New research links plant-sourced ultra-processed foods to poorer heart health

27 Jun 2024 --- Amid ongoing scientific evidence linking ultra-processed foods (UPFs) to increased health risks, dietary guidelines frequently advise adding plant-based foods to a diet. However, a new study reveals that UPFs with mainly plant-based ingredients are not necessarily healthier, linking these to a higher risk of cardiovascular diseases and death. Instead, the researchers advise to consume “fresh and minimally processed options.”

Nutrition Insight discusses the study’s findings and implications with its lead author, Fernanda Rauber, Ph.D. She is a researcher at the Centre for Epidemiological Research in Nutrition and Health at the University of São Paulo, Brazil, and its department of preventive medicine.

She highlights that the research aimed to investigate the influence of industrial food processing on the relationship between plant-sourced food consumption and heart disease. 

“Our findings have significant implications for public health and dietary guidelines. We initially hypothesized that industrial processing would impact this relationship, but the extent was unknown. Surprisingly, our results consistently demonstrated that consuming plant-based non-UPFs was associated with a lower risk of cardiovascular disease. In comparison, consumption of plant-sourced UPFs was linked to a higher risk.”

“These results highlight the importance of considering the level of food processing when promoting plant-based diets for heart health. Simply advocating for increased consumption of plant-based foods may not suffice. It’s crucial to emphasize the importance of choosing fresh and minimally processed options.” 

“By incorporating this understanding into dietary guidelines, we can better inform the public and healthcare professionals about the most effective dietary approaches for reducing cardiovascular disease risk.”

Product classification  
The study, published in The Lancet Regional Health, used data from 126,842 participants in the UK Biobank study who completed at least two 24-hour dietary recalls between 2009 and 2012. Moreover, the researchers linked these to data from hospital and mortality records. 

The researchers classified food groups as plant-sourced or non-plant/animal-sourced foods, further dividing these into non-UPF and UPF and expressing them as a share of total energy intake. 

The researchers stress the importance of including fresh and minimally processed options into a healthy diet.Increasing plant-sourced non-UPF consumption by 10% was associated with a 7% lower risk of cardiovascular diseases and a 13% lower risk of mortality. Meanwhile, plant-sourced UPF consumption was linked to a 5% increased risk and a 12% higher mortality. 

“We classified ultra-processed foods as either plant-sourced or animal-sourced based on whether they have animal origin food such as meat, eggs or dairy,” explains Rauber. “Our aim wasn’t to evaluate if the food was vegan or vegetarian, for instance. This method aligns with previous studies in the field.”  

“Our database allowed us to differentiate between animal and plant-based options for many foods, such as ice cream, rice pudding, canned soup with meat, cheese and white sauce (animal-sourced) vs. candies, canned soup without meat, tomato ketchup and pesto (plant-sourced). For the few foods we lacked sufficient information, we opted to use the most commonly consumed version based on data from the national survey of the UK.”

For example, Rauber details that sugar and vegetable oil are of plant origin and were therefore classified as plant-sourced foods. 

UPF research update 
There has been vast research linking diets high in UPFs to increased health risks. For example, studies published earlier this year found that UPF consumption is associated with a higher risk of developing 32 adverse health outcomes and a “slightly higher” risk of death. 

“While substantial evidence already exists regarding the negative impact of diets high in UPFs on health, there remains a gap in implementing effective public policies to discourage their consumption, particularly in countries like the UK,” underscores Rauber. 

“Plant-based foods are frequently recommended in dietary guidelines, and the food industry often leverages health claims (such as vegetarian, vegan or plant-based) to promote its products.”

The primary sources of plant-sourced foods included bread, pastries, buns, cakes and biscuits.She adds that as more people adopt plant-based diets, examining the role of food processing within these dietary patterns becomes crucial, particularly concerning cardiovascular diseases. “This research contributes by shedding light on how industrial food processing influences the health outcomes associated with plant-based diets, thereby informing the refinement of guidelines to better account for the effects of food processing.”

Healthy diet 
Last year, researchers found that while high UPF consumption was linked to health risks, not all food products carried the same association. Specifically, ultra-processed bread, cereals and plant-based alternatives lowered the risk of multimorbidity by 3%. They studied this co-occurrence of at least two chronic diseases, cancer and cardiometabolic diseases. 

Rauber highlights that the researchers intended to clarify that “a plant-based dietary pattern consisting of fresh and minimally processed foods may offer protection against cardiovascular diseases.” 

“Conversely, UPFs, which may even carry claims of being plant-based due to the absence of animal ingredients in their composition, such as certain snacks or biscuits, may increase the risk of cardiovascular diseases.”

Commenting on the study and its findings, Dr. Hilda Mulrooney, a reader in nutrition and health at the London Metropolitan University, UK, highlights that “what the evidence in the study shows is that poor diets are associated with increased risk of chronic diseases.”

“Too high an intake of any one group of foods is likely to result in imbalance, and I would have far more concern that healthy foods are made more affordable. Consuming lower quality foods is the only option for many people due to cost-of-living pressures.”

Mulrooney highlights that the study’s most significant contributor to plant-based UPFs are not meat alternatives, “but bread, pastries, buns, cakes, and biscuits, which arguably are not good markers of a plant-based diet since many people consuming meat will also be consuming those products.” 

Future studies should include different health outcomes and diverse populations, such as different ranges of UPFs in their diet.“The study authors take this into account by categorizing the foods people consume and then looking at the proportions consumed, but it seems an unusual way of classifying a diet as plant-based.”

She adds that high intakes of many of those products are markers of generally poorer diets and are likely to be associated with lower intakes of fruit and vegetables, for example. “This may be due to the higher costs, relatively speaking, of healthier foods like fruit and vegetables.” 

Next steps  
The authors suggest that the study has several limitations. For example, 24-hour recalls are susceptible to recall bias, misreporting and the accuracy of food composition databases. They note that the residual confounding cannot be completely ruled out, even though they adjusted for important confounders. Moreover, the study’s low response rate may limit the findings’ generalizability. 

Rauber highlights that future studies that incorporate different health outcomes and diverse populations, including those with varying contributions of UPFs in their diets, can enhance the generalizability of the results. 

“By conducting such studies, we can better understand whether the impact of food processing on the relationship between plant-based food consumption and cardiovascular disease, as observed among British adults, is consistent across different populations and health outcomes.”

“Currently, we are investigating the association between plant-based food consumption, considering the level of ultra-processing, and various health outcomes among British adults. Furthermore, we intend to explore these associations in other populations. For instance, the NutriNet-Brazil study is ongoing and already has over 110,000 registered participants. This study aims to identify dietary characteristics that increase or decrease the risk of chronic diseases in the Brazilian population.”

By Jolanda van Hal