Ketones or ketone bodies are produced from fatty acids by the liver as an energy source for the brain when glucose is not readily available. Examples of this would be during periods of fasting or prolonged exercise. Other organs in the body can burn fatty acids for fuel if glucose levels are depressed, but the brain is an exception to this rule. There are three types of ketones: acetoacetate, 3-betahydroxybutyrate and acetone.
Excess production of ketones can be dangerous because ketones are acidotic. Too many in the blood can lower the blood pH to a fatal level. However, in a normal metabolic milieu the production of ketones is tempered by adequate insulin reserves. Insulin works as a gatekeeper, carefully regulating the amount of fatty acids released from the liver. This is why ketosis-producing very low carbohydrate diets in those without diabetes usually aren’t a problem.
In type 1 diabetes, when insulin reserves are non-existent, fatty acid and ketone production is uncontrolled. This, coupled with rising glucose levels as the liver tries to meet the body’s continued demand for energy, sets up a perfect storm of an increased acid load in the setting of profound dehydration. Keto-acidosis is a medical emergency and should be attended to immediately.
Pregnancy is another time when there can be high levels of ketones in the blood. In pregnant women with diabetes whose glucose levels are well controlled, rather than signaling a depletion of insulin, large amounts of ketones in the blood (or urine) usually signals inadequate carbohydrate intake. Since ketones in pregnant women are associated with negative outcomes for the fetus preventing their buildup is important. Some studies have shown that ketones can damage brain cell development. Having a bedtime snack containing carbohydrate if there is a long period of time between dinner and breakfast will usually stop this so-called “starvation” ketosis.