Fact Check: Does Soy Cause Inflammation?

Soy is said to promote inflammation in the body. We look at whether soy products actually have a pro-inflammatory effect and should therefore be avoided in chronic inflammatory diseases, or whether the opposite might be the case.

Soy is said to promote inflammation

Soy products such as tofu, tempeh, edamame, soy drink, and soy yogurt are very versatile and can complement a healthy plant-based diet very well. Not everyone shares this opinion. And so one reads and hears again and again: “Soy promotes inflammation”.

Usually, several reasons are given for the supposed pro-inflammatory potential of soy products. We address each of these reasons below. You can read the individual claims in the four main headings (1st to 4th) in quotation marks. In the text below we address these claims:

Soy is pro-inflammatory because of the lectins it contains

Soy critics write that soy contains lectins that attack the intestinal walls, then enter the bloodstream and lead to a variety of inflammations. The source given on the Paleo page is a short blog article by Dr. called file. However, it does not mention soy at any point. Because it’s all about wheat and the wheat-specific lectin (WGA, wheat germ agglutinin), which is considered aggressive and heat-resistant.

Indeed, raw and unprocessed soybean contains lectins. You would actually damage the gut if you were to eat this soybean fresh from the field. But nobody eats raw and unprocessed soybeans.

Soy lectins are broken down during cooking

Unlike wheat lectin, soy lectin is not heat resistant. It is inactivated when processed into tofu, soy drink, etc. Soaking and then heating to 100 degrees Celsius — which is common when making soy products — can completely remove the lectins, not just in soybeans, by the way, but also in other legumes (e.g., kidney beans and lupins).

Since 1983, studies have shown that it is enough to boil the beans until they are soft enough to eat. This cooking time is more than sufficient to completely neutralize lectin activity, the researchers wrote in the study at the time.

Two other studies from 1989 and 2018 found the same thing, namely that soaking and cooking soybeans destroys more than 99.6 percent of the lectins present.

Soy lectins and fermentation

The above anti-soy article also claims that Asians have no problem with soy because they eat less soy “than you might think” and because they “eat most of the soy fermented”. During fermentation, most of the lectins and phytates would be removed.

Lectins can also be broken down by fermentation. That’s correct. However, as we have just explained, the statement that fermented soy products are better because they contain fewer lectins than non-fermented soy products is incorrect.

Soy phytates are not a problem

We have already explained in point 12 of our comprehensive main article on soy that phytates (phytic acid) in soy products are also not a problem. Please read there. There you will also find concrete quantities of how many soy products are consumed on average in Asia (although it must of course always be taken into account that THE Asians and the one typical Asian soy consumption do not exist. Asia is huge and includes many different countries and population groups with different eating habits!).

Soy is pro-inflammatory because of its fatty acids

The next reason for the supposed pro-inflammatory effect of soy products is said to be the fatty acid composition in soy products. Yes, soy would even have a “directly pro-inflammatory effect” due to its fatty acid composition, soy critics explain. Because the fat in soy consists of “95 percent pro-inflammatory omega-6 fatty acids”, which disturbs the sensitive balance with the anti-inflammatory omega-3 fatty acids.

Omega-6 fatty acids are not necessarily bad!

At this point, we would like to point out straight away that the omega-6 fatty acid in question – linoleic acid – is an essential fatty acid. This means that it cannot be produced by the body itself, so it has to be supplied with food and is absolutely necessary for many processes in the body (e.g. as components of cell membranes).

The linoleic acid or the omega-6 fatty acids are not bad per se and also not automatically pro-inflammatory. Yes, there are even studies showing that high intakes of linoleic acid can be very beneficial to your health.

On the other hand, there are initial indications that show that it is obviously dependent on the genes whether one reacts with increased inflammatory processes to excessive linoleic acid consumption or not.

The intelligent solution is not to consume too many omega-6 fatty acids and at the same time ensure a good omega-3 supply – and this is exactly where soy products can help, as you will soon find out.

Only 53 percent of omega-6 fatty acids

Now let’s look at the fatty acid composition of the soy fat/soy oil. According to our source, tofu (100 g) contains 8.7 g of fat (which of course can vary depending on the manufacturer and the type of tofu). The fatty acid pattern looks like this:

  • 1.25 g saturated fat
  • 1.6 g monounsaturated fatty acids
  • 4.6 g omega-6 fatty acids
  • 0.63 g of omega-3 fatty acids
  • (the missing approx. 0.6 g are glycerin and lipoids (fat-like substances))

This means that the fat in tofu is not 95 percent omega-6 fatty acids, but only 53 percent. The same goes for pure soybean oil, of course.

Do soy products contain too many omega-6 fatty acids?

The soy critics on the aforementioned Paleo page cite a study from 2006 as the source of the inflammation-promoting effect of soy products due to their fatty acid composition, but this does not deal with soy products or soy oil. It is, however, a study that warned against an excess of omega-6 fatty acids in general (including arachidonic acid, an omega-6 fatty acid found in animal fats) and recommended a lower omega-6 Aim for a 6-omega-3 ratio in your diet.

Even Professor Dr. Astonishingly, Stephan C. Bischoff, director of the Institute for Nutritional Medicine at the University of Hohenheim, writes on Eatsmarter that due to the high omega-6 content in soy products, one must ensure a balance with omega-3 fatty acids.

However, the meta-analysis cited by him as a source states something different. It is about the typical American diet, which u. a. is very high in omega-6 due to the large consumption of corn oil. For this reason, various studies have increased the omega-3 content and looked at how this change affects cardiovascular risk.

Do you know how some of these studies increased the amount of omega-3 in the diet? Some used cod liver oil. In others, however, people were given soybean oil instead of their usual corn oil.

Soybean oil has a good omega-6 to omega-3 ratio

As you can calculate yourself from the fatty acid composition above, soybean oil/soybean fat has an omega-6-omega-3 ratio of about 7:1. This is almost as good as the ratio in walnut oil (4:1) or hemp oil (5:5). 1), both of which are considered recommended oils precisely BECAUSE of their good fatty acid composition.

FYI: corn oil has a ratio of 83:1 (30), and sunflower oil is 278:1. So, so soybean oil contributes to a significantly better fatty acid ratio than many other commonly used oils.

What do you actually think of pumpkin seeds and pumpkin seed oil? Both can help with benign prostate enlargement, irritable bladder, and hair loss and even reduce the risk of breast cancer. Both are considered very healthy and hardly get bad reviews. But pumpkin seed oil has almost no omega-3s at all, and the omega-6 to omega-3 ratio is 102:1, which is even worse than corn oil. Conclusion: Never reduce food to just one aspect! Always look at it holistically!

Comparison: Omega 6 in soy and animal foods

Above we mention arachidonic acid, an omega-6 fatty acid found exclusively in animal products. However, while plant-based foods do not contain arachidonic acid (only linoleic acid), animal-based foods also contain linoleic acid in addition to arachidonic acid.

To get an overview of the arachidonic acid and linoleic acid content (per serving), we have put together a selection of foods for you here:

  • 245 mg in 50 g pork liver (and 230 mg linoleic acid and 150 mg omega 3)
  • 230 mg in 100 g fried chicken (and 2,050 mg linoleic acid and 241 mg omega 3)
  • 170 mg in 1 tablespoon of lard
  • 120 mg in 50 g of tuna
  • 115 mg in 50 g liver sausage
  • 55 mg in one egg (about 60 g)
  • 30 mg in 125 g lean pork escalope (and 177 mg linoleic acid and 25 mg omega 3)
  • 14 mg in 50 g Emmental (45% fat)
  • 8 mg in 200 g yogurt (3.5% fat)

Plant foods do not contain arachidonic acid. Here is a comparison of the linoleic acid content in soybean oil and tofu:

  • 5 mg in 1 tbsp (10 ml) soybean oil (and 0.7 mg omega 3)
  • 9.2 mg in 200 g tofu (and 1.26 mg omega 3)

As you can see from the list above, the omega-6 content of tofu is in the middle, even at the bottom of the list. Animal products, therefore, contain significantly more omega-6 fatty acids – depending on their fat content, of course. However, due to the relatively high omega-3 content, the omega-6-omega-3 ratio is not much worse than that of soy products. It’s about 8:1 to 9:1.

It must be noted, however, that it is the arachidonic acid that can have a direct pro-inflammatory effect. Linoleic acid itself is not pro-inflammatory. It is only considered a precursor from which the human body can produce arachidonic acid in several steps.

Linoleic acid is much better than thought

Now one might think that the more linoleic acid is eaten, the more arachidonic acid is formed and the more inflammatory processes occur. But this is not the case. Even if you reduce your linoleic acid intake by 90 percent, your blood arachidonate levels will not change. It’s the same the other way around: increasing your linoleic acid intake by 6 times doesn’t change arachidonate levels.

However, linoleic acid alone does not increase inflammatory markers, according to a 2012 review of several studies on the subject.

Conclusion: Linoleic acid is not nearly as bad as is often claimed. However, soy products contain very little linoleic acid anyway, so this aspect does not really need to be discussed in connection with soy.

Soy is pro-inflammatory because it contains trans fats

The next argument of soy critics is that soy products are always heat-treated and also low in antioxidants (such as vitamin E). The fats in soy products would oxidize due to the heat and the simultaneous lack of antioxidants, resulting in free radicals and even trans fats.

A study from 2005 is given as proof, which deals with trans fats and the resulting increased cardiovascular risk. The entire study is not about soy products such as tofu, tempeh, soy milk, soy yogurt, etc. Rather, the participants in the study were asked about the fats and oils they use for baking and frying and which margarines they use.

Tofu contains 0 percent trans fats

During production, tofu is heated for up to 10 minutes at 100 to 110 degrees Celsius. Trans fatty acids cannot be produced in this way. Therefore, tofu also has 0 percent trans fats. You would have to let the soybean through the extruder to potentially produce trans fats. The study is about soy flakes. But even these are no longer produced in the extruder in high-quality today but rolled.

Extruded soy products (soy granules, soy chunks) are also extremely low in fat. In addition, since – just like in margarine production – careful attention is paid to the trans fat content these days, extruded soy products should no longer pose a problem here, but we will check this more thoroughly.

Soy is rich in antioxidants

As far as the accusation of lack of antioxidants or vitamin E is concerned, tofu with 0.6 mg of vitamin E (per 100 g) with a daily requirement of 13 mg does not actually contain an excessive amount of it. A lean pork schnitzel does not contain very much vitamin E at 0.4 mg.

Since people like to rely on game in the Paleo diet, we looked for roast venison (medium fat), which contains even less vitamin E (0.13 mg). At 0.2 mg, the leg of wild boar is also not exactly a good source of vitamin E. It has to be offal, which in the form of the beef liver with just under 0.7 mg of vitamin E contains slightly more than tofu.

However, on the one hand, vitamin E can be consumed through other foods and, on the other hand, it is not the only antioxidant in existence. Because the secondary plant substances in particular – which are found in large numbers in soybeans and soy products – are very powerful antioxidants. Only the antioxidant potential of soybean oil is not good, but this is not about soybean oil.

Meat contains hardly any antioxidants

Compared to soy products, meat contains very few antioxidants or only those that are still present in the meat because the animal in question consumed plant foods rich in antioxidants. On the whole, however, the oxidative stress that the meat causes in the body of the consumer predominates, especially in the case of lavish meat consumption.

At best, the oxidative stress is reduced by the spices and herbs used to prepare the meat and, of course, by the vegetables and salads that are eaten with it, if they are eaten with it. So why shouldn’t you eat something that doesn’t cause so much oxidative stress in the first place with all the good vegetables and salads – e.g. e.g. tofu?

Soy damages the liver by causing inflammation

A mouse study in which the animals were fed either coconut oil, soybean oil, or fructose is cited as further evidence of the supposedly pro-inflammatory potential of soy products. “The liver of the soybean oil group was literally eaten away by the inflammation,” write the soybean critics.

However, the animals in the soybean oil group received 40 percent of their daily energy requirement in the form of soybean oil. For a person with an energy requirement of 2000 kcal per day, that would be 800 kcal in the form of soybean oil, which would correspond to almost 100 ml of soybean oil per day.

Apart from the fact that almost only genetically modified soybeans are used in the USA and the oil used could also have been a GMO soy oil, the effects of such a large amount of isolated soy oil can of course not be compared with the effects of tofu, tempeh, Compare soy milk or another food.

The higher the soy consumption, the rarer a fatty liver

If one examines the influence of the soy products mentioned on liver health, then it even shows – according to a study from 2020 – that fatty liver developed less often in people with higher soy product consumption. Animal studies have already shown that soy protein and soy isoflavones increase antioxidant capacity and improve insulin resistance, which in turn improves fatty liver or prevents it from developing at all – according to relevant scientists.

Soy milk improves liver function and reduces inflammation

In 2019, a clinical study was published in which 70 patients who already suffered from non-alcoholic fatty liver were asked to eat a calorie-reduced diet. In addition, half drank 240 ml of soy milk daily. The other half did not consume soy milk and just followed the diet.

After 8 weeks, liver function test results (ALT) had more than doubled in the soy group compared to the soy-free group. The inflammation value (hs-CRP) also fell by 1.32 mg/l in the soy group, compared to only 0.36 mg/l in the soy-free group.

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