IN 1968, a team of U.S. senators and physicians set out in search of hunger and malnutrition within this country. They were shocked by how much they found. Ten years later, many of the original team repeated their tour and reported with satisfaction that, thanks to numerous federal feeding programs, hunger was no longer a major problem within U.S. borders. Now a third team reports that much of that progress has been reversed.

The Physicians Task Force on Hunger in America is only the latest of many groups to note that millions of people in almost every part of the country cannot afford to buy enough food to keep their stomachs filled and their bodies adequately nourished. But its findings are especially noteworthy because the group includes many distinguished physicians and public health experts and its report is based on a large number of independent studies, reports from hospitals and feeding centers around the country and hundreds of interviews with hungry people and those who try to help them.

The task force estimates that 20 million people in this country go hungry at least periodically. Whether that number is correct, the evidence amassed by the task force should convince the most skeptical that hunger in the United States is not an isolated problem confined to a small group of hopeless derelicts. It extends to millions of families and elderly people as well. Moreover, the problem has worsened in recent years as the direct result of government policy.

Yes, it is true, as the Reagan administration frequently points out, that government still spends billions on food stamps and other food aid. But that aid has not kept up with growth in the number of poor people which has, unfortunately, resumed in the last few years. Even after two years of solid recovery, unemployment remains high by normal standards. High taxes, declining wages and lost welfare supplements have driven many working families into poverty. And, thanks to cutbacks in welfare aid, unemployment insurance and job programs, the number of very poor people has increased especially rapidly.

The task force recommends making food programs more generous and responsive. But it also points to an even more basic problem -- the deterioration of cash welfare programs. Food stamps are not meant to provide even a full diet -- much less other basic needs such as shelter and clothing. But many poor people have far too little cash both to supplement their diets and to buy other necessities. Most of the non-elderly poor aren't eligible for regular welfare aid at all either because they work at low wages or have no children. And, as a new Ways and Means Committee report points out, benefits for those families who are eligible for welfare have declined sharply over the last several years -- by more than 20 percent even when food stamps are included. The wonder is not that people are hungry in this rich country, but that so few of their leaders seem to care.