How sugar may damage the brain – continued
Insulin resistance, which now affects more than 50% of Americans and has reached epidemic proportions in many other countries around the world, is emerging as a potentially important factor in the development of most of the mental health problems we fear — from straightforward conditions such as depression to complex brain degeneration disorders like schizophrenia and Alzheimer’s disease.
As tragic as this may seem, understanding that insulin resistance of the brain strongly influences our risk for psychiatric disorders is tremendously empowering, because insulin resistance is a familiar beast we already know how to tame. High-sugar diets flood the bloodstream with too much glucose, placing pressure on the pancreas to produce high amounts of insulin to process it all. Over time, if insulin levels run too high too often, your delicate insulin signaling system can break down from overuse. The receptors that transmit insulin’s instructions can become damaged and dwindle in number, making it increasingly difficult for cells to respond to insulin’s important messages. The pancreas tries to overcome this “resistance” by releasing even more insulin into the bloodstream, creating a vicious cycle of climbing insulin levels and worsening insulin resistance.
In people with insulin resistance, the insulin receptors responsible for escorting insulin from the bloodstream into the brain’s interior can malfunction and shrink in number, restricting insulin flow into the brain. If you have insulin resistance or even type 2 diabetes, glucose will continue to waltz easily into the brain, but insulin will struggle to gain access.
Without adequate insulin, brain cells can’t process glucose properly, and will start to slow down. This sluggish glucose processing problem is called “cerebral glucose hypometabolism” and is a key feature of many brain disorders, particularly Alzheimer’s disease. For simple ways to figure out whether you have insulin resistance, see “How to diagnose, prevent and treat insulin resistance.”
How low-carbohydrate diets can improve brain metabolism
If high blood sugar and insulin jeopardize brain health through inflammation, oxidation, and insulin resistance, then reducing blood glucose and insulin levels should help improve brain health. A growing body of scientific literature supports the idea that ketogenic diets have the potential to address all of these underlying biochemical disturbances, and therefore hold great promise for the dietary treatment of psychiatric disorders.
As carbohydrates tend to raise glucose and insulin levels the most and fats raise insulin the least, it stands to reason that a low-carbohydrate, high-fat diet could be one of the best ways to target these root causes of brain malfunction, improve brain metabolism, and protect the brain from further damage. It has been known for nearly a century that ketogenic diets have the power to completely eliminate seizures in some children with epilepsy and significantly reduce the frequency of seizures in others.
If that isn’t an indication that low-carbohydrate diets can stabilize brain chemistry, what is? The brain is a highly-active electrical organ that demands a constant supply of high-quality fuel, and while it’s true that some of its fuel must be in the form of glucose, that glucose does not need to come from carbohydrates in the diet. In 2005, the (American) Institute of Medicine and the Food and Nutrition Board acknowledged that “the lower limit of dietary carbohydrate compatible with life is apparently zero, provided that adequate amounts of protein and fat are consumed.”
Through a natural process called “gluconeogenesis” (making glucose from scratch), the liver can make all the glucose we need from fat and protein and release it into the bloodstream for any cells that require it, including brain cells. When carbohydrate intake is sufficiently low and intakes of protein and fat are adequate, such as on a standard LCHF (low-carbohydrate/high-fat) diet, blood (and brain) glucose levels will typically stabilize in a healthy range. If insulin levels are sufficiently low, the body switches from primarily burning sugar to primarily burning fat. This shift is called “ketosis” because fat breaks down into fatty acids and “ketones” that are released into the blood to serve as sources of fuel for hungry cells. You can test to see if you are generating ketones with a blood ketone meter.
Although most cells in the body can burn fatty acids, brain cells aren’t equipped to burn them. So, they burn ketones instead. Ketones are an excellent fuel source for the brain — they burn more cleanly and efficiently than glucose, with much less oxidation and inflammation. Although some rapid-fire brain cells always require some glucose (because it burns faster than ketones do), ketones can meet up to a remarkable two-thirds of the brain’s total energy requirements. In fact, given the option, most brain cells will burn ketones over glucose, making ketones the preferred energy source for large portions of the human brain. Although insulin resistance of the brain makes it difficult for insulin to cross into the brain, it doesn’t interfere with the flow of ketones. Therefore the more ketones you have in your blood, the higher your brain ketone levels will be, and the more ketones your brain cells can absorb and use for energy. As an added bonus, it just so happens that ketones burn beautifully in a low-insulin environment, making ketones an ideal fuel source for the insulin-resistant brain. / Dr. Georgia Ede, MD