What’s the right dose of CBD when you take it orally? It’s a simple question with a muddled answer. One complicating factor is your most recent meal. Research has shown that only about 3-10% of CBD is absorbed into the bloodstream when taken on an empty stomach, but you may get up to five times as much if you first eat a fatty meal. Scientists at GW Research, which develops pharmaceutical cannabis extracts such as Epidiolex, recently organized a rather strange study to further assess this phenomenon.

They studied CBD absorption after five different meal conditions — 10 hours fasting, light breakfast, heavy breakfast, a tall glass of milk, and alcohol in lemonade. Participants also received a large dose of CBD, 750 mg. The results for the light and heavy breakfasts were consistent with previous data. A light meal tripled CBD exposure, and a heavy one quadrupled it. Taking CBD right after guzzling half a liter of milk also increased CBD absorption, but not to the same degree. Just under half of the subjects experienced minor adverse effects (like headache, tiredness, nausea) at this large 750 mg dose of CBD.

The fifth and final condition, taking CBD with alcohol, is hard to grasp. Participants took their 750 mg dose of CBD, then were required to drink 40 grams of alcohol — tantamount to five standard drinks — within five minutes. These participants hadn’t eaten in at least ten hours, having forgone breakfast for the experiment.

This experiment would be considered binge drinking in the US and probably (hopefully) would not have been approved by an ethics committee. But in the UK, where the GW study was performed, the National Health service suggests that it’s not binge drinking until a man has nine drinks in a single sitting, or until a woman has seven. Still, five shots instead of breakfast seems like a lot to imbibe. Unsurprisingly, the alcohol group had high rates of side effects — 80% of participants had problems like headache, dizziness, nausea, and fatigue, almost twice the rate of the other conditions — and side effects were more severe among this group.

Adrian Devitt-Lee, Project CBD’s chief science writer, is pursuing a PhD in math at the University College of London.

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