Interview: The Place of Soy in the Health Food Arena

Originally published in 2013, updated in January 2022

Health & Beyond editor Josh Day recently sat down with Dr. Kim to ask him a few questions on a topic that's always hot in the health food world. We're talking about soy... what it is, what it does in your body, and why you see soy this and soy that on almost every aisle of your local health food store.

Let's jump straight into the interview, shall we?

Josh: What exactly is soy?

Dr. Kim: Soybeans are legumes - they look like peas in a pod, but they're larger. Soybeans are rich in protein, omega-3 fatty acids, tryptophan, fiber, iron, and a bunch of other minerals.

All of the soy products on the market today - soy milk, tofu, soy sauce, miso, tempeh - they're made using soybeans, and in most cases, additional ingredients are added.

Josh: What’s up with everything we hear about fermented and unfermented soy?

Dr. Kim: Foods made with fermented soy are thought to be healthier than those made with unfermented soy. Examples of foods made with fermented soy are miso, tempeh, and naturally brewed soy sauce.

Tofu and soy milk are examples of foods made with unfermented soy, although sometimes, tofu, once it’s made, is fermented to produce fermented tofu dishes in East Asian cooking – mostly Chinese.

Josh: Is soy as good for you as many in the health food movement would have us believe?

Dr. Kim: To me, soy is just another food. I think that you can eat soy and be healthy, but you don’t need to eat it to be healthy.

Josh: In health food stores you see "soy" everything -- soy milk, soy dairy, etc. Many people, especially vegans, consume soy as if it were oxygen. They think they're doing their body good but perhaps they're not?

Dr. Kim: Right, I think the most important point here is that it’s best to eat a variety of foods. Anytime you eat too much of one specific food, especially if that food is rich in protein, you may increase your risk of eventually becoming intolerant to that food. I’ve seen this happen to people with soy milk, tahini, almonds, and a number of other protein-dense foods.

Lots of processed foods made with soy – like meat-substitutes – they’re made with soy protein isolate, which is a highly processed food that can’t be as good for us as soybeans that are minimally or naturally processed.

Fermentation is a “natural” type of processing that doesn’t have the potential to hurt the nutrient value of soybeans the way that high temperature processing techniques do.

I think I know what you’re getting at with this question. Some people become vegan and turn to soy cheese, soy burgers, soy hot dogs, soy nuggets, soy ice cream, soy yogurt, soy everything to feel like they aren’t depriving themselves of foods that they enjoyed in the past. The vast majority of these highly processed foods are made with soy protein isolate and preservatives, and in my opinion, they’re no better than French fries, donuts, and regular fast food fare.

Josh: Is "soy" milk or "soy" cheese any better than, say, the bottled parmesan "cheese" that comes in a cardboard can?

Dr. Kim: Soy milk - if it’s made with whole, organic soy beans and it’s not sweetened - I think can be a healthy food choice. But again, the key is to drink it in moderation. A cup or two of good soy milk a few times a week in your smoothies or on your cereal is fine, in my opinion. Soy milk that is made with soy protein isolate and/or has added sugar, even if the sugar is from a “natural” source, like evaporated cane juice, is probably no better for us than Tang. In fact, if it’s made with soy protein isolate, it‘s probably worse than Tang, because with Tang, you aren’t getting highly processed protein into your system.

Soy cheese – my understanding is that some brands of soy cheese contain casein, the protein found in animal milk. And casein is problematic for a lot of people. If you’re going to eat soy cheese, I would say to pick a brand that is casein-free and made with soy milk that is made with whole, organic soy beans. And again, I would recommend eating it in moderation, say a couple of times a week at most.

Parmesan cheese – I don’t know much about how the parmesan cheese that comes in a cardboard can is made, so I can’t say how healthy a food choice it is. What I can say is that any food that is made with pasteurized milk isn’t a great choice because it contains casein that’s been heated at a high temperature. I think that Dr. T. Colin Campbell of The China Study believes that there’s a strong association between casein intake and risk of different types of cancer and other degenerative diseases. I tend to agree with this, but I can’t say the same thing about raw dairy products. Casein that is unheated and found in milk that comes from a healthy animal that is allowed to live in a natural setting may be just fine – just look at groups of people out there – mostly Caucasians – who live long and healthy lives with raw dairy as staples – this includes different types of cheese made with raw dairy.

If you’re asking me to compare soy cheese that is casein-free and made with soy milk that is made with whole, organic soy beans vs. Parmesan cheese that’s grated fresh from one of those big cylindrical blocks made with raw milk, then I think the answer just depends on each person’s physiology.

For me, being of Asian descent, soy cheese is probably a healthier choice than Parmesan cheese. And for you, being Caucasian, assuming that you aren’t lactose-intolerant, fresh Parmesan cheese is probably the better choice. Just so you know, I don’t eat soy or dairy cheese. Well, sometimes, I get a bit in some food at a restaurant, but this probably happens about once a year at most.

Josh: Do you use soy products in your home? If so, what kinds, and do you believe there is any health benefit?

Dr. Kim: Sure, we use den jang, which is the Korean version of miso – it’s a paste that’s made with fermented soy beans. We get it from a Korean market in Toronto in a big tub. It’s made in Korea with organic soybeans. Mostly, we use it to make den jang soup, which is made by boiling onions, zucchini, spinach, and sometimes some mushrooms in vegetable broth, and adding some of the paste after the vegetables are ready and the heat is turned off. You have to smear the soybean paste along the sides of the pot to get it to blend in with the rest of the soap. Or what Margaret does is she holds a medium size strainer in the soup and uses a spoon to push the den jang through the strainer as it dissolves into the broth.

We also use soy sauce – we usually use Kikkoman – it’s naturally fermented for several months.

When we use soy sauce, we use just a bit, just to add a little flavour. You know you’ve used too much if you wake up the next morning with a swollen face. I did this once when I lived in Korea.

Naturally fermented soy sauce and den jang are rich in friendly bacteria, and den jang is rich in protein, iron, tryptophan – all of the nutrients that I mentioned before are in soybeans – I guess those are the health benefits. Oh, and soy sauce, if it’s made properly, is extremely rich in naturally occurring antioxidants – it’s a much richer source of antioxidants than most types of red wine.

Josh: I love fried rice. A lot of people don't know fried rice is simply cooked rice, white or brown, stir fried in a wok or hibachi grill with soy sauce. Now, I've heard soy sauce is not good for you. Is this true?

Dr. Kim: I think that it mostly depends on the brand that you use. Some companies make soy sauce by boiling soybeans for a day before adding color and artificial flavors – some of these brands contain MSG or compounds that very closely resemble MSG.

Most brands of soy sauce are pretty high in salt, so it’s best to use small bits at a time. People who have health issues that are exacerbated by significant salt intake should probably avoid soy sauce.

Also, a few years ago, a government agency in the U.K. found that some brands of soy sauce contained dangerous amounts of a couple of different chemicals. The thing is, these chemicals were found in brands that were made with the short-cut method. Bottom line: if you use small amounts of a high quality soy sauce that’s been fermented over several months, I think this is fine for most people.

Josh: How prevalent is soy in Korean cooking? I see soy sauce in Japanese and Chinese food all the time.

Dr. Kim: I think that it’s used about as often as we use it. Den Jang (miso) is used to make soup, which is probably eaten a few times a week in most Korean homes. Soy sauce is used to add flavour to some dishes, almost always in small amounts. Soy sauce is also used as a part of marinades for various meat dishes. Ah, and tofu – we sometimes add little cubes of tofu to our soups, and sometimes, Koreans will make a separate side dish with tofu – sometimes cooked, sometimes raw with a sauce that’s made with soy sauce, sesame seeds, and green onions.

Josh: What's the relationship between soy and MSG?

Dr. Kim: My understanding is that quality brands of naturally fermented soy sauce don’t have added MSG or MSG-like compounds. Cheaper brands use hydrolyzed vegetable protein, which behaves like MSG in the body.

Unless you’ve been eating foods with MSG for a long time, it’s likely that your body will let you know whenever you eat something that has added MSG or an MSG-like substance. Some of the more common symptoms that people experience after eating MSG are pounding headaches, heart palpitations, sweating, a flushed feeling, nausea, weakness, and shortness of breath.

Several people have told me that they tend to have really crazy dreams whenever they eat MSG – this makes sense, as MSG is considered an excitotoxin that can rapidly stimulate brain tissue. Bottom line: if you use a high quality, naturally fermented soy sauce, and you use it sparingly, you probably don’t have to worry about getting MSG from soy sauce.

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Note from Ben Kim: Eating large amounts of unfermented soy products on a regular basis is likely harmful to human health for a variety of reasons, including high phytate content and possible contamination with Aluminum.

Some in the anti-soy camp point to the potential that soy has to be an "endocrine disruptor," while others in this camp believe that the phytoestrogen content of soy can increase one's risk of developing breast cancer.

To the best of my knowledge, there are no definitive studies in the peer-reviewed, indexed body of literature that offer conclusive proof to back up these anti-soy claims. I find some of these claims to be in the alarmism zone - for example, to say that any food is an "endocrine disruptor" is a generalization that doesn't mean anything to me, as every food that we eat and every thought that we think technically disrupts our endocrine systems.

As I mentioned in this interview with Josh Day, I feel that it is prudent to eat foods - including soy - in moderation. And I do feel that it's better for human health to eat fermented forms of soy over unfermented varieties.

The bottom line for me is that I know enough healthy Korean and Chinese folks in their 80's and even their 90's who have long enjoyed den jang (miso) and tofu to believe that including some soy in one's diet is fine for most people. If you enjoy soy, my advice is to eat the best varieties available to you in moderation, and to be filled with peace and compassion as you eat it.