Coffee During the Vegetarian Festival: When to Drink It

Yes. Black coffee is made from a plant seed, so it fits the jay (vegetarian festival) diet. Watch out for dairy milk, condensed milk, and creamers containing milk protein, and watch your timing: coffee taken with a meal can sharply reduce absorption of plant-based iron. The simple fix is to drink coffee about an hour before eating, or between meals.

Can you still drink coffee during the vegetarian festival?

This year Thailand's Vegetarian Festival (jay, or 'gin jay') runs from 10 to 18 October 2026, and the same question comes back every year: what about my morning coffee?

The answer is yes. Coffee is the seed of the coffee fruit, roasted, ground and brewed with hot water. Nothing in it comes from an animal, so a cup of black coffee is jay from start to finish.

What needs checking is what goes into the cup. Dairy milk and condensed milk are clearly out. Creamers labelled 'non-dairy' deserve a second look too, because many contain sodium caseinate, a protein derived from milk. Read the ingredients list before you use one.

If you want a milky coffee, plant milks such as soy, oat or almond are the way to go, and there is an interesting story about soy milk further down.

Why does iron matter more during the festival?

Food contains two kinds of iron. Heme iron from meat is absorbed easily. Non-heme iron from plants, such as tofu, beans, black sesame and leafy greens, is absorbed less readily and is very sensitive to whatever else is in the same meal.

Picture plant iron as a passenger waiting to board a bus in your gut. Vitamin C is the friend who helps it on board. Some compounds, though, grab its hand and won't let go, and the passenger misses the bus and leaves the body unused.

Coffee contains polyphenols, the same family of compounds behind many of coffee's benefits, and they can bind to plant iron. On a normal week, meat helps make up the difference. During nine days of plant-only eating, almost all your iron comes from plants, so coffee timing suddenly matters.

How much does coffee reduce iron absorption?

The most widely cited study is by Morck, Lynch and Cook, published in the American Journal of Clinical Nutrition in 1983. Volunteers ate meals containing labelled iron, and the team measured how much their bodies actually absorbed.

One cup of coffee with a meal reduced iron absorption by 39% (tea reduced it by 64%). In a second set of tests using a standardised meal, a cup of drip coffee made absorption fall from 5.88% to just 1.64%, and stronger coffee had a bigger effect.

The most useful finding is about timing. Coffee taken one hour before a meal caused no drop at all. Coffee taken one hour after a meal reduced absorption just as much as drinking it with the meal. The habit of finishing lunch with a coffee is the one that matters most.

To be clear, this is an older, small study that measured single meals in people with normal iron levels. It does not show that coffee will make you anaemic in nine days, and healthy people need not worry. But if you know you are at risk of low iron, for example women with heavy periods, pregnant women, or anyone told by a doctor they are anaemic, moving your coffee away from meals is an easy change. If you already have anaemia, talk to your doctor before changing your diet.

So when should you drink coffee during the festival?

Based on that study, the simplest rule is to take coffee off the dining table.

Brew your first cup about an hour before breakfast, or drink coffee mid-morning and mid-afternoon, well away from meals. If you have just eaten, wait longer than an hour, because the study found one hour after a meal was not enough.

Add vitamin C to your jay meals, such as guava, orange, lime, bell pepper or fresh vegetables, to help plant iron absorb better, and eat a variety of plant iron sources such as tofu, beans, black sesame and leafy greens.

For evening coffee and sleep, the same timing logic from our article 'Why does coffee wake you up?' still applies.

Why does soy milk curdle in coffee?

If you have ever poured soy milk into hot coffee and watched white flakes appear, don't worry. The milk hasn't gone off. Soy proteins clump together when they meet heat and coffee's acidity, much like the way tofu is made.

A 2019 study from the University of Strathclyde, published in Food Hydrocolloids, looked at exactly this. It found that separation happens above a certain temperature, and that threshold depends on the ratio of soy milk to coffee. The change is reversible: cooling the drink or adding more soy milk can bring it back to a smooth single phase.

From the barista's side, a few practical tips help. Let the coffee cool slightly before adding milk. Pour the soy milk into the cup first, then add the coffee slowly. Use a barista-style soy milk if you can find one. And choose a medium-dark to dark roast, which is less acidic than a light roast. Preda's French Roast, intense yet smooth, pairs well with the richness of soy milk.

Oat milk is another popular option if you'd rather not take chances, but check the label for sugar, as many plant milks are sweetened.

What coffee goes best with jay food?

Many jay dishes are fried, stir-fried and fairly salty, and jay desserts are often very sweet. Unsweetened black drip coffee adds nothing extra on days when the food is already heavy.

Plenty of keen coffee drinkers prefer black coffee during the festival for taste reasons too: its gentle bitterness and roasted aroma cut through oiliness on the palate.

For home drip brewing, Preda Roasting House's House Blend range, such as Original Blend, is an easy everyday black coffee. For a soy latte, French Roast is a good match. If you're in Lampang, drop by Go+ Café throughout the festival 

In short, you don't need to give up coffee for the festival. Choose what you add carefully and keep coffee away from mealtimes, and you'll stay refreshed without losing the iron your body needs.

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