Nutrition and Immunity

The body’s ability to fight infection is determined by nutrition. Nutrition has a direct link to how effectively the immune system works. During the Nestlé Nutrition Institute’s Workshop 98, Professor Martin Kohlmeyer presented on nutrition and immunity, with a specific focus on upper respiratory tract infections. He noted the importance of vitamins, particularly the role vitamin D plays, in ensuring adequate recovery. He also delved into the findings made during the COVID-19 pandemic.

Immune system response

The immune system responds to cold or flu viruses the moment a pathogen is inhaled. Within minutes, the innate immune system starts to slow the infection.  

• Infected cells are being neutralised and viral replication is blocked.
• Nutrients that support the proliferation and differentiation of immune cells, such as natural killer cells and cytotoxic  lymphocytes, determine the immune system’s response.
• Macrophages and dendritic cells process fragments of the virus to trigger the production of specific antibodies by the T and B lymphocytes. This process is lengthy and does not occur in the first week of infection.

Critical nutrients for early response

A well-functioning immune system requires a variety of nutrients to function optimally.:

• Vitamin A, vitamin D and zinc are essential for cell differentiation and proliferation
• Copper and iron are responsible for sustaining cellular metabolism and other immune system functions
• Selenium plays an important role in the generation and the regulation of the production of protective enzymes

The omega-3 and omega-6 balance in the immune system

Omega-3s and -6s play a vital role in the management of inflammation:

• Omega-6 (Linoleic and Arachidonic acid): These serve as precursors for pro-inflammatory cytokines needed to initiate the response to injury or infection.
• Omega-3 (EPA and DHA): The oils are precursors for mediators that resolve inflammation and restore balance in the body.

Many modern diets contain large amounts of Omega-6, which can promote chronic inflammation and contribute to the  "cytokine storm" seen in severe infections. Omega-3s are essential for terminating inflammatory responses and preventing tissue damage.

COVID-19 and the role of vitamin D

Studies conducted during the COVID-19 pandemic found a correlation between patients’ vitamin D levels and clinical outcomes. The studies highlighted how geographical and biological factors can impact survival rates due to insufficient exposure to sunlight.

Early pandemic data from the United States demonstrated a stark "latitude gradient": northern states, exemplified by North Dakota, recorded mortality rates 8 to 10 times higher than their southern counterparts, a disparity largely attributed to the prevalence of profound vitamin D deficiency at higher latitudes. This protective association of southern latitudes (areas with higher UVB exposure) remained consistent across all ethnic groups, although darker skin pigmentation and obesity are significant biological modifiers that lower circulating vitamin D levels.

Statistics from the UK Biobank and Israeli healthcare suggest that habitual vitamin D supplementation confers a 20 to 30% lower risk of primary infection, reinforcing the importance of maintaining adequate serum baselines for innate immune readiness. Crucially, clinical trials indicate that the timing of intervention is the primary determinant of efficacy: while supplementation initiated at the onset of infection can significantly reduce mortality, high-dose administration started two weeks post-infection often yields no measurable benefit. This finding suggests that while vitamin D is vital for preventing immune system dysregulation, it is largely ineffective once a systemic "cytokine storm" or advanced immune failure has already taken hold, underscoring the clinical necessity of prophylactic adequacy over acute, late-stage intervention.

A strong immune system begins with sufficient intake of nutrients before exposure to viruses. Those living in high-latitude regions require vitamin D supplementation to increase vitamin  D levels. Coupled with vaccination and other protective measures, sufficient nutrition is the best option to enable patients to recover from respiratory infections with minimal damage.