One of the several causes of heartburn is eating acidic foods.
Since soy sauce is an acidic food, with a pH usually ranging from 4.5-5.5, soy sauce can cause heartburn in some people.
If you’d like to understand why soy sauce affects acid reflux and possibly how to prevent it, read on.
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Acid Reflux 101
Acid reflux is typically used interchangeably with heartburn.
It happens when the valve that separates the throat and stomach doesn’t close when it should, so stomach acid can come back up, and it burns. Heartburn doesn’t have anything to do with the heart, despite the name.
GERD is simply a disease that’s essentially a more intense, more frequent, and long-term version of acid reflux.
Minor cases of acid reflux can be managed at home as you figure out which foods trigger it for you, but GERD requires professional medical care to treat.
Certain foods and other variables can interfere with the seal that keeps stomach acid in the stomach, which leads to heartburn.
Common Causes of Heartburn (and Where Soy Sauce Fits In)
The causes of acid reflux vary substantially among individuals. It can depend on genetics, weight, lifestyle habits, and diet.
The most common causes are:
- Eating highly acidic foods
- Eating large meals
- Not chewing foods well
- Consuming fatty foods
It’s clear that soy sauce can only potentially cause heartburn through the first mechanism. Acidic foods like tomatoes are often triggers for heartburn, and it turns out that soy sauce is quite acidic.
How Acidic is Soy Sauce?
The more acidic a food is, the more it’s a problem.
When you ferment foods, they produce acidic byproducts like alcohol and vinegars. Since soy sauce is made from fermented soybeans (and sometimes wheat), it’s not surprising that it’s an acidic food.
Soy sauce includes multiple acids in the final product, including: lactic acid, oxalic acid, tartaric acid, malic acid, and more (source).
Fermented foods are acidic, alcohol
What’s the pH of Soy Sauce?
Most soy sauces have a pH in the range of 4.4 to 5.5.
In a blog post by Kikkoman, the most well-known soy sauce manufacturer, they state that it has a pH of 4.8, which likely reflects their own products.
Other research shows that most soy sauce has a pH around 5, up to a pH of 5.5 (source 1, source 2).
If you need a refresher, water has a neutral pH of 7.0 (in theory at least). Any value lower is acidic. Since pH is a log scale, soy sauce is quite acidic.
It’s clear that soy sauce is acidic enough to cause heartburn in people sensitive to acidic foods, especially if consumed in large servings.
Can You Still Have Soy Sauce If You Get Heartburn?
If you find that soy sauce gives you heartburn, you may still be able to have it, but you obviously need to make some adjustments.
Things you can try to reduce the risk of acid reflux (or reduce severity) include:
- Eat soy sauce along with alkaline (basic) foods – For example, nuts, vegetables, and legumes. Many Thai recipes mix soy sauce with peanut butter, which reduces the acidity of the meal.
- Add a teaspoon of baking soda to soy-based sauces – Just like above, this reduces the overall acidity without much affect to the taste.
- Chew better
- Eat smaller portions
- Don’t lie down within an hour or two of eating
- Lay on your left side if you need to lie down (due to the shape of the stomach, it limits any leaking)
If you do most of these things, you may find that having some soy sauce with your meals is fine.
You also want to keep in mind that there are other triggers of acid reflux like fatty foods, so avoid eating these close together with acidic foods like soy sauce.