Beans and Paleo Dieting?

“What about beans?” is a frequently asked question by many just learning about Paleo dieting and nutrition. Some people seem puzzled about the mention of beans when told what foods to avoid on a Paleo-style diet. Often they had heard that “beans are good for you” and are not sure of the rationale behind the Paleo / Primal / Cave-man diet aversion. 

If one is “orthodox” Paleo, then the answer is pretty straightforward. Dry beans are a Neolithic food that became a common food only after our Paleolithic ancestors abandoned hunter-gathering and became farmers. It is avoided simply because it is not a Paleolithic food.

Some people are not totally orthodox though and do make exceptions for certain Neolithic foods. Butter and cream are allowed by some people for example. Others might allow white polished rice or potatoes with the idea that these are “clean” choices. Others might allow tomatoes and peppers. Some of the same arguments used to “justify” the inclusion of these foods on a paleo-friendly diet plan can also apply to beans (though not necessarily all legumes).

Moving past the orthodox view, a frequent argument against beans is the presence of lectins and phytic acid (saponins and insoluble fiber could be argued as well). These same arguments, though, could apply to Night Shades (potatoes, tomatoes, peppers) and the non-gluten grains (rice, corn) that are sometimes consumed by less orthodox paleo practitioners. These arguments may sometimes even be stronger against these other foods. 

(This represents my own personal view on the matter, though not likely a common one among Paleo practitioners, and my viewpoint is always subject to change with additional information and more learning.)

Lectins

Many in the paleo world looking for a scientific rationale behind avoiding certain foods have latched onto lectins. Grains, legumes, dairy, and nightshades contain lectins. So too, though, does some paleo food like some fruit, vegetables, nuts, and seafood. This “lectin rationale” can become strained when certain lectin-containing Neolithic foods are allowed and some are not.

Lectins are a class of sugar-binding proteins found in many plants and some animal food, and while their study in humans is pretty sparse, certain kinds of lectins are known to be bad for you. For example, the chemical warfare agent ricin is a lectin derived from the castor oil plant. WGA (wheat germ agglutinin), a lectin in wheat, does seem particularly problematic because it can mimic insulin in the body. In general there does seem to be some tendency to vilify the whole class of lectins based upon the actions of specific ones.

Lectins can bind with the intestinal wall, and some may be able to pass into the blood stream. Each type of lectin has a very specific binding though; Different lectins will have different physiological effects, and not all lectins are necessarily bad for you. Many lectins are not well studied in humans, so in many cases it is difficult to access the true risk. Often the general fear of lectins is rooted in speculation based upon the effects of specific lectins being translated to all lectins in general. An advantage to dealing with bean lectins is that there actually have been some scientific study on the issue, and it appears that proper cooking pretty effectively destroys the lectin.

Phytohaemagglutnin is a lectin found in various types of beans (and especially high concentration in red kidney beans) that can be toxic. If the beans have not been properly cooked, food poisoning like symptoms such as diarrhea can occur, typically lasting for a few hours. Long term effects in humans are not well studied. In some instances, improper cooking (such as a slow cooker) is worse than no-cooking as partial cooking will liberate (but not destroy) more lectins that were bound-up in the food.

Proper cooking does, however, seem to remove the lectin problem in beans. Some lectins are resistant heat, but the main lectins in beans do seem to respond well to typical cooking. This may have to do with the fact that for beans to become tender and edible, it does require intense or long term cooking. Hard boiling pre-soaked beans for just 15 minutes seems to remove all detectable lectin activity. This study showed that lectin was below detectable levels after proper cooking (boil at 100 C for 15 minutes or 2 hours at 80 C). Canned beans are pressure cooked, and this study found no lectin activity in canned navy beans. 

So in regard to lectins, it does not appear that properly cooked beans are any more problematic than other “reformed” paleo foods like boiled potatoes and polished rice or even strictly orthodox paleo (but lectin-containing) foods like some vegetables, fruits, nuts, and seafood. It is not clear that foods like potatoes or rice are cooked enough to destroy their lectins like it occurs in beans, and some lectin containing foods may not be cooked at all. Science might eventually reveal a more substantial problem with lectins in beans, but for right now the “lectin rationale” appears pretty weak for avoiding beans when one allows other lectin-containing foods.

Phytic acid

Phytic acid is the other compound that is frequently mentioned in the case against beans. It binds with certain minerals and prevents those minerals from being properly absorbed in the intestines which can lead to mineral deficiencies over time. Seed, nuts, and grains are the most common places to find phytic acid, but even potatoes and sweet potatoes contain it, though in smaller quantities.

Phytic acid is more difficult than lectin to remove in beans. Traditional cultures were apparently aware of the problem and developed various strategies to remove phytates. Even in modern times it is common to soak the beans before cooking. One study suggested that soaking in warm water (140 F) achieved the best phytate reduction, even at only 3 hours. Some recommend at least 18 hours if the water is room temperature. In general, soaking (without a starter) will remove around 50% (very loosely) of the phytate, though it can vary between types of beans and other factors. There are various ways to possibly improve on this, including using a starter to encourage phytase activity (an enzyme that breaks down phytic acid), germination, and fermentation. These links discuss these methods in more detail:

http://wholehealthsource.blogspot.com/2010/05/traditional-preparation-methods-improve.html

http://www.westonaprice.org/food-features/1893-living-with-phytic-acid.html

(explore both of these site for more interesting and useful information)

This study had an interesting finding. Storing the beans for 5-6 years before cooking reduced phytic acid levels by 94% to 98%.

The Wikipedia entry for phytic acid has a table that lists the phytic acid content for various foods. Google Books has this table for beans from Phytates in cereals and legumes by N. R. Reddy.

Phytic content of beans range around 0.26% to 2.78% depending upon the type of bean and other factors. The median values for many of the beans appear to be a little over 1% or so. A 50% reduction via soaking would bring the phytate content of many beans down to around 0.60% as a very, very loose average.

According to the Wikipedia chart, polished rice has phytate content of 0.14 to 0.60% (so a rough average of 0.37%). Polished rice has a generally lower phytate content, but not by a whole lot (0.37% to 0.60% based upon very loose “averaging”). Phytate content will vary by bean and other factors as well. From the table in the Reddy book, California Small White Beans for example has a phytic acid content of 0.26 to 1.03, so a 50% reduction via soaking would bring it down to 0.13 to 0.52%, which is actually lower than polished rice.

Looking at nuts though, brazil nuts ranged from 1.97 to 6.34% and almonds ranged from 1.35 to 3.22%, so this orthodox paleo food is generally higher in phytate than unsoaked beans.

The phytic acid argument against beans is a little stronger than the lectin argument, but advanced prep techniques and/or bean selection can put beans near polished rice in terms of phytic acid content. Bean phytate content in most cases will still be above that of polished rice and tubers, so if one were to make beans a staple of a diet, it would probably be worthwhile to learn the best techniques and bean varieties to minimize phytate.

Occasionally eating pre-soaked beans is probably pretty similar in terms of phytate to occasionally having nuts, avocados, chocolate, or double helpings of rice or tubers.

 Saponins

Saponins are another compound found in beans that some may argue that prevents beans from being “reformed” like polished rice on a less orthodox paleo approach. More research is required on this though, and I may come back to this later. Some actually promote saponins as beneficial compounds, whereas Dr. Cordain at least calls them toxins when talking about those found in potatoes. Though again, if one is willing to allow saponin-containing potatoes on a paleo-friendly diet plan, then the argument against saponin-containing beans becomes more complex.

Insoluble Fiber

For those skeptical about insoluble fiber, polished rice and potatoes do have an advantage over beans in this respect. More research is required though I think in accessing insoluble fiber.  Nuts for example, an orthodox paleo food, can be high in insoluble fiber.

Interestingly, while the Polyp Prevention Trial (PPT) failed to find any benefit from high fiber foods as a general class, dry beans do seem to be the only subgroup so far analyzed from the PPT data that showed a reduced risk of colorectal cancer.

 Conclusion

Again, from an orthodox paleo viewpoint, the question of beans is pretty easy – they are Neolithic and should be avoided. For those less orthodox who might allow potatoes, polished rice, tomatoes, peppers, avacodos, and other Neolithic foods as part as their diet, the arguments against beans in terms of lectins and phytic acid can sometimes be kind of weak.

Lectins – no lectin activity in properly cooked beans, so less than or equal to potatoes, rice, nuts, certain vegetables, and certain seafood.

Phytic acid – pre-soaked beans have a fair amount more than potatoes, a little more than yams, tomatoes, and polished rice, about the same as avocadoes, and less than chocolate and nuts. It is not clear how much phytic acid constitutes a problem.

In terms of lectins and phytic acid, beans fair better than nuts, an orthodox paleo food.

Lectin and phytic acid arguments in general, while sometimes convenient in framing a rationale, sometimes could really use more scientific study to clarify the issues. It is possible that these issues are overly generalized and overblown at times in an attempt to develop another scientific rationale that endorses Paleo food over Neolithic food and might not be that useful in “rating” one Neolithic agent against another.

One could for example if they were so inclined create the rationale that beans are more paleo-friendly than rice or potatoes because the soluble fiber in beans helps to slow down digestion of carbohydrates, and controlling blood sugar seems to be a strong undercurrent in the paleo movement. Again, this is just a way of framing a rationale, and one could argue this rationale is just as valid as the lectin rationale in choosing one Neolithic food over another.

I think the issue can be pretty complex, and even if one is just looking at individual food constituents it is not likely that we have identified all the problematic components in a particular food. Lectins themselves are a fairly new “discovery.”

If one does use beans as a staple food in their diet though, then phytic acid might be a long term concern, and specific strategies to reduce phytates should be explored. It is not clear how much phytate is a real problem though. Occasionally eating  beans  might not be any worse than occasionally eating rice, potatoes, nuts, or salsa.  While the Okinawans seem to have done not too bad eating rice and the Kitavins seem to have done not too bad eating tubers, the Kuna also seem done to have done so bad eating beans and corn.

The orthodox rationale of just avoiding all Neolithic foods is convenient, but once one steps past that and starts allowing foods on a case-by-case basis, then incomplete information will be a concern. An argument can be made that one way to limit risk is by limiting the number of Neolithic exceptions one allows in their diet, but I think there is something to be said for diversifying risk from unknowns by including variety in one’s diet. In many ways it is just an educated guess as to what makes certain Neolithic foods more problematic compared to Paleolithic foods.

In the particular case of rice or potatoes being incorporated into a paleo style diet, I think there is some possible risk reduction benefits to be had by alternating between rice, potatoes, and beans instead of just sticking with rice all the time or potatoes all the time.

I do think of course that omega-6 seed oils, man-made transfats, and wheat should be avoided, but if one is open to having some white rice or potatoes occasionally, then for me personally changing it up with beans occasionally doesn’t seem to be much of a leap. (As always though, this viewpoint is subject to change with additional information.)

ADDENDUM – One more point – this is more “ancestral” than “paleo” rationale, but beans don’t seem to be correlated too well with the diseases of civilization. Bean consumption peaked in the US during WWII then went down from there. Beans are often one of the starches being replaced by wheat and sugar when a Western diet and lifestyle is adopted by a previously less industrial culture.