I realize that up to this point I haven’t said anything directly in this recent slew of entries about why I would need to give some thought to how to incorporate beans and cereals into my diet if I wanted them there. The answer is that, as with any foods, there are pros and cons to beans and cereals. The pro of beans is that they are relatively high in protein and carbs, while having pretty much no fat to speak of. Similarly, the pro of cereals is that they are high in carbs with pretty much no fat to speak of. At the same time there are some issues that must be kept in mind with these food groups. The first is nutrient absorption and the second is blood sugar.
The nutrient absorption issue is reasonably well established. Basically, beans and cereals are essentially seeds. As a result they have various chemicals in them that are common to seeds. And one of the effects these chemicals have on humans is that they make it harder for people to digest certain other nutrients, like iron, when they are eaten at the same time. As a result, to continue with the iron example, the iron passes right through the person, instead of being absorbed into the blood stream (you can do a search on my blog using the terms ‘iron’ and ‘phytate’ to get some nitty gritty details on this. There are several entries scattered about.). The absorption rate can be as low as 2% of the iron available in the food itself. Fortunately, you can balance this situation out by eating a good amount of vitamin C at the same time, because vitamin C enhances the absorption of iron. The two chemicals basically balance the situation out. But it’s important to keep this in mind. Otherwise, your cream of wheat iron boost could well be letting you down.
The second issue is a bit more controversial. Basically, some scientists measured what happened to the blood sugar levels of people eating various foods. They found that, for some individuals, eating foods like potatoes resulted in a large and immediate release of sugar into the blood. Basically, most of the available carb in the food was being quickly converted to sugar and dumped into the blood stream.
So- what does this mean, exactly? Well, it means that if you are one of these individuals, and you are about to run a marathon, then potatoes might be awesome! It also means that if you are one of these individuals and you have diabetes, then maybe you really shouldn’t eat potatoes. What it means beyond this, however, is all a bit murky. First of all, it seems hard to say how likely you are to be one of these individuals, or, put more precisely, what the general variability is in the population in terms of their glycemic response, and I haven’t been able to find any hard data on this.This conference abstract gives a good overview of the issues, without providing any particular answers about the situation. It’s also the case that the preparation of the food in question also very much changes its effects, as this page discusses. And lastly, it isn’t entirely clear what the implications of having a spike in blood sugar actually are. We know it causes the body to release a bunch of insulin, to compensate (which is why it’s a problem for diabetics, who don’t have enough insulin to compensate), but beyond that, it isn’t clear. People are doing a lot of research about this at the moment, because it is a real hot potato (no pun intended) in the nutrition world right now, and people are making a lot of heated claims in one direction or the other, but the bottom line is that the jury is still out.
At the moment, my own position on what we know is this: We know that for some people, certain foods, like potato, pasta, and rice, cause a rapid rise in blood sugar. My opinion is that the body usually only needs to change rapidly *internally* in response to a rapidly changing, or somewhat out of the ordinary *external* situation. If it’s changing rapidly internally (blood sugar spiking), but there’s no external change (I’m still sitting at my desk), then there’s a bit of a mis-match going on. So, that makes me think- if, on a day to day basis, it is possible to still get the nutrients required without eating mainly or exclusively these foods, then- why not? Why not avoid eating bowls of only pasta (which I have been know to do), and instead eat lots of veggies, with a (small?) side of pasta? Why not eat the soup with cubes of potato in it for lunch rather than eating the baked potato (which I have also been known to do)? It’s a bit of a Pascal’s wager situation.
On the other hand, if I’m canoeing for five hours straight, pass the rice.
posted at 14:03 on Sat, 28 Oct, 2006 |
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