The link between nutrition and health
A range of factors influences health, including genetics, lifestyle, environmental factors, and diet. Unraveling the complex relationships between these factors is a challenge.
09 February 2021 | Health
In what is described as the world’s largest nutrition study, the NutriNet-Santé study is an ongoing investigation into the relationship between nutrition and health.
MedicalNewsToday in a special feature, looked at some of the project’s findings and spoke with Principal Investigator Dr. Mathilde Touvier, who has been involved in the study since its inception.
For many reasons, it is incredibly difficult to investigate the role of nutrition in health and disease. For instance, no two people eat the exact same diet, and very few people eat the exact same food 2 days in a row.
As it is neither feasible nor ethical to ask thousands of people to follow a strict diet for 10 years to see what happens, researchers have to find other ways of unpicking the links between diet and disease.
Beginning in 2009, the NutriNet-Santé study was the first internet-based study of its kind. By the start of 2021, the team was regularly collecting data from 171 000 people aged 15 years and older, making it the largest ongoing nutrition study in the world.
Specifically, the researchers set out with the following aims:
Investigate the relationship between nutrition, health, lifestyle factors, and mortality and examine the factors that influence dietary patterns, such as economic and cultural factors.
The researchers keep a biobank of serum, plasma, and urine from about 20 000 people. They also collect stool to monitor and analyze gut bacteria.
Alongside questions about food intake, the NutriNet-Santé team collects information about food packaging, cooking practices, mode of production, physical activity, tobacco, drugs, environmental factors, and domestic and professional exposures.
Importantly, data from the NutriNet-Santé study are linked with medical and insurance records to improve accuracy regarding medications, diagnoses, and long-term sick leave.
Over recent years, data from the NutriNet-Santé study have revealed associations between diets high in ultra-processed foods and an increased risk of cancer, cardiovascular disease, mortality, depressive symptoms, type 2 diabetes, obesity, and gastrointestinal disorders.
As an example, one paper based on data from the NutriNet-Santé cohort, which appeared in the BMJ in 2018, concluded:
“In this large prospective study, a 10% increase in the proportion of ultra-processed foods in the diet was associated with a significant increase of greater than 10% in risks of overall and breast cancer.”
Another study using their data, which also appeared in BMJ, concludes:
“[H]igher consumption of ultra-processed foods was associated with higher risks of cardiovascular, coronary heart, and cerebrovascular diseases.”
Yet more research, which appeared in BMC Medicine in 2019, investigated ultra-processed foods and their links with depression. The authors write:
“Overall, [ultra-processed food] consumption was positively associated with the risk of incident depressive symptoms, suggesting that accounting for this non-nutritional aspect of the diet could be important for mental health promotion.”
Understanding which foods are associated with which health conditions is important, but the next step — changing behavior — can be even more challenging.
To address this, the NutriNet-Santé study focused on food labeling. Although product labels already provide information about levels of fat, sugar, and other ingredients, as Dr. Touvier pointed out, quickly gauging whether a product is healthful as you rush around a grocery store is not easy.
With this in mind, the NutriNet-Santé group designed Nutri-Score. This simple label gives each product a score from A to E, with A being the most healthful and E the least healthful.
The scoring system takes into account the amount of sugar, saturated fats, sodium, protein, fiber, fruits, vegetables, nuts, and legumes to provide a score.
“The score has been validated against many health outcomes, using the NutriNet-Santé cohort [and other cohorts]. So we showed that people who ate foods with a better score had less risk of cancers, cardiovascular disease, obesity, and so on. We also validated it in other independent cohorts,” explained Dr. Touvier.
“We also used the NutriNet-Santé cohort to validate how the score is understood and used by participants to rate nutritional quality.”
And, even more importantly, the research has shown that in a grocery setting, people with access to this type of labeling choose more healthful foods. As the authors of one paper explain:
Dr. Touvier and the team are currently trying to convince the European Union to roll out the scoring system throughout the E.U. in 2022. However, they are facing stiff resistance from certain large food corporations and their lobbying groups.
More than 40 published studies back the benefits of the Nutri-Score. Dr. Touvier hopes that “it will be adopted because, for the consumer, we really showed it will have a great impact.”
The benefits of organic
Over the years, there has been a fair amount of controversy around the benefits of eating organic produce. As Dr. Touvier explained, until recently, there were simply not enough data to make connections between these products and health outcomes.
Once again, the NutriNet-Santé study has begun to fill these gaps. According to Dr. Touvier, the team found “an association between higher concentrations of organic food and a lower risk of breast cancer and lymphoma.” Similarly, the data “showed a lower risk of obesity, overweight, and metabolic syndrome.”
The researchers have also demonstrated that people who eat more organic foods have “lower levels of pesticides in their urine.” Next, they plan to quantify exposures to the various types of pesticides and identify “cocktails” of pesticide exposures. They are in the process of assessing whether certain pesticidal cocktails might be associated with specific health outcomes.
According to Dr. Touvier, one such study, which has just been accepted for publication in the International Journal of Epidemiology, found that:
“People exposed to these cocktails of pesticides had a higher risk of postmenopausal breast cancer.”