What to Know About Soy Sauce

Medically Reviewed by Christine Mikstas, RD, LD on July 10, 2023
5 min read

‌Soy sauce is a popular food used as a cooking ingredient and a condiment. 

‌Soy sauce is known as shoyu and soya sauce. It’s made with soybeans, wheat, salt, and a fermenting agent. 

The history of soy sauce goes back over 2,000 years in China. It was developed to help keep food from spoiling and add flavor to it, as salt was expensive at the time. It was introduced to Japan in the 7th century and later to Korea and Southeast Asia. It is now popular in many other parts of the world. 

‌The traditional brewing method to make soy sauce involves soaking soybeans in water for several hours and steaming them. Wheat is then roasted, ground into flour, and mixed into the steamed soybeans. Fungal spores, usually Aspergillus coryza, A. sojae, and A. tamarii, are added in and left for 3 days. 

The next step is fermentation, where a brine solution is added. This may be left to ferment for 1 month up to 4 years. For some premium soy sauces, such as double-fermented soy sauce (saishikomi shoyu), a raw soy sauce mix is added. After fermentation, the mixture is pressed to filter the solids, heated to remove molds and yeasts (pasteurized), and packed. 

The acid hydrolysis method is much faster, taking just a few days. This uses soybeans without the oil, wheat gluten, and hydrochloric acid. The mixture is heated for 20 to 35 hours to break down the proteins. 

Some soy sauces are a mixture of traditional brewing and acid hydrolysis, which makes them cheaper but less tasty. A longer brewing time means better flavor.

‌Soy sauces differ according to the country they’re made in. Japanese soy sauces use equal amounts of soybeans and wheat. Chinese soy sauces use a higher ratio of soybeans to wheat.

There are two main types of Chinese soy sauce. The more common one is light soy sauce. It’s light brown with a thin consistency. Dark soy sauce is thick and darker brown in color because of the longer fermentation time. It may also have molasses or sugar added, making it sweeter, less salty, thicker, and more full-bodied than light soy sauce.

There are five types of Japanese soy sauces. ‌

  • Dark soy sauce, or koikuchi shoyu. This is the most common type found in Japan and overseas. 
  • Light soy sauce, or usukuchi shoyu. Due to a shorter aging time, this type is lighter in color and has a milder taste.
  • Tamari soy sauce, or tamari shoyu, has very little (about 10%) or no wheat. As a result, it has a mild aroma and a darker color. 
  • White soy sauce, or shiro shoyu, has a much higher ratio of wheat to soybeans. Because of the way it’s fermented, it has a light yellow color.
  • Double-fermented soy sauce, or saishikomi shoyu, is more expensive and usually used for sushi and sashimi.

‌A 15-milliliter (about 1-tablespoon) serving of soy sauce contains:‌

  • 8.5 calories
  • 1.3 grams of proteins
  • 0 grams of fat
  • 0.8 grams of carbohydrates
  • 878 milligrams of sodium (38% of daily value)

‌Soy sauce tends to be used in small quantities. As such, it’s unlikely to have many health benefits. Soy contains isoflavones, which are compounds said to have benefits such as reducing menopause symptoms and improving cholesterol. If you’re interested in including the benefits of soy in your diet, tofu or other soy products like soy milk may be a better option.

‌‌Antioxidants in soy sauce. A study found that dark soy sauce may be high in antioxidants. Antioxidants may delay or prevent cell damage from free radicals. But as this evidence is limited, we need more studies to be sure. 

Is soy sauce high in sodium? Just 1 tablespoon of soy sauce contains nearly 40% of the daily recommended 2,300 milligrams of sodium. Salt is a nutrient that our body needs to function. But too much of it can increase blood pressure and lead to heart disease and stroke. The average American takes in more than 3,400 milligrams of sodium a day.

Allergens in soy sauce. Soy is a common cause of allergy, especially in children. Soy sauce also contains wheat, which some people may be allergic to. People who have celiac disease, an autoimmune disorder caused by eating gluten, should avoid soy sauce that has gluten. 

Most soy sauces contain wheat, but some brands produce gluten-free soy sauces. Tamari is a category of soy sauces that can be made with less or no wheat, so you should check the label for ingredients if you have any allergies. 

Soy sauce is a powerful flavor in any dish, but it’s more than just salty. This sauce typically contains monosodium glutamate, also known as MSG. This type of sodium gives soy sauce a savory flavor called umami.‌

MSG has been in the spotlight for decades. People reported negative symptoms after eating food containing MSG. 

The symptoms were probably caused by an allergic reaction to MSG or eating too much of it. Several studies have shown no direct link between MSG and those symptoms. Simply eating it in moderation as you would sodium is fine.‌

Umami is the fifth flavor alongside sweet, salty, sour, and bitter. It is a savory flavor that is often linked to meat, cheese, and certain vegetables like mushrooms. Soy sauce, made with MSG and filled with umami flavor, can be a great low-sodium flavoring option.

‌Soy sauce can be added to dishes such as stir fries, stews, or soups. You can use it as a dip, as with sushi or sashimi. You can put it in a marinade or a glaze for meats. You can also use it to season rice and noodles. Try it as a salad dressing with sesame oil, honey, and rice vinegar. There are even desserts that use soy sauce, such as soy sauce caramel and soy sauce brown sugar ice cream.