Infection is the result of invasion of the body by microorganisms, including bacteria, viruses, or fungi.
Not all microorganisms cause infections in the body, and exposure to a disease-causing microorganism does not always result in symptoms. The immune system plays a large role in determining the body’s ability to fight off infection.
Some examples of infection are common cold/sore throat, influenza, cough, recurrent ear infections, urinary tract infection, yeast infection, athlete’s foot, cold sores, HIV, shingles, and parasites.
What are the symptoms of infection?
Symptoms of infection include localized warmth, redness, swelling, discharge, foul-smelling odor, and pain to the touch. In more serious cases, symptoms may also include fever, chills, nausea, vomiting, diarrhea, and fatigue.
Dietary changes that may be helpful for infection
Nutrition is a major contributor to the functioning of the immune system, which in turn influences whether or not the body is resistant to infection. Specifically, it makes sense to restrict sugar, because sugar interferes with the ability of white blood cells to destroy bacteria.1 Alcohol also interferes with a wide variety of immune defenses,2 and excessive dietary fat reduces natural killer cell activity.3 However, there is no research investigating whether reducing sugar, alcohol, or fat intake decreases the risk of infection or improves healing.
Allergy, including food allergy, has been suggested to predispose people to recurrent infection,4 and many doctors consider allergy treatment for people with recurrent infections. The links between allergy and ear infections,5 6 urinary tract infections in children,7 and yeast vaginitis in women8 9 have been documented.
Lifestyle changes that may be helpful for infection
Stress can depress the immune system, thus increasing the body’s susceptibility to infection. Coping effectively with stress is important.10 Exercise increases natural killer cell activity, which may also help prevent infections.11
Nutritional supplements that may be helpful for infection
Nutrients useful for maintaining healthy immune function are also applicable for preventing infections. Vitamin A plays an important role in immune system function and helps mucous membranes, including those in the lungs, resist invasion by microorganisms.12 However, most research shows that while vitamin A supplementation helps people prevent or treat infections in developing countries where deficiencies are common,13 little to no positive effect, and even slight adverse effects, have resulted from giving vitamin A supplements to people in countries where most people consume adequate amounts of vitamin A.14 15 16 17 18 19 20 Moreover, vitamin A supplementation during infections appears beneficial only in certain diseases. An analysis of trials revealed that vitamin A reduces mortality from measles and diarrhea, but not from pneumonia, in children living in developing countries.21 A double-blind trial for vitamin A supplementation in Tanzanian children with pneumonia confirmed its lack of effectiveness for this condition.22 In general, parents in the developed world should not give vitamin A supplements to children unless there is a reason to believe vitamin A deficiency is likely, such as the presence of a condition causing malabsorption (e.g., celiac disease). However, the American Academy of Pediatrics recommends that all children with measles should be given high-dose vitamin A for several days.
Vitamin C has antiviral activity, and may help prevent viral infections23 or, in the case of the common cold, reduce the severity and duration of an infection.24 Most studies on the common cold used 1 to 4 grams of vitamin C per day.
Lactobacillus acidophilus (the friendly bacteria found in yogurt) produces acids that kill invading bacteria.25 The effective amount of acidophilus depends on the strain used, as well as the concentration of viable organisms. These and other friendly bacteria known as probiotics inhibit the growth of potentially infectious organisms (pathogens) by producing acids, hydrogen peroxide, and natural antibiotics called bacteriocins and microcins, by utilizing nutrients needed by pathogens, by occupying attachment sites on the gut wall that would otherwise be available to pathogens, and by stimulating immune attacks on pathogens. Infections that have been successfully prevented or treated with friendly bacteria include infectious diarrhea, vaginitis, and urinary tract infections.26
Marginal deficiencies of zinc result in impairments of immune function.27 Supplementation with 50 mg of zinc three times per day for 30 days has been shown to increase immune function in healthy people.28 However, such large amounts of zinc can potentially cause adverse effects. Some doctors recommend lower amounts of supplemental zinc for people experiencing recurrent infections, such as 25 mg per day for adults and even lower amounts for children (depending on body weight). Zinc lozenges have been found helpful in some studies for the common cold. Zinc has not been studied as prevention or treatment for other types of infection.
A multiple vitamin-mineral formula helped elderly people avoid infections in one double-blind trial, but not in another.29 30 In a double-blind study of middle-aged and elderly diabetics, supplementation with a multiple vitamin and mineral preparation for one year reduced the risk of infection by more than 80%, compared with a placebo.31 In another double-blind trial, supplements of 100 mcg per day of selenium and 20 mg per day of zinc, with or without additional vitamin C, vitamin E, and beta-carotene, reduced infections in elderly people, though vitamins without minerals had no effect.32 That study suggests that trace minerals may be the most important components of a multiple vitamin and mineral formula for preventing infections.
Premature infants with very low birth weight have an increased susceptibility to infections. In a double-blind trial, premature infants were given either selenium supplements (5–7 mcg per 2.2 pounds of body weight) or placebo. Those receiving the selenium supplements had fewer hospital-acquired infections.33
Athletes who undergo intensive training or participate in endurance races (such as a marathon) are at increased risk of developing infections. In a double-blind study, marathon runners received either glutamine (5 grams immediately after the race and 5 grams again two hours later) or a placebo. Compared with the placebo, supplementation with L-glutamine reduced the incidence of infections over the next seven days by 62%.34
Are there any side effects or interactions with infection?
Refer to the individual supplement for information about any side effects or interactions.
Herbs that may be helpful for infection
The main herbs for infection can be broken down into three basic categories: those that support a person’s immune system in the fight against microbes, those that directly attack microbes, and those that do both. These categories are summarized in the table below. Note that this table does not include herbs that are largely used for parasitic infections of the intestines.
Are there any side effects or interactions with infection?
Refer to the individual herb for information about any side effects or interactions