ABOUT A YEAR AGO, when the Federal Trade Commission voted to consider imposing major restrictions on television advertising aimed at young children, we objected to the idea of the federal government's becoming the great national nanny. Now, after reading the testimony presented about those restrictions, we have decided there is need for a national nanny after all. Her job, however, should not be the one the FTC has in mind -- to supervise the ads and influence the eating habits and buying desires of young children. What is needed is a nanny to supervise the adults who are arguing about what the children should see.

Take, for example, the impression that comes through from some witnesses who do not want the FTC to restrict the advertising of heavily sugared foods. They seem to be making these points:

(1) The human body needs sugar. Sugared products contain lots of it. Therefore, sugared products are good for you and the more you eat of them, the healthier you are.

(2) Sugar doesn't cause cavities in teeth, microorganisms do. Therefore, sugar-coated cereals, candy and other sweets have nothing at all to do with dental health.

(3) The right of food processors to advertise is protected by the First Amendment. Therefore, the FTC can't regulate them.

There is a grain of truth in each of these arguments. But the "therefores" don't work, the sequiturs don't follow. Of course, the arguments are never made as starkly as we have summarized them. They are hedged and qualified and, no doubt, technically correct if you read all the footnotes and small print. One witness, from the Grocery Manufacturers of America, Inc., presented a table that at first glance suggested that sugar-coated cereals are better for you than peas, carrots, apples and orange juice. You discover, in a footnote, that he is talking about the percentage of the calories in each food that comes from sugar -- an essentially meaningless statistic. (To be fair about it, we should note that some of those on the other side of this argument use the same statistical measure, but count as relevant only the sugar man adds to foods, not those nature puts in them -- an equally meaningless statistic.)

These distortions of the health issues are equaled by distortions of the child-parent relationship. It is quite possible to infer from some recent testimony that a parent who says "no" to a child's demand for sugar-coated cereal is increasing the risk that the child will become a delinquent. It is also possible to conclude from what some witnesses have said that children get inferiority complexes when their parents refuse to buy the products advertised on television.

The more we hear, the more sympathy we have for the administrative law judge into whose lap the FTC dropped the case. The issues he has before him are serious -- should the FTC bar all advertising on programs aimed at young children and advertising for sugared food products on programs aimed at children under 12? Much of the evidence being presented to him is not serious; it is so full of exaggeration, Madison Avenue hype, theories and guesses as to be almost useless. None of it has persuaded us that American families need a federal agency to tell them what their children should see or be permitted to hanker for or urge their parents to buy. Much of it suggests that the adults arguing the issue could use a lot more common sense.