or Paleo lifestyle, sooner or later they come across the concept of ‘anti-nutrients’. Anti-nutrients are generally defined as “natural or synthetic compounds that interfere with the absorption of nutrients”. Anti-nutrients decrease bioavailability of nutrients by modifying the molecular structure, or by hindering digestion and/or absorption of foods. A real-world example of an anti-nutrient in effect would be seen in Nigeria, as stated in this study. I’ve highlighted the most important parts: “Plant protein is the cheapest source of protein available to mankind but unfortunately the protein is accompanied by antinutrients. The quantity of oxalate and tannin in acha, bambara groundnut, guinea corn, millet, sesame seed, soybean and tiger nut were chemically analyzed. The white variety of sesame seed and soybean have the highest oxalate and tannin contents of 8.25 mg/g and 0.15 mg/g respectively. Among the cereals the black and brown varieties of millet have the highest oxalate and tannin contents of 4.65 mg/g and 0.07 mg/g respectively. The presence of these antinutrients makes plant (especially legumes) protein partially available and of poor quality.”
So, in this example, we see a few typical anti-nutrients. The examples cited are oxalate and tannins. Oxalate is found in spinach and chard, and of course in the above-cited examples of cereals, soybeans, sesame seeds, etc. Tannins are found in the above-listed foods, as well as blackberries, blueberries, cranberries, raspberries, strawberries, etc. Another good primer study, can be found here. This study discusses saponins. To summarize saponins: “they occur widely in plant species and exhibit a range of biological properties, both beneficial and deleterious…many of these compounds have been characterized only during the last 2 decades.” Saponins are found in a large variety of foods. In the bean family alone, saponins are found in chickpeas, kidney beans, navy beans, soybeans and haricot beans. Quinoa also contains saponins. One interesting inclusion is oats, which have two different varieties of saponins.
Then we have glycoalkaloids. A good primer on glycoalkaloids can be found here. These are found in potato skins, as well as tomatoes. Eggplants and peppers also contain glycoalkaloids. What you’ll begin to notice, is that these so-called “anti-nutrients” exist mainly in the skin of plants, which evolved as such, in order to protect them from predatory consumption. These anti-nutrients can have toxic effects. This leads us to lectins. Lectins are a protein that bind to cell membranes. Of all the anti-nutrients, lectins are arguably the most toxic. As stated in the former study: “ingestion of the lectins present in certain improperly cooked vegetables can result in acute GI tract distress”. While lectins are in vegetables, like potatoes, tomatoes, peppers and eggplant, they are most noteworthy in grains, beans and the peanut. Peanut lectin alone is very problematic. As stated in that study: “it is possible that dietary lectins such as PNA, which bind to the TF antigen, promote cell proliferation and thus cancerous growth, while galactose-containing vegetable fiber would inhibit this effect by competing for binding by these lectins”. Peanuts are also problematic because they contain a multiplicity of allergens.
This brings us to phytic acid, or phytates. Perhaps the most well known anti-nutrient, phytic acid is found in a wide variety of foods, and not just in those foods deemed “not paleo”. Phytic acid occurs in green leafy vegetables, for starters. “Paleo friendly” vegetables such as spinach and kale. This may come as a shock to those who are ill-informed, and think that “anti-nutrients” only occur in grains or legumes. Bioavailability of nutrients is almost ALWAYS better from animal sources, rather than plant sources. This is important to keep in mind, especially if you know someone who is on a vegan or vegetarian diet. I will often have clients that have chosen these diets, and the standard low blood level tests which come back, are nearly always for iron and vitamin B12. So just remember this, the next time you are eating kale and think you’re getting all the iron listed on the packaging. You’re not.
This is due to a variety of factors, phytic acid being one of them. Phytochemicals from plants can also block absorption of nutrients and minerals. Oxalic acid is present in vegetables, like spinach. It helps to block absorption of calcium, for example. But when we look at the actual structure of phytic acid, we realize that it is simply the main storage form of phosphorus, in the organisms that have it. This list includes: linseed, sesame seed, almonds, Brazil nuts, coconut, hazelnut, peanuts, walnuts, corn, oats, brown rice, wheat, beans, chickpeas, etc. Note that many “paleo friendly” nuts have significant amounts of phytic acid.
It’s common to hear phytic acid cited as a reason not to eat grains and legumes. However, this is a somewhat flawed argument, since, if phytic acid were an issue, wouldn’t we be avoiding nuts as well? The truth is, there are lots of other reasons not to eat grains and legumes. Whether it’s the lack of nutrient-density, incomplete proteins, gluten, prolamine proteins, etc. Throwing phytic acid in the argument is somewhat foolish, and doesn’t do anyone any favors.
But say you REALLY are worried about phytic acid in some of your favorite foods. What can you do to limit it? Well, soaking is one way to go. As stated in this paper, “soaking or extracting in aqueous solutions can remove up to two thirds of the phytic acid by the action of endogenous phytase activity, but loss of minerals, water-extractable proteins and vitamins also occurs (Hurrell, 2004).” However, fermentation has been proven superior, if removing phytic acid is your goal, as seen in this paper. As stated in that paper: “a slight drop of the pH (pH value around 5.5) is sufficient to reduce significantly the phytate content of a wholemeal flour”. If one were to look at why this works, structurally, fermentation cleaves off the phosphate group.
It is interesting that ancient cultures figured this out, presumably through trial and error, and have been soaking and fermenting their foods for thousands of years. As is stated in the linked paper: “as our knowledge of the human microbiome increases, including its connection to mental health (for example, anxiety and depression), it is becoming increasingly clear that there are untold connections between our resident microbes and many aspects of physiology. Of relevance to this research are new findings concerning the ways in which fermentation alters dietary items pre-consumption, and in turn, the ways in which fermentation-enriched chemicals (for example, lactoferrin, bioactive peptides) and newly formed phytochemicals (for example, unique flavonoids) may act upon our own intestinal microbiota profile.” So we truly have come full circle, with the science now confirming what our ancient ancestors had instinctively figured out and practiced, long before we had iPads, iPhones, etc.
The paper also goes on to further cement my point, with this quote: “our Paleolithic ancestors had plenty of opportunity for the consumption of food products (for example, honey, fruits or berries, and their juices) that had been unknowingly subjected to natural microbial fermentation. Without knowledge of microbes, our ancestors recognized, over time, the palatability, preservative, analgesic, and mentally stimulating or sedating qualities of fermented foods and beverages.” This is a truly fascinating development, with current science now going on to state that 90% of your serotonin is made in your bowels. Your gut is truly your second brain.
The issue of anti-nutrients has now become more interesting since we now know that your gut can influence serotonin biosynthesis. But how does this affect the bigger picture? If you’re suffering from leaky gut, which can come about from consuming processed foods, anti-nutrients may be problematic, since you’re not getting enough nutrients to begin with. Another specialized case where anti-nutrients may be a factor, is in developing countries. As stated in this study: “proteolytic inhibitors, phytohemagglutinins, lathyrogens, cyanogenetic compounds, compounds causing favism, factors affecting digestibility and saponins…these factors are shown to be widely present in leguminous foods which are important constituents of the diet of a large section of the world’s population, and particularly, of people in the developing countries.”
But at the end of the day, are anti-nutrients TRULY something you need to be worried about? Well, if you’re eating a diet filled with foods low in nutrient density, and then those foods have anti-nutrients, which will further impede your ingestion of essential vitamins and minerals – yes. In that scenario, you are in trouble. But it is not due to the anti-nutrient content of your foods, it is due to the overall food quality, or lack thereof, in your diet.
However, if you are eating a whole foods, nutrient-dense diet, such as the Paleo diet, you have no need to be concerned about anti-nutrients. Yes they are fascinating from a food science perspective, and from a biochemical perspective, but for the average person, they are not something you should spend your time thinking about.