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There are many CBD oil products on the market, from drops, sprays, capsules and gummies through to vapes, infused drinks and food and topical balms.
CBD (cannabidiol) is extracted from industrial hemp plants and, in its natural state, dissolves in fat rather than water. Therefore, it is usually combined with a quality oil, such as olive oil or hemp seed oil, to create CBD oil supplements.
If taking CBD by mouth (via drops or capsules), then it's a good idea to take it with a high-fat meal, as this boosts absorption into the bloodstream by as much as fives times compared with taking it on an empty stomach. By contrast, taking CBD with a low-fat meal increases absorption 2.7 times more than taking it without any food at all.1
When taking CBD oil as drops or a spray, you can boost absorption by holding the liquid under your tongue for a couple of minutes. This allows oil-based CBD to pass across the mucous membrane lining of the mouth directly into the bloodstream.
As a result, two or three times more will reach the bloodstream quickly compared with swallowing the whole dose immediately, and you may notice a relaxing effect within a few minutes.
When you swallow the rest of the CBD oil, a small amount is broken down by stomach acid, but nine per cent of the remaining dose will pass down into the small intestines.
As it is not water-soluble, CBD oil tends to break up into fatty globules. Most oil-based CBD is absorbed via the wall of the small intestines, along with dietary fats, directly into the lymphatic system.
When CBD is in the lymphatic system, it has direct access to cells (e.g. lymphocytes) that circulate within the lymph vessels and lymph nodes. From here, the CBD is delivered into the bloodstream, which avoids initial breakdown in the liver.
This is why taking CBD with a fatty meal can increase blood levels by three to five times, as the dietary fats help the CBD enter the lymphatic system directly. The overall result of swallowing CBD drops is a delay of 30 to 90 minutes before you may notice an effect, compared with absorbing CBD under your tongue.
Please note: One drawback of taking higher doses of CBD oil from droppers is that some people develop reflux or nausea.
Many people prefer CBD oil capsules to droppers, as they don't really taste of anything (although filter-clear CBD oil tastes a lot less 'grassy' than other types). They also provide an exact dose (as long as they are made to GMP standards), so you know how much CBD you are taking rather than the guesswork of using a dropper and counting drops.
A gel capsule must dissolve in order to start the absorption process. Most capsules (e.g. Healthspan's CBD Oil Capsules 192mg to 384mg) dissolve in the stomach, and the released CBD oil is then absorbed in the same way as for drops.
A few capsules (eg Healthspan's CBD Oil Capsules 450mg to 900mg) have a 'delayed release' mechanism that is designed to dissolve in the small intestines, directly where absorption occurs, to avoid any reflux or nausea.
As with swallowing CBD oil, you may notice an effect within 30 to 90 minutes after swallowing a CBD capsule. The maximum effect usually occurs two to three hours after swallowing CBD and typically lasts for three to five hours, and up to 12 hours with higher doses.2
Normal CBD oil is not water-soluble, so molecules will clump together in the digestive tract, creating a small surface area and making them harder for the body to absorb.
Fortunately, technology now exists to make CBD water-soluble through advanced liquid micellar technology. This wraps tiny amounts of CBD oil inside water-soluble spheres, meaning that they can be dispersed as tiny globules (liquid micelles) across a larger surface area, for better absorption.
This makes the optimised CBD highly absorbable and more bioavailable; 'bioavailability' describes the relative ease with which a substance is absorbed into the blood stream and remains free to produce an active effect.
In studies, Opti-CBD was absorbed 16 times more quickly during the first hour compared with standard CBD, so you notice a faster effect.
See the micellation process in action.
As CBD is oil-soluble, very few CBD products are formulated as tablets, although some capsules are filled with crystalline powder extracts from hemp oil – especially when these are combined with other plant ingredients that have complementary effects.
Tablets, if available, would contain additional ingredients (known as excipients), such as flowing agents (to prevent them caking during processing) and binders (to prevent tablets crumbling back into powder).
The rate at which the resulting tablet would break down in the intestines would affect how much CBD is absorbed, and this would generally be slower than when CBD is taken in liquid form.
CBD gummies are increasingly popular as they can taste delicious – so much so that you may need good self-control not to exceed the recommended dose. To produce gummies, a CBD extract is combined with fruit juice, a gelling agent such as pectin or gelatin, and sweeteners plus natural flavourings to produce a flavoured, edible pastille or chew.
Some gummies have no added sugar and are sweetened with agents such as Stevia or sorbitol, while others are sweetened with sugar, glucose or cane syrup. Sucking or chewing the gummy will allow some CBD to be absorbed within the mouth lining, so you may notice a more rapid effect than when swallowing a capsule.
CBD is readily absorbed through the skin (transdermal delivery) via patches, salves, lotions, creams or balms. The CBD in these products interacts with local receptors in skin cells, skin nerve fibres and skin glands.3 4 5
Some CBD is also absorbed into the circulation to produce more widespread effects. Rubbing in a CBD Balm can complement the effects of a CBD supplement taken by mouth.
Dr Brewer is the author of CBD: The Essential Guide to Health and Wellness (Simon & Schuster).
Dr Sarah Brewer is Healthspan's Medical Director and holds degrees in Natural Sciences, Surgery and Medicine from the University of Cambridge. Having worked as a GP and hospital doctor, Dr Sarah now holds an MSc in Nutritional Medicine from the University of Surrey and specialises in nutrition. She is also an award-winning writer and author.
Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.
1Crockett J et al. (2020). A phase 1, randomized, pharmacokinetic trial of the effect of different meal compositions, whole milk, and alcohol on cannabidiol exposure and safety in healthy subjects. Epilepsia 61(2)
2Grotenhermen, F. (2003). Pharmacokinetics and pharmacodynamics of cannabinoids. Clinical Pharmacokinetics 42(327-60)
3Stander S et al. (2005). Distribution of cannabinoid receptor 1 (CB1) and 2 (CB2) on sensory nerve fibers and adnexal structures in human skin. Journal of Dermatological Science 38(3)
4Sheriff T et al. (2019). The potential role of cannabinoids in dermatology. Journal of Dermatological Treatments. 10(1-7)
5Palmieri B et al. (2019). A therapeutic effect of CBD-enriched ointment in inflammatory skin diseases and cutaneous scars. La Clinica Terapeutica 170