In the wide world of CBD, bioavailability is one of the most important concepts for users looking for the proper treatment method and dosage.
What is Bioavailability, and why does it matter?
Bioavailability relates to how quickly your body absorbs CBD, and how much of a CBD dosage will be able to have a therapeutic effect. Different methods of CBD ingestion have differing levels of bioavailability. That means that the proper dosage for one ingestion method may be different than the proper dosage for another method.
As such, users should have at least a baseline understanding of each method’s absorption rates; such understanding allows users to receive a more consistent and precise treatment, regardless of the type of CBD product that they use.
First-pass metabolism and first-pass elimination:
First-pass metabolism and first-pass elimination are key concepts for understanding bioavailability. With most methods of ingestion, the body must first digest or otherwise break down the CBD product. During this process, some amount of the CBD will escape the metabolism, and will therefore not have an effect on the body. This “eliminated” CBD is passed out of the body as waste, while the successfully digested and metabolized portion enters the bloodstream. From there, it contributes to CBD’s therapeutic effects through its interactions with the body’s endocannabinoid system.
Different methods of CBD ingestion interact with the digestive and metabolic processes differently, either increasing or reducing the proportion of CBD that is usefully metabolized.
Bioavailability of Different CBD Ingestion Methods
Your body is made up of complex systems, and each such system absorbs substances like CBD somewhat differently. Different methods of CBD ingestion interact with different bodily systems and their respective absorption rates. The following is a brief overview of the most common ingestion methods, and of current research on their respective bioavailability. We will also provide a brief description of each method’s biomechanics, which are responsible for the differing bioavailabilities.
If you’re just looking for a quick-and-easy rule of thumb, these are the most common CBD ingestion methods, listed from highest bioavailability to lowest bioavailability: Inhalable CBD > Sublingual CBD > Edible CBD. Topical CBD is something of a special case, and should be considered separately from these other traditional methods.
Bioavailability of inhalable CBD:
Inhalable CBD, such as CBD vapes and smokable flower, has the highest bioavailability of all popular ingestion methods.
Inhalable CBD bioavailability rates:
According to most studies, inhalable CBD has a bioavailability of 34-46%. However, some studies suggest that the bioavailability can be even higher, with absorption rates up to 56%. This wide variance is due to differences in individual’s smoking or vaping technique, including differences in “number, duration, and spacing of puffs, hold time, and inhalation volume”.
The biomechanics of inhalable CBD:
Inhalable CBD (such as CBD vapes and smokable flower) is taken directly into the lungs, where it is rapidly and efficiently absorbed into the bloodstream. Because it bypasses the digestive system, inhalable CBD bypasses first-pass metabolism; this accounts for inhalable CBD’s comparatively high bioavailability.
Bioavailability of sublingual CBD
Sublingual CBD (meaning CBD taken under the tongue, such as with CBD oil tinctures) has the second highest bioavailability of popular ingestion methods.
Sublingual CBD bioavailability rates:
Most studies find that sublingual CBD has a bioavailability in the range of 20-35%. Variance is largely due to differences in dosing technique; the longer that an oil tincture is held under the tongue before swallowing, the greater the bioavailability.
The biomechanics of sublingual CBD:
Sublingual CBD such as CBD oil tinctures are held under the tongue before being swallowed. While under the tongue, a large portion of the CBD dosage is efficiently absorbed by the densely-clustered capillaries located there; like with inhalable CBD, this direct absorption largely bypasses first-pass metabolism. After a period, the remaining oil is swallowed; whatever CBD remains unabsorbed at this point is now digested identically to edible CBD, which is subject to first-pass metabolism and reduced bioavailability.
Bioavailability of edible CBD
Edible CBD bioavailability rates:
Most studies find that edible CBD has a bioavailability in the range of 13-19%. Some early studies suggested lower bioavailability, but current research suggests that the 13-19% range is more accurate.
The biomechanics of edible CBD:
Edible CBD, including both food and beverage products, must be swallowed and digested in a manner identical to traditional (non-CBD) foodstuffs. As a result, edible CBD is subject to the full effects of first-pass metabolism and first-pass elimination, which accounts for the method’s comparatively small bioavailability.
Special Cases for CBD Bioavailability
Some other CBD ingestion or application methods complicate the basic concept of bioavailability. These include common products like topicals, less popular products like suppositories, and developing technologies like nano-CBD.
Bioavailability of Topical CBD
Topical CBD is a special case, and its bioavailability is strongly determined by the type of topical used, by the amount used in a single treatment, and by the length of exposure. Most traditional topicals, including lotions and balms, never reach the bloodstream — and, by strict definition, have virtually zero bioavailability. That’s somewhat misleading, however, as topical CBD still has a therapeutic effect.
Unlike more traditional treatment methods, which enter the bloodstream and interact with endocannabinoid receptors found throughout the body, most CBD topicals interact only with receptors found in the skin at the site of application.
When topicals are applied in great quantities, or when topicals are applied for long periods of time (as with CBD patches), CBD can be absorbed through the pores in the skin. This phenomenon allows CBD to enter the bloodstream, and such applications do meet the traditional definition of bioavailability.
Bioavailability of CBD Suppositories
CBD suppositories have only recently emerged as a treatment method, and very little formal research has been done into the absorption and bioavailability rates of CBD suppositories. However, research on suppository drug treatments generally suggests that suppositories are a terrifically effective treatment option. This research further suggests that, like CBD topicals, suppositories will have a predominantly localized effect, but that a significant amount of the contained CBD will also be absorbed. At the time of writing, however, there is insufficient clinical evidence to make a precise numeric claim about the bioavailability rates of CBD suppositories.
Nano-CBD and its effects on bioavailability
Nano-CBD, also frequently referred to as “water soluble CBD” or “nanoemulsified CBD”, is a newly developed form of CBD whose molecular size has been reduced through a number of enzymatic or other chemical processes.
By reducing the size of the CBD molecule, these processes allow CBD to more easily and efficiently enter the bloodstream. Two clinical studies, conducted in 2017 and 2018, suggest that these nano products dramatically improve bioavailability compared to traditional (non-nano) CBD products of the same type.
Some manufacturers of nanoemulsified CBD claim 100% bioavailability. However, such claims have not yet been substantiated by comprehensive clinical testing. Existing research does, again, show that these nano treatments have a significant positive effect on bioavailability, but claims advertising a precise bioavailability percentage should be regarded critically.