NEW ORLEANS — While food technologists have been and remain important, their work generates mistrust in the public eye, said Joanne L. Slavin, a professor of food science and nutrition at the University of Minnesota.

In a June 23 presentation, Dr. Slavin discussed food technology and the nutrients targeted for reduced intake. She spoke at the Institute of Food Technologists annual meeting and food exposition at the Morial Convention Center in New Orleans. Her presentation, titled “Eat less of this: Dietary guidance for reduction of sodium, sugar and fat,” was part of a larger panel discussion titled “Healthy reduction: Perspectives on improving nutrition in prepared foods by reducing or replacing targeted ingredients.”

Dr. Slavin was sympathetic to the plight of today’s food technologists and was encouraging at the same time.

“There is a lot of mistrust of food technology and very little appreciation of it, which is unfortunate,” she said. “For people at I.F.T., that’s our job, explaining to people the advantages of it. I think it will continue, even if food technology solves nutrition issues. Nutritionists say, ‘We need to reduce this, reduce this and reduce this.’ Food technologists come up with solutions that continue to be criticized. It’s frustrating, and those solutions will continue to be needed, like decreasing calories, decreasing sodium and decreasing added sugar. And improving the fat profile of the product.”

The entire “eat less of this” approach, so popular in the media, is on shaky ground from a scientific perspective, Dr. Slavin said.

“We’re very adaptable to a wide variety of foods,” she said. “We can live on almost anything. People argue about whether we should have high carbohydrate diets, high fat diets. Looking at healthy diets, there are Arctic diets where some people live very long, where 80% of the calories are fat. Some of the African diets are 80% carbohydrates. Those can both be healthy diets. So when we start arguing about carbohydrates and fat, and that’s all we seem to do, obviously you need protein first, and then fill in with carbohydrates and fat.

“Sweet foods traditionally have been pretty safe, versus bitter foods, so everyone has a sweet tooth. Taking sweet out of food is pretty difficult because people do prefer it.”

Dr. Slavin traced the endless tug of war between macronutrient categories to the 1977 eating recommendations issued by the U.S. Senate Special Commission on Nutrition and Human Needs, a committee led during the late 1960s and into the 1970s by Senator George McGovern of South Dakota.

“Remember, this is political, this is not generated by scientists,” Dr. Slavin said, noting that increased intake of carbohydrates was recommended as a way to combat heart disease. The recommendations also called for a 40% reduction in sugar intake. All in all, the guidance made no sense, she said.

“How are you going to increase carbohydrate intake by 10% when you’re reducing sugar by 40%?” she said. “No one ever looked at the numbers and said they don’t make sense. This wasn’t a diet. These were just numbers, pulled out from wherever. You look at salt. There is a recommendation to reduce intake to 1,200 mg. That’s been around since 1977. So there always has been this recommendation to lower sodium intake to levels that are ridiculous.”

Since that time, dietary recommendations have changed only slightly, Dr. Slavin said. An exception was 2005, when the elimination of trans fatty acids from the diet was recommendation as was increased intake of whole grains.

“Getting half of your grains from whole grains was a policy shift, and if you look at sales, you can see the effect,” she said.

Commenting on her time on the Dietary Guidelines Committee for the 2010 edition of the Dietary Guidelines for Americans, Dr. Slavin said ensuring an adequate focus on protein was a principal objective for her.

“That really had gotten lost,” she said. “A lot of the old recommendations had gone away from recommending high quality animal protein products.”

She had criticisms for the earlier guidelines. In particular, she offered a negative view of the third chapter, which begins with a recommendation to reduce intake of sodium to 2,300 mg and further reduce consumption to 1,500 for individuals who are 51 or older or are African American or suffer from hypertension, diabetes or chronic kidney disease.

“This was not the science committee that said, ‘Let’s put sodium first,’” she said. “Of all the things, why would sodium lead? Everyone agreed calories should lead. Once recommendations like these are in the dietary guidelines, they are going to stay forever, and they will bite you. There are recommendations for 1,500 mg, which are a struggle, whether it is in school lunches or elsewhere.”

She also noted an emphasis on four nutrients Americans need to consume in larger quantities: fiber, potassium, vitamin D and calcium.

She called the proposal to included “added sugar” on Nutrition Facts panels “more confusing than necessary” and reminded the audience that comments may be submitted and that the change had not yet been finalized.

“Also, vitamin C and vitamin A go away,” she said. “Those are really big changes and are based on the ‘need more’ nutrients.”

She warned that proposal requires food manufacturers to demonstrate the physiological effect of fiber content and noted the recommended fiber intake level has been raised to 28 grams per day from 25.

“If you own a fiber ingredient and have no human data to show a physiological effect, I’d start right now preparing to make the case for it,” she said.

Another trend of concern identified by Dr. Slavin is a movement against all processed foods, which she described as “a way to get a lot of people off the playing field” rather than singling out sodium, sugar or other ingredients one or two at a time.

She cited an article in The Lancet, in which this case was framed in particular lystrident terms: “(We) conclude that unhealthy commodity industries should have no role in the formation of national or international non-communicable disease policy. Despite the common reliance on industry self-regulation and public-private partnerships, there is no evidence of their effectiveness or safety. Public regulation and market intervention are the only evidence-based mechanisms to prevent harm caused by the unhealthy commodity industries.”

Examples of ultra processed foods cited include burgers, pizza, pasta, nuggets and biscuits, sugared drinks and snack products.

Looking at the 2015 guidelines, Dr. Slavin said little attention will be devoted to matters of “settled science” while the emphasis will be on a move toward “whole foods” and away from nutrients.

“The idea is that whole foods are good, and you just need to get more whole foods into people’s diets and that will somehow magically improve people’s nutrients,” she said.

Other topics that could arise that haven’t in the past include sustainability, gluten and even vegan diets.

“We can’t eat just protein,” Dr. Slavin said. “There isn’t enough money in the world. So we have to base our diet on some kind of starch — rice, potatoes, pasta, bread, all of those things and then you build up from there. Unfortunately we’ve moved away from that.”

She cited the 1992 Food Guide Pyramid as a good illustration of this approach (building up from the base) and called the 2005 revision a “disaster” that wasted a lot of money.

Dietary guidance will continue to support eating less sodium, less sugar and less fat, and the subjects will remain controversial. Among these controversies, Dr. Slavin said saturated fat intake will continue to be discouraged because “there is still a lot of acceptance that it contributes to cardiovascular disease.”

The voice of food technologists must be heard in the public discourse over nutrition, Dr. Slavin said.

“It’s critical that we have people skilled in food technology and production on scientific panels that determine nutrition policy,” she said.

She cited the latter point as a “real problem” with the advisory committee working on the 2015 Dietary Guidelines. The lack of a food technologist may lead to impractical recommendations, she said.