Q: Hey Matt. Got a good topic you might be interested to discuss.
I have been eating more tofu recently but from reading your blog in the past few days I noticed your talk of anti-nutrients which I was not aware of.
I did some further research on my own and saw soy is one of the most anti-nutrient rich foods. I was wondering just how bad consuming tofu on a daily or every other day basis is? Do you have any more advice on this matter?
Also, what other veggies are best to avoid that have anti-nutrients?
A: Thanks for your question Blaine. You’re spot on with your research – tofu does contain a high-concentration of anti-nutrients (otherwise known as lectins and phytates), not to mention some other problematic elements. I’m going to get to your specific questions, but first I’d like to do a quick rundown of the issues with soy in our diet.
Why this matters for everyone
Tofu (and other soy products) have been touted as “health” foods for years in the media, (I cringe at classifying them as food because of all the processing required), especially for vegetarians looking to replace animal protein in their diets. Even if you don’t eat tofu, there’s a good chance that your diet contains more soy than you think. Soy derivatives are commonly used in processed foods. The average American can get up to 9% of total calories just from soybean oil alone! Whether you are a health-conscious tofu-lover or just an innocent bystander in the world of processed food, most likely soy IS a part of your diet. Unfortunately, there is a STRONG case against keeping soy products on your plate.
The case against legumes and soy
I don’t want to go into too much detail on this topic, as it has already been expertly covered on other sites, but the basic gist of it is this: soybeans and soybean-derived products are part of a larger food group called legumes (think beans, peanuts, etc.) which have a high anti-nutrient (i.e. lectin) content.
Anti-nutrients are proteins that bind to nutrients in the gut, preventing their absorption. Lectin in particular damages the gut lining, reducing absorption of minerals and protein, and potentially leading to “leaky gut”, where toxins and other undesirables make their way through the gut-lining into our bloodstream. This in effect negates all those healthy veggies that you are eating with your beans, and can even lead to disease besides! Lectins have potential ties to diseases such as autoimmune disease, rheumatoid arthritis, and insulin dependent diabetes. Even cancer!
Legumes are also high in Omega-6 fatty acids. If you have read up on your ancestral biology, you know that for most of our hunter-gatherer existence, we had about a 1:1 ratio of Omega-3 to Omega-6 fats. Today, that ratio is heavily skewed, sitting at 1:10 in most humans. The cause? Corn, soy, safflower, and other vegetable/seed oils chalk-full of Omega-6s.
Omega-3 and Omega 6 fats are critical in regulating inflammation in the body, and have been linked to elements of cancer, Parkinson’s, Alzheimer’s, and fertility. (Hence the recent popularity of fish oil heavy in omega -3s.) Balancing these fats is essential to maintaining health. The easiest (and best) way to do this is to eliminate the sources of excess Omega-6 fats from our diet.
Recently, Chris Kresser of “Healthy Skeptic” fame addressed some of the other negative effects of soy in his “Don’t Eat Toxins” post. I’m going to repost the appropriate section here for ease of access:
- “Soy contains trypsin inhibitors that inhibit protein digestion and affect pancreatic function;
- Soy contains phytic acid, which reduces absorption of minerals like calcium, magnesium, copper, iron and zinc;
- Soy increases our requirement for vitamin D, which 50% of American are already deficient in;
- Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women.
- Vitamin B12 analogs in soy are not absorbed and actually increase the body’s requirement for B12;
- Processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic (cancer-causing) nitrosamines;
- Free glutamic acid or MSG, a potent neurotoxin, is formed during soy food processing and additional amounts are added to many soy foods to mask soy’s unpleasant taste; and,
- Soy can stimulate the growth of estrogen-dependent tumors and cause thyroid problems, especially in women.”
(credit: Chris Kresser, thehealthyskeptic.org)
Okay, now that we’ve covered the basics, let’s get to Blaine’s specific questions.
Question 1: How often should/can I eat tofu?
A: Based on the evidence above, I’d have to honestly say “never” is a good place to start from. There are plenty of other, healthy protein sources out there, and it just doesn’t seem worth the risk to introduce something that will not only bind up nutrients in your gut, but that could potentially introduce other carcinogenic toxins into your body. Not to mention this study from Harvard showing that men who drank the equivalent of 1-cup of soy milk per day had a 50% lower sperm count (double yikes!).
Now, if you end up having some tofu with a salad/soup/meal sometime, or get soybean oil, is it the end of the world? Of course not. But I wouldn’t go LOOKING to add soy products to your diet. If it happens, it happens. Hopefully it won’t make you too sick and you can move on.
If for whatever reason you decide NOT to eat meat, then I would recommend getting some fermented soy products. The process of fermentation deactivates the lectins in soy. So if you’re in the mood for miso, tempeh, or natto, then pony up! But personally, I’d still be worried about the other side-effects of soy consumption, and I can’t imagine replacing smartly raised animal products with tempeh and natto for the rest of my life.
Question 2: Are there other vegetables I should avoid because of anti-nutrient content?
A: We briefly touch as this before, but all legumes have anti-nutrient properties and thus are best avoided. Legumes include: alfalpha, peas, beans, lentils, soy, and peanuts. Possible exceptions to this rule (ALA the Whole30 Program) are green beans, sugar snap peas, and snow peas, which are more “pod” than “bean”.
Although not a “vegetable”, I’ve also found that limiting my consumption of nuts has really helped. Nuts also have some anti-nutrients, and are high in omega-6s. Though they might not be as problematic as legumes themselves, once I started thinking of nuts as a garnish rather than a staple, my digestion got better, my energy went up, and I felt happier/healthier. Now, I like to save my nut consumption for special dessert occasions (such as almond meal treats.)
Finally, there are some vegetables with anti-nutrients in the skin – namely sweet potatoes – that I recommend skinning before eating. Sweet potatoes are an EXCELLENT way to replenish your glucose stores post-workout, and are delicious to boot.
Bonus: my n=1 experience with Tofu and soy
Here’s my own story with tofu. Before I started a fully Paleo-diet, I considered myself to be “health conscious” and tried to eat well every day. The media had me convinced of the health benefits of soy, and had tried to mix it into my meals with various degrees of success (one batch of “healthy tofu chili” in particular still haunts me to this day).
It wasn’t until I came to Japan that I had a meal where I fully replaced protein with tofu. One hour later, I was curled up in a ball on my bed with the most intense intestinal pain I’ve ever felt. I tried drinking some water but even that hurt. Three hours later, the symptoms eventually subsided, though trips to the bathroom were unpleasant for several days.
I tried my best to think of what caused that bout of intestinal grief. In my mind, tofu was healthy – I must have just used a little too much oil in the pan, or maybe it was a bad batch of broccoli? Eventually about a month later, I decided to give tofu another go — with the same result. After I finally was able to stand up from the bed, I vowed to never eat tofu again…and I haven’t. (Though admittedly, it wasn’t hard to give up.)
This is a classic n=1 experiment – the only subject was myself, and there is no way to account for all of the possible variables. That being said, knowing what I know now about soy, it’s not a far stretch of the imagination to figure out what the likely culprit was.
Still unconvinced? Why not give it a go yourself? As always, I recommend you pull it out of your diet for 30 days, re-introduce it, and see how you feel. Your own n=1 experiment is far more likely to convince you than mine, though I hope you do take the scientific literature into mind as well and don’t just go on “feel”.
Thanks again to Blaine for submitting a question, and I hope I covered all the bases. Remember you can always submit questions/topic ideas to me at firstname.lastname@example.org or through the contact page.
-Stay healthy everybody.