What Is Cannabidiol (CBD)? A Plain-English Explainer

Cannabidiol, usually shortened to CBD, is one of the most talked-about plant compounds of the last decade. It turns up in oils, gummies, capsules, creams and coffee, and the claims made for it range from sensible to absurd. This page explains, in plain English, what CBD actually is, where it comes from, how it differs from THC, what scientists think it does in the body, and what the different product types mean. Where we describe research, we label it as human or preclinical (cells and animals), because that difference matters more than anything else.

Cannabidiol in one paragraph

Cannabidiol is a natural compound made by the plant Cannabis sativa. It belongs to a family of around 100 or more related compounds called cannabinoids. Unlike THC (tetrahydrocannabinol), the best-known cannabinoid, CBD does not produce a "high" and is not considered intoxicating. Most CBD sold in Ireland and Europe is extracted from hemp: varieties of cannabis that are grown for fibre, seed and food and contain only tiny amounts of THC.

Where CBD comes from

Hemp and "marijuana" are the same species. The difference is in how the plants have been bred. Hemp varieties registered for farming in the EU are bred to produce very little THC, while drug varieties are bred for high THC. CBD is concentrated in the flowers and leaves, in tiny resin glands called trichomes, rather than in the seeds or stalks. That is why hemp seed oil, the cooking oil sold in health food shops, contains little or no CBD, even though it comes from the same plant.

To make a CBD product, manufacturers extract the cannabinoids from the dried plant material. The main methods are:

• Supercritical CO₂ extraction: carbon dioxide under pressure acts as a solvent. It is clean and controllable and is widely used for higher-quality products.
• Ethanol extraction: food-grade alcohol pulls out the cannabinoids, then is evaporated off.
• Oil infusion: the oldest home method, warming the plant in a carrier oil. It is simple, but the strength is hard to control.

The raw extract is then refined, tested and usually diluted into a carrier oil such as MCT (from coconut) or hemp seed oil.

CBD vs THC: the key differences

The practical point for Irish consumers is that THC is the line that matters legally. A good CBD product should come with a recent, independent lab report showing THC as "not detected". We explain how to read one in our CBD oil explainer.

How CBD acts in the body: what scientists think

Humans and other animals have an endocannabinoid system: a signalling network made up of receptors (mainly CB1 and CB2), the body's own cannabinoid-like molecules (such as anandamide), and the enzymes that make and break them down. It is involved in many routine processes, from appetite to pain signalling to stress responses.

THC works mainly by switching on CB1 receptors. CBD is different. In laboratory research preclinical, CBD binds only weakly to CB1 and CB2. Instead, researchers have observed it interacting with a range of other targets, including:

• 5-HT1A receptors, part of the serotonin system;
• TRPV1 channels, involved in pain and temperature sensing;
• GPR55, sometimes described as an "orphan" cannabinoid receptor;
• FAAH, the enzyme that breaks down anandamide, which CBD may slow in some experiments.

This "many targets" picture is one reason CBD is studied for such different things. It is also a reason for caution: a compound that touches many systems can interact with medicines, which we cover in our safety and interactions guide.

The main types of CBD extract

• Full spectrum: contains CBD plus the plant's other cannabinoids, terpenes and flavonoids. Depending on processing, it may contain trace THC, so lab results matter. Some products are refined to remove THC while keeping the rest of the profile.
• Broad spectrum: a wide range of plant compounds with THC removed.
• Isolate: purified CBD, typically over 99% pure, with nothing else from the plant.

You will often read that full spectrum products work better because of an "entourage effect", the idea that plant compounds work together. That idea is plausible and widely discussed, but strong human evidence comparing these product types directly is still lacking. Choose on transparency and testing rather than marketing language.

Common CBD product formats

• Oils and drops: taken under the tongue or swallowed. Flexible amounts.
• Capsules and softgels: fixed amounts, no taste.
• Gummies and edibles: pre-measured and easy, but with sugar and other ingredients.
• Topicals: creams, balms and gels applied to skin. Very little reaches the bloodstream.
• Vapes: fast-acting but involve inhaling heated liquids; we don't recommend them.

How much CBD reaches your bloodstream depends heavily on the format. Swallowed CBD has low and variable absorption (researchers commonly estimate around 6 to 20%), and taking it with food, particularly fatty food, tends to increase how much is absorbed.

Is CBD the same as medical cannabis?

No. The only CBD-based medicine licensed by medicines regulators in Europe is a prescription product (Epidyolex) used under specialist care for specific rare forms of epilepsy. It contains highly purified CBD at doses far higher than anything in a consumer product. Consumer CBD products are sold as foods, food supplements or cosmetics, and the law does not allow them to claim to treat, prevent or cure any disease.

A short history

CBD was first isolated in 1940, and its chemical structure was worked out in 1963 by Raphael Mechoulam's group in Israel, the same team that later identified THC. Research picked up sharply after the endocannabinoid system was described in the late 1980s and 1990s, and again in the 2010s as consumer CBD products spread. In 2018 the World Health Organization's Expert Committee on Drug Dependence reported that CBD showed no evidence of abuse or dependence potential.

How to use this site

cannabidiol.ie is a research hub. Each guide labels evidence by type and links to the studies behind it. Start with:

• What the research actually shows: an honest evidence map.
• CBD safety and drug interactions: what to know before you take it.
• CBD oil explained: spectrums, strengths and lab reports.

Common myths about CBD

• "CBD is a cure-all." No compound helps everything. Human evidence is strong only in a narrow medical area, at prescription doses.
• "Natural means safe." CBD can cause side effects and interact with medicines. Natural and harmless are not the same thing.
• "More is always better." Some research suggests effects don't simply increase with dose, and side effects become more likely at higher amounts.
• "Hemp seed oil from the supermarket is CBD oil." It isn't. Seed oil contains little or no CBD.
• "CBD shows up as cannabis on a drug test." Tests look for THC, not CBD, although products containing trace THC can cause problems.

Sources

1. World Health Organization Expert Committee on Drug Dependence. Cannabidiol (CBD) critical review report, 2018.
2. Mechoulam R, Shvo Y. Hashish I: the structure of cannabidiol. Tetrahedron, 1963.
3. Millar SA et al. A systematic review on the pharmacokinetics of cannabidiol in humans. Frontiers in Pharmacology, 2018.
4. Ibeas Bih C et al. Molecular targets of cannabidiol in neurological disorders. Neurotherapeutics, 2015.