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Legumes = Good after all?


Guzzi

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So, I came across this article the other day about whether or not beans are good for you.

 

The paleo diet disallows legumes of any kind and the thinking behind this is (in laymens terms) that A.) some people have an intolerance to them which causes inflammation and "bad stuff", and B.) because they contain phytate acids and lectins (a form of protein) and these bond with certain vitamins and minerals, making them difficult for you body to absorb the nutrients from your food. 

 

The article above claims to debunk the second point. I'd like to make it clear, before anyone jumps on me, that I'm just sharing this with you fine people, not arguing that anyone has got it wrong. I just thought it would be interesting to see what people have to say on the subject. :) 

 

Some highlights for those of you who are to lazy to read the article. 

 

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The craziness over phytates originates from a study done on puppies and published in 1949.The study suggested that high-phytate diets prevent the absorption of calcium and other minerals, and therefore have a bone-softening effect.1 However, newer studies on humans strongly suggest that those who consume the highest amount of phytates actually have the strongest bone density 

 

 

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When it comes to lectins, there shouldn’t be any cause for concern either. There are many kinds of lectins, most of which are not toxic, and those that are toxic are neutralized to tolerable levels when beans are cooked. In particular, the lectin that receives the most attention, phytohemagglutinin, is reduced to safe levels after cooking.

 

 

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Beans contain the highest amount of resistant starch of any food. Resistant starch, although technically a carbohydrate, acts more like fiber because it’s resistant to digestion and doesn’t break down into sugar. It’s also a prebiotic, meaning that it feeds and promotes growth of probiotics - the healthy bacteria that you need in your gut.

 

 

Your thoughts please. :) 

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The most commonly mentioned issue I've heard of in regards to phytate is it's tendency to strongly bind to zinc & iron, potentially causing deficiencies - this has been fairly well documented in cultures where beans/grains make up the majority of the diet. However, the deficiencies can often be corrected by adding phytase (enzyme that breaks down phytate, prevents the mineral binding) to the meal preparation. To be fair, casein also inhibits the bioavailability of iron, and supplemental iron (ie. from pills, not food) itself can in turn reduce the absorption of zinc. IMO, if you have a zinc deficiency you can either supplement, eat more zinc heavy foods (seafood, sunflower seeds, grass fed beef, etc.) or add phytase. Bearing in mind of course that an excess of zinc can in turn affect copper absorption - huh, this nutrition stuff is complicated. ;)

 

As for lectin, as your article mentions, it's almost entirely mitigated by either cooking or sprouting (NOTE: DON'T sprout kidney beans, they can make you very very sick). Fermentation also removes many lectins - but not all. Obviously, combining methods can be the golden solution - eg. soaking, sprouting, and then cooking or fermenting. There is a small part of the population that is either A} exceptionally sensitive to lectins and/or B} have a pre-existing digestive permeability issue (eg. IBS, Crohn's, etc.) - and they may choose to limit or eliminate lectin entirely from their diets to prevent digestive upset.

 

But, for the most part, the traditional preparation methods for legumes & cereals (ie. sprouting, soaking, cooking, fermentation, nixtamalization) take out the vast majority of the nasty stuff and make everything else easier for us to digest. Which, if you think about it, is really cool how in many ways indigenous cuisines already addressed modern nutritional concerns. These 'antinutrients' are also one of many reasons why strong diversity of bioflora in our digestive systems is so important - and why a regular and varied intake of probiotics (supplementary, fermented foods like sauerkraut, etc.), prebiotics (inulin, polysaccharides, etc), and ezymes (bromelain in pineapple, papain in papaya, and countless more in sprouted & fermented foods) can help maintain a healthy microbiome & digestive system.

 

Personally, I think that as long as you pay attention to how you as an individual react to different foods & preparation methods, and ensure a good variety of nutritional sources (ie. don't eat the same thing week in week out), these concerns are mitigated. But, it still comes down to what works for each of us!

 

 

EDIT: Sorry for the rant, I actually forgot what I was originally going to say - which is that the link between phytate and bone density is still being studied. And some of the studies that suggest phytate is protective against osteoperosis are actually just researchers taking surveys to ask what people eat - for obvious reasons, any study based on self-reported intake is limited in it's application for clear and unambiguous conclusions or correlations. Personally, I think the examination is additionally confounded by the sheer number of different dietary sources of phytate, and how those interactions can cloud the true mechanisms at work (ie. maybe something else is helping or hindering, or it only works in combination with). Some studies also refute the phytate/zinc deficiency connection, typically by analysing trace amounts of zinc in fecal samples - which only tells half the tale. But then, I'm biased, because I really like beans, lentils, cereals, and other 'bad' foods (according to some paleo circles). ;) Again, nutrition is complicated - which is why it's so much fun to study! :D

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Wow! Thanks @Defining, that makes for very interesting reading.  Nutrition is indeed a very complex and interesting subject.  I find it difficult to place any faith in a nutritional belief when it's presented as "This is bad for you because of **insert singular reason here**".  There is usually so much more to the story than any one aspect, you shouldn't form an opinion based on one thing alone without taking into account any/all the evidence to the contrary.  In the case of beans and pulses there is a real weight of evidence to suggest that they are really good for you.  

 

One of the things it says in the article I posted is that "eating beans or other legumes twice a week reduces your risk of colon cancer by 50%"  Now when I read that I think - surely that's more to do with the fact that type people who eat beans twice a week are far more likely to eat a lot of vegetables and other healthy foods too???  My dad has colon cancer so my risk of developing it at some point is automatically raised but I'm not about to rush off and eat beans twice a week from now on.  I do however eat a fair amount of beans already.  

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Actually, the colon cancer link is thought to be due to the production of butyrate, which the digestive system increases in the face of higher levels of resistant carbohydrates - which in turn reduces risk markers for cancer, and can slow the development of tumours. But it does in fact have to be fairly regular consumption to maintain sufficient levels in the colon to have an effect. The studies are both rat studies with controlled intake, as well as tracking risk factors in humans when instructed to change their diet.

 

Other cancers that have been reputed to have lowered risk with bean consumption include breast (due to flavanoids) and prostrate (hypothesized due to increased fiber intake, which is not bean specific). Also really interesting, phytate supplements can apparently reduce the side affects for chemo in some patients.

 

I share your general distrust for sweeping statements about any food, which is what sparked my interest in nutrition to begin with! :D I will admit though, I have seen very little academic material to redeem consumption of more than 25g of refined sugar a day, or an excess of bleached/sifted flours, or more than 1 serving of cured or smoked foods every day. But again, I'm fully aware of where my own biases lie: whole foods (including pulses, cereals, and legumes), varied proteins (including grass fed/free range/pastured animal proteins), lots of fermented stuff, tons of veggies & fruit, and as many spices & herbs as I can get. ;) 

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I don't know man, since I'm vegan I get most of my proteins from legumes and beans. I also have some friends that study food & health topics who say that nothing is really research that extensively whether something is really that good for you, or not. One week, beans are bad, the other week, people are told to eats loads of them. 

 

Just everything in moderation (for me, sans animal products) and a general clean eating heath plan should be fine I guess.

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