So you’re wondering, what are neurotoxins? Neurotoxins are substances that are toxic to the central or peripheral nervous system, or both. The central nervous system is comprised of your brain and spinal cord. The peripheral nervous system refers to the nerves and axons that carry signals outside of the brain and spinal cord. A complete list of neurotoxins can be found here. Some examples of neurotoxins include:
- Methylmercury (found in seafood, particularly shark and swordfish)
- Lead (extremely toxic to the developing brain)
- Acrylamide (neurotoxin found in potato chips and french fries)
- Botulinum toxin (neurotoxin produced by bacteria that is also used for cosmetic purposes)
Neurotoxins are ubiquitous. They’re present in cosmetics, the environment, and even food (in small amounts).
Avoiding neurotoxins is important for maintaining brain health. Some neurotoxins are benign in small quantities (like alcohol). Other neurotoxins will swiftly and irreversibly damage the brain in small amounts. Domoic acid, a neurotoxin in shellfish, is dangerous even in microgram quantities (one microgram = one-millionth of a gram).
Dietary choices significantly affect both brain health and the risk of developing neurodegenerative disease. Foods can be either neurotoxic (bad for your brain) or neuroprotective (prevent or even reverse cognitive decline).
There are a number of neurotoxic foods, so we’re going to focus on the five worst offenders.
Potato Chips and French Fries (Acrylamide)
These starchy foods are high in saturated fat which isn’t great from a health standpoint, but that’s actually not the reason we’ve added them to the list.
Potato chips and french fries contain acrylamide, a neurotoxic chemical compound that’s formed when certain foods are heated over 120 degrees celsius. Since acrylamide interferes with the neurotransmitter release machinery in the brain, acrylamide neurotoxicity is caused by the direct inhibition of neurotransmission. Toxicologists are most concerned about cumulative acrylamide burden from multiple sources over decades. Other sources of acrylamide besides potato chips and french fries include cigarette smoke and coffee.
Alcohol-induced neurotoxicity is a major public health concern. Chronic alcohol consumption is dose-dependently associated with loss of white matter in the brain.
Interestingly, moderate alcohol consumption may confer cardiovascular benefits. It turns out that rapid changes in blood alcohol content (BAC) are what’s toxic to the brain. For this reason, binge drinking adversely affects cognitive health whereas having a glass of wine with dinner may actually be beneficial. Also, don’t forget to take vitamin B1 (thiamine), if you drink. Vitamin B1 is depleted by the metabolism of alcohol, and therefore alcoholics are invariably B1 deficient.
Soda (Excess glucose/fructose)
We picked soda as an example, but really any food that contains a lot of sugar is bad for brain health. Excess sugar consumption results in chronic low-grade hyperglycermia (elevated blood sugar). It also causes insulin resistance, where insulin is less effective at activating certain receptors, like glucose transporters. Alzheimer’s disease has been called “Type 3 Diabetes” precisely because glucose homeostasis is so intimately linked to cognitive function. Pre-diabetic and diabetic patients are also markedly more likely to get Alzheimer’s disease.
Shark and Swordfish (Methylmercury)
Both of these fish contain especially large concentrations of methylmercury, which is a potent neurotoxin. Bioaccumulation is the process by which methylmercury accumulates in predatory animals that are at the top of the food chain. Shark and swordfish contain nearly a 50-fold higher concentration of methylmercury compared to Salmon, which is considered a brain-healthy food.
Shellfish (Domoic Acid)
Shellfish, if prepared improperly, contains the neurotoxin domoic acid. Domoic acid damages the hippocampus (the brain structure implicated in learning and mood), resulting in amnesic shellfish poisoning. Domoic acid is one of the most potent and insidious of neurotoxins and domoic acid-induced neurotoxicity results in irreversibly impaired working memory.
Now that we’ve outlined the neurotoxic foods, lets end on a positive note and consider the foods that enhance cognitive function! You may find this brain food pyramid helpful.
The brain foods with the most evidence supporting their effects are:
- Cacao – increases cerebral blood flow and cognitive flexibility
- Blueberries – neuroprotective antioxidants with anti-dementia properties
- Curcumin (Tumeric) – novel antioxidant that may explain why Indian’s have a much lower incidence of neurodegenerative disease
- Medium Chain Triglycerides (MCT, e.g., from coconut oil) – Provide an alternative fuel source for the brain besides glucose
Tried-And-Tested Brain Health Tips
- Vigorous exercise (has a robust effect on brain function)
- Seeking out novel experiences
- Socializing will help you stay sharp
- Practicing good sleep hygiene
- Avoiding medications associated with dementia (anticholinergic drugs, benzodiazepines)
- Sexual activity increases neurogenesis (the birth of new neurons) in rodents and probably humans too
- Eating more fruits and vegetables relative to the other foods groups (your parents were right!)