Hate broccoli? Spinach? Blame your genes

If you can’t stand black coffee, chances are good that you also turn up your nose at bitter-tasting grapefruit juice, broccoli, spinach, green tea or soy products. You may be a genetic “super-taster” -- with more specialized taste buds on the tip of your tongue than the average person.

For you, tasting foods can be the equivalent of feeling objects with 50 fingers instead of five -- due to tiny genetic differences you share with fellow super-tasters.

The super-taster story goes back decades. In the early 1930s, a DuPont chemist named Arthur L. Fox was synthesizing a chemical called phenylthiocarbamide, or PTC, in his lab. While he was pouring the PTC into a bottle, a bit of it flew into the air -- and, apparently, right into the mouth of Fox’s lab partner. The partner commented on how bitter the substance was -- yet Fox, who also got splashed, couldn’t taste a thing. Fox later found that response to bitter taste runs in families.

These days, a related, but equally bitter, compound called 6-n-propylthiouracil (known as PROP for short) is used in research to determine sensitivity to bitter taste. About 25% of people (so-called super-tasters) find PROP unbearably bitter. Another 25% (nontasters) can’t taste PROP at all. The remaining 50% just find PROP moderately repugnant.

Researchers have identified a taste gene, called TAS2R38, that’s responsible for these differences in response to PROP as well as our perception of certain other foods. It all depends on what variant of the gene a person has. Scientists have also found that people with the super-taster version of the gene have a greater number of specialized structures, called fungiform papillae, on the tip of the tongue.

Women are more likely to be super-tasters than men. And, interestingly, many chefs are super-tasters. Most parents probably assume that their children are super-tasters, given that so many children have an aversion to vegetables. But although the desire for sweets or rejection of vegetables is certainly influenced by a child’s genetic makeup, studies in children with various types of TAS2R38 gene have shown that cultural and economic forces also influence their taste preferences.

Whatever version of TAS2R38 someone has, it’s true to say that many people, young and old, don’t like vegetables. In evolutionary terms, that makes some sense. Plants produce natural bitter pesticides to protect themselves from being eaten, and sometimes these substances are toxic. No wonder humans have evolved to instinctively avoid very bitter foods. Luckily, the amounts of these natural toxins found in fruits and vegetables aren’t harmful to us. (We’re considerably larger than the average garden pest, after all.)

Scientists hypothesize that the genetic differences in response to bitterness may have evolved according to the natural environment in which ancient humans found themselves. Perhaps in one environment -- one rich with bitter and potentially toxic plants -- possessing the super-taster gene might have been a plus, assuring survival. In relatively safer surroundings with fewer toxic plants, possessing the nontaster gene would be more beneficial, because nontasters would readily consume a wider range of foods, thus reaping the health benefits of a varied plant-based diet.

You might think that in our modern world, super-tasters would be at a disadvantage because they may avoid cabbage, broccoli, cauliflower, tea, soy and many other foods that contain healthful but distasteful plant nutrients. But there may be a plus side to the super-taster trait. Some super-tasters find sweet foods too sweet, and very fatty foods unpalatable. As a result, they’ll eat less of those things and their risk of obesity and heart disease might be lower. And super-tasters generally find scotch and beer undrinkable, so perhaps they are less likely to become alcoholics.

With all the evidence that vegetables are good for us, what’s a health-conscious super-taster to do? Here are some ways to take the bitter edge off vegetables.

Salt helps to block the bitter taste of foods, so a pinch of salt or a salty condiment on bitter vegetables might do the trick. A dash of soy sauce or a sprinkle of garlic salt on spinach can work wonders.

Lightly steaming broccoli, cauliflower and other bitter vegetables can help to make them more palatable than when they are eaten raw.

Sometimes a little bit of fat helps. Stir-fry vegetables in a dash of flavorful olive or sesame oil, or add avocado to a salad of deep green spinach to help take the edge off the taste.

You can also opt for less bitter, but no less nutritious, vegetables such as sweet carrots or mild baby bok choy. Or try sneaking finely diced, sauteed vegetables into soups, stews, casseroles or a meatloaf where their strong flavors will be less noticeable.

These tricks won’t work for everyone. Many super-tasters, knowing what’s good for them, just decide to grin and bear it.

Susan Bowerman is a registered dietitian and assistant director of the UCLA Center for Human Nutrition.

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Take the super-taster test

Want to know if you’re a super-taster? To test this in a laboratory, scientists place pieces of paper impregnated with the bitter substance PROP on a person’s tongue. These aren’t available at your local drugstore.

You can determine if you are a super-taster or not using the following home test.

You’ll need some blue food coloring, a magnifying glass and a piece of paper with a 1/4 -inch hole punched in it. (A paper hole reinforcer will also work.) Put a drop of food coloring on the tip of your tongue, rinse your tongue with a swig of water, and then dab your tongue dry. The result of this exercise? The fungiform papillae will stay pink, and look like little polka dots. The rest of the tip of your tongue will be stained blue.

Now for the moment of truth. Place the piece of paper with its hole over the stained area of your tongue, and count the number of pink papillae inside the hole.

Fewer than 15 papillae means you’re probably a nontaster. More than 35 means you are probably a super-taster. Any number in between 15 and 35 would mean you are an average taster.

-- Susan Bowerman