When it comes to nutrition and brain function, there is a lot of misinformation out there.
Probably the most well-known myth is that your brain needs you to eat at least 130 grams of carbs a day to function. In reality, the brain requires no dietary carbs to work properly. It does need about 50 grams of glucose a day, but this doesn’t need to come from carbs. Rather, glucose is produced in the liver via the process known as gluconeogenesis from three sources other than dietary carbs:
- Glycerol, produced from dietary fat or fat tissue in the body
- Lactate and pyruvate, produced from glycolysis
- Amino acids, produced from protein
The rest of the energy the brain requires can be derived from ketones—a product of fat metabolism— that are produced in the liver from glycerol when insulin levels are low. In many cases, such as with aging, cognitive decline, depression, or seizures, having the brain run on ketones is protective. The mechanisms can be confusing and are more complicated by the fact that different kinds of dietary fat affect brain function differently.
Let’s consider depression. Many factors impact depression but one that stands out is nutrition. Mood and depression are partly regulated by two chemical messengers in the brain: GABA, a major inhibitory neurotransmitter (meaning that in the right amounts it can have a calming effect), and glutamate, a major excitatory neurotransmitter. When glutamate is overly abundant it’s easy to experience neurotoxicity, which in simple terms is too much excitement in the brain. An extreme example is seizure, but neurological problems including depression, migraines, and dementia are also linked to excessive glutamate.
Ketogenic diets can change the ratios of glutamate and GABA, lowering the levels of glutamate present for a better functioning brain. Another important factor to consider is that when the brain is running on glucose, you have a lower seizure threshold (making seizures more likely). However, when ketones are fueling the brain, seizure risk decreases. In fact, the ketogenic diet was originally developed to treat epileptic seizures.
Ketones also lead to less inflammation in the brain. Ketones are a more efficient energy supply than glucose, making it easier to produce energy with fewer destructive free radicals. Unfortunately for everyone who enjoys eating carbs, an adult’s brain will only use ketones for energy if glucose is not sufficiently available. Babies are different: Even when glucose levels are adequate, babies maintain a moderate level of ketones in the blood to supply their growing brains.
Adults aren’t so lucky: You must either be fasting or restricting carbohydrates to get the body to produce ketones in adequate quantities. The liver won’t produce ketones unless blood sugar (and insulin) levels are low.
Interestingly, specially designed studies show that when both ketones and glucose are present in the body, ketones enter the brain in proportion to the plasma concentration. Brain glucose uptake decreases accordingly, indicating that ketones are the brain’s preferred fuel.
What about if you don’t want to do a ketogenic diet, is dietary fat still considered good for the brain?
This is where things get a little trickier. You’ll find claims on the internet that a high saturated fat intake is recommended for brain health. Unfortunately, for all you bacon and ice cream lovers out there, this is a distortion of the evidence.
It is true that you need some saturated fat in the diet for optimal health and cognition. Your brain is mainly made of cholesterol and fat and a very low-fat diet is unlikely to optimize brain health. For example, adequate intake of healthy fats help prevent depression and one side effect of the typical low-fat diet that is erroneously recommended to lower cholesterol levels is an increase in suicides. This is caused by a deficiency in neurotransmitters such as serotonin that make you feel good.
However, study after study shows poorer cognition and greater risk of brain disease in people with the highest saturated fat intake. Granted, the average westerner who eats a lot of saturated fat is also consuming a lot of sugar with a lack of phytonutrient vegetables, fruits, and other protective foods. Nonetheless, encouraging people to go hog wild with saturated fat is not the best approach for a healthy brain.
You want to get a variety of different forms of fat in the right ratios, and eat them in the context of a healthy diet (whole foods, high quality protein, healthy complex carbs, low sugar and refined foods). Which brings us to the omega-3 essential fatty acids—DHA and EPA from fish oil, and ALA from nuts and seeds.
Association studies consistently show that the omega-3 fats have a protective effect on the brain. The more fish people eat, the lower their risk of brain disorders. Some randomized trials show that fish oil supplementation also improves brain function and lowers risk of cognitive impairment.
Most people hone in on DHA because it maintains the structural integrity of the membranes of the brain and has a direct impact on neurotransmitter function. The thing is that both DHA and EPA need to be present to see significant brain benefits, with EPA in roughly a 2:1 ratio to DHA. This why you’ll find that most of our fish oils are formulated to have close to double the EPA to DHA.
It’s one reason some fish oil supplementation trials may have shown no benefit. It’s also possible the treatment period was too short or there is limited benefit of supplementation in healthy individuals.
There are other ways EPA and DHA are protective for the brain:
EPA and DHA have an anti-inflammatory effect and DHA reduces the formation of amyloid plaques that lead to Alzheimer’s.
The brain is not dependent on insulin for it to use glucose, however, people with insulin resistance don’t get adequate glucose into the brain. DHA is an important regulator of brain glucose uptake, particularly in the aging brain, and it’s possible that supplementation can improve glucose uptake and cognition in people with insulin resistance.
EPA and ALA (the omega-3 derived from nuts and seeds) have supporting roles in maintaining brain function during aging by helping to produce ketones so that the brain can bypass problems of impaired glucose use with insulin resistance. ALA is an efficient ketogenic fatty acid, while EPA promotes fatty acid oxidation.
The precise characteristics of the lipid layer of brain neurons influences electrical properties, impacting everything from mood to neuromuscular function to cognition.
Getting adequate EPA and DHA can prevent depression and risk of psychotic brain disorders. In one long-term 7-year study, teenagers who were at risk of developing a psychotic disorder who took 1.2 grams of fish daily had a much lower risk of full blown psychosis compared with a placebo group. This study highlights the importance of fish oil intake during the “critical period” when the brain is still developing.
Take Away Points:
Adequate dietary fat is essential for a well-functioning brain, throughout the life cycle. Fat should come from a variety of sources:
- Get omega-3s from fish (2 to 3 servings weekly of low-mercury fish).
- Eat monounsaturated fats from nuts, olive oil, and avocados.
- Include walnuts and chia and flax seeds to provide ALA.
- Eat reasonable amounts of saturated fat from coconut oil, butter, and other animal products.
- If supplementing with fish oil, choose one that provides roughly a 2-to-1 ratio of EPA to DHA.
Avoid unhealthy fats: Trans fat and vegetable oils in processed foods—especially soy oil.
Eat an overall healthy diet based on an array of nutrient-rich whole foods: Vegetables, fruit, nuts, dairy, eggs, fish, meat, beans, and whole grains.
Consider trying a ketogenic diet for anti-aging and cognitive benefits. Don’t be scared off by the misconception that you need to eat carbs for a healthy brain. Your body is capable of getting all the glucose it needs once you go through the keto adaptation process.
When dealing with cognitive decline and other brain disorders, ensure you are getting adequate fish oil. EPA, DHA, and ALA may improve glucose uptake when insulin resistance is present. Pairing a ketogenic diet with adequate fish oil may enhance the anti-aging and cognitive benefits.