Why Am I So Red?

Ever wondered why a glass of wine can sometimes leave you looking a little flushed?

Redness after drinking alcohol is surprisingly complex. While alcohol itself can cause blood vessels to dilate, there is also some interesting chemistry happening inside the body as alcohol is broken down.

And wine makes this even more interesting because it contains far more than just alcohol.

What happens to alcohol in the body?

The alcohol in wine is ethanol. When we drink it, our bodies begin breaking it down through a series of metabolic reactions.

First, an enzyme called alcohol dehydrogenase, or ADH, converts ethanol into acetaldehyde.

Acetaldehyde is a chemical compound belonging to a group called aldehydes. It is also a toxic and carcinogenic compound, which is why the body needs to process it further.

The next step involves another enzyme called aldehyde dehydrogenase, or ALDH, particularly ALDH2.

ALDH converts acetaldehyde into acetate.

The simplified pathway looks like this:

Ethanol → Acetaldehyde → Acetate

Once acetate has been formed, it can be further converted into acetyl-CoA, which enters normal energy metabolism. From there, it can ultimately be broken down into carbon dioxide and water while contributing to energy production.

So, in simple terms, the body is trying to move alcohol through a series of steps from ethanol, through the more problematic intermediate acetaldehyde, and eventually into compounds that can be handled through normal metabolism.

So why do some people flush?

For some people, genetic variations can mean that ALDH2 does not work as efficiently.

When this happens, acetaldehyde can accumulate after drinking alcohol.

This can result in symptoms including:

• Facial flushing
• Feeling hot or warm
• A racing heart
• Headaches
• Nausea

Importantly, not every person who goes red after drinking has reduced ALDH2 activity.

Alcohol itself can cause vasodilation, meaning it can widen blood vessels and increase blood flow towards the skin. Other individual factors can also influence how someone responds to wine or other alcoholic drinks.

But what about the wine itself?

This is where things get particularly interesting from a winemaking perspective.

Wine contains hundreds of different chemical compounds, not just ethanol.

One group that can be relevant to some people's reactions to wine is biogenic amines. These include compounds such as histamine and can be produced during fermentation and other stages of winemaking.

Biogenic amines can contribute to symptoms such as flushing, headaches and other reactions in susceptible individuals.

Their concentration can be influenced by a range of factors, including the grapes themselves and what happens during winemaking. Yeast and bacterial populations, malolactic fermentation, pH, grape condition, hygiene and storage can all play a role.

Grape variety can influence the chemical composition of grapes, including the availability of compounds that microorganisms can use as precursors for biogenic amines. However, it would be too simplistic to say that one grape variety will automatically make someone flush more than another. Winemaking conditions and individual sensitivity are also important.

So, when someone says a particular wine gives them a headache or makes them flush, there can be several different things worth considering..

What does this mean for alcohol and health?

There is an important health consideration when it comes to acetaldehyde.

Acetaldehyde is recognised as a carcinogen. If someone has reduced ALDH2 activity, drinking alcohol can result in greater exposure to acetaldehyde because it is not converted to acetate as efficiently.

Research has linked this increased acetaldehyde exposure, particularly in people with certain ALDH2 variants who continue to consume alcohol, with an increased risk of some alcohol related cancers, including cancers of the oesophagus and head and neck.

This is different from saying that flushing itself causes cancer. The concern relates to exposure to acetaldehyde and alcohol, particularly where acetaldehyde is not efficiently metabolised.

Wine really is chemistry in a glass

As a winemaker, one of the things I find fascinating about wine is that what we experience in the glass is the result of an enormous number of chemical and biological processes.

The grape variety, yeast, bacteria, fermentation, pH, oxygen, alcohol, ageing and many other factors all contribute to the final wine.

And then there is another layer: the person drinking it.

Two people can drink the same wine and have completely different experiences.

So, if a glass of wine leaves you looking a little flushed, there may be more going on than meets the eye.