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The Truth About Flax and Other “Superfoods” & “Toxic” Foods

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Quick Summary tl;dr

Whether a food is “super” or “toxic” depends almost as much on you as it does on the food.

The exceptions may be ultra-processed foods, sugar, and processed seed oils. But are these even true foods?

The words “superfood” and “toxic” are intended to be attention grabbing. That’s the game content producers often need to play to be effective.

Consider “superfoods” good options that many people might want to consider including their diets. They aren’t requirements.

Beware fear mongering about real foods. It’s usually not helping the big picture.

Table of Contents

There are a lot of claims in the low-carb nutrition and health media about amazing “superfoods” that will transform your body and health. In reaction to the superfood sensationalism, there are an equal number of fear-mongering blogs about the dangerous properties of certain "so-called" health foods.

This post isn’t about selling you on any particular health food, but instead helping you to understand:

  • Whether a food is “super” or “toxic” depends as much on you as it does on the food itself (with some exceptions).
  • Bloggers and authors choose to use these polarizing terms because they are part of playing the media game.

Whether a food is “super” or “toxic” depends almost as much on you as it does on the food itself (with some exceptions).

Flaxseed and Flax Meal

Flaxseed is commonly promoted as a “superfood.” It contains certain micronutrients like magnesium, manganese, and thiamin. It is among the richest vegetarian sources of omega-3 fatty acids. And it contains loads of fiber with almost 0 net carbs.

But all these super claims come with caveats. The phytic acid in the flax can bind up minerals, like magnesium, making them less available to the body. Yes, flax is rich in omega-3, but the type of omega-3 it contains is short-chain ALA, which is inferior to long-chain EPA and DHA. Flax is certainly rich in fiber, but a high-fiber diet may not be desirable for all people. (Kok-Sun Ho et al, 2012)

But wait! It gets messier. The phytic acid won’t bind up all the micronutrients found in flaxseeds. The ALA omega-3 can be minimally converted into EPA and DHA, a process that can be enhanced by curcumin, which is found in the “super-spice,” turmeric. ( Aiguo Wu et al, 2015) Plus, certain foods that you might eat alongside flax alter ALA metabolism. Sesamin in sesame, for example, blocks the conversion of inflammatory omega-6 fats into inflammatory molecules at the enzyme delta-5-desaturase, without impairing ALA conversion to EPA/DHA (we'll have a blog about the "superfood" sesame coming soon...)

Maybe you can start to see how complicated even the smallest niche of nutrition science can be and why words like “Super” and “Toxic” often don’t capture the full picture.

Other Low-Carb “Super” and “Toxic” Foods

Honestly, one could make an argument that any superfood is actually a toxin in disguise.

Cauliflower is loaded with vitamin C, amazing! Cauliflower is also rich in raffinose, which can irritate many people’s guts. Salmon is a great source of long-chain EPA and DHA, plus it’s loaded with the astaxanthin and vitamin B12! Oh, but fish can contain mercury, which is a heavy metal. Liver is the superfood, with no other food coming close in terms of nutrient density! Oh, darn. Liver contains enough vitamin A that were you to eat it every day you could risk vitamin A toxicity.

Certainly, I think some arguments have more validity than others (and personally will always hail liver over acai) but the point remains: all foods have pros and cons.

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It’s About You and Bioindividuality

When it comes down to it, whether a food is super or toxic depends on you as an individual.

Are you sensitive to phytates, oxalates, and lectins? If so, there are probably certain plant foods you should avoid. Are you plant-based and prioritize fiber? If so, maybe flax and chia and avocado are great options. Or maybe you’re animal-based. If so, best eschew the ruffage for a ruminant.

Also consider what the “superfood” is doing in your diet. Are you using flax meal to replace white flour? Good for you! Even those who may criticize flax as a fake superfood would probably admit that it’s the lesser of those two “evils” (irony intended)…

Beware the Fear Mongering

A little lesson in psychology: fear spreads fast. A fear-mongering post is more likely to capture your attention and spread like wildfire on the internet. Therefore, there is an incentive for media personnel to use negative and inflammatory language.

You can easily look for it. Does the title have negative terminology like “not” “don’t” or “fake”? Do you see a lot of exclamation points or capital letters around negative words or phrases? It doesn’t take a genius to observe when someone is intentionally trying to be inflammatory.

More often than not, the fear mongering is overblown. Take flax as our case in point. I’ve seen claims implying that that flax is carcinogenic because it contains phytoestrogens. True, flax is rich in phytoestrogens and if this is a concern to you are free to set that as a nutritional priority and avoid the seed altogether. But, as always, the issue is more complicated…

Phytoestrogens come in many flavors. Some mimic estrogen and others compete with estrogen and other change estrogen metabolism in ways that might be good under some circumstances and bad under others. The main phytoestrogens made in the body from flax are enterolactone and enterodiol, both of which are anti-estrogenic, and studies in animals suggest that flax may help to reduce tumor cell growth in combination tamoxifen, an estrogen modulator used to treat breast cancer. ( Calado A. et al, 2018)

Most importantly, I am aware of no studies showing that eating flax causes cancer. Not one.

A little lesson in psychology: fear spreads fast. A fear-mongering post is more likely to capture your attention and spread like wildfire on the internet. More often than not, the fear mongering is overblown.

The Truth About Flax and Other “Superfoods” & “Toxic” Foods

The “Toxic” Exceptions: Ultra-Processed Foods, Sugar, and Industrial Oils

Lest I leave myself vulnerable to the obvious criticism, there are at least three exceptions of foods that either are, or border on being, “toxins.” Ultra-processed foods (UPFs), processed sugar and vegetable oils have no place in a human diet.

Whether that be an Oreo cookie or a BOOST Sooth “Balanced Nutrition” drink, these “UPFs” are unnecessary at best. In my opinion, UPFs aren’t even food but are better classified as hyperpalatable edible synthetic substances.

Processed sugar is another exception that has no role in a healthy human diet. And, it is everywhere. Take the example from above. BOOST Balanced Nutrition contains 65 grams of net carbohydrates and no fiber but has only 15 grams of sugar from cane sugar. Where are the other 50 grams? The first ingredient after water is brown rice syrup, which contains 65-85% of the highest glycemic index sugar, maltose. But, legally, brown rice syrup doesn’t need to be labeled as sugar. Hmm?

Most processed vegetable and seed oils are also on my personal “best avoided” list. Their fragile omega-6 fats are overrepresented in modern diets and are usually already highly oxidized by the time they get to your home. Importantly, they serve no function that’s not better served by an alternative fat source.

But just because I like to imagine your head spinning, I’ll note exceptions to the exception! Avocado and olive oil are not vegetables or seeds. Macadamia and hazelnut oils are low-polyunsaturated fat oils and contain as much or more monounsaturated fat than olive oil. And sesame oil contains certain compounds that stabilize the omega-6 fats, increase fat burning beta-oxidation enzymes, block the production of inflammatory prostaglandins, and increase heat stability. I personally avoid UPFs, sugar, and most processed seed oils, but that it not to say even these issues aren’t somewhat complicated.

Ultra-processed foods (UPFs), processed sugar and vegetable oils have no place in a human diet. UPFs aren’t even food but are better classified as hyperpalatable edible synthetic substances.

Am I a Hypocrite? Some Transparency…

As a PhD scientist, I try to be measured and precise in my language as much as possible. When I’m writing a scientific paper or giving a professional lecture, I avoid language like “superfood” as if the word itself were toxic.

But I’ve come to realize this moderate approach doesn’t entirely translate to lay public education. When you have knowledge that you think can help people and want to compete with the nutrition nonsense that is propagated in the news, you may decide to start a Twitter account or write a book. This is what I did because I wanted, and want, to help people.

What I quickly discovered is that Twitter’s character limit doesn’t leave space for nuance. At the same time, the competition for attention on a platform built for quick satisfaction essentially requires exclamation points, emojis, and sometimes exaggerated claims or implications. Every time I put out a Tweet, I try to balance the positive educational impact against the lost nuance. Sometimes I miscalculate, but I try my best. In my experience, it has also been interesting to observe how reasonable some of the sensationalists on Twitter are when you have to chance to have a conversation with them in person.

Book writing, to my surprise, can be just as much of a negotiation. I can tell you from personal experience writing our cookbook, that I needed to agree to use terms with which I myself wasn’t entirely comfortable, including “superfood.” But it was that or no book. Publishers have the power. So, what am I to do? Compromise with respect to a bit of sensational language with respect to liver, salmon, olive oil, and dark chocolate or walk away from the opportunity to generate content that I believe can help people. What would you do?

The bottom line is, I get it. I do. But I also think that there is a difference between promoting potentially healthy options to people and fearmongering. The former increases the set of tools available to people to make improvements in their lives (take the flax for flour substitute), while the latter just creates negativity and, usually, fights against the greater purpose of the low-carb, ketogenic diet, and metabolic health movement. If we are in-fighting, we are divided and distracted.

Is flax the enemy, or is it that 60% of American’s calories come from ultra-processed foods and our society is addicted to sugar and ultra-processed foods? ( Steele E.M. et al, 2016)

The Truth About Flax and Other “Superfoods” & “Toxic” Foods

What Do I Do? What Should You Do?

At the present time, I eat a mostly animal-based low-fiber diet. I love big omelets, liver, and seafood. I also adore my homemade macadamia nut oil mayo, guzzle high-quality olive oil as if it were water, and treat myself once or twice a week to a whole fat rack of slow-cooked pastured pork ribs topped with crumbled Roquefort cheese and a mix of sesame and olive oil. (For the inevitable haters out there, my labs look great, with no insulin resistance, oxidative stress or inflammation to speak of and a triglyceride to HDL ratio of 0.34.)

But what I eat now is probably entirely different than what you should eat. As a PhD and metabolic health practitioner (MHP), I’ve worked with a diverse group of individuals, some of whom do well on plant-based low-carb and other who do well on carnivore. Some people do better with targeted carbs, and others with intermittent fasting.

Personally, I’m not a proponent of a low-fat diet for metabolic health as I believe that style of eating is counter to our biology, but I also know there are some who would disagree with me. We’d probably rage against each other on Twitter, but I’m also happy to have a real respectful discussion as well.

I don’t know what you should do. So, when you read anything that I or others produce that makes strong claims, I encourage you to consider these options, not requirements. There is no “superfood” that is absolutely required in any diet. Oh, and keep an eye on the fear mongering. It can be exciting, but it usually doesn’t help.

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Comments (16)

Would you recommend taking the flax seed out of the multi seed cracker recipe, replacing it with another seed?

Hi Kate, I would not recommend substituting the flax meal in the crackers. The closest alternative would be chia seeds which might work well but I haven't tried that. If you want to use almond flour (or nut flour in general), the recipe would need to be modified as the dough would be too fragile and would not bind well. If that's something you want to try, I suggest you try adding 1-2 egg whites. I hope this helps!

Thanks Martina. I love those crackers and I think the amount of flax is really nothing to be too concerned about, so I will keep them in. Also, I cut these into bite size pieces, so I get lots. Yum 😋

Oh my god thank you, what a refreshing read! Sometimes it feels like I'm constantly being patronized by crazies who learn from sensationalist websites. The same people often believe that foods are just a sum of nutrients... I think Michael Pollan calls it that "nutritionism". If only it were that simple.

Nick you are amazing!

Thanks Sonia! Tell my mother? ;)

Years ago, in a blog far, far away, I read that "there are no superfoods--just foods."

I have a t-shirt that says “Carb Wars: Ketones Strike Back” ;)

This is different from what I've read about flax. I've been avoiding it mainly due to cancer running in my family. I don't believe it's carcinogenic but what do you think about people who are already undergoing cancer treatment or have an increased risk of developing it (genetically)? How about cooking with flax? Would you only recommend eating it unheated? Thank you!

I wouldn't be concerned about eating flax because of cancer. As noted in the article, there isn't evidence to support this claim. There are also hyperbolic leaps from mechanistic speculations. No strong evidence based on which to change your behavior if I were you. But, I you want to have a long deep talk with your oncologist - should you seek one out - you can get their take based on specific genetic polymorphisms and/or cancer types. IMO, if you want to not irritate a tumor then cut the sugar and refined carbs first, not flax. Sugars (at least spot solid tumors) love sugar. That's clear. There's also evidence that ketones can help shrink tumors. So if you're in ketosis with flax it's probably better than being eating a typical mixed diet with sugar and no flax. That said, flax is also not a necessary food so eliminate it if you want. I don't typically eat flax because it provides nothing to my diet not better provided by another food. So, for me as an individual, it's neither toxic nor a superfood. It just is a food. I don't fear it or have any personal affinity for it. If you like it, eat it, if you don't then don't. Given the high ALA content of flax I wouldn't heat it too much. A little bit of flax meal in a baked item is fine.

Thank you Nicholas, I did not expect you to reply in such great detail! There's so much scare talk about flax and vegetables in the keto community... People are taking extreme measures when they don't need to. It's good to get things into perspective. Keep up the good work!

My pleasure KJ! I aim to reply to every comment or message directed at me always until time absolutely becomes limiting. It’s the greatest privilege to be able to disseminate knowledge or options that I think could help people. My only ask ever is that if I live written something you think could help someone you know that you consider sharing. -Best, Nick
P.S. have set aside 6 hours 4-10 am to reply to the 213 personal emails follow-up publication of this in Boston Health News yesterday. Looking forward to every minute and keystroke. 😊

Excellent write up Nick. Just keep doing what you are doing. Give people the evidence as you know it, share what has worked for you and others and keep stressing the that UPF stuffs should not be included in any diet.  April

Thank you April. Will do.

Wow. This is novel. I can honestly say I’ve never read a nutrition blog like this. It’s refreshing. Thank you. I wish other doctors and nutrition influencers could be so forthcoming and honest. - with gratitude

Always my goal to be honest. Thanks for this Rucker. - with gratitude