Reading time: 6 minutes
Walk down any supermarket coffee aisle this autumn and you will find a growing shelf of coffees that promise more than coffee. Lion's mane for focus. Reishi for calm. Chaga, cordyceps, ashwagandha, collagen, protein. The labels are earthy, the prices are high, and the language is confident.
We roast coffee for a living, so it is a category we get asked about. We don't sell a functional coffee, and we want to be upfront about that before we go any further. What follows is our honest attempt to set out what these products are, what the research does and doesn't support, and why the answer is more interesting than either the marketing or the scepticism tends to suggest.
What "functional coffee" actually means
"Functional coffee" is an umbrella term rather than a defined category. It covers any coffee sold with an added ingredient intended to do something beyond flavour and caffeine. The most visible version is mushroom coffee, which is usually instant coffee blended with powdered extracts of lion's mane, reishi, chaga or cordyceps. Alongside it sit coffees with added adaptogenic herbs such as ashwagandha, collagen blends, and protein coffees, which some of the larger chains have now moved onto their permanent menus.
Interest is real and it is not slowing down. UK search interest in both "mushroom coffee" and "lion's mane" has climbed steadily since 2021, following the pattern of a genuine shift in habits rather than a passing moment. That alone makes it worth understanding properly.
What the research says
The short version is that some of these mushrooms have been studied, a few results are genuinely intriguing, and almost none of it tells you much about the product in your cup.
Lion's mane has the most attention. The best-known human trial is a small Japanese study from 2009 in which older adults with mild cognitive impairment took lion's mane for 16 weeks and scored better on cognitive tests than those taking a placebo. There is also laboratory work on compounds that may stimulate nerve growth factor. It is a promising line of research, but it is early, the trials are small, and a review by the Center for Science in the Public Interest described the overall evidence as thin.
Chaga has much less behind it. The same review could not find a single peer-reviewed brain-health trial of chaga in people. Reishi has some immune-related data but few high-quality studies on sleep or stress, and cordyceps has shown modest effects on endurance in some exercise studies.
Then come two practical problems. The first is dose. Many mushroom coffees contain only a few hundred milligrams of extract per serving, below the amounts used in the trials. The second is what the "mushroom" actually is. A lot of product sold as mushroom is mycelium grown on grain rather than the mushroom itself, which can mean a meaningful share of the powder is simply starch. And finally, virtually no research has been done on mushroom coffee as a finished product: brewed, at a normal serving, drunk daily.
The caffeine question
Plenty of people who switch to mushroom coffee say they feel calmer, less jittery and more even through the day. We don't doubt them. But there is a simpler explanation that the labels rarely mention: many of these products contain noticeably less coffee than a standard cup, and therefore less caffeine.
If you have cut your caffeine intake and started sleeping better, that improvement may well have more to do with what was taken out than with what was added. We looked at this in more detail in our post on what caffeine actually does to your sleep. The practical takeaway is that if a calmer afternoon is what you are after, there are straightforward ways to get there: a smaller cup, an earlier cut-off, or a well-made decaf later in the day.
What the UK rules say
This is the part most coverage skips, and it is useful to know as a shopper. In Great Britain, food and drink can only carry health claims that have been formally authorised on the GB Nutrition and Health Claims Register. According to the Advertising Standards Authority, there are currently no authorised health claims for mushrooms themselves. The ASA has also indicated that some mushrooms found in these products, including turkey tail and certain species of cordyceps, are likely to be treated as unauthorised novel foods that should not be sold in the UK at all.
The ASA has also ruled that words like "adaptogen" and "nootropic" count as specific health claims, even if many shoppers are not sure what they mean. So when you see them on a UK label or advert, it tells you something about how carefully that product has been put together.
The same rules apply to ordinary coffee, including ours. This summer the ASA upheld complaints against a London coffee brand that had claimed its coffee could slow ageing and support brain and gut health. That is why you won't find us telling you coffee is good for you. It is not our place to make that claim, and it would not be allowed.
One sensible note of caution: concentrated mushroom extracts are not inert, and there are case reports of problems linked to heavy chaga use. If you take regular medication or have a health condition, it is worth speaking to your GP or pharmacist before adding mushroom supplements to your routine.
Where we stand
We are not here to tell anyone to stop drinking mushroom coffee. If you enjoy it, the ritual works for you, and you have read the label with clear eyes, that is entirely your call.
What we would say is this. Much of the appeal of functional coffee is the idea that your morning cup should be doing more. Our view is that a well-sourced, carefully roasted coffee is already doing a great deal. The origin, the farm, the processing method and the roast all shape what ends up in your cup, and none of it needs an additive to justify itself.
If you are drawn to functional coffee because you want a gentler afternoon, our Mexico Chiapas Decaf is 99.9% caffeine free, decaffeinated using water rather than chemical solvents, with the chocolate and caramel notes intact. And if you simply want coffee that tastes of where it came from, our specialty coffee range is the place to start.
Nothing added. Nothing to explain.
