Why did we evolve a taste for sweetness?
Over the past few days, I’ve been busy working on a paleo archiving project. I’m really excited about it. The one post I have posted below, I think, is just the beginning, and I have about a billion tabs open on my computer, trying to organize everything. Because this has taken up so much time, I haven’t been thinking much about disordered eating. But it’s kind of a nice break. Food and negativity on the mind is food and negativity on the mind, no matter which way you’re looking at it.
In any case, in my archiving I came across this post by Paul over at Perfect Health Diet. I’m amazed that I missed it before because I read his blog religiously. In the post, Paul asks a question I had always wondered about: “Why did we evolve a taste for sweetness?” and he provides an answer I had never thought of before.
What if, says Paul, our taste for sweetness was “hijacked” by fruit? What if our original taste for sweetness was much more subtle?
Paul proposes here that we evolved a taste for sweetness because red meat is the sweetest of any animal. Other hypotheses are that a) we need fruit for a variety of reasons, particularly vitamin C, b) that we need glucose and therefore evolved craving carbohydrate in general, or c) that benefit from a bit of fruit and a bit of starch in our diets, but fruits were so scarce and “tart” back then that their actual contribution to human health was negligible. I believe that I’ve heard a refutation to this last point recently, but I can’t remember where. Paul’s own refutation of them all is as follows:
“But what of the sweet taste? Is it really a sensor for carbohydrates? If so it does a rather poor job. The healthiest carbohydrate source – starch, which is fructose-free – hardly activates this taste, while fructose, a toxin, activates it in spades. If this taste evolved to be a carbohydrate sensor, it should have made us aversive to the carbohydrates it detects, as the bitter taste makes us avoid toxins. But sweet tastes are attractive!”
Right. So he then discusses how red meat is the sweetest meat (read the post! there is a lot more science going on than I am addressing), and proposes that we crave this sweetness more when we have nutrient deficiencies. Fascinating, right?
The implication of this for binge eaters, which Paul points out in his post, is that a part of our craving for sweets may be nutritionally derived. As such, binge eaters have a stronger than average inclination to binge because their bodies need something only available, or at least most abundantly available, in meat. This idea relies on the theory that cravings are driven by nutrient needs. Unfortunately, the jury is definitely out here. Dr. Briffa thinks this occurrence is rare, and this organization and this review paper think is false. On the flip side, Pica, a condition marked by cravings for inanimate objects such as sand or dirt, is very often (but not always) hypothesized to be caused by nutrient deficiencies. As such, it supports, in the extreme spectrum, Paul’s theory.
Since so much of the science lacks consensus in this issue, I don’t have a set opinion. It makes sense to me, that we would crave meat if it’s the best source of nutrition. Paul’s reasoning is solid, too. But I also know that many intelligent people, including Paul, think that we need a hundred grams or so of glucose each day. Should that include fruit? Who knows.
Finally, I look to my experiences. I know that I have rectified some nutrient deficiencies since going paleo. My thyroid is working a bit better, my skin is nicer and my hair no longer comes out in strands as thick as a mongoose. These changes are positively correlated with my cravings. Those have decreased without question. But how do I suss out the reasons? Is it nutrient deficiencies? A lack of blood sugar fluctuation? The elimination from fructose in my diet, which helps stabilize leptin levels? Or is it psychological? Habitual? Have I finally, after all this time, just kicked the bucket on sweets?
Yes, I think, and no. The fact that I can binge on non-sweet foods says No. I’ve put away entire chickens before without blinking an eye. Many of my readers can do this, too. As can rats. Yet Paul again has a rebuttal lined up. He asserts that people reach for sweets because they are denied their first, true, and most important craving: fat. Interesting. It’s an idea I wouldn’t elbow people to get in the front of the line to sign up for, but I can also totally see it being the case. If anyone was fucked by conventional nutrition, it was me. Did you know I ate almost no fat for three years?
That said, I don’t think this fat-deprivation entirely drove my bingeing behavior. There were a lot of factors as play, worst of which, I think, was my fructose consumption. Yet weight loss, frustration, stress, body image, and lack of fat and protein leading to an inherently unsatisfying diet were also big components. Meat-as-craving-for-sweetness is a fascinating theory. It has definite potential as a component of disordered eating. But there are millions of things going on in my body and in my brain at any given time, and I think many other disordered eaters would agree. What comes first? What follows? What triggers the worst binges? What is the most effective bingeing salve? It’s all very complicated stuff. In any case, we should address the physiological as soon as and as diligently as possible. We should eat animals, stop eating fruit, and make sure we get as much fat and protein as we need. We should consider supplementation if we’ve really been beating up our bodies. And we should stop doing chronic cardio and do our best to sleep at night. We can, then, at the same time, start chipping away at the psychological factors. The hope is then that, as we move forward with both psychological and physiological healing, we can recover as smoothly and quickly as possible.
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Hi Pepper,
I’m glad you found that post interesting. It was speculative; putting forth an idea in response to an alternative theory by Seth Roberts which was also quite interesting.
The bigger subject of taste and food reward is an interesting one. Stephan has been posting recently on the idea that diets with high food reward cause obesity. I’m more inclined to the view food reward evolved to get us eating in the healthiest way, and that obesity is caused by food toxicity. What’s new is that for the first time in history we have, thanks to industrial food engineering, the opportunity to eat toxic foods with high food reward.
So my prejudice is that positive tastes guide us toward healthy food, and I don’t believe sugars are notably healthy, so I was looking for an alternative explanation for the attraction to sweetness.
Best, Paul
Absolutely, Paul. Food reward evolved to get us eating the healthiest way–I don’t see how it could be otherwise–but I do have to wonder. You write very often “the dose makes the poison,” so why do you write off fruit as the primary motivator for the sweet taste immediately because it is “a toxin”? I agree: fructose is the devil. But perhaps the vitamin C/nutrients from fruits argument has some merit. This might explain why fructose activates the sweet sensor at all.
Dear Paul,
Well, I don’t want to take back anything I’ve said. Haha. But I do want to thank you. I have been eating only a few different vegetables and fish for the past few weeks, since I have been dealing with some stomach comfort issues and inflammation issues (I think). In any case, I finished my first, big meal today and afterwards I was still hungry. I went to to the gym and had a great workout, but was still hungry, again. Normally, I lose my appetite when I exercise. I kept craving those giant carrots I eat by the dozen in the fridge. I had one and it didn’t satisfy me, like I suspected it wouldn’t. But then, because of what we have been talking about for the past few days, I let my mind go free and thought about what I REALLY wanted. And what was that? Pork stomach. I have barely had any red animal meat in the last month or so, and I think my lack of satisfaction with vegetables and with a big, buttery, fishy meal today is that I need meat. I’m not sure if I would have thought about that without this coming up for me yesterday. So– thank you! What a good perspective.
I’ve noticed when I increased my consumption of red meat (I average a pound and half a day) that my cravings for sweets and my binging on sweets hasn’t been as extreme. It’s still there. I’m trying to work my way off of it but I find it harder with the red meat. Although, I seem to have nut cravings to and I haven’t figure that one out.