Soy Sauce

Health Benefits
(Source: World's Healthiest Foods, George Mateljan)

Overall Nutrient Benefits, Including Great Antioxidant Benefits

Thanks to the unique soy sauce fermentation process, this food is a rich mixture of nutrients not typically present in as concentrated amounts in other foods. Peptides from proteins (smaller and often bioactive protein "building blocks"), oligosaccharides and polysaccharides from carbohydrates (smaller starch-like components) and other fermentation-based nutrients are characteristically present in soy sauce. These breakdown components from protein and carbohydrate provide us with immune system, digestive system, and cardiovascular support.

Soy sauce also contains many different types of antioxidants. It is a good source of the mineral antioxidant manganese. It also contains valuable amounts of antioxidant phenolic acids including vanillic, syringic, coumaric, and ferulic acid. Isoflavonoid antioxidants in soy sauce include glycitein, daidzein, genistein, and genistin. (It's worth noting here, however, that the soy sauce production process may sometimes involve steps that lower the concentration of these isoflavonoids significantly and leave soy sauce with a much lesser concentration than other soyfoods.) Interestingly, some studies have shown more phytonutrient antioxidant density in soy sauce than red wine! In terms of its antioxidant benefits, soy sauce also appears to have a special ability for decreasing formation of hydrogen peroxide in the body. Since formation of hydrogen peroxide can be involved in unwanted oxidative stress, this special ability on the part of soy sauce may be an important antioxidant benefit. However, researchers have yet to determine exactly how soy sauce works to decrease hydrogen peroxide formation.

In our food rating system, we classify soy sauce as a "good" source of protein. But soy sauce actually deserves special mention in this protein category, since it ranks 9th among all of the World's Healthiest Foods in terms of protein density. In other words, if you obtain one gram of protein from soy sauce, it will cost you fewer calories than if you try to obtain one gram of protein from more than 100 other WHFoods. The protein density of soy sauce is actually greater than the protein density of animal foods like lamb, fish like salmon, or soybeans themselves!

Possible Digestive Tract Benefits

The unique fermentation process used to produce soy sauce may bring with it a long list of digestive tract benefits. First is the breakdown of large protein and carbohydrate molecules into smaller units, including dipeptides or polypeptides from proteins and oligosaccharides or polysaccharides from carbohydrates. This breakdown of proteins and carbohydrates would typically be carried out in our digestive tract by chemicals, enzymes, and bacteria. By carrying out breakdown through food fermentation, there may be less work needed in our digestive tract and that decreased "workload" may be helpful to our digestive tract under various circumstances.

Fermentation of soy sauce is also known to produce higher concentrations of oligosaccharides which support the growth of "friendly" bacteria in our large intestine. Here's how that process works: some of the micro-organisms involved with soy sauce fermentation contain enyzmes that can break apart unique fibers (hemicelluloses) found in soybeans. When these hemicelluloses are broken apart, oligosaccharides are produced, and these oligosaccharides can help support the growth of lactic acid bacteria including Lactobacillus bulgaricus and Streptococcus thermophilus. These bacteria in turn help us obtain nutrients from food and provide for chemical balance inside of our large intestine.

Fermented Soy Foods and Vitamin K

Even though soy sauce is often fermented with the help of bacteria, as a general rule, Bacillus bacteria are not used in soy sauce fermentation. An exception to this rule involves the production of some Korean-style soy sauces, which do make use of Bacillus bacteria to help with fermentation.

From a health standpoint, one of the reasons why Bacillus bacteria - and especially one species called Bacillus subtilis - are so interesting is their ability to create a form of vitamin K2 called menaquinone-7 (MK-7). Vitamin K (in all forms) is an important nutrient for bone health. Sufficient intake of vitamin K is associated with decreased risk of osteoporosis, since this vitamin is involved with maintenance of bone mineral density and also with shaping of bone structure (through gamma-carboxylation). In the case of MK-7 (the form of vitamin K produced by Bacillus bacteria, and a member of the vitamin K2 menaquinone family), we know that higher levels of MK-7 in the blood correspond to lower risk of hip fracture in older Japanese women, and that higher MK-7 levels correspond to increased intake of soy foods that have been fermented with Bacillus bacteria. One fascinating aspect of Bacillus-fermented soy foods is the potential ability of these bacteria to stay alive in our lower intestine after these foods are consumed. We've seen one study in which 1.6-20 million Bacillus bacteria (per gram of feces) were found to remain alive up to 6 days following consumption of natto (a sticky form of whole soybeans that have been fermented with Bacillus bacteria). If Bacillus bacteria from fermented soy foods can remain alive in our digestive tract, they may keep providing us with vitamin K benefits many days after their consumption.

If vitamin K is a nutrient of special concern in your meal plan, you may want to consider Korean-style soy sauce as a preferred choice. However, we still recommend that you contact the manufacturer to determine what information is available about fermentation and vitamin K content, since Korean-style soy sauces are not always fermented with the help of Bacillus bacteria.

Other Health Benefits

Health benefits from soy sauce appear likely in several additional areas, even though these areas lack a large number of studies specific to soy sauce.

Immune and inflammatory system support from soy sauce is likely to come from its unique concentration of polysaccharides. Researchers have already identified at least one mechanism of action involved with this immune system support. Some polysaccharides within the carbohydrate family of molecules can lessen the activity of an enzyme called hyaluronidase. Overactivity of this enzyme is associated with increased inflammation and also with increased likelihood of allergic reaction. By lowering its activity, soy sauce polysaccharides may be able to lower the chances of an allergic reaction. The presence of unique polysaccharides in soy sauce appears to make soy sauce one of the least allergy-triggering forms of soy.

In this area of immune and inflammatory system support, preliminary studies suggest that soy sauce polysaccharides might be able to lower our risk of seasonal allergy symptoms. In these preliminary studies, small groups of students were given supplements containing soy sauce polysaccharides and were determined to experience fewer seasonal allergy symptoms following 4-8 weeks of supplementation. Students in the studies were given soy sauce polysaccharide supplements rather than soy sauce itself, with the polysaccharide content of the supplements being equivalent to approximately 2 ounces of soy sauce each day. Without additional studies involving soy sauce itself, we can't know if soy sauce will provide the same benefits as these polysaccharide supplements. Still, this research appears to point in the direction of immune and inflammatory system benefits from soy sauce as a food.

There has also been some preliminary research to suggest possible soy sauce benefits for prevention of type 2 diabetes. For soy foods in general, there is an association between dietary intake and risk of type 2 diabetes. This association makes sense because a major problem in the development of type 2 diabetes is loss of function in the beta cells of the pancreas which manufacture insulin. This loss of function is sometimes due to a process called "apoptosis" in which the cells undergo a type of pre-programmed shutdown. Intake of many different food phytonutrients can lower the risk of apoptosis in certain cells, and included in these phytonutrients are the isoflavonoids naturally present in soybeans. These interrelationships between soy isoflavonoids, pancreatic cell function, and type 2 diabetes make soybeans a logical choice for decreased risk of type 2 diabetes. However, in the specific case of soy sauce, these interrelationships don't make the same degree of sense because the soy sauce production process can sometimes lower the amount of isoflavonoids to a level far below the amount present in most other soyfoods. For this reason, the jury is still out in this area of potential health benefits.

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