Nearing the end of Summer, it is time to make preparations for the upcoming Winter season that is so often referred to as “cold-and-flu-season”. In order to avoid a Winter of misery, it’s critical to have a strong immune system. Relying on vaccines for protection is a fool’s game. In terms of the flu shot, given the yearly mutation of the Influenza virus, even on a good year, you’re lucky if it’s 50% effective.
Immune Health = Metabolic Health
Immune health is intimately tied to overall health. In case we had forgotten, the recent pandemic reminded us of this immutable fact, when the viral pandemic exploited the ongoing pandemic of poor metabolic health. There is no substitute for a solid immune system. The immune system is very dependent on one’s overall health status, so much so that even vaccines are significantly less effective in the setting of impaired metabolic health. Several aspects of metabolic health have direct negative effects on immune health.
Elevated glucose levels, whether prediabetes or diabetes, are associated with worse outcomes related to infectious diseases. Recent observations confirm that hyperglycemia (elevated glucose) is a strong predictor of mortality and of in-hospital adverse outcomes in COVID-19. Individuals with elevated glucose levels face a 7-fold higher risk of mortality compared with individuals with well-controlled glucose levels.
“Hyperglycemia is a clear and strong poor prognostic factor in COVID-19, borne out in multiple studies.“
There appears to be an immediate negative effect on the immune system from consumption of carbohydrates, which increases blood glucose. Ingesting 100 grams of various forms of carbohydrates (glucose, fructose, sucrose, honey, and orange juice; not starch) caused a 40% decrease in the effectiveness of neutrophils (a type of white blood cell) against bacteria.
It has long been known that obesity is associated with the following in regards to Influenza A:
- increased severity of infections
- prolonged transmission of virus
- increased viral load in exhaled breath
Regarding COVID-19, obesity is associated with a 3-fold increase in severe disease, with risk particularly associated with the presence of visceral obesity. In the setting of obesity, there is increased viral replication and prolonged viral shedding.
Thus, an overweight/obese population will suffer increased disease burden. Furthermore, obesity causes decreased efficacy of vaccination.
Several studies have demonstrated that exercise is associated with less frequent respiratory infections.
Specifically, regarding COVID-19, exercise capacity (as measured by METs achieve during treadmill stress tests) was inversely associated with the likelihood of hospitalization – those with lower fitness levels were more likely to be hospitalized. It’s not all about aerobic exercise capacity, though. For individuals who were hospitalized with moderate to severe COVID-19, muscle strength and muscle mass were predictors of length-of-stay.
Vitamin D is critical for the immune system, and low levels of vitamin D are associated with increased risk of infection, including respiratory infections, colds, influenza, and COVID-19. The seasonal surge in Influenza cases correlates well with reduced vitamin D levels in the winter months, indicating a decrease in natural defenses. Vitamin D supplementation eliminates the seasonality of Influenza (see graph below).
Adequate sleep is vital to maintaining proper immune health. Not only does sleep deprivation have short-term negative effects on immune system functioning, but also sleep deprivation impacts overall health, including worsening insulin resistance.
Strategies to Improve Immune Health
- Reduce bodyfat, especially visceral fat
- Eat nutrient-dense, real foods
- Prioritize quality sleep
- Exercise regularly
- Ensure adequate vitamin D levels, preferably via exposure to natural sunlight
These interventions collectively will help you to bolster your immune system to protect yourself against the inevitable exposure to pathogens. It’s not IF, it’s WHEN. There’s not a single intervention that can protect you quite like a healthy immune system.