Unpacking the inflammatory impact of diet on immune function

Have we ever thought on a deeper level on how significantly our daily food choices influence inflammation and immune response?

Food is a significant part of the functional medicine picture and "crap food" is often the culprit of numerous health complications and issues. I find it funny that the Standard American Diet (SAD) encompasses precisely the diet that we should avoid.

What is the SAD diet?

The Standard American Diet (SAD) is a dietary pattern commonly associated with Western countries, especially the United States, which is best described as:

• High in processed foods: The SAD includes large amounts of pre-packaged, processed foods like snacks, frozen meals, and fast food, which are often calorie-dense and nutrient-poor.
• High in added sugars: Foods and beverages high in added sugars—like soda, sweets, and sugary cereals—are staples in the SAD, contributing to blood sugar spikes and insulin resistance over time.
• High in refined grains: Refined grains such as white bread, pasta, and pastries, are stripped of their fibre and many nutrients during processing, leaving them less filling and causing rapid spikes in blood sugar.
• High in unhealthy fats: Especially saturated and trans fats, commonly found in fried foods, pastries, and many processed snacks, which promote inflammation and cardiovascular risks.
• Low in fibre, fruits, and vegetables: These are rich in essential nutrients, antioxidants, and fibre. Fiber helps with satiety, digestion, and blood sugar control, while antioxidants combat inflammation and oxidative stress.
• High in animal products: These especially include red and processed meats, which can increase the risk of heart disease and inflammation when eaten in excess.

Profound effects of the SAD 

Mechanism of inflammatory response

Studies reveal that postprandial (after-eating) inflammation kicks in within one hour after a high-glycemic, low-nutrient SAD meal, with markers like nuclear factor kB (NF-kB) and high-sensitivity C-reactive protein (hsCRP) rising and staying elevated for over three hours (Patel et al., 2020; Calder et al., 2017).

• NF-kB is known as the "master switch" of inflammation; it regulates numerous cytokines (signalling proteins) that drive immune response. When activated repeatedly by the SAD diet’s high glycemic index and refined fats, NF-kB fosters chronic low-grade inflammation, taxing our immune resilience over time (Lawrence, 2009).
• hsCRP: As a nonspecific marker, hsCRP indicates systemic inflammation and immune stress. Elevated hsCRP has been linked to an increased risk of metabolic and cardiovascular diseases, partly because it reflects the body’s long-term response to inflammatory triggers such as refined oils, sugars, and food additives (Ridker et al., 2002)

What’s triggering these reactions?

The SAD diet is characterised by several inflammation-driving components:

• High glycemic load: Rapidly absorbed carbs raise blood glucose, sparking insulin spikes and oxidative stress, which in turn activate NF-kB and inflammation (Lassenius et al., 2020).
• Refined fats and oils: Omega-6-rich refined oils, often used in processed foods, disrupt omega-6 to omega-3 balance, favouring pro-inflammatory pathways (Simopoulos, 2002).
• Chemical additives: Common additives, including preservatives, disrupt the gut microbiome and contribute to immune dysregulation, further promoting inflammatory signalling (Alissa & Ferns, 2012).
• Lack of fibre and phytonutrients: Fiber plays a crucial role in gut health, while phytonutrients reduce oxidative stress and support anti-inflammatory pathways. Without these, the body lacks essential resources for managing inflammation (Pérez-Cano et al., 2020).

The long-term impact

When high-glycemic, low-fibre, and refined meals are repeated every 4–5 hours, we set up a cycle of chronic NF-kB activation, oxidative damage, and immune disruption. These repeated insults can fuel conditions like metabolic syndrome, cardiovascular disease, and other chronic inflammatory disorders (Hotamisligil, 2006).

After all, food is important and yet very much underestimated. We are the choices we make on a daily basis. What is your choice?

References

Patel, H., et al. (2020). Diet-induced inflammation and its impact on immune function. Journal of Inflammation Research, 13, 41-52.

Calder, P.C., et al. (2017). Role of nutrition in immune function. Nutrition Reviews, 75(8), 616-632.

Lawrence, T. (2009). The Nuclear Factor NF-κB pathway in inflammation. Cold Spring Harbor Perspectives in Biology, 1(6), a001651.

Ridker, P.M., et al. (2002). Inflammation and heart disease. The New England Journal of Medicine, 347(20), 1557-1565.

Simopoulos, A.P. (2002). Omega-6/Omega-3 fatty acids and inflammation. Biomedicine & Pharmacotherapy, 56(8), 365-379.

Alissa, E.M., & Ferns, G.A. (2012). Dietary antioxidants and coronary heart disease. Public Health Nutrition, 15(6), 958-965.

Pérez-Cano, F.J., et al. (2020). Role of dietary fiber in immune function. Journal of Functional Foods, 64, 103638.

Hotamisligil, G.S. (2006). Inflammation and metabolic syndrome. Nature, 444(7121), 860-867.