Friday, August 23, 2013

Anti-nutrients: And Why I Don't Eat Peanut Butter



Let me start by saying that I've eaten my fair share of peanut butter in my time. I used to love the stuff. It's cheap, high energy and one of those universally delicious foods (like bacon), that makes everything taste amazing. 

So if you love the stuff and don't want some really bad news or don't care that much about optimizing your health then I would stop reading right now! 

If you're still reading, I'm going to explain why I avoid peanuts and peanut butter these days.

Peanuts are phonies! 
Contrary to popular belief, peanuts ARE NOT NUTS. They are LEGUMES. They are the seeds of a plant pod, which grows UNDERGROUND. This basic fact should probably start to make you suspicious about these shady characters already. 

Nuts are the fruits (shell + seed) of trees, and thus grow above ground. Nuts are typically encased in very hard shells to protect them not only from the elements but from predators. (More on that later). 

The fact that peanuts are an underground legume and often cultivated in rotation with cotton plants (whose production uses the most pesticides of any crop) also probably says something about their potentiality for toxicity.

The DL on lectins...
There has been a lot of arm-flapping in the Paleo sphere about anti-nutrients in grains and legumes, and this is often cited as one of the main reasons to avoid them. 

An aside into evolution...
The other argument against grain and legumes is that agriculture is relatively recent (10-15,000 years) in terms of our evolution (2.5 million years) and that we likely haven't had enough time as a species to PROPERLY and FULLY adapt a tolerance to grains and legumes. 

In some cases it is possible for humans to adapt relatively quickly when it comes to a single gene mutation such as lactase enzyme persistence - which today is present in 99 percent of the Dutch but zero percent of Native Americans or only 2 percent of Thais (Flatz, 1987; Kretchmer, 1972). 

In studies of the DNA of human remains from 7,000 - 8,000 years ago in Northern Europe, none had lactase persistence at that time, which suggests that almost an entire population evolved this genetic mutation in just a few millennia (Kresser, 2012). 

However, for the human species to adapt to thrive on grains and/or legumes it would take a fairly complex genetic adaptation across numerous genes, which would require a much longer period of time (Kresser, 2012).

Now I'm not saying that evolutionary adaptation to certain foods is the be all and end all argument for the Paleo diet. It would be crazy to only eat food that we are fully adapted to as this would exclude the possibility of finding new sources of nutrition. 

The human species wouldn't have survived if we weren't capable of adjusting our diet to our surroundings and finding new sources of food. 

I mean, I eat a ton of dark chocolate and coconut oil, which certainly weren't food options to cavemen, but are highly nutritious and well tolerated foods that make me look, feel and perform well.

Nevertheless, the fact that our health continues to deteriorate as our reliance on grain agriculture and industrialized foods grows does suggest that many of these modern foods are detrimental to our health. 

It makes sense that eating real foods that we have been eating for tens of thousands of years makes us thrive, while eating processed foods that have only existed a few hundred years or less makes us sick, fat and die.

Anti-nutrients… are they really that evil?
Dr Loren Cordain, author of 'The Paleo Diet' has made a massive deal about anti-nutrients, such as lectins in legumes, as being a serious concern to health due to a variety of mechanisms. 

My cursory understanding of anti-nutrients is as follows: 
[warning: I am completely paraphrasing here and am not claiming to fully understand the science behind this]
  • anti-nutrients, for example phytic acid (present in nuts, seeds and grains) bind to minerals such as calcium, magnesium, iron, copper and zinc and prevent the absorption of these minerals in the body. So while "healthy whole grains" may contain reasonable levels of micronutrients such as iron and zinc, the argument goes that the anti-nutrients also present in these foods prevent the absorption of the nutrients, making those foods either not healthy or even harmful. 
  • furthermore, other anti-nutrients, for example lectins (a sugar-binding protein found in legumes), tend to cause a lot of irritation to the gut lining, can potentially penetrate the intestinal wall entering the blood stream and causing all kinds of havoc due to the subsequent immune response - whereby these protein molecules are attacked by the body as foreign invaders, resulting in inflammation - potentially systemic and chronic - and leading to diseases such as leaky-gut, other gastrointestinal issues and even auto-immune disease. Leaky-gut syndrome has been linked to a host of serious diseases, from rheumatoid arthritis to autism and even depression (Kresser, 2013). 

Sounds pretty bad right? Well, let's go a little deeper (said the actress to the Bishop). The first issue, where anti-nutrients bind to nutrients and prevent their absorption does seem to be a valid concern, but probably not as bad as Dr Cordain has made out. 

You see, most of Dr Cordain's studies were conducted in vitro and not in humans. Effectively he fed RAW legumes or pure isolated proteins to animals and yes, it was very harmful. But we don't tend to eat raw legumes or grains. In fact if you were to eat raw lentils or wheat right off a stalk you would get very ill. Try it!

Importantly, many anti-nutrients such as phytates and lectins are broken down either during preparation (e.g. washing and soaking legumes), cooking and digestion. That is, heat destroys most of these harmful proteins (Lalonde, 2012).

Furthermore, while anti-nutrients from grains and legumes were made out to be these bad ass ninjas that go around binding to every nutrient you've consumed for the whole day this doesn't seem to be the case. From what I've read, the anti-nutrients in foods only affect the absorption of nutrients in that particular food and don't necessarily interfere with other (free) nutrients already in your system. 

So it's not like if you eat one piece of bread you are going to not absorb and zinc, iron and magnesium for the whole day. 

However, if you get a substantial proportion of calories from grains and legumes at all of your meals (and most people following a Standard American Diet do) the chances are that anti-nutrients could become a legitimate concern and you may well become deficient in some of these key minerals. 

The fact that such high proportions of Americans are deficient in these four key minerals (zinc, iron, magnesium, calcium) when they seem to be getting at least the daily recommended intake from all these "healthy whole grains" definitely supports this hypothesis. 

To address the second point - the role of lectins in gastrointestinal issues, leaky gut and systemic inflammation - these proteins can be nasty buggers if they manage to escape from your digestive tract and enter the blood stream. 

However, given that they stay where they belong or are effectively broken down by cooking or digestion, which they seem to be in most healthy individuals, they probably aren't the devil incarnate. 

Lectins are present in nearly all plant food and some animal foods. Think of them as a protective toxin to prevent plants being eaten. Unlike animals, plants can't run away or hide from predators (although that would be totally awesome if they could!) so they need other means of defense. Enter anti-nutrients. 

I mean if you were a peanut plant and you wanted to have lots of baby peanut plants wouldn't you protect your seeds (peanuts) at all costs? Peanut shells are pretty flimsy and they also grow just below the ground so any ground-dwelling rodent could easily scratch them out of the ground, chew through the shell and eat them.

So what do you do to stop those dirty rats eating your babies? You evolve toxins that make animals sick when they eat them - peanut lectins… I told you those peanuts were shady bastards, didn't I?

Unfortunately for them (and us) those peanuts didn't realize how delicious they were when roasted and crushed up with salt, so we eat them anyway. However, peanut lectin in particular seems to be uniquely harmful to humans. Here's why:

Unlike most lectins which are broken down by heat, food preparation or digestion, peanut lectins remain intact - even when roasted. 

This explains why peanuts are especially allergenic and irritating. Peanut lectin is one such lectin that is not deactivated by heat and survives digestions, making its way into the bloodstream (Lalonde, 2012).  

It has been well researched that "if you have people eat raw or roasted peanuts and you look at the level of lectin that goes into their blood within one hour of consuming those peanuts, you see the lectin levels rise" (Lalonde, 2012).

So now it kind of makes sense how a seemingly innocuous, tasty little peanut can cause even lethal allergic reactions in the worst case scenario.

Of course, every human is different and some people will react more than others to peanut lectin. Many people may not react in any noticeable way to peanuts. If you are one of these people then I'm not necessarily telling you to quit peanuts for good. But I certainly don't think that they should be something you consume often. And to clarify, peanuts are legumes and are therefore NOT Paleo, lectins aside.

There are far more nutritious options than the shady peanut that are less harmful or even beneficial in moderate quantities. 

Almonds, for example, are a far better choice. And I would argue that almond butter is even more delicious than peanut butter. Macadamias are probably the best choice, if only they weren't so expensive! 

As I've mentioned in other posts though, don't go nuts on the nuts and nut butters though, please! Most nuts are very high in pro-inflammatory omega-6 fats and should be treated as a condiment, not a meal option! A cake made of three cups of almond flour may be "Paleo" but it is definitely NOT healthy!

My take away from the peanut story...
Anti-nutrients such as lectins are probably not something that you need to worry about if you follow a Paleo/Primal diet, in most cases. It seems that one exception to this is peanut lectin, which seems to be one of the most potentially harmful lectins commonly consumed.

Put it this way: you certainly won't be any less healthy by avoiding peanuts completely. There are far better options. And if you do continue to eat them in great quantities, that's totally on you. Just don't say I didn't warn you about these shady bastards!

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References:

Flatz G (1987). "Genetics of lactose digestion in humans". Adv. Hum. Genet. 16: 1–77. PMID 3105269.

Kretchmer N (1972). "Lactose and lactase". Sci. Am. 227 (4): 71–8. PMID 4672311

Kresser, C (2012). 'What Science Really Says About the Paleo Diet - With Mat Lalonde', Revolution Health Radio Podcast Transcript, 13 June 2012, http://chriskresser.com/rhr-what-science-really-says-about-the-paleo-diet-with-mat-lalonde [Accessed 26 May 2013]

Lalonde, M, PhD (2012). 'What Science Really Says About the Paleo Diet - With Mat Lalonde', Revolution Health Radio Podcast Transcript, 13 June 2012, http://chriskresser.com/rhr-what-science-really-says-about-the-paleo-diet-with-mat-lalonde [Accessed 26 May 2013]

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