrients in the test bars helped, and of course, you won’t be able to find breakfast bars that are exactly the same as those used in the study, since they were specially formulated. And since commercially available breakfast bars tend to be packed with sugar and refined carbs, a better way to start the day when you can’t eat whole foods is to make a smoothie. The chocolate protein smoothie is designed to give you nutrients similar to those in the bars used in the study to give your morning the right boost to fight ADHD.

Caffeine

One notable factor in the breakfast bar study was the caffeine. In animals, caffeine has been shown to have beneficial effects on attention and memory, and a 2011 study demonstrated that tea might be an effective treatment for adult ADHD. Presumably, the caffeine in tea increases people’s motivation, alertness, vigilance, efficiency, concentration, and cognitive performance. On the other hand, caffeine may cause overexcitability too, so it’s important not to overdo it.

Our guideline is no more than 400 mg of caffeine per day for adults. I do not recommend giving children caffeine, even if it could be beneficial—it’s just too hard to determine a safe dose for their smaller bodies.

Polyphenols

In 2018, Annelies Verlaet, PhD, and her colleagues found that natural antioxidants like dietary phenols could be useful in combating ADHD, helping to alleviate oxidative stress on the brain.

Studies have shown that people with ADHD are at a greater risk of oxidative stress in brain tissue. This can lead to damaged brain cells and altered neurotransmitter levels (like dopamine) and electrical-signal transmission, which can make ADHD worse. Since ADHD sufferers appear to lack some of the natural ability to fight off oxidative stress, it is particularly important for them to get as many antioxidants as possible through food in order to alleviate their symptoms and prevent brain cell damage.

One crucial type of antioxidant is polyphenols. Polyphenols are chemical weightlifters for the body’s immune response. They act as low-dose toxins that train the boxy to mount an immune response in a process called hormesis. Polyphenols can also exert other biological effects that are helpful to the brain; for example, they influence the survival and regeneration of neurons.

The richest sources of polyphenols are berries, cherries, eggplant, onions, kale, coffee, and green tea.

Dietary Micronutrients

Some animal and human studies have indicated that when there is a deficiency of zinc, hyperactivity may occur. Indeed, zinc deficiencies are associated with ADHD in children, in part because it’s absence reduces the activity of reward pathways that rely on dopamine.

Other studies have shown that children with ADHD have lower levels of iron and magnesium than controls, both of which are involved in dopamine synthesis.

In 2017, neuroscientist Kin Young Kim, PhD, and her colleagues studied 318 healthy children to see if their diets impacted their cognition. They used the Symbol Digit Modalities Test (SDMT), a test of speed of information processing, to see which dietary elements were beneficial. They found that the consumption of vitamin C, potassium, vitamin B1, and nuts all increased performance on the SDMT. In addition, the more mushrooms people ate, the better they were able to reason, while noodles and fast food decreased SDMT scores.

A Focus on Food

It’s clear that being able to focus is incredibly important to success, whether you’re a kindergartener developing the skills to read and reason and socialize, a college student studying for exams and writing papers, or an adult like Sanjay who is struggling to succeed at a fastpaced, high-pressure job.

If you’re looking to support clearer thinking and strengthen your brain’s natural pathways, consider making some of the nutritional changes we’ve discussed. To help you get started, try my Brain Boosting Chocolate Protein Smoothie recipe—it’s a delicious, nutrient-rich way to nourish your mind and put these strategies into practice.

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Dr. Uma Naidoo is a Harvard trained nutritional psychiatrist, professional chef, and nutritional biologist and author of the national and international bestseller: This is Your Brain on Food. Her most recent best-selling book is Calm Your Mind with Food.

The late Michelin-starred chef David Bouley described Dr. Uma Naidoo as the world’s first “triple threat” in the food and medicine space as the nexus of her interests have found their niche in Nutritional Psychiatry. US News & World Report calls her “America’s Nutritional Psychiatrist.” She is also pioneering a new area of mental wellness called Culinary Psychiatry where she teaches mental health professionals how to integrate their clinical training with principles of nutritional psychiatry and cooking.

Her first book has already been published in twenty-three countries and nineteen languages. Dr. Naidoo founded and directs the first and only hospital-based Nutritional Psychiatry Service in the USA. She is the Director of Nutritional, Lifestyle and Metabolic Psychiatry at Massachusetts General Hospital & Director of Nutritional Psychiatry at the MGH Academy while serving on the faculty at Harvard Medical School.

She was recently awarded the international honor of being the 2024 Rundle-Lister Lectureship in Transformative Nutritional Medical Education by the University of Toronto. She serves as a regular media contributor at CNBC and is on the Harvard Health Publishing Editorial Advisory Board. She works at the World Economic Forum (New Frontiers of Nutrition). She is also on a United Nations task force for mental health.

After being one of only four US physicians to be invited to meet personally with the former HRH The Prince of Wales, now King Charles III, she was asked to lead a public health Food for Mood Campaign with the UK College of Medicine, where she serves as the US Ambassador for Mental Health.

She designed and released the first and only CME based educational program at Massachusetts General Hospital/Harvard to educate other clinicians globally about nutrition for brain health. Dr. Uma has appeared as a Nutritional Psychiatry expert on Live with Kelly & Ryan, Today Show, 700 Club, ABC, and been featured in the New York Times, Wall Street Journal, Fast Company, Thrive Global, Harpers, Shape, Parade, Boston Globe, AARP, and more. Visit her at: https://umanaidoomd.com/

Well Being Journal adapted the above excerpt from This is Your Brain on Food by Uma Naidoo, MD. Copyright © 2020 by Uma Naidoo, and reprinted with permission by Little, Brown Spark, an imprint of Hachette Book Group, Inc.