You can tell Americans to spend a Thanksgiving or two without cranberries, you can make them avoid a certain brand of canned vichyssoise, you can coax them to turn their thermostats down and you can try luring them into fuel-saving car pools.

But can you, in the name of all that's flabby, take away their Tab Cola?

There are signs that you can't. The American people are taking the government-announced plan to ban the artificial sweetener, saccharin, lightly. They are taking it heavily. They are bombarding the Food and Drug Administration (FDA) with angry phone calls and some are beginning to hoard sugar-free soft-drinks and artificial sweeteners.

"Let yourself be heard!" urged an anti-FDA, two-page ad in Sunday newpapers, paid for by the diet food industry's Calorie Control Council. But the American people don't need to be told to be heard. Ask the folks at the FDA, where the decision to propose a ban was announced last week.

"This saccharin business has stimulated more calls than we've ever received on a single subject that I can recall," said Wayne Pines of the FDA's Bureau of Foods yesterday. "The phone is just ringing off the hook. Wait, here comes another one. Hold on for a second."

People have actually wept on the phone, says the FDA's Emil Corwin, but most of them are angry and, like a particularly furious, recent caller from Texas, many of them are diabetics restricted to minimal sweets or have diabetics in the family.

Many other, however, are just fat Americans who rely on Tab, Diet-Pepsi, and other diet sodas to hold their weight down. Americans consume 5 million pounds of saccharin yearly, 70 per cnet of it in soft drinks.

The FDA has opened a Pandora's box and fallen into a fine kettle of fish.

"One diabetic called from Jacksonville, Fla., and said he was a personal friend of Jimmy Carter's," says Pines. "He was especially furious. I sent him a copy of the law that was the basis for this action. Congress passed the law, we didn't."

The law states that any food additive causing cancer in humans or laboratory animals must be banned. Researchers fed lab rats saccharin equivalent to an 800 can daily intake of diet soda for a human lifetime. Some rats developed bladder tumors.

There has been no evidence of human cancer developing as a result of saccharin.

Nor have there been any cases of humans developing cancer of the rat's bladder. Most humans have human bladders. No rats do.

Pines said the FDA is aware of the argument that if you feed enough of anything to a rat, the rat will get sick. "But it is a popular misconception that if one feeds anything in large quantities to an animal it will get cancer," he said. "Even water in large enough quantities can make people ill, but it doesn't cause cancer."

Still, Americans are not taking this lying down. They are taking it standing up behind shoping carts and raiding food stores for diet drinks and artifical sweetners containing saccharin, even though the ban cannot possibly take effect, by FDA estimate, until July 9 at the earliest.

So at Katz's supermarket in Rockville, manager Stuart kauffmann recently noticed a woman shopper checking out with 12 large boxes of Sweet'n Low, a sugar substitute.He thought that was unusual.

"And my diet sodas are almost gone," said Kauffmann. "I haven't got many flavor left."

Asked how saccharin sales are going at the Fairlington, Va., Co-Op supermarket, manager Bob Lilly replied, "Let's just say I'm sold out. Does that answer your question? There's no doubt people are hoarding. I've sold more in the last week or 10 days than I had been selling in a month."

"It appears that people are over-buying on saccharin and saccharin-related products," said Safeway spokesman Ernie Moore. "Over-buying" sounded like a euphemism for hoarding. "Yes, it appears that people are hoarding," Moore conceded. "And it's not surprising."

But Barry Scher of Giant food stores was anxious to prevent a saccharin panic, a run on Tab, a Diet-Rite dementia. He said there was "heightened busines activity" on saccharin-containing products but wanted to avoid any self-fulfilling hoarding prophecies.

"The last thing we want is another toilet paper scare," said Scher. Scher was referring to the brief 1973-74 flurry of toilet paper hoarding that resulted from rumors that America was about to run short. Those were the times that tried men's stuls - but not very much.

The diet soda rush could make that toilet paper panic look like a slow boat to China. Dieters as well as diabetics depend on Tab cola or its competitors not only as adjuncts to low-calorie regimens but also as the all-purpose elixir that washes away, ceremonially at any rate, over-consumption transgressions in other areas. There used to be people, for instance, who drank Metrecal with a full, fattening lunch just because of the psycholoigcal, guilt-reducing effects.

Connoisseurs of Tab can tell you that nothing is quite so ironically yummy with a "21-fl. oz." cherry pink can of the "sugar Free!" sugar Free!" beverage as a Hershey bar.

Of course Tab does not wash such sins as a candy bar away. But at least you can say to yourself, "It could have been worse; I could have had a Coke."

The FDA's Pines admitted yesterday that he is partial to Diet 7-Up and Diet Pepsi. But, he insisted, "I don't think I need them, really."

He also pointed out that there is as yet no official ban on saccharin or foods which contain it. The FDA has decided to propose a ban. Within 30 days it will propose a ban. Then there will be 60 days of "public comment" and a public hearing.

So that the very soonest a ban could take effect, Pines said, is July 9. "If people want to stock up, that'd be the time to do it," he said.

But if people want to stock up now, in the great American tradition of conspicuous consumption and of expecting the worst, nothing anybody says is going to stop them.

Whether or not saccharin itself is banned, the word itself is probably going to stay a part of the national vocabulary, particularly among critics of the arts, who have long relied on it as a synonym for material that is sickly sweet. You may be able to stop dieters but you won't be able to stop critics.

This double-meaning for the word "saccharin" was stressed in a joke on last week's edition of "NBC's Saturday Night," during which it was reported that "The FDA has just announced that in addition to saccharin it is also placing a ban on Florence Henderson and David Hartman, effective in July.