By focusing on the reactions that occur in our digestive system after meals, researchers show that vitamin C could limit the formation of compounds suspected of increasing the risk of cancer. An advance which nourishes the hope of more detailed prevention, but which also calls for caution in the face of simplistic discourse on food supplements.
In our modern plates, a silent chemistry that worries researchers
We often consume them without thinking about it. Cold meats, processed meats, industrial foods: nitrates and nitrites have become omnipresent in Western diets. These compounds, used in particular as preservatives, are also present in certain vegetables grown in polluted soil or water.
However, in the stomach, these substances can participate in a chemical reaction called “nitrosation”. This can lead to the formation of nitrosamines, molecules that many scientists have long suspected of being involved in certain digestive cancers (ANSES also recommends not exceeding 150 g of cold meats per week, or approximately half a slice of white ham (20–25 g) per day).
It is precisely this mechanism that the team from the University of Waterloo wanted to explore, this time using sophisticated mathematical models capable of simulating what happens in the digestive system according to different dietary profiles.
The finding is intriguing: when vitamin C is present at the same time as nitrates and nitrites in the diet, it seems to limit the formation of these potentially carcinogenic compounds. Researchers have particularly observed this effect in foods like green leafy vegetables, which naturally contain both nitrates… and vitamin C.
Dr. Gordon McNicol, first author of the study and a postdoctoral researcher in applied mathematics, summarizes the issues this way:
“Since at least the 1990s, researchers have studied the link between cancer and these compounds, with conflicting results. Our work suggests that the presence of dietary vitamin C could help explain these inconsistencies.”.
This hypothesis could shed light on an old paradox: why do certain foods rich in nitrates, such as certain vegetables, not seem associated with the same level of risk as processed meats? The answer may lie not in any single nutrient, but in the overall balance of foods.
Vitamin C, a promising ally… but far from an anti-cancer miracle
These results could be tempting to overinterpret. However, the researchers themselves remain cautious. Because the relationship between vitamin C and cancer has been studied for decades, with often contradictory results.
Large epidemiological studies generally show that a diet rich in fruits and vegetables is associated with a lower risk of several cancers. But it is difficult to know whether this effect is linked only to vitamin C or to all the protective compounds present in these foods: fibers, polyphenols, antioxidants, micronutrients, etc. The data concerning food supplements are much less convincing.
A large meta-analysis published in the scientific literature already concluded several years ago that there was “no evidence” to support the use of vitamin C supplements to prevent cancer. Same caution from the American health authorities. The National Institutes of Health recalls that the results of clinical trials remain “inconsistent” concerning a possible protective effect of vitamin C on the risk of cancer.
In other words: eating fruits and vegetables rich in vitamin C seems beneficial for overall health. But swallowing massive doses of supplements does not mechanically protect against cancer. Some work even suggests that at very high doses, certain antioxidants could have undesirable effects in certain specific situations, notably in patients already suffering from cancer.
What is emerging today is therefore a more nuanced vision of nutrition: it is not an isolated nutrient that acts alone, but a complex set of biological interactions.
Behind the scientific promise, a deeper message about our diet
Beyond vitamin C itself, this study tells us something else: our food is a living ecosystem, where molecules interact constantly. For a long time, nutrition has looked for simple culprits and absolute heroes: fat, sugar, vitamins, “superfoods”. But contemporary research is gradually moving away from this binary logic.
What recent work shows is that the same compound can have different effects depending on the dietary context in which it is consumed. The nitrates in a spinach salad do not necessarily behave like those in ultra-processed meat. This more global approach also meets the recommendations of oncologists and public health agencies: favor minimally processed foods, diversify intakes, reduce industrial products rich in additives and preservatives, and focus more on fruits, vegetables and fibers.
“Ultra-processed foods increase the risk of colon cancer because they are high in added sugars, saturated fats, salt, and contain many industrial additives, such as emulsifiers, which disrupt the gut microbiota and promote chronic inflammation. This inflammation creates a breeding ground for carcinogenesis in the colon,”
confirms Dr Gérald Kierzek, medical director of True Medical.
Vitamin C therefore does not appear here as a protective potion, but as one of the elements of a broader balance. A piece of an infinitely complex biological puzzle.
And this is perhaps where the real significance of this study lies: to remember that cancer prevention does not depend on a spectacular gesture or a miracle capsule, but often on an accumulation of daily, modest, silent choices – those which, meal after meal, shape our health in the long term.