How many times have you seen an ad for some wonder ‘erb or other that’s supposed to boost the immune system. It’s echinacea today and some Chinese herb the next, as well as a vast array of products that the supplement industry claim “support the immune system” — whatever that means.
Diet and Immunity
I’m not suggesting that diet and nutrition don’t have an important role to play in maintaining a healthy immune system. Meeting the recommended intake of macronutrients, vitamins and minerals and fats, and consuming copious quantities of antioxidant nutrients as part of healthy eating is bound to promote good immune system function — as far as it goes. However, the evidence for consuming individual dietary components or special foods or supplements beyond the RDI (recommended dietary intake) is mostly speculative or at least inconclusive.
Exercise and Immunity
If you follow a healthy lifestyle approach with healthy eating and a program of physical activity, here are a few things to note about how the immune system responds to exercise:
- A regular, low to moderate intensity exercise habit is associated with a reduced incidence of infection compared with those who do very little exercise or physical activity.
- Heavy, and or prolonged exercise training can impair the immune system, possibly leading to susceptibility to infection, particularly in a period of up to 24 hours after a heavy training session or event.
- Exercising at high intensity for prolonged periods without food — 90 minutes and beyond for example — may make you especially vulnerable to infection as a result of immune system depression.
- Consuming carbohydrate at the rate of 30-60 grams an hour during intense and prolonged exercise can help to maintain immune system function. That’s 1-2 sports drinks and hour or equivalent. (One drink is probably adequate for most situations except for extreme conditions and intensity.)
- Meeting your daily requirements for micronutrients like zinc, iron, and B and C vitamins is essential. Although a multivitamin supplement may help, consuming mega quantities of vitamins and minerals may be counterproductive. See article on Vitamin C and training adaptation.
- A recent review confirmed the value of carbohydrate supplementation and a possible role for vitamin C (note caution above), but no other supplement showed up as useful for heavy exercisers.
It’s worth noting the value of carbohydrate to immunity in a balanced diet and exercise program. Low-carbohydrate intake with low blood glucose, plus the stresses of exercise, increases cortisol production to the point where the immune system is compromised. Low-carb, high-fat diets, especially saturated fat, are not appropriate if you have a robust exercise program. In addition, saturated fat has been shown to impair immune response. Low-carb is not where you want to be if you exercise a lot.