The Taste of Pleasure: of Sensitivity and Sentinels

Addicted to sweets? Blame your ancestors.

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There are many silly questions in nutrition, and many more silly answers. Sometimes, a rather silly question is very well disguised as serious, deep and important. A noteworthy example of this is: Can food be addictive?

Eat + Run -- David Katz
David Katz
This question has received considerable attention in pop culture and scholarly circles alike and seems anything but silly at first blush. And there is, I suppose, a case to be made for its legitimacy, at the level of competing and detailed definitions of addiction, or the release and metabolism of specific brain chemicals.

But in all the ways that matter, silly it is. Of course, food can be addictive. Food is why addiction exists.

Well, food and sex.

Addiction doesn't exist because addiction is useful. Addiction exists because survival is useful.

The neural circuitry that gets taken over by drugs or tobacco or alcohol or willfully addictive junk food has long served the purposes of survival. In the long sweep of human history, getting food—in adequate quantity, quality and diversity—was hard and often dangerous work. But it was, of course, important work. Those who did it lived to pass on their genes; those who didn't—well, not so much.

[See How to Conquer Food Cravings.]

So, predictably, those members of our prehistoric clan who were motivated to work hard for food were the survivors. Part of what made them work hard was a robust system of positive reinforcement in their nervous systems. Starving felt very bad; eating felt very good. We can well imagine that some alternative version of Homo sapien that was agnostic on the subject of eating versus starving would be at a distinct competitive disadvantage. Certainly, we see precious few of their descendants around today!

The same, of course, is true of sex. In native context, mating means competition, and as we've all seen on nature programs, fights even to the death. To justify such risks, sex had to be pretty darn rewarding—as I trust most agree it is.

[See G-Spot, Schmee-Spot. Will the New Discovery Affect Your Sex Life?]

All other addictions are really accidents in which some compound or chemical hijacks the wiring laid down by eons of eating, and eons of sex. Wiring laid down in the service of survival.

All of which invites another question, with opposite characteristics. It seems silly, but is actually serious, deep and important; namely, what are taste buds for?

We may be inclined to take the answer for granted. Taste buds are for tasting, of course, and tasting is what makes food good or bad. Taste buds are for pleasure.

But really, taste is just means to an end. And pleasure, along with displeasure, is really just a method to get an important job done. And once again, that job is survival.

Taste buds are sentinels. They are the guardians at the gates to our inner selves.

Dispensing with metaphor, taste buds increase the surface area of our tongues and house specialized cells of the nervous system with sensitivity to specific classes of chemicals. Depending on the chemicals and the cells involved, we can register up to seven distinct flavor categories: sweet, salty, sour, bitter, savory, astringent and umami. There is some debate about whether this list should be a bit longer or shorter, but for our purposes here, that's an unimportant detail.

The simple registration of flavors is then sent to our brain, in combination with the registration of other flavors, and scent signals. Those messages are blended, and we wind up with all of the intricacies of taste—from the sublime to the repulsive.

[See Guts and Glory: Mary Roach Tackles Digestion.]

But that perception is really just the way the hard wiring of our brains interprets a symphony of chemically mediated signals. And once again, that hard wiring was laid down in the service of survival.

We like sweet. What that means is anything that registers as sweet on our tongues induces a pleasure response in our brains. There is nothing intrinsically "good" about the taste of sweet. Sweet is really just the interaction of certain food chemicals with certain neural receptors in our taste buds. Our brains then say "this is good" in the language of neurophysiology: activation of brain areas and release of other chemical messengers that register as pleasure.

That pleasure is a reward for working on behalf of survival. And in native context, that's generally just what eating "sweets" meant. The only sweets to which our ancestors had access were fruits and honey, and these were very valuable sources of quick and concentrated energy. Sweet also tends to be a reliable indication that a food is not toxic. In contrast, most toxins register as bitter—and for that very reason, bitter is something we either don't like or for which a taste preference must be acquired.

[See Are We Sugar Crazy?]

We also tend to like salty, savory and umami—a taste associated with meat and cheese. Taste buds issue an "all clear" at the gate when they encounter a flavor likely to do our bodies good; they issue a "not so fast" as we mull over flavor mixes inducing ambivalence; and they issue a "none shall pass!" when encountering a flavor harboring potential peril.

These considerations have an array of implications for our relationship with food in the modern context.

First, that vexing tendency of kids not to like a food before they've even tried it actually makes sense. Familiarity is a potent determinant of food preference, because, in native context, a food we've eaten before without ill effect is unlikely to kill us. Any new, untried food could well be poison. Our taste buds are reticent when encountering the unfamiliar. They can be won over, of course, by giving them time to make a new friend. Multiple introductions of a new food over time allow it to become familiar—and that changes the reception it gets at the gate.

[See Easiest Diets to Follow: in Pictures.]

We absolutely cannot rely on cravings to tell us what our bodies need! Our cravings are also byproducts of how we interpret taste, and that is a holdover from the Stone Age, when the relevant wiring was laid down. We like— and tend to crave—sugar, salt and fat, because these helped keep our ancestors alive.

We now have too much of all three—along with calories, and often protein—but are still subject to Stone Age cravings. Your sweet tooth is likely to cause you and your health nothing but trouble; but your sweet tooth's ancestor helped keep your ancestor looking for fruit and fighting bees for honey. That, in turn, helped keep your ancestor alive long enough to procreate, which made him or her a much better ancestor!

So, you cannot really trust your taste buds. They are excellent sentinels, but they are guarding the gates from largely extinct threats and welcoming in modern wolves wearing prehistoric sheep's clothing.

This is fixable. Taste bud responses can be updated. Taste preferences can be rehabilitated.

First, referring back to the issue of food addiction with which we began, the more we encounter a flavor we like, the more of it we need to feel satisfied. This is a well-established element of all addictions known as "tolerance."

So, the more sweet and salty you encounter every day, the more you will tend to crave. Fix this by sending your taste buds to rehab, in the form of less sugar and less salt. Look for salt hidden even in non-salty foods (such as breakfast cereals) and sugar hidden in non-sweet foods (such as pasta sauce), and get it out of your diet.

[See 10 Things the Food Industry Doesn't Want You to Know.]

Dial down your exposures, and you will steadily become sensitive to, and satisfied with, less. In this way, rehabilitating your taste buds can help you come to love foods that love you back.

Second, make use of the fact that where taste buds are concerned, familiarity breeds acceptance, not contempt. Take your time and proceed incrementally, but get yourself and your family accustomed to "better" foods. Trade up your choices in every category, and introduce highly nutritious foods into your repertoire—with an emphasis on diverse foods including vegetables, legumes, beans, herbs and spices. Not liking something at first is not a permanent commitment. It's just the guardians at the gate being cautious about the unfamiliar. Give them time to make new friends, and they'll come around.

Our relationship with food is, fundamentally, about survival. Everything makes good sense in that context and offers us an understanding we can leverage to our advantage. We can resist efforts by food industry elements to addict us to junk food. We can learn to love foods that love us back. We can get health in the pursuit of pleasure, and pleasure in pursuit of health.

[See How to Take a Stand Against Junk Food.]

Taste buds guard the gate. They work for us, as they always have, but their marching orders are apt to be out of date. You can fix that by updating the taste of pleasure, and resensitizing the sentinels.

Hungry for more? Write to eatandrun@usnews.com with your questions, concerns, and feedback.

David L. Katz, MD, MPH, FACPM, FACP, is a specialist in internal medicine and preventive medicine, with particular expertise in nutrition, weight management, and chronic-disease prevention. He is the founding director of Yale University's Prevention Research Center, and principal inventor of the NuVal nutrition guidance system. Katz was named editor-in-chief of Childhood Obesity in 2011, and is president-elect of the American College of Lifestyle Medicine.