Fresh foods are healthier than highly processed products with lots of additives. A large epidemiological study now reveals a possible link between numerous preservatives and cardiovascular disease. These also include surprising candidates such as vitamin C and citric acid, which were previously considered more protective. Further investigations should now clarify to what extent the observed associations are really based on causal relationships and through which mechanisms the additives develop their potentially harmful effects.
Most processed foods contain numerous preservatives designed to extend their shelf life. So-called non-antioxidant additives such as nitrites and sorbates inhibit the growth of harmful microbes such as mold and bacteria; On the other hand, antioxidant additives such as vitamins C and E prevent food from discoloring or becoming rancid due to oxidation. Which preservatives are contained in a product can be seen from the E numbers in the list of ingredients.
Large epidemiological study
“Experimental studies suggest that some preservatives could be harmful to cardiovascular health, but until now we have not had enough evidence on the effects of these ingredients on humans,” says Anaïs Hasenböhler from the French National Institute for Health and Medical Research INSERM. In order to uncover possible harmful influences, Hasenböhler and her team have now evaluated the results of a large epidemiological study in France for possible associations between preservatives and cardiovascular diseases.
A total of 112,395 volunteers took part in the study called NutriNet-Santé and kept a food log for one to three days every six months. Additionally, they provided extensive information about their health and lifestyle. The researchers evaluated which and how many preservatives the people had consumed and related this to cardiovascular diseases that occurred within the observation period of an average of seven to eight years.
It’s the quantity that counts
As the research team found, almost all test subjects consumed foods with preservatives. However, there were significant differences in the amount – and these were also reflected when looking at cardiovascular diseases: people who consumed the largest amounts of non-antioxidant preservatives had a 29 percent higher risk of high blood pressure than those who ate the least of them. Their risk of cardiovascular diseases such as heart attack, stroke and angina pectoris was increased by 16 percent. Antioxidant additives were also associated with an increased cardiovascular risk: people who consumed a particularly large amount of antioxidant preservatives had a 22 percent increased risk of high blood pressure.
Hasenböhler and her team also individually evaluated the respective risk association for the 17 most frequently consumed preservatives. They identified eight candidates that are classified as harmless under current food law, but were linked to high blood pressure in the analysis. In addition to potassium sorbate (E202), potassium metabisulfite (E224) and sodium nitrite (E250), this also included vitamin C (ascorbic acid, E300) and its related compounds sodium ascorbate (E301) and sodium erythorbate (E316) as well as citric acid (E330) and rosemary extracts (E392). The researchers also observed an association with vitamin C with cardiovascular diseases.
Causality still unclear
Some of these compounds, including citric acid and rosemary extracts, were previously considered protective factors against high blood pressure. “In animal models, they showed potential blood pressure-lowering effects,” report the researchers. As an explanation for why these actually protective compounds might have the opposite effect, the team speculates: “Low exposure in humans could lead to long-term adaptation in which initial blood pressure-lowering responses and blood pressure-increasing responses balance each other out. Further research is needed to clarify how these additives affect vascular function.”
Vitamin C is also actually considered to be beneficial for heart and vascular health. The structure of the vitamin is always the same, whether it comes from fresh fruits and vegetables or is consumed as a food additive or vitamin supplement. But the researchers speculate that the dose and interactions with other food ingredients could possibly influence whether vitamin C has a positive or negative effect on the cardiovascular system.
They also emphasize that their study is not designed to prove causal relationships. Instead, it can only reveal associations that then need to be tested in further studies. The team now wants to carry out such studies to better understand whether and how certain additives increase the risk of disease. “In the meantime, our results support existing recommendations to favor unprocessed and minimally processed foods and to avoid unnecessary additives,” says Hasenböhler’s colleague Mathilde Touvier.
Source: Anaïs Hasenböhler (Université Sorbonne Paris Nord and Université Paris Cité, INSERM) et al., European Heart Journal, doi: 10.1093/eurheartj/ehag308