What is CBD bioavailability and how does it effect Absorption?

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Cannabis is flying high on the wellness radar, because of Cannabidiol (CBD). 

There are now a countless number of choices when deciding what type of CBD products to purchase and use. 

Your choice of how you take CBD will impact how much of the compound reaches its final destination.

What does that mean?

Well, CBD and any other cannabinoid has to enter the endocannabinoid system and meet receptors in our body to be processed. But, this isn’t as simple as it might sound as it first needs to enter your bloodstream.

The amount of CBD which actually enters your bloodstream from consumption is a concept more commonly known as CBD bioavailability. 

In this article, we will cover the most common ways to take CBD and discuss what current science suggests in regards to their advantages and disadvantages for absorption.

Before we dive in, let’s define how this happens within our body and what factors influence it.

Pharmacokinetics and CBD Bioavailability

Which method you use to administer your CBD will alter how much CBD gets absorbed and used by the body.  

This process is more formally known as pharmacokinetics, which defines how compounds are processed within our body. 

In this specific case, we are referring to how CBD is absorbed, metabolised, distributed and excreted.

The choice of administration method determines how quickly and how much of the cannabinoid enters our bloodstream, which is referred to as the bioavailability of CBD.

Which brings us nicely into our next point, covering the differences in CBD bioavailability between conventional consumption methods.

Bioavailability of CBD: Capsules, Pills, Edibles

Most of us are familiar with oral consumption when it comes to taking other supplements. 

Oral CBD products are relatively popular, especially with people who are unable to use CBD tinctures for one reason or another. Edibles are also a booming segment, with CBD gummies becoming more commonplace day by day.

While popular, oral consumption, unfortunately, has the lowest rate CBD bioavailability. 

With current research suggesting an absorption rate of somewhere between 13-19% and half-life of between roughly 1-2 hours.

Why so low?

When you consume oral CBD, most of it is wasted in the process of digestion via a process called the first-pass effect, leading to low bioavailability. 

The fact CBD is fat-soluble makes it harder for our body to absorb. Additionally, our digestive enzymes destroy most of the compound before being metabolised by the liver. Thus, little CBD can enter the bloodstream. 

On the more positive side, it might be possible that using oral CBD may lead to a more balanced set of effects across time when compared to say vaping CBD. 

While the data is limited, animal-based research suggests that oral CBD consumption could lead to a longer duration of effects when compared to other methods of use.

CBD Inhalation: Vaping and Smoking

Inhaling CBD is a useful way to take CBD as it bypasses the first-pass effect by avoiding your digestive tract.

Instead, the CBD is inhaled directly into the lungs, where it is absorbed via membranes which cover the lungs called alveoli, after which the CBD can directly enter the bloodstream.

This is why when CBD is inhaled, the effects are felt rapidly but are also short-lasting compared to other methods

There are two main methods to inhale CBD, vaping and smoking:

Vaping: If you vape CBD the flower or concentrate is heated to a specific temperature where the cannabinoids in the bud or extract turn into an inhalable vapour. While there is no smoke and no combustion, there are still some risks associated with vaping, although these are significantly less than those related to smoking.

While it’s relatively clear vapourising CBD makes the compound more bioavailable for absorption in the bloodstream, the exact figures around how much are less precise.

This is because historical research has primarily focused on the bioavailability of THC when vapourised. Consequently, most research references assume the same absorption rate for CBD.

Nonetheless, based on this, research suggests the bioavailability of CBD, when vapourised, could be as high as 56%.

Smoking: Historically, this was the typical way to use cannabis. There is a piece of research which analysed the absorption rate of smoked CBD in the form of hemp flower-based cigarettes—concluding that smoking CBD had a bioavailability rate of 31%, with the half-life of smoked CBD being 31 hours.

Sublingual CBD Oil Consumption

sublingual cbd oil absorption

The most popular way to use CBD in the UK today is via CBD oil spray or drops held under the tongue to be absorbed into the bloodstream. These products are often full or broad spectrum and contain a variety of terpenes.

While there isn’t a study examining the use of sublingual CBD oil or spray in humans outside of Sativex (a 50:50 CBD/THC medicine) we are aware of, it’s thought that sublingual bioavailability of CBD sits somewhere between CBD taken orally and when vaped (between 6% and 54%).

Anecdotally, the reports of people using sublingual CBD oil are increasing rapidly and we anticipate future studies will focus on the bioavailability of CBD when used sublingually to fill the current knowledge gap.

Transdermal and Topical CBD

Transdermal is probably the least commonly used method to use CBD. It includes a CBD patch which is placed on the skin.

The ECS has receptors all across our skin, and if the CBD product can permeate through the skin via a transdermal application, it’s expected to have a higher bioavailability.

At the time this article is published, specific data around the bioavailability of human-based transdermal CBD isn’t something we have come across yet in a study. However, there is still some interesting information available which we have shared below. 

Transdermal delivery can be ineffective if it is not combined with another more water-soluble compound. As discussed earlier, CBD is fat-soluble, and as a result, it doesn’t mix well with the skin due to the high levels of water. 

A study on the transdermal applications of CBD (and a variant of THC called delta-8) found that adding roughly one-third ethanol in the application improved bioavailability nearly four times. 

Overall, transdermal application of CBD is useful in ensuring a consistent dose across time, but on the flip side, it is slow to work and absorb.

Water Soluble CBD

We mentioned that CBD is not water-soluble (neither are most cannabis compounds), and while this is usually the case, there are now exceptions to the rule.

Innovations in cannabis science, borrowing methodologies applied in other supplement niches such as vitamins have been utilised to create CBD products with a much higher (hypothesised) bioavailability.

What do we mean?

Well, water-soluble CBD is thought to improve CBD bioavailability significantly and its the primary reason it was developed. However, as it’s so new, there isn’t any clinical backing behind how much better it is at helping our bodies absorb it vs say the oral administration of CBD (which we just discussed is poor).

There are a couple of different types of water-soluble CBD. But in summary, they all work on the premise that if you break down the CBD molecule, you can improve bioavailability.

This works by increasing the overall surface area for a dose, and encapsulating or emulsifying it in another molecule. This other compound is water-soluble, and consequently, you have the availability to increase the bioavailability of CBD through this trick.

It’s important to note that most water soluble CBD for sale today contains no terpenes (aromatic metabolites), which are thought to work synergistically with cannabinoids via the entourage effect.

To learn more check out our detailed post discussing the potential benefits of water-soluble CBD.

Bioequivalence

If you have used CBD in one form, but are wondering what the equal dose for another format is, you need to work out something called bioequivalence.

As each method doesn’t deliver the same dose to the bloodstream, 10mg of a vape isn’t going to equal 10mg of CBD oil administered under the tongue.

Bioequivelence is just a fancy term for working on the same dose you would need for another consumption method to deliver the same amount to your bloodstream.

Don’t worry, it sounds trickier than it is. In the example below, we use the lower end of the anticipated ranges, as quoted by the studies discussed in this post:

  • 20mg consumed orally. How much would I need to consume sublingually or via vaping? Based on the data used in this post, 20mg orally equates to roughly 2.6mg entering the bloodstream. In which case the equivalent dose when vaping would be 2.6 / 0.56 = 4.64mg. 

Note – this is an estimation of CBD bioavailability based on the data provided by the research articles linked to in this post and are strictly informational figures used for demonstration.

Factors which can influence bioavailability

While the data points presented above are useful as average indicators and good to keep in mind, there are other specific localised factors which can affect how compounds like CBD are absorbed into the bloodstream.

These include

  • Pre-existing health conditions: CBD is known to interact with the liver. According to this study, individuals with a lower than average liver function are more probable to a lower absorption rate of CBD. As always, especially if you have a pre-existing condition, talk to your doctor before using CBD.

Fed vs fasted: According to a study by the University of Minnesota, CBD is absorbed more effectively if consumed with a high-fat meal and up to four times more when compared to taking CBD when fasted.

Piperine and Bioavailability

black pepper

Similar to CBD, turmeric isn’t highly bioavailable. 

Piperine is an alkaline commonly found in black pepper that has been used to improve the bioavailability of Curcumin. 

Curcumin is a part of a family of compounds called curcuminoids, commonly found in turmeric. 

Researchers interested in the use of black pepper as a tool to improve the bioavailability of turmeric classified piperine as an active compound of interest in improving absorption. 

What’s this got to do with CBD?

Well, now scientists are studying if black pepper and nano-emuslifying could help improve the poor availability rate of CBD.

There is nothing super conclusive yet on this topic from clinical studies. However, it’s easy to replicate at home (albeit without the same standards). 

Bottom Line and Summary

CBD bioavailability appears to be somewhat in flux depending on how you take it, what you take it with and other localised factors. 

Finding what works for you is essential. It’s your own journey, trial and error is just part of the process. 

In summary, you need to consider the points below and decide what’s right for you:

  • It’s unknown if CBD Isolate has a different absorption rate when compared to a full spectrum CBD product (containing terpenes and other metabolites). 
  • Oral CBD has the lowest level of bioavailability of all options but could lead to a more extended set of effects. If consuming it orally, taking your CBD with fat might be helpful.
  • Inhaling CBD offers a high absorption rate, and the effects are felt near instantaneously. 
  • Sublingual absorption rates are thought to be somewhere between the previous two.
  • Transdermal applications can deliver titrated amounts of CBD across time but are slow to take effect. 

Frequently Asked Questions

CBD has a low bioavailability when consumed orally (<5%).

This is one of the reasons sublingual oils and vapes are more popular instead of CBD capsules.

Where CBD oil drops and vapes have a bioavailability of approx 30%/55%.

Vaping CBD has the highest rate of absorption when compared to other common consumption methods (approx 55%).

However, anecdotal reports suggest the duration of the effects is shorter.

Yes, CBD oil can be absorbed by the blood vessels under the tongue.

If using CBD drops, place the drops under the tongue and hold them there for 60 seconds before swallowing.

Yes, and the effects are felt locally. This is possible as we have endocannabinoid receptors under the skin.

However, topical CBD has the lowest (estimated at <5%) bioavailability of all conventional consumption methods.

There is no recorded overdose of CBD, and the WHO has declared it safe.

However, the UK Food Standards Agency has advised a maximum daily dose of 70mg CBD unless instructed by a doctor.

As science progresses, it’s likely we will see new methods to improve absorption.

While water soluble CBD is said to help absorption rates, this isn’t currently backed by clinical research.

This is a debatable question, and there isn’t a clear answer to this at the moment.

Although, in theory, it depends on what method of consumption you use along with your endocannabinoid system.

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Disclaimer: Views expressed here do not necessarily reflect those of Nature & Bloom and its staff. This article is not intended to provide medical advice, diagnosis, treatment, cure or prevention for any disease. Nature & Bloom products have not been evaluated by the MHRA.