I was recently having a discussion with a few people on the reasons I eat a Paleo diet. Like most discussions on religion and politics, it quickly degraded in to more of a name calling contest. Rather than get involved in any of that, I simply provided my case and let it be. However, I realized there's probably quite a few people who don't know why they are eating Paleo or why it may be a healthier way of eating. In this blog we will go over why much of the data you read on nutrition is probably wrong, why there is a lack of evidence for Paleo, and the primary reason grains and legumes are probably not wise nutritional choices if health is your goal.
Many people point to the data that shows grains and legumes to be healthy food options. The problem is this data doesn't show what they propose that it does. Most of this data is epidemiological data. The researchers provide food questionnaires that people fill out and the researchers compare this data to predetermined health outcomes. There are many problems with this type of data. The primary reason it is faulty is that the researchers are not controlling extraneous variables. For example, if you tell a population that whole grains are healthy, people who are interested in health will gravitate towards eating whole grains. People who are interested in health also tend to exercise, limit alcohol consumption, don't smoke, and keep a pretty regular sleep schedule. As such, these people will skew the results toward better health outcomes, not necessarily because whole grains are healthy, but because these people lead otherwise healthy lives. Because of this, epidemiological can show that there is a relationship between two variables, it cannot say the direction of the relationship. In other words, it could be that people who eat whole grains are healthy, but it could also be that people who are healthy eat whole grains. This means that this type of data is good for establishing relationships that can be further studied in a controlled clinical trial, not to say whether something is healthy to consume or not.
The other studies typically cited to show that grains or legumes are healthy foods don't have a proper control group. When you are trying to determine whether something is beneficial or not, you would want to compare a diet that is otherwise identical between two groups with the exception that one group contains that food and the other doesn't. Obviously this is very difficult to do, few people want to be locked in a metabolic ward and have their food weighed and prepared for them for long periods of time. In addition, you would have to do these studies over very long periods of time which is probably not something you're going to see happen. This is why most of the data is epidemiological. Of the few studies we have, none compare eating whole grains to eating no grains, they compare eating whole grains to refined grains. If a study shows a difference between the two, and most do, it doesn't necessarily mean that the one that is better is a healthy food. If you ran a study and compared heroin to crack and heroine was better than crack, that wouldn't make crack a healthy option, only healthier than crack.
This presents a problem. At the end of the day, research is unlikely to give us solid answers as to what is healthy. So if the studies don't appear to be of any help, how do you make a decision? When studies are of no help you want to look at mechanism. Mechanism refers to a specific way that something could lead to beneficial or bad health outcomes. The criteria I use is whether a food provides a wide range of essential nutrients, contains some nutrient that is hard to get from other foods, or contains some nonessential nutrient that provides a health benefit. When you look at grains and legumes, none of these apply. For a more thorough explanation of why watch this.
Now, is there something in grains or legumes that should give you reservations in consuming them? Many things have been brought up that really didn't pan out in the research such as phytic acid and lectins. However, there is one potential issue that has been supported by the research that should give you concern with consuming grains or legumes. Grains and legumes contain hard to digest storage proteins called prolamins. Humans do not produce enough of the enzymes used to digest these proteins so they pretty much go through the intestinal tract untouched. Gluten is probably the best known prolamin, is contained in wheat, and causes major problems in people with celiac disease. This may not seem like an issue, but these prolamins have other insidious properties. All of the prolamins in grains, particularly the gliadin in gluten, are immunogenic. In fact, gluten will elicit an immune response, and it will do this in all people whether they have celiac disease or not(1). This doesn't mean they are necessarily toxic, but firing off the immune system without reason shouldn't be one of your primary nutritional goals if health is your goal. The prolamins in legumes haven't been specifically studied, but given that their structure is basically the same as the prolamins in grains, I see no reason to test the waters.
If grains and legumes provided something you couldn't get elsewhere, were loaded with nutrients that are hard to get, or possessed some phytonutrient that is of benefit I would say go ahead and eat them. But their lack of nutrient density coupled with their immunogenic properties give me good reason to not recommend people consume them on a regular basis, and certainly not as a staple in their diet. Will you die if you eat a sandwich? Nope. Are you ever going to find a solid clinical study showing them to be unhealthy over the long term? Probably not. Just ask yourself, would you submit yourself to stay in a metabolic ward away from your family for 6-9 months while you eat a strict diet of measured food that may or may not contain legumes or grains. Do you think researchers are going to find 100 people to do so and who would fund that study? If the day ever comes that we see that study and the data supports grain and legume consumption I'll be all in. Until that day, I am going to go with my N=1 study that shows I am missing nothing from passing on those foods and potentially improving my health by avoiding them. I certainly feel better, have more energy, and get sick far less often.