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Anti-nutrients in Whole Grain Foods: Friend or Foe?

This post was prompted by an email from a past participant of our Dietitian’s Guide to Weight Loss nutrition course. She had recently read a popular new book opposing the current ‘sugar is evil’ media mantra. But this book made a surprising recommendation. The author advised us to choose refined grain foods over whole grain foods, due to the presence of ‘anti-nutrients’ and ‘defensive substances’ in whole grains. Hmm.. not exactly in line with what Dietitians and other nutrition professionals are currently recommending! Let’s take a look at why:

Legumes- source of phytate

Legumes- source of phytate. Are anti-nutrients good bad or indifferent?

What are Anti-nutrients?

Anti-nutrients are compounds in foods that interfere with absorption of another nutrient in some way. The most common naturally occurring anti-nutrient is phytic acid (sometimes referred to as ‘phytate’), and it’s actually a type of fibre. Anti-nutrients like phytic acid aren’t exclusive to whole grains either. All plant foods contain them. Especially legumes and nuts. 

Why would anyone be worried about anti-nutrients?

The confusion about these compounds is understandable. Phytate, for example, binds with minerals like iron, zinc, and copper to form complexes that we can’t absorb from our gastrointestinal tracts. Presence of things like phytate is part of the reason why people who choose a vegetarian diet are advised to aim for a higher intake of these necessary minerals!

But it’s definitely not a problem for us, because humans have already adapted to these compounds and figured out how to get enough of the minerals we need. The most important thing to realise is that all of these minerals already compete for absorption with each other, regardless of any anti-nutrients we also consume. If you can think back to high-school chemistry (eek, that’s nearly 20yrs ago!) and picture the periodic table, all the elements with a ‘2+’ above them are called ‘divalent cations’. Divalent cations share a type of transporter that scoops them up from our intestine and lets them into our bloodstream, and an excess of one mineral will compete with the others.

Fortunately, we have a lot of backup methods to keep enough of each mineral coming in. So, a normal healthy person should be able to ‘upregulate’ absorption of any minerals they need more of. I.e., we can turn up the dial and make those alternative absorption methods work harder, whenever it’s necessary. This might happen because we’ve started eating more plant foods with more phytate (awesome!), or it might be because our stocks are running low. E.g., losing iron due to a bleeding stomach ulcer, or using more due to pregnancy.

Now for some anti-nutrient benefits…

Firstly, whole grains, legumes and nuts are some of the best sources of fibre. And on average, Aussies generally don’t get nearly enough of it! In fact, many of us only just reach around 20g fibre per day. But, the amount thought to be adequate for most adults is 25-30g per day, and there is plenty of research to support benefits from higher intakes still. Especially when it comes to preventing many chronic diseases.

Not surprisingly then, it also turns out that higher intake of phytate has been associated with lower rates of chronic disease like type 2 diabetes and heart disease, as well as lower rates of some cancers. Maybe this reduced risk is really due to a more plant-based diet in general, rather than the phytate itself (the research doesn’t look very conclusive on this, and it’s notoriously difficult to separate effects of single nutrients on health in the context of the whole diet).  It is thought, however, that phytate itself may have an anti-oxidant effect. And we know that when anti-oxidants come from foods (but importantly not when they come from supplements- antioxidant supps can have the opposite effect), they do lower rates of heart disease.

So I hope that clears up any confusion, but of course if there’s anything else I can explain, drop me an email any time. And feel free to share using the buttons at the top and bottom of this page.

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