Our immune system is the primary tool we have to defend ourselves against various pathogens such as viruses, bacteria, fungi and parasites. This system is characterised by great complexity, not only because of the wide variety of cells involved in these responses, but also due to the biochemical reactions that regulate our defences. Over time, scientific evidence has increasingly highlighted the importance of factors such as physical exercise and diet in ensuring the proper functioning of the immune system. This is the case with vitamin C.
When it comes to nutrition, there are several nutrients that act as regulators of both cellular responses and the reactions that govern our immune defences. One of the most crucial nutrients for the immune system is vitamin C.
What is vitamin C?
Vitamin C is a water-soluble vitamin that is considered an essential nutrient. What does this mean? It means that we cannot synthesise it ourselves (as humans), because we lack the metabolic pathway required to do so. This vitamin is widely known for its antioxidant capacity, but this is not the only reason it is of interest.
One clear example of the importance of vitamin C is scurvy, a condition suffered by people who spent weeks sailing to other continents without access to fresh fruit and vegetables. This disease is characterised by weakness in collagen structures, poor wound healing, a weakened immune system, and an increased risk of potentially life-threatening infections such as pneumonia.
Habits and vitamin C
To prevent scurvy, the minimum amount of vitamin C required is quite low and can therefore be easily achieved. However, not everyone meets their daily needs of this vitamin to maintain optimal blood levels. This may be due to dietary habits, tobacco and alcohol consumption, and genetic variants that can influence individual requirements.
Among all the cells of the immune system, some are particularly sensitive to blood levels of vitamin C, neutrophils. These cells have been shown to contain significantly higher concentrations of vitamin C than those found in the bloodstream. Moreover, an adequate intake of this vitamin is associated with proper functioning of this cell group. This improved function includes enhanced properties such as chemotaxis, oxidative activity, antioxidant enzyme function and apoptosis of these cells.
Vitamin C not only improves immune system responses, but can also enhance certain characteristics of the barriers that protect us against pathogens. Collagen is the main protein in many of these barriers (such as the skin), and vitamin C has been shown to improve its synthesis. In addition, it can accelerate the recovery of damage to these barriers, such as in the case of pressure ulcers. Its strong antioxidant action also protects these barriers from oxidative damage that could compromise their integrity.
What about athletes and vitamin C?
Athletes may be a population at risk of needing an additional intake of this vitamin to support their immune response. It is well known that high-performance exercise can lead to immunosuppression, impairing proper immune function. However, a meta-analysis showed that vitamin C can be a very important nutrient for athletes, as its supplementation was associated with a lower frequency of upper respiratory tract infections compared with individuals who did not receive this additional intake.
For all these reasons, it is essential to ensure an adequate intake of this vitamin and to consume it regularly, especially because another characteristic of vitamin C is that it has a very short half-life in the bloodstream. Citrus fruits are well known for their vitamin C content and are a good option, but it is important to bear in mind that many foods contain much higher concentrations of this vitamin.
Finally, it is worth highlighting that, in order to meet our vitamin C requirements, we must consider the many factors that influence its levels, such as our habits, genetics and dietary intake, among others.
The better we understand our bodies, the better we can look after our health.
