Saturday, April 21, 2007

The underweight epidemic

What is going on with obesity? For a long time now I have been walking around thinking that our modern society has some serious negative consequences in terms of diet. Our evolved preference for foods rich in fat and sugars together with fast food chains and supermarkets which put the candy where you cannot avoid it, should naturally result in an increased consumption of such foods and in consequence more obesity. Indeed this seems to be the case. Since the 1970s obesity levels have been steadily rising. However, the interesting question to ask is "what effects this increase in the average BMI (body mass index) has on our health?"

When I lived in California I was constantly exposed to commercials in which you would view pictures from a childhood where the protagonist ate way to much sweet stuff. Following these pictures a man would say something like, because of what I ate in my childhood my life has been shortened by five years. I believed this, just like I believed that obesity was indeed a dangerous epidemic, why should I not believe it?

Now I think I know better though, all thanks to a professor at Berkeley who's lectures I have been following via Berkeley's webcast (which I can warmly recommend by the way). In her lectures she presents apparently uncontroversial data showing clearly that the deaths due to diabetes have not increased one bit in the past 40 years or so. What is even more interesting, and indeed more concealed, is the fact that obesity is not associated with an increased risk of dying. In fact, if you have a BMI between 25-30, which is considered overweight, then you have the best possible prognosis. If you are underweight on the other hand (BMI less than 18.5), then your chance of dying increase substantially! Have anyone heard of an underweight epidemic? I certainly haven't! Yet, an underweight epidemic is what we should really be worrying about since it is, unlike overweight, claiming quite a few deaths in our modern society (and in developed countries as well of). Of course it should be mentioned that severe obesity, that is when BMI gets above 30, is associated with increase health problems as well.

In the light of this information I think that it is insane, the way that overweight/obese people are treated in today's society. To have some fat reserves is good. To not have any reserves is dangerous. Yet those with the more healthy bodies are dragged into shame exactly because of their bodies.

Saturday, April 14, 2007

”Natural Foods” contain more carcinogens than ”Unnatural Foods”

If you are like me, the first thing you will react to in the headline is my discrimination between natural and unnatural foods. It is my impression that people who call natural foods "natural foods" refer to foods which have not been treated with pesticides. Personally I don't think this makes them more natural, and it definitely does not necessarily make them better. I suppose that natural foods are more natural in the sense that it is what we used to eat back in the days when we did not have the kind of technology that we have today, though based on that one could argue that primitive foods would be a more appropriate label. I must admit that I have never actually heard anyone talk about unnatural foods, I just assume that if someone asserts that foods which have not been treated with pesticides are natural, then they must think that foods which have been sprayed with pesticides must somehow be unnatural.

In any case, people who eat natural foods often claim that it is better for you. Why? Well according to the people I have talked to, natural foods are less toxic to you because they have not been sprayed with pesticides. Pesticides, according to these people are quite poisonous and ingesting them will result in all kinds of bad effects such as cancer. Therefore natural foods, which have not been sprayed with any pesticides must be better for you. The problem is that all foods, including natural foods, produce their own pesticides. In a moment I will argue (convincingly I hope), that natural foods in fact have a larger concentration of pesticides and that the pesticides in natural foods are even more toxic than the synthetic pesticides that we produce and spray on our "unnatural foods".

So how come natural foods have pesticides in them? If you think about it the answer is quite obvious. All plants need defenses against plant eaters. If a plant cannot avoid predation, then natural selection will take care of that plant in no time. That is, any plant without defenses will die and only the ones that do have a proper defense will be able to survive, reproduce, and thus send their genes into the next generation. Now plants are not particularly mobile, and therefore they cannot run away from their predators. So what do they do? They evolve defenses which either makes them hard to eat (e.g. thorns on cactuses), or they evolve chemical or pesticides that will either kill or hurt the predator when they try eating the plant. These substances are called natural pesticides. Natural pesticides are the chemicals contained within plants in order to make organisms that eat them sick or even kill them.

So we have two types of pesticides. There are pesticides that we produce in our industries and spray on plants to protect them from other organisms, and there are pesticides that the plants make themselves for the very same reason. What is the difference between these two types of pesticides? You may be thinking that since we have been exposed to natural pesticides (the ones the plants make) for a longer time, we would be able to handle them better, not so. The defenses we have in our body to protect us from pesticides are general, that is they don't care whether it is a natural pesticide or a synthetic pesticide, in fact they treat almost all different pesticides the same way. Throughout our evolutionary history, as we have included more things in our diet, we been exposed to new "natural pesticides". To our body the synthetic pesticides that we spray on plants are simply yet another novel pesticide. If you are still not convinced, consider the fact that there are quite a few types of pesticides that we have been exposed to for thousands and thousands of years which still today can be very bad for us.

I hope to have established that there is no general qualitative difference between the pesticides that we produce in our industries and the pesticides that plants produce. However, in all fairness this is not entirely true. The synthetic pesticides that we use today are selected based on their ability protect the plants on which they are sprayed, and importantly only mild toxins are used, that is our body can take care of them relatively easily. This means that if a plant is sprayed with synthetic pesticides that plant doesn't need to make its own pesticides because it is already protected. Of course, to the extent that the synthetic pesticide is toxic, the plant will also become more toxic, but normally this effect is very small. Now if, on the other hand, you do not spray a plant, then that plant will have to form its own pesticides, and the stronger the better. The plants that do not do this, as I mentioned before, will die. In consequence, each new generation of natural food crops will be the offspring of the most toxic plants in the previous generation. This should logically mean that the natural pesticides in natural foods are much more toxic than the natural pesticides in foods that have been sprayed.

This question has in fact been tested experimentally by Bruce Ames at the University of California, Berkeley. How did he test this? Well first, being a cruel scientist, he created a bacteria that lacked an enzyme that was critical for its survival. The only way for the bacteria to survive was if it, through random mutations got a working gene capable of producing the vital enzyme. Now, Ames would create say a thousand colonies of these unfortunate bacteria. Then he would squirt something, say a natural pesticide, on all the different colonies and see how many would grow. Ames could infer that if a bacterial colony would start growing then mutations had occurred in that colony, in other words the substance squirted on them must have been mutagenic and therefore carcinogenic. If you compare natural pesticides and synthetic pesticides in this type of test you will see that the natural pesticides will leave much more survivors than the synthetic ones. This may be good news for the bacteria, but not for us, because more mutations means higher risk of cancer. In other words the predictions stated above has been confirmed in the experiments performed by Ames.

What do I want to say with this? Well, I do not want to give the impression that I think natural foods are necessarily bad. Doing a very quick literary review I found a few studies claiming that there are more nutrients in organic relative to normal foods (organic foods is an extreme form of natural foods). However, all I want to say is that I think that our fear of synthetic pesticides is probably a little bit exaggerated, and that in many cases the toxins produced by the plants themselves are far worse.

Ps: For a good chapter on carcinogens in foods see Ames here in Handbook of toxicology

Thursday, April 12, 2007

Manchester United vs. Roma 7-1

Since I have been a United fan for no less than 18 years I have to sidetrack from my normal subjects and write a few lines about the magnificent game they played the other night when they completely demolished Roma in the Champions League quarter finals. It was quite an amazing experience to watch the game, the goals just kept on coming, and in the end I almost felt a bit sorry for Roma and the Roma fans.

Totti, Roma's perhaps best player said in an interview prior to the first encounter "that 'I don't like the way English football is even if some great players play there. 'I don't like English football and I don't like England either because of the weather.'" (no Totti is not a teenager, he is 30 years old).

Following their humiliating defeat Totti, to my satisfaction said that "Unfortunately, we have come across a better team." Poor Totti…

Tuesday, April 10, 2007

Learning described at the cellular level: Finding from our laboratory in Lund

Today I want draw the attention to some very exciting discoveries from our neurophysiology laboratory here in Lund. Because I have just started working in the lab I cannot take any credit for the work, though I have been spending a lot of time lately, trying to develop the experimental setup further. Instead it is Dan Anders Jirenhed, Fredrik Bengtsson, and Germund Hesslow who have worked for several years to achieve the experimental setup that allowed the findings that you can read about here.

The findings have already received quite a lot of attention from places with more readers than my blog. See for instance the article in New Scientist, or if you understand Swedish you can listen or read about the discoveries on Sveriges Radio homepage. If you are interested in the technicalities I recommend that you read the original article which was published in the Journal of Neuroscience.

What has been found is a perfect correlate between behavioral learning and cellular behavior. To explain what this means you first have to know what classical conditioning is. To understand what classical conditioning is, imagine that you sit in a comfy chair (doesn't really matter whether it is comfy or not). Suddenly you hear a loud tone, and immediately after that you get a puff of air in your eye. If you have a normal brain you will blink when your eye is hit by the air. Now imagine that this occurs over and over again, first the tone, then the unpleasant air puff. Again, if you have a normal brain it will eventually realize that "aha, if I blink when I hear the tone, I can avoid that nasty puff of air in my eye, I think I will do that".

Though you may be conscious of the association between the tone and the air puff, this type of learning does not take place in the cortex of our brain, but rather in the cerebellum. Take away the cerebellum and this type of learning is severely impaired if not entirely abolished. In our laboratory we used tiny winy electrodes to measure the activity of single purkinje cells (see picture) in the cerebellum while presenting tones and air puffs. Purkinje cells are a type of neuron located in the cerebellar cortex (near the surface), which because of their morphology appear to be particularly good candidates for the learning that occurs during classical conditioning.

So in essence we could see what happened to the activity in this single purkinje cell when we were applying a classical conditioning paradigm (presenting tones and air puffs). If you just leave them alone, purkinje cells will fire action potentials at a rate of about 60Hz (60 times every second), however, amazingly during the learning paradigm described above the purkinje cells started to show a very distinct pause just prior to the presentation of the air puff (see picture). Change the time lag between the tone and the air puff, and the timing of the pause in the purkinje cell will change so that it is always perfectly synchronized with the air puff. Eliminate the association between the tone and the air puff by presenting only the tone without the air puff and the pause will disappear. Re-establish the association between the tone and the air puff and the pause in the purkinje cell will rapidly re-appear. In essence there is a perfect agreement between the behavior of the animal and the behavior of the purkinje cell.

So why is this so important? Well first of all it is just super interesting, I mean it appears that we can start to describe learning in terms of patterns of neuronal firing. This also means that we will soon be able to see what happens to learning during different treatments. One question that I find interesting is what would happen to the activity in the purkinje cell if we squirt some narcotics (e.g. Cannabis) onto the cell. Will the learning be damaged in some way. There are probably millions of follow up questions that we can now start to explore. All this because of the work done here in Lund, Sweden.