Speaking of eating, the Heritage Foundation has given a fresh boost to a good, solid, conservative, impeccably Republican idea for feeding the world's hungry. It's in the Washington-based think tank's 3,000-page set of advisories to President-elect Ronald Reagan. Purdue economist emeritus Don Paarlberg, a former Agriculture Department official, wrote it.

"Increased populations in the poorer countries of Asia, Africa and Latin America require vastly more food," the report says. "What are our opportunities and responsibilities in helping meet these needs?"

The Heritage answer: "There is now the scientific knowledge and the institutional arrangement which makes it possible to overcome hunger, not only within the United States but throughout the world. This can be done within the lifetime of people now living, if there is the political will to do so. The Department of Agriculture, the Land Grant Colleges, the Experiment Stations and the Extension Service have the greatest body of scientific knowledge and practical know-how anywhere in the world. If this is used effectively, the world's well-being will be significantly advanced and the place in history of the USDA and its allied institutions will be one of honor."

Out in Lafayette, Ind., Paarlberg was delighted to say more. "We have hundreds of agriculture scientists helping foreigners with agricultural problems," he said. "A whole range of agricultural disciplines is being adapted -- through the Land Grant college system, through AID, through the international research network. But these efforts are still of a modest scale and encounter some opposition -- they're in a holding pattern.

"Some people, especially in Congress, deny we have a responsibility beyond our borders -- they call any kind of help 'giveaway.' Some farm people fear that if we help, say, Malaysia produce palm oil, it will compete with our soybeans. They fear building up our competitors. But on the whole, the record shows that as we help others, in time they become paying customers for our agricultural and non-agricultural products.

"At first we exported capital-intensive technology -- tractors, which liquidate small farms. It was disruptive and disappointing. Some then went to the opposite extreme in 'appropriate technology': build a better hoe. But now after 30 years we've found a middle way.

"Look at India. It was written off in the '70s, but now it's self-sufficient in grains. We shouldn't overpromise, but we can fix hunger in this generation if there's the political will -- with greater support for development, more acceptance of interdependence, opening our borders to the products of those countries and more emphasis on population control. The Republicans should be nudged to use our agricultural capability in this way. Agriculture should be considered not so much a 'problem' as a great resource."

I bounced Paarlberg's ideas off Montague Yudelman, World Bank agriculture director. He praised the USDA as "one of the greatest research machines ever." He also noted that the international research institutes do more than the USDA in the tropical agriculture relevant to many poor countries' needs.

The Republicans, Yudelman suggested, would do well to "stick to the World Food Conference [1974] consensus: most problems must be solved in the countries concerned. Research, financing and institution development are all necessary, but there are no shortcuts. In the end, you must deal with hundreds of millions of individual farmers."

Then I went to a panel of experts at the Agency for International Development, who were eager to nurse along any signs of Republican interest in hunger. They noted that food and nutrition constitute AID's single biggest development account (population is next) but that other projects with more political muscle keep bumping food production down. About three times as much is spent on the Food for Peace surplus-distribution program, for instance, as AID spends on agricultural development.

These experts also drew a distinction between the Heritage Foundation's supply-side approach to the world food problem and AID's own demand-side approach to world hunger. "India produces enough to feed all its people, but major parts of the population are malnourished because of a lack of purchasing power," the panel said. "We don't argue with the emphasis on science and technology transfers to improve supply, but the critical factor is demand, something recognized only in the last half-dozen years. Demand is the political dimension."

Well, nothing is simple. But the differences are of emphasis, not purpose. There's every good reason not to quibble with eminent and eminently Republican advice to a Republican administration to fight what the Heritage Foundation justly calls "man's oldest enemy": hunger.