When we say ketones, we are referring to the main circulating fatty acid metabolites beta-hydroxybutyrate (OHB) and acetoacetate (AcAc). Much more on ketone basics here. Exogenous ketones (also called ketone supplements) and well-formulated ketogenic diets share one or more thing in common. They both bring about increased circulating concentrations of beta-hydroxybutyrate (BOHB), but ultimately are related to very different patterns of ketosis, as well as differing metabolic and physiologic outcomes. In short, they should not be assumed to have equivalent effects simply because they achieve similar BOHB blood levels. Having said that, there are many reasons we need to continue to study the different forms and potential applications of vitamin supplements for keto.
Within the last few million years, the only method for humans to utilize ketones for fuel would be to restrict carbohydrates low enough and long enough to induce the liver to ensure they are. This really is admittedly hard for many individuals to do in a world that still believes that dietary carbs are great and fats are bad. An emerging alternative is always to consume ketones being a nutritional supplement. The investigation into how these function in your body and what benefits they could confer remains early stage, but we already have numerous such products on the market. Within this section, we are going to discuss how exogenous ketones affect blood ketone levels, and exactly how they could influence health insurance and disease in comparison to ketones produced within your body.
Both predominant ketones made by the liver are beta-hydroxybutyrate (BOHB) and acetoacetate (AcAc). Here’s a short review of basic information regarding these ketones:
It is actually estimated that the keto-adapted adult will make 150 or more grams of ketones daily after adjusting to an overall total fast (Fery 1985), and possibly 50-100 grams each day on the well-formulated ketogenic diet.
Some AcAc naturally stops working to make acetone, which will come out through the lungs and kidneys, giving a chemical odor for the breath when ketones are high.
Most of the AcAc produced in the liver is acquired by muscle and transformed into BOHB.
As part of the keto-adaptation process, how muscles and kidneys handle BOHB and AcAc changes over the first weeks and months, and so the ratio of AcAc to BOHB within the blood changes considerably within the first couple of weeks.
As the ultimate fate of many ketones in the blood is going to be burned for fuel, BOHB and AcAc appear to have differing roles in regulating genes and cellular functions.
Particularly with gene regulation, BOHB seems to play a much more significant regulatory role than AcAc, but AcAc could have a particular role in signaling muscle regeneration .
Sources and Formulations of Exogenous Ketones – The two compounds commonly referred to as ‘ketone bodies’ (BOHB and AcAc) are made and utilized for multiple purposes across nature from algae to mammals, but seldom in concentrations useful for extraction as human food. Because of this, the source of many exogenous ketones is chemical synthesis. Furthermore, most current research and make use of of ketone supplements focuses on BOHB. That is because AcAc is chemically unstable – it slowly breaks down to form acetone by releasing loejbp one molecule of CO2.
In a keto-adapted individual where ketone metabolism is brisk with up to 100 grams or maybe more being oxidized (i.e., ‘burned for energy’) daily, the little amount lost in breath and urine as acetone is minor. But because this breakdown occurs spontaneously without the need for the aid of enzymes, it also happens to AcAc in a stored beverage or food (even in an aura-tight container), making the shelf-lifetime of AcAc-containing products problematic. Thus all current ketone supplements include BOHB in some form as opposed to the naturally sourced mix of BOHB and AcAc created by the liver.
Another significant difference between endogenous and exogenous BOHB is the fact that most synthetic BOHB used in health supplements is a blend of both ‘D’ and ‘L’ isomers, whereas endogenously produced BOHB consists of just the D-isomer. Metabolically, the two isomers are very different, and current published information shows that the majority of the energy and signaling advantages of BOHB derive from your D-form. This is potentially problematic as the L-isomers are certainly not metabolized using the same chemical pathways because the D-forms (Lincoln 1987, Stubbs 2017), and it remains unclear whether humans can convert the L-form for the D-form.
Thus, as the L-isomers do not seem to be toxic, they are certainly not likely to impart the same benefits because the D-forms. Additionally, the existing assays for blood ketones are specific for the D-isomer, so it will be hard to track blood levels and clearance of any L-isomer taken in a supplement.