If you experience brain fog after you eat, you need to look at your diet. Follow these steps to uncover the offending foods and clear your fuzzy thinking.
You’ll eat a meal, but instead of feeling energized you feel exhausted, mentally fuzzy, and you just can’t think.
When you experience brain fog after eating, your brain is telling you there’s a problem.
Certain foods, additives, an imbalance of macronutrients, or the amount you eat can all be culprits.
Finding the answer requires some detective work.
How Food Allergies Can Cause Brain Fog
If you have brain fog after eating a certain food, you may be allergic to it.
Here’s a list of the top allergenic foods known as “The Big 8.” (1)
- tree nuts
It can be hard to detect if any of these are the cause of your brain fog since these foods are commonly hidden ingredients.
FoodAllergy.org has compiled an extensive list of hidden sources of these and other top food allergens.
Go to their food allergens page and select the food in question.
You’ll find comprehensive information on foods to avoid, plus lists of unexpected sources.
And while this top 8 list accounts for 90% of food allergies, it’s possible to be allergic to any food. (2)
Some people are allergic to just one specific meat, fruit, vegetable, seed, and even spice.
Food Sensitivities and Intolerances Cause Brain Fog Too
You don’t have to be truly allergic to a food for it to cause brain fog.
Mental fuzziness can also be caused by a food sensitivity or intolerance.
These are not the same thing as a true food allergy.
Food allergies are due to an overreaction of the immune system. (3)
Intolerances, on the other hand, work by other mechanisms and are much more common than true food allergies. (4)
They can occur when enzymes needed to digest a food are lacking, such as with lactose intolerance.
At other times, intolerances are caused by compounds present in foods such as additives, histamines or salicylates. (5)
- dairy products
- eggs, particularly egg white
- food additives including MSG
- strawberries, citrus fruits and tomatoes
- histamine-rich foods such as fermented foods, vinegar, red wine, cured meats, and aged cheese
Learn more —
Brain Fog: Causes, Symptoms, Solutions
How Wheat and Gluten Contribute to Brain Fog
For thousands of years bread has been the staff of life.
But unfortunately, modern wheat bears little resemblance to the wild wheat that was cultivated thousands of years ago.
It has been hybridized and crossbred to increase yields, with little consideration as to whether these new strains of wheat are healthy to eat.
There are other compounds in wheat that can trigger negative reactions, but, for most people, the main culprit is gluten. (11)
The Problem With Gluten
Until recently, it was not understood how ubiquitous problems with gluten have become.
Celiac disease is quite serious and, if left undiagnosed, is linked to a nearly four-fold increased risk of death. (14)
Studies suggest that modern wheat has a unique ability to trigger an autoimmune reaction in the gut.
This is thought to be the main reason that celiac disease and gluten sensitivity are on the rise. (15)
It’s been known for decades that gluten can cause a long list of neurological problems including depression, dementia, cognitive decline, memory loss, schizophrenia, autism, epilepsy and ADHD in those who are gluten-sensitive. (16, 17, 18, 19, 20, 21)
One Mayo Clinic study found that celiac disease goes hand in hand with dementia and other forms of cognitive decline. (22)
Cognitive decline could often be stabilized or even reversed when patients stuck to a gluten-free diet.
Gluten is most commonly associated with wheat, but can also be found in other grains like rye, oats and barley, prepared foods of all kinds, beer, medications and nutritional supplements. (23)
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Natural Remedies for ADHD: An In-Depth Review
Why “Gluten-Free” Foods Are Not the Answer
If you experience brain fog after eating, eliminating wheat and gluten is definitely something to consider.
However, avoiding gluten should not have you running to the gluten-free aisle of your grocery or health food store.
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Gluten-free food has become a big business and you can easily find “faux foods” like gluten-free cake mix, pizza crust, bread and crackers.
These aren’t health foods — they are junk foods in disguise — and won’t make your brain work better at all.
If you aim to eliminate gluten from your diet, stick with real, unprocessed foods.
It will be only a few weeks until you know if they are the root cause of your lack of mental clarity.
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How the Blood Sugar Roller Coaster Causes Brain Fog
Your brain’s main fuel source is glucose.
Complex carbohydrates, the kind found in unprocessed fruits, vegetables, whole grains and legumes, provide your brain with a steady supply of the energy it needs.
Simple, or refined, carbohydrates like sugar, high-fructose corn syrup, and flour products send your blood sugar level on a roller coaster ride, first up and then down.
When brain glucose gets low, you’ll experience a host of mental symptoms: brain fog, mood swings, irritability, tiredness, mental confusion, and impaired judgment.
Besides reactivity to gluten, there’s another good reason to avoid wheat.
Regular consumption of white sugar and other refined carbohydrates can lead to insulin resistance and diabetes.
Learn more —
The Role Sugar Plays in Depression and Anxiety
If you fall into a mental fog within a few hours of eating, you may be experiencing a condition known as reactive hypoglycemia.
This occurs when the symptoms of low blood sugar are experienced a few hours after a meal even though blood glucose levels remain normal.
This is also known as postprandial (“after eating”) hypoglycemia or postprandial dip.
Besides brain fog, other brain-related symptoms include hunger, dizziness, shaking, and anxiety. (27)
How Too Many Carbs, Too Little Fat, Leads to Brain Fog
Dr. David Perlmutter is uniquely qualified to speak about the effects of food on the brain.
He is a neurologist, a Fellow of the American College of Nutrition, and author of the bestselling book Grain Brain: The Surprising Truth about Wheat, Carbs, and Sugar–Your Brain’s Silent Killers.
He only recently retired from an active practice at the Perlmutter Health Center where he used a variety of complementary nutrition techniques to treat neurological problems including dementia, stroke, and Alzheimer’s.
Dr. Perlmutter concluded after decades in practice that nothing is worse for your brain than a low-fat diet.
The brain is 60% fat by weight and according to Dr. Perlmutter, the ideal brain-healthy diet contains 50-60% good fats (by calories).
In his practice, he had excellent results putting his patients on a diet rich in healthy fats like olive oil, coconut oil, butter, grass-fed meat, wild salmon, nuts, and eggs.
You, too, can get off the blood sugar roller coaster by removing simple carbohydrates from your diet and having some complex carbohydrates, protein, and healthy fats at each meal.
Also, give your brain an added boost by including plenty of proven brain-healthy foods such as salmon, blueberries, kale, nuts, coconut oil, olive oil, and green tea.
And lastly, don’t overeat.
Too much food at one sitting, regardless of what it is, will make you lethargic and unable to focus.
The US Food and Drug Administration (FDA) allows 3,000 food additives to be used in our food supply. (28)
Whenever you eat processed food, fast food, or restaurant food, you really don’t know what you are getting.
This is another good reason to make unprocessed foods the major part of your diet.
According to the FDA’s website, some ingredients can be lumped together and listed as “flavors,” “spices,” “artificial flavoring,” or “artificial colors” without naming each ingredient.
Two common food additives, monosodium glutamate (MSG) and artificial sweeteners, are notorious for causing brain fog.
Monosodium Glutamate (MSG)
Not everyone is bothered by this ubiquitous flavor enhancer, but, in sensitive individuals, it can cause myriad problems.
Reported side effects from MSG ingestion include brain fog, dizziness, lightheadedness, headache, sweating, abdominal pain, hives, muscle tightness, numbness, tingling, general weakness, heart palpitations and flushing. (29, 30, 31, 32)
This chemical food additive gets broken down into glutamate, a known neural excitotoxin that, in excess, can stimulate brain cells to the point of damage and ultimately to death. (33)
Avoiding MSG can be tricky since it’s not always required to be listed as an ingredient.
Innocuous-sounding ingredients like seasoning, spices, natural flavors, and hydrolyzed soy protein can contain hidden MSG.
The FDA states that naturally occurring MSG doesn’t need to be included on food labels — no consolation if it’s a trigger for you.
Foods high in naturally occurring MSG include seaweed, soy sauce, parmesan cheese, tomatoes, hydrolyzed vegetable protein, autolyzed yeast, soy extract and protein isolate. (34)
Some of the worst sources of MSG are foods high in sodium: Chinese carryout food, canned soups, salty snacks, ramen noodles, and veggie burgers.
In fact, a good rule of thumb is that the saltier the food, the more likely it contains MSG.
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5 Neurotoxins Found in Popular Foods
Artificial sweeteners like aspartame and sucralose have been controversial since they hit the market, but they are bad news for your brain.
Over 7,000 aspartame side effects were reported to the FDA between 1982 and 1995.
Aspartame is comprised of three brain-damaging chemicals: aspartic acid, phenylalanine, and methanol.
Reported side effects of aspartame include brain fog, migraines, dizziness, mood swings, and even serious memory loss. (37)
It also has a long list of common neurological side effects including brain fog, headaches, migraines, dizziness, anxiety, depression, tinnitus and, ironically, weight gain. (40)
If you want to learn more about the hazards of artificial sweeteners, MedicineNet.com has compiled a comprehensive list of side effects for these and other non-nutritive sweeteners.
Determine the Source of Your Brain Fog with an Elimination Diet
You may be able to figure out which foods are troublesome for you by keeping a food diary — making note of everything you eat and how you feel afterwards.
If that doesn’t provide the answer, you can largely rule out food intolerances with an elimination diet.
This involves avoiding a food for two weeks, then reintroducing it gradually and noting your reactions.
For instructions, you can download the elimination diet patient handout created by University of Wisconsin Integrative Medicine.
This includes a chart you can use as a food diary.
Interestingly, this usually works better than having food allergy tests done.
Such tests often don’t reveal food sensitivities even though they are much more common than true allergies.
Overcoming Brain Fog After Eating: The Bottom Line
The modern diet is loaded with pitfalls that can trigger brain fog.
If you experience brain fog after you eat, start a food diary.
It’s the simplest way to determine the foods that contribute to your brain fog.
Look for correlations between your brain fog and specific foods or eating patterns.
Start with the foods you suspect might cause you a problem or with foods most likely to trigger reactions.
Get processed foods out of your diet as much as possible.
They are likely sources of additives and hidden allergenic ingredients.
Be sure to include in your diet plenty of brain-healthy foods that contain nutrients particularly helpful for foggy brains.
And lastly, if you still can’t figure it out which foods cause your brain fog, try an elimination diet.