Demonizing diets? Experts say linking ultra-processed foods to poor health is “too easy”

10 Oct 2022 --- A study has linked an increased risk of obesity and obesity-related diseases in children with their mothers’ consumption of “ultra-processed” foods during pregnancy. However, some experts believe that the correlation is less than clear and such assertions shame people who may not be able to afford healthier diets. 

The researchers have also stated that these conclusions should be used to refine dietary guidelines for pregnant women and women of childbearing age. It further recommends that the social and financial barriers to better nutrition should be investigated and removed as a means to improving mother’s nutrition and lessening the rate of childhood obesity.

“This is an observational study, and like pretty well all observational studies, doubts remain about whether the higher levels of obesity in children, whose mothers ate larger amounts of ultra-processed foods, are actually caused in some way by the mothers’ diet,” states Dr. Kevin McConway, emeritus professor of applied statistics at The Open University, UK. 

“Instead of demonizing foods and making people feel guilty for not being able to afford more expensive foods, it would be better to understand the physiological reasons and find ways to mitigate those,” states Dr. Gunter Kuhnle, professor of nutrition and food science at the University of Reading, UK. Ultimately, this would also require addressing existing health disparities.” 

Finding the enemy
In the study, published in The BMJ, the World Health Organization found that 39 million children under the age of five were either obese or overweight in 2020 worldwide. The authors state that this can lead to increased risks of diabetes, cancer, heart and cardiovascular disease and early death. 

Some experts state that researchers could never consider all possible factors, but others say they do not need to.The study affirms that what it terms ultra-processed foods – sugary cereals, packaged snacks and baked goods, soft drinks and other foods common to the modern Western diet – have long been correlated with weight gain and a host of noncommunicable diseases in adults. 

To explore how a mother’s diet may also influence obesity in children, data from 19,958 children and 14,553 mothers was drawn for the Nurses’ Health Study II, which started in 1991, and the Growing Up Study, which began accumulating data in 1996. Overall, 2,471 children, about 12% of the total participants, became overweight or obese by the time they were four years of age.

“The results show that ‘ultra-processed breads and breakfast goods’ are the main contributor to the observed effect – from a nutritionist’s view, this finding is highly problematic as it combines two very different types of food,” Kuhnle elaborates. 

“Highly processed and oft very sugary breakfast cereals are likely to increase the risk of weight gain, and this is something that is well known. However, the definition used classifies virtually all bread bought in supermarkets as ‘ultra-processed,’ and for many people it would be impossible to avoid – but this is also not necessary as there is no reason to suspect this bread to have an adverse effect on health.”

Kuhnle further explains that food production measures changed during the study, forcing the researchers to institute a “voting system” to decide which products would be considered ultra-processed. Among those included was bacon, though he believes that not all types of bacon would be included in the category.

Exploring other factors
The study recognizes that there is a range of potential factors that are correlated with childhood obesity. The mother’s amount of physical activity, whether she smokes or not and her body weight may all be factors as well as the child’s own amount of physical activity and consumption of ultra-processed foods.

Another problem the researchers faced was that the mothers included were predominantly white, all were American and all came from similar socio-economic backgrounds, meaning that the results may not be applicable to other groups or nationalities. 

“The researchers recognize this issue, of course,” says McConway. “They made statistical adjustments to allow for a number of factors that could have been involved in the patterns of cause and effect, and even after those adjustments, the pattern of association between the mothers’ consumption of ultra-processed foods and the level of obesity in their children still remained.” 

Impossible to consider everythingAbout 12% of children whose mothers ate ultra-processed foods while pregnant became obese or overweight.
McConway further explains that no researcher can ever be certain that they have adjusted for all of the relevant factors and that some doubt as to the cause of the observed correlations will always exist. The study researchers admit that it can only attempt to prove correlation, not causation.

“The results of the study by Wang and colleagues are therefore hardly surprising,” says Kuhnle. “The problem with the study is one that plagues most research into ultra-processed foods: the dietary data used are based on food-frequency questionnaires that were never designed to capture the consumption of ultra-processed foods and were never validated for that use.”

Not all experts agree that the totality of factors need to be considered since much of the science and research has already been done.

“We have known for a long time that maternal diet is an important risk factor for children and that healthy eating in pregnancy and during childhood is not just important for adequate nutrition for children but for role modeling of the behaviors you want to embed,” says Dr. Hilda Mulrooney, associate professor of nutrition at Kingston University, UK. “If you want children to eat healthy foods, you eat healthy foods yourself – you model it so it is their norm.”

Sarah Coe, a nutrition scientist from the British Nutrition Foundation, also states that it is known that a mother’s diet can affect a child’s health both early and later in life, and holds that numerous human and animal studies show that fetal nutrition can be a precursor for diabetes, heart disease and even osteoporosis.

Yet, some maintain that this obfuscates the possible root causes of obesity.

“In my opinion, such studies detract from the real problem by focusing on a fashionable but wrong definition” affirms Kuhnle. “Many of the foods classed as ‘ultra-processed’ can be part of a healthy diet and there is no need to avoid them.” 

By William Bradford Nichols