Thank goodness we can hold to certain truths passed on by our parents, that inspired us: What goes up must come down.

A penny saved is a penny earned.

Don’t count your chickens before they’re hatched.

But something happened with the food truths. A little stirring of the pot. A pinch of half-truth. And suddenly, a crock of old wives’ tales. So it only seems right that we should lift the veil of mystery from a few “truths” that might be a trifle false. Here then, are the myths:

* How to Keep From Crying When Cutting an Onion. Oh, there seem to be as many methods as there are cooks to stop the sobbing, but few methods have any basis in fact.

“My mentor and good friend, [food writer) Bert Greene, swore a wooden spoon clenched between his teeth helped,” says food writer Sharon Tyler Herbst, whose book The Food Lover’s Tiptionary (Hearst Books, 1994) offers some tear-stopping tactics.

“But it’s really subjective. I just chop the onion fast. I hold my breath. Or one of my favorite ways is to throw those suckers in a food processor . . . and have a pan ready.”

As anyone knows, cutting into an onion can be hazardous to your tear ducts; a knife ruptures an onion’s cells, throwing together sulfur compounds and enzymes, which waft straight to the eyeball. About the only sure-fire method to keep from crying is to avoid cutting the onion.

To lessen the offensive vapors, though, you could try chopping the onion on top of the stove _ exhaust fan running _ so most of the vapors will be sucked away. You also can try freezing the onion for 30 minutes first; enzymes are slowed by cold.

And if nothing else works, don goggles to shield your eyes.

* Chocolate Causes Acne. “For the most part, acne is caused by a hormonal change in adolescence,” says Mark Meskin, a dietitian and professor. Few, if any, studies exist showing links between diet and acne.

Ultimately, a balanced diet combined with regular exercise, adequate sleep and good health habits can promote clear skin.

* A Pregnant Woman Must Eat for Two.

“Boy, I made that mistake,” says Nancy Rommelmann, author of Everything You Pretend to Know About Food and Are Afraid Someone Will Ask (Penguin Books, 1998). You really need only 300 extra calories a day _ that’s 11/2 yogurts, she adds. Expectant mothers should focus on their intake of iron and calcium, the most important nutrients for a growing fetus, dietitian Meskin says.

Some expectant mothers don’t eat enough, says Meskin, so the advice could have been a way to get a woman to eat more.

Or, a woman might figure she needs to make up for not having eaten much during the first few months of pregnancy when she’s nauseated, says Dr. Dean Edell.

Interestingly enough, several old wives’ tales deal with pregnancy and food _ everything from drinking a lot of milk to produce a lot of milk, to avoiding sour foods when pregnant so you won’t wind up with a child who has a sour disposition.

* Fish Is Brain Food.

Recent studies in the nation’s leading health journals confirm that fish is good heart food. The omega-3 fatty acids, found almost exclusively in fish, help keep arteries open by discouraging the buildup of artery-clogging plaque. They may also discourage high blood pressure. Eating a couple of servings of fish a week may help reduce the risk of heart disease. Fish is also fairly low in calories and fat compared with other sources of protein.

Some scientists think that omega-3 fatty acids may play a role in mental development at a time of rapid brain growth _ childhood _ but studies are still inconclusive.

* Pasta Sticks to The Wall When Done.

Today’s palate likes pasta al dente _ firm to the bite. Yes, well-cooked pasta might be gummy enough to cling to anything. A better way of checking is to fish a piece from the cook pot and taste it. If the center is still hard and floury, it’s not done. You want it tender but firm. Keep in mind that pasta still cooks a little after you pull it from the pot because of the residual heat.

* Eat Your Carrots and You’ll Have Good Vision.

Years ago, when vitamin deficiencies and poor nutrition were more common, this statement probably held some truth. Such a deficiency is uncommon in Western countries today, but the idea persists. Carrots are high in vitamin A and beta carotene, and the eyes need these nutrients to make the pigments that absorb light within the eye.

Carrots remain the leading source of vitamin A in our diets, and some research shows that eating carrots may lower blood cholesterol levels.

* Water Will Stop the Burn From Hot Chili Peppers.

Gulping water if your mouth is on fire is about the worst thing you can do, says Anne Gardiner, who teaches in British Columbia and co-writes a food-science column called The Inquisitive Cook (also on the Web, ). Much of the heat in chili peppers comes from capsaicin, the fiery compound found mostly in a chili’s seeds and membranes. Drinking water or beer further disperses the heat throughout your body. Uh-oh.

Dairy products such as milk, yogurt and ice cream are the answer. They seem to neutralize the chili’s oils. Bread, rice and tortillas also seem to absorb the chili oils and help lessen the burn.

You can learn to tolerate hot foods by eating them fairly often.

* Browning meat seals in juices.

Uh-huh.

When it comes to meat, any heat causes the muscle fibers to shrink and expel moisture, making meat drier. Browning does create color and flavor, however, Gardiner says.

* Giving Kids Sugar Makes Them Hyper. “N one has been able to reproduce this in a scientific setting,” Meskin says. “This is one of those old wives’ tales that is so entrenched in the face of a tremendous amount of data to the contrary that you can’t convince people otherwise.”

Adds Edell, “Parents will give a kid an artificially sweetened soda with a lot of caffeine, then they blame the candy bar.”

What sugar does is encourage the growth of oral bacteria, the cause of cavities.

* Put the Seed Back in an Avocado To Keep It From Browning.

About the only thing that will do is keep the flesh beneath the pit from turning brown. The best thing to do: Drizzle a little lemon juice on the sliced avocado, according to the California Avocado Bureau, and don’t wait too long to eat it.

* If You Swallow a Fruit Seed, a Tree Will Grow in Your Stomach.

The idea terrorized you as a kid. But nope.

“The seed just goes straight through” the digestive system, Meskin says.

* Eating the Crusts of Bread Will Make Your Hair Curly.

No doubt just wishful thinking from a straight-haired mother or grandmother.