EVEN WITHOUT any of the cutbacks the Reagan Administration plans to make in the Food Stamp Program, the current allotments do not entitle the vast majority of recipients to a nutritionally adequate diet. They never have. They never could because the allotments are based on a food plan that has been nutritionally inadequate for almost every American family since its inception. When the Department of Agriculture devised the plan in the '60s they said it was for "temporary or emergency use when funds are low. Not for long-term use."

As recently as April 1980, USDA acknowledged the plan's faults in the Federal Register.

"The Department recognizes that a number of factors make it difficult for many families to obtain an adequate diet on the amount of money which represents the cost of the Thrifty Food Plan. In fact, data on food consumption among low-income households indicates that fewer than one in ten families spending an amount of money equivalent to the cost of the Thrifty Food Plan received 100 percent of the Recommended Daily Allowances. Less than half received even two-thirds of the Daily Allowances. . . The average food purchaser, without specific nutritional skills and training, would find it difficult to make the food choices which provide an adequate diet on the amount of money which represents the cost of the plan."

Study after study of the Thrifty Food Plan has reached the same conclusions.Yet proposed cutbacks in the Food Stamp Program would make it even more difficult to obtain an adequate diet. Joan F. is one of those food stamp recipients. She lives in Prince George's County with her three sons and her husband, a construction worker who brings home $150 a week. Joan F. is worried:

"They're getting ready to slash it now because these people don't have enough voice. Oil companies can have thousands of lobbyists. Poor people have got to get together. You have to stick up for your rights."

Joan F. gets $71 per month in food stamps. With that she buys her staples -- 3 packages dried beans, 6 pounds of spaghetti, one gallon cooking oil, 10 pounds of rice, 10 cans canned milk, 12 loaves bread, 20 ounces instant coffee, 15 dozen eggs, 15 pounds sugar, 5-pound box hamburger patties and 5-pound box pork chops. The rest of the family's food is purchased from her husband's salary, more than half of which must go to rent.

When the family had a car they shopped at stores where they could save money: Marlin Annex, Plus, Hampshire Open Air Market, Ottenberg's Bakery Thrift Store. Without the car Joan F. must shop at the supermarket up the street where everything costs more.

"Produce is a luxury. We buy a lot of hamburger, pork neck bones, eggs. Soaps and cleaning products we search the ads for. We can't buy them with food stamps. I didn't know being clean was considered a luxury."

Joan F. could be considered an average food stamp homemaker, which is a problem in itself, according to one critic of the Thrifty Food Plan and food stamp allotments: "A homemaker needs considerable skill and interest in buying and preparing food if she is to provide her family with a good diet for as little as the cost of the plan. Many homemakers with limited budgets do not have the skill or interest or equipment needed to do this."

But even a qualified nutritionist could not provide a nutritionally sound diet on food stamps for most families. Following USDA's Thrifty Food Plan menus would provide enough protein, calcium, iodine, vitamin A, vitamine C, phosphorous, vitamin B-12 and riboflavin. but the menus do not provide enough iron, zinc, vitamin E, niacin, vitamin B 6, folacin, magnesium and pantothenic acid. They also do not provide enough energy (calories).

The shortages are traceable to the small amounts of meat provided in the plan -- approximately 2 1/2 pounds a week when the plan was formulated, less for today's food stamp recipients since prices have outpaced their allotment increase. Nutritional deficiencies also result from the lack of dark green vegetables and the use of enriched breads and cereals instead of whole grains. (Whole grain products cost more than enriched.)

In addition to the fact that there never was enough money in the Thrifty Food Plan to provide an adequate diet, food stamp allotments have not kept up with inflation. Food price inflation was 11.5 percent in 1978 and 10.1 percent in 1979, but the value of the plan increased only 9.7 percent and 7.3 percent, respectively.

In addition, the allowance for food stamp allotments is based on the cost of food three months to a year prior. So recipients are always behind in real-dollar terms.

No allowance is made for regional price differences. In some cities there is a sales tax.

The cost of the plan is based on averages of retail food prices for cities, but food costs more in inner-city neighborhoods where many food stamp recipients live.

Buying in bulk helps reduce the cost of food, yet many poor people lack adequate refrigeration or storage space.

There is very little allowance for waste -- 5 percent, half the amount of waste USDA calculates most families have.

No allowance is made for the special diets old or ill people may need.

The plan is based on a hypothetical family of four, but a household with two adolescent boys would need $60 more than a household with two pre-school children to achieve nutritionally adequate diet. Joan F. has three teenage boys:

"It's real hard with kids. They eat so much. It takes two chickens to feed this family fried chicken."

Joan F.'s family doesn't have fried chicken very often. It's usually chicken with noodles. That way one chicken is enough. The children also get free breakfast and lunch at school. That helps provide a more balanced diet. But one of the budget-cutting suggestions is to count the free school lunch against the food stamp allotment.

Supporters of this argument, known as the Helm's amendment, say that with free school lunch the children are getting "four meals a day." But when the food stamp program was inaugurated, free school lunches were factored in when figuring allotments. Figuring in the school lunch again would be the equivalent of counting it twice, like double jeopardy.

The food Stamp Program provides an average of $1.30 a day or 43 cents per person per meal. A recent newspaper editorial asked how the program could be cut any more when a cup of coffee costs 35 cents. "Surely Mr. Stockman [a reference to the director of the Office of Management and Budget] cannot wish to be remembered for a policy of 'let them eat coffee,'" it said.

On 43 cents a meal plus some money from her husband's salary, Joan F. fed her family the following last week:

"Monday night we had no stamps. It was the end of the month. We had some leftover frozen hamburger patties with french fries and rice. Sometimes at the end of the month we just have pancakes for supper, sometimes just canned vegetables, even just rice. Tuesday the stamps came and we went shopping. We're so tired when we get home after shopping and carrying all those bags from the store, we just help ourselves. We had balogna and cheese sandwiches with potato chips and iced tea. Wednesday we had barbecued chicken and scalloped potatoes. Thursday was stew made of pork neck bones, mixed vegetables and potatoes with gravy mix. Sometimes we have bread. We usually drink iced tea or Kool-Aid.

Organizations that work with the poor, like Food Research Action Council, worry that a reduction intghe Food Stamp Program will return the country to the days when many Americans were suffering from serious malnutrition.

Lynn Parker, nutritionist with FRAC, said; "The kinds of stories we heard in 1967 just aren't heard as much today, thank goodness. However, if the food stamp allotments are decreased or if large numbers of poor families become ineligible for the program, we will be turning back the clock and will return to the old horror stories. People on the nutritional/economic borderline will slip back into real problems."

Last year the overwhelming majority of the membership of the American Public Health Association and the Society for Nutrition Education passed resolutions calling for upgrading of the Thrifty Food Plan. Their resolutions said the plan should allow for 100 percent of the Recommended Daily Allowances for nutrients and should incorporate Dietary Guidelines. Other groups have urged that at a minimum, the Thrifty Food Plan should be upgraded to USDA's Low Cost Food Plan which would provide a family of four with about $15 more a month.

These resolutions are unlikely to be enacted when the country is in a budget-cutting mood.