by Patrick Holford
For many, the day doesn’t truly begin until that first cup of coffee hits the system. It sharpens the mind, lifts the fog, and gives an instant boost of focus – which explains why, in the UK alone, we drink an astonishing 100 million cups every single day, about two per person. But is this daily ritual really fuelling your brain, or quietly robbing it of long-term vitality?
Coffee is more than just a stimulant. Yes, it contains polyphenols – those antioxidant compounds that can protect the brain. But it also delivers caffeine, which fires up your adrenal hormones to give that short-term buzz. The problem is that this instant lift comes with a hidden cost: over time, it can deplete energy reserves and, more worryingly, raise homocysteine – one of the strongest predictors of dementia and Alzheimer’s.
How Much Coffee is Too Much?
So, does coffee protect against dementia – or put you at greater risk? The answer depends on quantity. A UK Biobank study involving 400,000 participants compared those drinking 1-2 cups a day with those drinking six or more cups a day and found both a 53% increased risk of dementia and smaller brain volumes in those drinking 6 or more cups. The UK Biobank didn’t measure the homocysteine of the participants, but this is the most plausible mechanism.
Yet the story isn’t entirely one-sided. A review of all studies up to 2020 concluded: “Caffeine effects were more often positive when consumed in moderate quantities (100–400 mg/day), consumed in the form of coffee or green tea, and in women.” The most recent UK Biobank findings confirmed that moderate coffee or tea drinkers had a lower risk of cognitive decline than abstainers.
A double espresso delivers 200–300 mg of caffeine, so moderation seems to mean no more than two to two and a half cups a day — and only if unsweetened.
Sweetened or Unsweetened – Does it Matter?
It matters a lot. The UK Biobank found a modest reduction in risk in those drinking up to 2.5 cups a day, compared with non-coffee consumers, but only in those drinking unsweetened coffee. Those drinking sweetened coffee had a higher risk.
This is consistent with research at Canada’s University of Guelph. Participants were given a carbohydrate snack – such as a croissant, muffin, or toast – together with either a decaf or regular coffee. Those having the coffee-carb combo had triple the increase in blood sugar levels. In addition, insulin sensitivity, the hormone that controls blood sugar levels, was almost halved. The lesson? Enjoy your coffee on its own, without sugar or a carb-laden pastry.
Don’t Drink Coffee on Waking
Timing also matters. In the first hour after waking, your body naturally peaks in cortisol, the long-acting adrenal hormone that gets you going. That is why it is probably better not to have coffee, which further promotes adrenal hormones, for at least an hour after waking. Otherwise, you may stop producing enough of your own cortisol and become dependent on the caffeine hit.
In the evening, it’s the opposite story. Cortisol should be reducing and melatonin rising, but caffeine can affect this for up to 10 hours. The results? Over time, poorer sleep, which can contribute to a whole host of health problems, and greater difficulty waking in the morning, leading to a cycle of dependency on coffee.
One cup of coffee a day, in the morning, ideally not on waking but at least 30 to 60 minutes later, seems optimal. However, the more tea you drink, the better, according to two studies, with green tea being the most beneficial. This benefit, however, was not found in a UK Biobank study, which reported tea and coffee drinking to be associated with worsening cognition compared with abstainers.
The Japanese have a tradition of making a pot of green tea and, if they want a second, simply add hot water to the teapot. I do the same with coffee – if I have a second cup I run the coffee through the filter paper again. In this way it is progressively weaker.
But let’s be honest: coffee is an addictive stimulant and, while it may not be as harmful as alcohol, it is ultimately an energy robber. Having used coffee to help me through an intense month of early mornings and book writing, I quit and experienced a severe withdrawal headache that lasted 36 hours!
In Short …
- One to two cups of unsweetened coffee a day, taken 30–60 minutes after waking, is probably optimal.
- Avoid combining coffee with sugar or high-carbohydrate foods.
- Consider switching to green tea or more weakly brewed coffee where possible for a gentler stimulant effect.
- Avoid caffeinated drinks after noon, especially if you have difficulty getting to sleep or staying asleep.
- If you rely on caffeine to function or alcohol to unwind, it may be time for a reset.