Cheers! But Why Do Some Feel It More Than Others?

As we head into the festive season, gatherings, celebrations, and year-end functions often come with a familiar question — why can some people enjoy a few drinks effortlessly, while others feel lightheaded after just one?

The answer lies deep within our biology, in a remarkable enzyme called Alcohol Dehydrogenase (ADH).

The Science Behind the Sip

When you enjoy a glass of gin, your body immediately starts to process the alcohol (ethanol).

1. ADH (Alcohol Dehydrogenase) — the first enzyme in the chain — converts ethanol into acetaldehyde, a highly reactive and toxic compound.

2. ALDH (Aldehyde Dehydrogenase) — the second enzyme — then converts acetaldehyde into acetate, a harmless substance eventually broken down into water and carbon dioxide.

If this process runs smoothly, you experience the pleasant warmth of a drink without too many side effects.

But when it doesn’t, that’s when the familiar facial flushing, nausea, rapid heartbeat, and headaches can appear.

ADH and ALDH: Not the Same for Everyone

There isn’t just one version of these enzymes. Humans have several forms, called isoenzymes, which work at different speeds.

• ADH1B (previously called ADH2) and ADH1C (ADH3) are genetic variants that affect how quickly ethanol is converted to acetaldehyde.

• ALDH2, on the other hand, determines how efficiently acetaldehyde is cleared from the system.

These genetic differences explain why alcohol tolerance varies so widely among people and populations.

How Genetics Shapes Your Reaction

• East Asian populations — particularly those of Chinese, Japanese, or Korean ancestry — often have a variant called ALDH2*2, which makes ALDH2 far less effective. As a result, acetaldehyde accumulates quickly, leading to the “Asian flush” reaction: redness, dizziness, nausea, and a rapid heartbeat even after small amounts of alcohol.

• Certain populations of European or African descent more commonly carry faster versions of ADH1B, which means alcohol is converted to acetaldehyde very rapidly. If their ALDH2 is normal, they can metabolise alcohol efficiently — but if not, the quick spike in acetaldehyde can also make them feel ill.

• Others, especially in Western Europe and parts of Africa, often have balanced ADH and ALDH variants, allowing a more even and comfortable breakdown of alcohol — which can translate to better tolerance, though not immunity from the effects of overconsumption.

In essence, your body’s response to alcohol is written, in part, in your genes.

A Gentle Reminder for the Festive Season

As we raise our glasses this holiday season, it’s good to remember that our capacity to “handle our drink” isn’t about experience, willpower, or strength — it’s about biochemistry.

So whether you’re sipping a gin cocktail, a glass of wine, or a craft beer, take it slow, savour the flavour, and respect your body’s limits.

After all, the best celebrations are those we can all remember clearly the next morning.