What matters more? What you eat or how it’s made?

By Stephen Beech

Diet quality matters more than food processing levels when it comes to long-term health, suggests new research.

Healthy diets with high nutritional quality lower risks while unhealthy diets raise them — regardless of the level of food processing, according to the findings.

A study of more than 200,000 people found that the overall quality of a person's diet was strongly associated with their risk of heart disease, Type 2 diabetes and dying young.

However, those associations did not appear to substantially differ based on food processing levels.

Xiaowen Wang said: "While many ultra-processed foods tend to be of poor nutritional quality and should generally be limited or avoided, processing itself is not inherently harmful."

Based on the study results, she said people should "focus on what you're eating overall, not just whether it's processed."

Wang, a postdoctoral research fellow at Harvard T.H. Chan School of Public Health in Boston, added: " A healthy plant-based diet rich in whole grains, fruits, vegetables, nuts, legumes and healthy plant oils is beneficial, even if it includes some processed foods."

She says the nutritional quality of a person's diet and the amount of ultra-processed foods they consume are often intertwined.

Many ultra-processed foods are high in added sugars, salt and refined carbohydrates, so eating a lot of those foods is associated with poor dietary quality.

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But some ultra-processed foods — such as fortified breakfast cereals, whole grain products, canned beans or plant-based dairy — can still provide important nutrients, fiber, antioxidants and other beneficial compounds, contributing to a healthy diet.

The research team sought to separate overall diet quality from the level of food processing.

Using data from three studies that collectively followed more than 200,000 American adults from the 1980s through the 2020s, they used a framework known as the plant-based diet index to assess the degree to which each participant emphasized plant compared to animal food products in their diet, the overall quality or healthfulness of their diet, and their consumption of plant-based foods across a range of processing levels.

The study was not limited to vegans or vegetarians, but to enable consistent comparisons, the analysis focused on the plant-derived components of participants' diets rather than animal-derived foods.

After assessing each participant's overall diet and using the Nova classification system to categorize the processing level of the foods they consumed, the researchers grouped participants according to their plant-based eating habits.

For example, healthy/ultra-processed included whole grain breakfast cereal with fortified plant-based milk, plant-based yogurt, whole-grain bread and canned fruit.

Healthy/minimally processed included oatmeal with fresh fruit and nuts, quinoa and vegetable salad with olive oil, and homemade lentil soup.

Unhealthy/ultra-processed consisted of fast food meals, French fries, soda, packaged desserts and refined snacks.

Unhealthy/minimally processed included white rice, fruit juice, potatoes, and homemade desserts made with refined flour and sugar.

About half of the study participants eventually died or developed heart disease or Type 2 diabetes.