Certain foods and environmental influences can keep the immune system army from doing a good job. Watch out for these threats to your body's defenses.

Overdosing on sugar: Eating or drinking 100 grams (8 tbsp) of sugar which is the equivalent of about two cans of soda, can reduce the ability of white blood cells to kill germs by forty percent. The immune-suppressing effect of sugar starts less than thirty minutes after ingestion and may last for five hours. In contrast, the ingestion of complex carbohydrates, or starches, has no effect on the immune system.

Excess alcohol: Excessive alcohol intake can harm the body's immune system in two ways. First, it produces an overall nutritional deficiency, depriving the body of valuable immune- boosting nutrients. Second, alcohol, like sugar, consumed in excess can reduce the ability of white cells to kill germs. High doses of alcohol suppress the ability of the white blood cells to multiply, inhibit the action of killer white cells on cancer cells, and lessen the ability of macrophages to produce tumor necrosis factors. One drink (the equivalent of 12 ounces of beer, 5 ounces of wine, or 1 ounces of hard liquor) does not appear to bother the immune system, but three or more drinks do. Damage to the immune system increases in proportion to the quantity of alcohol consumed. Amounts of alcohol that are enough to cause intoxication are also enough to suppress immunity.

Food allergens: Due to a genetic quirk, some divisions of the immune army recognize an otherwise harmless substance (such as milk) as a foreign invader and attack it, causing an allergic reaction. Before the battle, the intestinal lining was like a wall impenetrable to foreign invaders. After many encounters with food allergens, the wall is damaged, enabling invaders and other potentially toxic substances in the food to get into the bloodstream and make the body feel miserable. This condition is known as the leaky gut syndrome.

Too much fat: Obesity can lead to a depressed immune system. It can affect the ability of white blood cells to multiply, produce antibodies, and rush to the site of an infection.