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            Low-carb and ketogenic diets have many health benefits.

            For example, it is well known that they can cause weight loss and help fight diabetes.

            However, they are also beneficial for certain brain disorders.

            This article explores how low-carb and ketogenic diets affect the brain.

What Are Low-Carb and Ketogenic Diets? Although there is a lot of overlap between low-carb and ketogenic diets, there are also a few important differences.

Ketogenic diet:

•           Carbs are limited to 50 grams or less per day.

•           Protein is often restricted.

•           A major goal is to increase blood levels of ketones, molecules that can partly replace carbs as an energy source for the brain.

Low-carb diet:

•           Carbs can vary from 25–150 grams per day.

•           Protein is usually not restricted.

•           Ketones may or may not rise to high levels in the blood.

            On a ketogenic diet, the brain is mainly fueled by ketones. These are produced in the liver when carb intake is very low.

            On a standard low-carb diet, the brain will still be largely dependent on glucose, although it may burn more ketones than on a regular diet.

            BOTTOM LINE:Low-carb and ketogenic diets are similar in many ways. However, a ketogenic diet contains even fewer carbs and will lead to a significant rise in blood levels of ketones.

The "130 Grams of Carbs" Myth

            You may have heard that your brain needs 130 grams of carbs per day to function properly. This is one of the most common myths about low-carb diets.

            In fact, a report by the US Institute of Medicine's Food and Nutrition Board states:

            "The lower limit of dietary carbohydrates compatible with life apparently is zero, provided that adequate amounts of protein and fat are consumed."

            Although a zero-carb diet isn't recommended because it eliminates many healthy foods, you can definitely eat much less than 130 grams per day and maintain good brain function.

            BOTTOM LINE:It is a common myth that you need to eat 130 grams of carbs per day to provide the brain with energy.

How Low-Carb and Ketogenic Diets Supply Energy For The Brain

            Low-carb diets have a fascinating way of providing your brain with energy via processes called ketogenesis and gluconeogenesis.


            Glucose, the sugar found in your blood, is usually the brain's main fuel. Unlike muscle, your brain can't use fat as a fuel source. However, the brain can use ketones. Your liver produces ketones from fatty acids when glucose and insulin levels are low.

            Ketones are actually produced in small amounts whenever you go for many hours without eating, such as after a full night's sleep.

            However, the liver increases its production of ketones even further during fasting or when carb intake falls below 50 grams per day (1Trusted Source, 2Trusted Source).

            When carbs are eliminated or minimized, ketones can provide up to 70% of the brain's energy needs (3Trusted Source).


            Although most of the brain can use ketones, there are portions that require glucose to function. On a very-low-carb diet, some of this glucose can be supplied by the small amount of carbs consumed.

            The rest comes from a process in your body called gluconeogenesis, which means "making new glucose." In this process, the liver creates glucose for the brain to use. It manufactures the glucose using amino acids, the building blocks of protein.

            The liver can also make glucose from glycerol. This is the backbone that links fatty acids together in triglycerides, the body's storage form of fat.

            Thanks to gluconeogenesis, the portions of the brain that need glucose get a steady supply, even when your carb intake is very low.

            BOTTOM LINE:On a very low-carb diet, up to 70% of the brain can be fueled by ketones. The rest can be fueled by glucose produced in the liver.

Low-Carb/Ketogenic Diets and Alzheimer's Disease

            Although few formal studies have been done, it appears that low-carb and ketogenic diets may be beneficial for people with Alzheimer's disease.

            Alzheimer's disease is the most common form of dementia. It's a progressive disease where the brain develops plaques and tangles that cause memory loss.

            Many researchers believe it should be considered "type 3" diabetes because the brain's cells become insulin resistant and are unable to use glucose properly, leading to inflammation (26Trusted Source, 27Trusted Source, 28Trusted Source).

            In fact, metabolic syndrome, a stepping stone towards type 2 diabetes, also increases the risk of developing Alzheimer's disease (28Trusted Source, 29Trusted Source).

            Experts report that Alzheimer's disease shares certain features with epilepsy, including brain excitability that leads to seizures (30Trusted Source, 31Trusted Source).

            In one study of 152 people with Alzheimer's disease, those who received an MCT supplement for 90 days had much higher ketone levels and a significant improvement in brain function compared to a control group (32Trusted Source).

            Animal studies also suggest that a ketogenic diet may be an effective way to fuel a brain affected by Alzheimer's (27Trusted Source, 33Trusted Source).

            As with epilepsy, researchers aren't certain of the exact mechanism behind these potential benefits against Alzheimer's disease.

            One theory is that ketones protect brain cells by reducing reactive oxygen species, which are byproducts of metabolism that can cause inflammation (34Trusted Source, 35Trusted Source).

            Another theory is that a diet high in fat, including saturated fat, can reduce the harmful proteins that accumulate in the brains of people with Alzheimer's (36Trusted Source).

            BOTTOM LINE:Ketogenic diets and MCT supplements may improve memory and brain function in people with Alzheimer's disease, although research is still in its early stages. Other Benefits For The Brain

            Although these haven't been studied as much, low-carb and ketogenic diets may have several other benefits for the brain:

•           Memory: Older adults at risk of Alzheimer's disease have shown improvement in memory after following a very-low-carb diet for six weeks (37Trusted Source).

•           Brain function: Feeding older and obese rats a ketogenic diet leads to improved brain function (38Trusted Source, 39Trusted Source).

•           Congenital hyperinsulinism: This condition causes hypoglycemia and can lead to brain damage. Congenital hyperinsulinism has been successfully treated with a ketogenic diet (40Trusted Source).

•           Migraine headaches: Researchers report that low-carb or ketogenic diets may provide relief to migraine sufferers (41Trusted Source, 42Trusted Source).

•           Parkinson's disease: In a small, uncontrolled study, five out of seven people with Parkinson's disease who completed a four-week ketogenic diet experienced a 43% improvement in self-reported symptoms (43Trusted Source).

•           Traumatic brain injury: Patients with a severe head injury who were fed a carb-free formula were able to obtain nourishment while avoiding high blood sugar, which can hinder recovery (44Trusted Source). 

            BOTTOM LINE:Low-carb and ketogenic diets have many other health benefits for the brain. They can improve memory in older adults, help reduce migraines and reduce symptoms of Parkinson's disease, to name a few.

Potential Problems with Low-Carb and Ketogenic Diets

            There are certain conditions for which a low-carb or ketogenic diet isn't recommended.

            If you have any sort of medical condition, then you may want to speak with your doctor before starting a ketogenic diet.

Side Effects of Low-Carb or Ketogenic Diets

            People respond to low-carb and ketogenic diets in many different ways. Here are a few potential adverse effects:  

•           Elevated cholesterol: Adults may experience elevated cholesterol levels, and children may have increases in both cholesterol and triglyceride levels. However, this may be temporary and doesn't appear to affect heart health (45Trusted Source, 46Trusted Source, 47Trusted Source).

•           Kidney stones: These are uncommon but have occurred in some children on ketogenic diet therapy for epilepsy. Kidney stones are usually managed with potassium citrate (48Trusted Source).

•           Constipation: This is very common on ketogenic diets. One treatment center reported that 65% of children developed constipation (48Trusted Source). This is usually easy to remedy with stool softeners or dietary changes.

            Children with epilepsy eventually discontinue the ketogenic diet once seizures have resolved. Most of them do not experience any negative long-term effects (49Trusted Source).

            BOTTOM LINE:A very-low-carb ketogenic diet is safe for most people, but not everyone. Some people may develop side effects, which are usually temporary.

Tips for Adapting to The Diet

            When transitioning to a low-carb or ketogenic diet, you may experience some adverse effects.

            You may develop headaches or feel tired or lightheaded for a few days. This is known as the "keto flu" or "low-carb flu." Here are some suggestions for getting through the adaptation period:

•           Make sure to get enough fluid: Drink at least 68 ounces (2 liters) of water a day to replace the water loss that often occurs in the initial stages of ketosis.

•           Eat more salt: Add 1–2 grams of salt each day to replace the amount lost in your urine when carbs are reduced. Drinking broth will help you meet your increased sodium and fluid needs.

•           Supplement with potassium and magnesium: Eat foods high in potassium and magnesium to prevent muscle cramps. Avocado, Greek yogurt, tomatoes, and fish are good sources.

•           Moderate your physical activity: Don't exercise heavily for at least one week. It may take a few weeks to become fully keto-adapted, so don't push yourself in your workouts until you feel ready.

            BOTTOM LINE:Adapting to a very-low-carb or ketogenic diet takes some time, but there are a few ways to ease the transition.

These Diets Have Powerful Health Benefits

            According to the available evidence, ketogenic diets can have powerful benefits for the brain.

            The strongest evidence has to do with treating drug-resistant epilepsy in children.

            There is also preliminary evidence that ketogenic diets may reduce symptoms of Alzheimer's and Parkinson's. Research is ongoing about its effects on patients with these and other brain disorders.

            Beyond brain health, there are also many studies showing that low-carb and ketogenic diets can cause weight loss and help treat diabetes.

            These diets are not for everyone but can have incredible benefits for a lot of people.

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Updated: August 16, 2017