 |
| Pork chops and bean stew, hyper-palatable? |
Stephan Guyenet posted
this interesting essay about weight and the reward hypothesis there of. So I thought I would try to articulate my own theory in the simplest possible terms, which I think incorporates many of the things I have read about food reward. Keep in mind I am an art teacher who has read a lot about diet and nutrition. I am certainly not up to date in all of the research. But the current consensus, while having a lot of merit doesn't include many of the observations I have made about my own body.
As I understand it there are two ways to sense flavor in food. The taste buds are a sort of blunt instrument which perceive saltiness, bitterness, sweetness, sourness, and perhaps umami and fat, though perhaps fat is a mouth feel/consistency perception. We also have scent receptors which perceive the direction an odor is coming from, if it comes in through your nose (ortho nasally) it is registered as a smell, if it comes up from your throat and mouth (retro nasally) then it registers as a taste. Depending on whose theory you believe those odor/taste molecules are perceived because of their shape or their vibration. They are more and less precise depending probably on genetics, use, and skill. There are well recognized super smellers or "noses" who have incredibly discriminating scent/taste perceptions. But everyone can detect a remarkable range of chemicals with their scent/flavor receptors. There are also "taste" receptors in your digestive system.
Interesting side note: even though the chemicals are the same, and the sensor is the same, smells and taste molecules are processed in totally different parts of the brain. I need a term to differentiate the taste bud taste from the aroma taste by the way. At any rate, the smell of strawberries is processed in a different place than the strawberry gas that drifts up through your sinuses retro nasally. How cool is that? I am not a super smeller like my mom, but I have a very acute sense of flavor molecules, I suspect that's because I focus on aroma and flavor. The part of my brain that processes that information is rehearsed.
So the question is, why? Why do we have these taste systems? People who lose their sense of smell are at significant risk of eating rotten food and getting sick. We are pretty good at smelling when food has gone bad. That's a good reason. My mom is a super smeller, she can detect smells in minute amounts and long before anyone else. But she doesn't like cooking and can't recognize small amounts of herbs in a dish like I can. She can smell slightly off milk from a mile away. My mom throws away a lot of food other people would keep using for days.
The taste buds seem to be a system for making sure we can recognize macronutrients, our salty and bitter receptors help us perceive minerals in our foods, our sweet receptors help us perceive carbohydrates, our umami sense helps us perceive amino acids, etc. I would love to see research into people without a sense of smell and their habits around macronutrients and their micronutrient status. Some people have a much denser distribution of taste buds than other people, my family always calls me a super-taster, but I am not. Super tasters often don't enjoy food as much as non-super tasters, they have a lot of aversions. I would love to know if there is a relationship between super-tasting and weight. I would predict super tasters would be more slender than not.
As Proust pointed out, our sense of smell, and in my personal case my sense of taste, are directly wired into our strongest memories. I believe that we come to associate specific tastes and smells with the nutrients those foods contain. That all that direct connection between smells and tastes and learning are to help us remember where to find food (I smell honey, I remember getting lot's of carbs when I smelled that before, reward-anticipation kicks in, I find honey, I eat honey, my body registers carbs, I am rewarded, I remember.) We also, and often very dramatically use our senses of taste and smell to learn aversions, I couldn't eat pizza for years after an unfortunate morning sickness pizza incident.
The sense of smell and taste are very discriminating, I can often identify individual herbs in a dish. And sometimes I have huge overwhelmingly strong cravings for specific herbs. I figure that is my body saying, hey, remember the last time you smelled that smell? Tasted that taste? When that happened I got something I needed, do that again, 'kay?
This is of course directly related to all the reward and palatability Stephan and his fellow researchers are talking about. I eat something my body needs, it likes it, it rewards me, I do it again, I (and my body, which seem to have become separated in this little narrative) win. Where I differ from the direction the current research is going is that I don't buy that crappy processed food is "hyper-palatable." (Though, according to the glossary Stephan has started to put at the bottom of his posts it is, so maybe I just have a nomenclature disagreement with him.) I don't think our bodies are that stupid. That the food companies have figured out what ingredients they can add to food cheaply to make us eat a lot is clear, but I don't think that's the whole story.
Here is my thought, I think the food learning process is being interrupted/fooled by foods that have the tastes and smells of nutrients that aren't there. My body learned to associate citrus aromas, and sour taste bud stimulus with vitamin C, and probably all manner of bioflavonoids and other nutrients in citrus. I often have strong cravings for citrus aromas and sour tastes. When I am camping and don't eat fresh foods that have vitamin C I get overwhelming cravings for sour things. Sour candies can help in the short term, they have the aromas and taste I am craving. But my body isn't getting what it wants, so the craving comes back making me eat another sour candy. That sets up an addictive cycle.
Interesting side note, I am not the only one. People living in Minnesota forts in pioneer times ate mostly salt pork and grains and beans. They had casks of citrus juice shipped to them, which they fermented and added to alcohol. If you are camping a flask of lemon juice/honey/brandy which you add a dash of to your tea can stave off the citrus cravings. The pioneers called it shrub.
I suspect that after enough learning the body starts rewarding the taste, rather than wait for conformation from the digestion about the actual nutritional content of the food. That's the reward the researchers are talking about. If I really need a nutrient such as C, or perhaps something else in citrus, my body will reward me for eating the sour/fruity candies, even though the nutrients aren't there, but it will send me the craving signal again as soon as it realizes I was faking it out. Research into drug addicts shows that the dopamine starts flowing as soon as they anticipate the dose. More dopamine - reward occurs as they ready their paraphernalia, the sensory information is ahead of the actual chemical stimulant.
If I find a patch of fresh raspberries or thimbleberries while I am camping I get immediate physical feedback from my body that make me want to eat them. My sour craving intensifies, I produce saliva, and even if I am near my camp site or have a really heavy pack I will stop and pick and eat those berries. When I do, my sour craving is satisfied and doesn't come back. I don't have to eat sour candies if there are berries around. The berries are satiating, or they satisfy my craving. But I have a raspberry patch in my garden and I almost never go out and eat every berry I can find, because my at home diet probably has plenty of whatever the raspberries have. I have often been in a situation where I could eat all the berries I want, and I stop after about 300-400 calories of berries, which is a heck of a lot, but not outrageous.
If I could carry enough sour candies I would probably eat thousands of calories of them while camping. I would never get the signal to stop because they don't have what my body wants, even though they taste like they do. If I carry vitamin C lozenges they are more satiating, though not as satiating as the berries, there are probably any number of not-yet-discovered nutrients that my body gets from the berries that are not in the lozenges, but at least I am getting the C.
I think the issue with modern processed foods isn't that it is hyper-palatable, I think the issue is that it is carefully crafted to communicate that it has certain nutrients, but it doesn't actually have them. The flavor triggers the reward, like the sight of a needle will trigger dopamine for a heroin addict, but the food can't deliver, so like the heroin addict isn't satisfied with the little hit of dopamine, the eater isn't satisfied with the food. But they are motivated to try again, because the cue their body has learned was present, the reward was triggered. The problem with modern processed food is that it is nutrient poor, while having the flavors of foods with nutrients. The problem is, it lies.
But all that sophisticated communication about what we are eating isn't just about getting us to eat the right nutrients, it's also about processing the things we eat. The tastes we taste are how our body knows what enzymes, what hormones to release as we eat. Even thinking about eating specific foods can cause those physical changes. But what happens when we lie to our body with our food? I believe that our body learns we are unreliable. Take diet soda for an example, you taste the sweet taste, your body releases insulin to deal with the sugar... that never arrives. Now the closely regulated sugar that was circulating in your blood is getting shuffled off to storage because of all the extra insulin. Half an hour later you have to either release some glycogen from your liver or eat some carbs. Also, next time you taste something sweet your body might not release enough insulin, it's not dumb, it learns. But what if this time that sweet taste is a real soda? Crap, now you are damaging your tissues with too much blood sugar.
I suspect that the more unreliable messages you send your body over time the higher your body moves it's set point. I also suspect that some people who are over weight are either not getting the nutrients they need so their body in a desperate attempt to get those nutrients just keeps sending out the hunger signals hoping to get enough. As our food has become less nutrient dense (which lot's of research says it has) we need to eat more to get the basic nutrients we need. Set point moves up, that's how many calories we need to get the basics. I think one of the benefits of exercise is that it uses the extra calories that you need to eat to get the nutrients, and if you are some how damaged in your ability to get enough nutrients, or you have taught your body that you are completely unreliable no amount of exercise will matter.
Many magazine articles suggest that we eat less dense foods, watery soups to fill the tummy and "satisfy us" or fill us up. I think that is the exact opposite of what we should do. I think we should eat the most nutrient dense lowest volume foods. I think way to much attention is paid to the stretch receptors in the stomach, and nowhere near enough attention is paid to the nutrient composition of our food. If my body gets the message that no matter how much I stretch my tummy I won't get enough nutrients, than I will only stop eating when my stomach is super stretched. If my body gets the message that I will get all that I need in a moderate amount of food, then I will be satisfied with less. That has absolutely played out for me. A few ounces of meat satisfies me like cups and cups of bean and whole grain salads didn't. Because the meat has the protein I need, but maybe also because it has carnatine, or usable iron, or some other thing I needed that wasn't in the way more caloric beans and grains.
I haven't quite worked them in to this theory yet, but I am interested in Seth Roberts
Shangri la diet, which is the opposite of diet soda, in other words lots of calories no taste. Also, even though I give myself permission to eat whatever I want at Thanksgiving, including massive amounts of carbohydrates, my blood sugar never goes very high. Whereas if I eat an entire baked potato with a normal dinner my blood sugar shoots up. Thanksgiving is a high anticipation meal for me, I think about what I am going to cook, and what I am going to eat, for days. I cook all day long and think about what I will be eating. And when I eat it, my body is ready for it. I remember hearing a study of diabetic Muslims who had no problem with controlling their blood sugar during religious fasts, but would have serious problems with low blood sugar if they missed a meal. Our anticipation and thinking about foods is powerful. So if we consume a lot of food related media, might that be interpreted as unreliable information for our body? I love reading cooking magazines, I have a very vivid taste memory/imagination and can often taste the recipe as I read it. Am I getting the little hit of dopamine when I do?
What happens to people who never get nutrients they need? Who never have the opportunity to learn the flavor associations with vital nutrients? Is this why formula fed babies have a greater risk of obesity? Is there a window of opportunity beyond which you cannot learn those relationships? Can we create people who have a complete disconnect between their sense of taste/smell and what their body needs?
Another interesting thought I have had is that I seem to be controlling my blood sugar much better since I started planning my meals. I know what I am going to cook, and I can mentally prepare for it. Also, the amount of carbohydrate is predictable, and my meal times are more regular too. However, my weight set point has gone up about 10 pounds. My anticipation helps me process the food, but am I lying to my body by thinking about what I am going to eat?
I don't disagree entirely with the reward research in weight, in fact my recommendations are probably exactly the same as Stephan Guyenet's, I just think there is more going on then that crappy processed foods taste so good we over eat them, which is what a lot of the writing about food reward seems to boil down to.
Edited to add:
I think Melissa at Hunt.Gather.Love may share many of my reservations about the current theory of food-reward. Please read her article
here.
Paul Jaminet
seems to agree with me as well. Or, at any rate isn't quite on board with food-reward as it is currently advertised.
Though, let me take this moment to re-iterate that Stephan Guyenet is a very excellent blogger, seems to be a level-headed scientist, and also seems to be a nice guy. I have no argument with him, and his reporting of the research and consensus amongst obesity researchers. I do believe that respectful disagreement is one great way to increase the total of knowledge.
