

Once “keto-adapted,” many tissues increase their capacity to utilize ketones for fuel. Some tissues even prefer to use ketones for their cellular energy needs. For instance, the heart, as well as many areas of the brain, prefers to use ketone bodies as opposed to glucose. One interesting fact is that Dr. Stephen Cunnane found that the uptake of ketone bodies in the brain is proportional to their production.[12] Additional research has also demonstrated that as uptake of ketones increases, the uptake of glucose decreases in brain tissue.[13][14] In contrast, there are certain cells that cannot use fatty acids or ketone bodies, and are considered “obligate glucose users.” Red blood cells and specific parts of the brain are obligate glucose users. Don’t stress, however, because even though you may not be consuming a lot of carbohydrates, these cells can obtain glucose through a biological process called gluconeogenesis (the production of glucose from other non-glucose materials).