Determine Whether Vitamin A Enhances Immune Response

Several approaches have been taken in an attempt to determine whether Vitamin A supplementation enhances immune response and resistance or recovery from infection. In some investigations, researchers have attempted to correlate plasma concentrations of beta-carotene or retinol with immune response or susceptibility to infection. One limitation of this approach is related to the fact that plasma concentrations may have depressed plasma retinol levels as a result of disease. Therefore, it is not possible to establish whether low plasma retinol levels resulted in suppressed immune response or if plasma retinol levels decreased in response to disease or infection. Another approach used is to supplement the diet with retinol precursors and examine immune response at a later time point. This approach may be useful in examining the particular aspects of immunity that may be altered by supplementation, but additional studies are necessary to determine whether these effects have clinical significance in terms of disease outcome. Vitamin A has been fairly well studied in terms of its immunomodulatory effects, and we will review the evidence from randomized controlled trials as well as potential mechanisms of action. Vitamin A supplementation may afford some protection from infection in malnourished individuals, but the potential benefits of supplementation in normal wellnourished individuals remain to be established. There is evidence from several studies that suggests that vitamin A deficiency is associated with depressed immune function and an impaired response to influenza infection. Supplementation of vitamin A is associated with a reduction of mortality and morbidity among certain populations. It appears that populations suffering from malnutrition may benefit from adequate or additional vitamin A supplementation. However, it is less clear if normal, healthy, well-nourished individuals will benefit from additional supplementation with respect to enhanced immunity. The results from several studies involving beta-carotene supplementation in the diet of healthy individuals suggest that certain aspects of innate immunity, such as NK cytotoxicity and monocyte production of the cytokine TNFcx, are enhanced. It appears that lymphocyte subsets or the lymphocyte response to mitogens are not altered. In addition, one study of healthy older individuals found that vitamin A supplementation was associated with a reduction in the number of T lymphocytes. Whether these observed changes of immune function in response to supplementation actually result in reduced susceptibility to infection in healthy individuals is not well established. The results from one study demonstrated no association between vitamin A supplementation and incidence of bacterial infection. we are not aware of any long-term, randomized clinical trials that have evaluated the incidence of viral infection in response to supplementation with vitamin A alone. However, several studies have examined the possibility that supplementation with several multivitamins and or trace elements such as zinc, may alter susceptibility to infection. In general, the findings from these studies show no protection from infection in association with vitamin intake, but a slight decrease in the incidence of infection in those individuals consuming supplemental trace elements such as zinc and selenium. At this time, the potential benefits of vitamin A supplementation for healthy well-nourished individuals regarding susceptibility to infection remain to be established. A high beta-carotene intake has also been associated with a reduced risk of cancer. Earlier epidemiological studies suggested a high natural (fruits and vegetables) intake of beta-carotene was associated with reduced risk of cancer. However, more recent studies have not observed any benefit of beta-carotene intake on incidence of cancer and two studies actually observed an increased incidence of lung cancer in those participants consuming beta-carotene supplements. The presence of other carotenoids in fruits and vegetables has been suggested to be the protective factor in regards to cancer incidence in the early epidemiological studies based on the findings from these recent studies, dietary supplementation with high doses of synthetic beta-carotene may be contraindicated for smokers. As a reminder, it has been known for some time that a high intake of vitamin A results in adverse effects (neurologic, dermatologic, musculoskeletal, gastrointestinal, birth defects) and the results from the most recent studies suggest a potential risk of high doses of synthetic beta-carotene in certain populations. At this time it is probably safest to follow the National Cancer Institute recommendations that suggest five or more servings of fruits and vegetables per day. Immune Effects and Exercise We are currently aware of only one study that has examined whether vitamin A supplementation is associated with a reduced incidence of infection in athletes. Several studies have shown that the risk of upper respiratory infection is increased following competition in marathons or ultramarathons However, vitamin A supplementation before marathon competition did not reduce the incidence of infection in the postrace period. Therefore, to our knowledge, vitamin A supplementation has not been associated with enhanced resistance to infection in healthy athletes.

Asian Ginseng - Uses of Ginseng

Asian ginseng is perhaps the most widely recognized of the plants used in traditional medicine and plays a major role in the herbal health market. It has been used for more than two thousand years. At least six species and varieties of Panax have been used in traditional medicine. It is a popular ingredient in herbal teas and cosmetics. It is promoted for its antistress effects.Ginseng’s dried root is medicinal. It contains triterpenoid saponins called ginsenosides that appear to be the active ingredients responsible for the plant’s immunomodulatory effects. Ginsenosides seem to increase natural-killer cell activity, stimulate interferon production, accelerate nuclear RNA synthesis, and increase motor activity.The ginsenosides have been found to protect against stress ulcers, to decrease blood glucose level, to increase high-density lipoprotein level, and to affect central nervous system activity by acting as a de pressant, anticonvulsant, analgesic, and antipsychotic.Ginseng is available as powdered root, tablets, capsules, and tea. Common trade names include Centrum Ginseng, Chikusetsu Ginseng, Gin-Action, Ginsai, Ginsana, Ginseng Manchurian, Ginseng Power Max 004X G-Sana, Ginseng Up, Gin Zip, Herbal Sure Chinese Red Ginseng, Herbal Sure Korean Ginseng, Korean White Ginseng, Lynae Ginse-Cool, Power Herb Korean Ginseng, Premium Blend Korean Ginseng Extract, Sanchi Ginseng, The Ginseng Solution, Time Release Korean Ginseng Power, and Zhuzishen.Reported usesAsian ginseng is used to manage fatigue and lack of concentration, and to treat atherosclerosis, bleeding disorders, colitis, diabetes, depression, and cancer. It’s also used to help recover health and strength after sickness or weakness.AdministrationPowdered root: For a healthy patient, 0.5 to 1.0 g of the root may be taken by mouth, every day, in 2 divided doses for 15 to 20 days. The morning dose is usually taken 1 to 2 hours before breakfast; the evening dose, 2 hours after dinner. If a second course of therapy is desired, patient must wait at least 2 weeks before starting ginseng again. For an elderly or sick patient, 0.4 to 0.8 g of the root by mouth every day taken continuouslySolid extracts in tablets and capsules: Dosage is 100 to 300 mg by mouth three times a dayTea: Dosage is 1 cup every day, up to three times a day, for 3 to 4 weeks. The tea is prepared by steeping 3 g (1 teaspoon) of the herb in a cup of boiling water for 5 to 10 minutes.

Antioxidant Function of Vitamin A, C , E-Vitamin

Vitamin C, vitamin E (tocopherols), and some precursors to vitamin A (the carotenoids) exhibit antioxidant activity. Each of these vitamins has independently been shown to alter immunity. The antioxidant function of these vitamins is of interest to some athletes primarily because exercise increases the production of reactive oxygen species (ROS) which have been associated with muscular fatigue and muscular damage. In addition, neutrophils and macro phages produce ROS. The ROS produced by the immune system may have a role in modulating postexercise muscle damage. The other reason that vitamins A, C, and E may be of interest to athletes relates to their potential immunostimulatory properties. The antioxidant properties of the vitamins may differ from the immunomodulatory effects.Reactive oxygen species (ROS) are produced during strenuous exercise, result in oxidative stress, and are associated with a depletion of antioxidants, muscle damage, and fatigue. High concentrations of antioxidants may protect against the damaging effects of ROS. An assumption has been made that a high intake of vitamins A, C, E, or betacarotene may protect against the exercise-induced oxidative stress and several studies have examined this possibility. Vitamin E (alpha-tocopherol) is considered the most important scavenger of ROS at the level of membranes and is probably the most well studied with respect to exercise. Several studies have established that exercise training is associated with a decrease in the accumulation of the products used to assess oxidative stress or an enhancement of antioxidant enzymes. The findings from some studies suggest that vitamin E supplementation may protect against the oxidative damage induced by exercise. However, the results from both human and animal studies show that vitamin E supplementation does not improve performance and may not attenuate muscular damage following a marathon. An understanding of interactions between the immune system, ROS production, and muscle damage may provide some insight regarding antioxidants and exercise-induced muscle damage. Although these interactions are not completely understood at this time, it appears that the production of ROS by cells of the immune system may be an important part of the postexercise muscle repair process. Neutrophils and macrophages appear to infiltrate sites of postexercise muscle damage and both of these cell types produce ROS. The release of ROS can enhance the release of cytokines and cytokines can induce the production of ROS The release of both cytokines and ROS are important in removing damaged muscle tissue and may assist in the repair process. The findings from a recent study suggest that the generation of ROS postexercise may be beneficial in the repair process. In this study, normal mice demonstrated greater oxidative stress postexercise than mice with inhibited neutrophil function; however, 4 days later normal mice showed evidence of less muscle damage Based on this evidence and findings from other studies mentioned previously, it should be noted that the production of free radicals or ROS during exercise may be an important part of the muscle tissue repair process and the consumption of high levels of antioxidants may not necessarily be beneficial. Some researchers have examined life span and whether it can be extended by increased antioxidant intake. The evidence from two recent studies suggests that supplementing diets with high levels of antioxidants does not increase maximum life span and exercised rodents fed a diet containing additional antioxidants did not have a greater life span than exercised rodents on a normal diet. It appears that although exercise may be associated with a greater production of ROS, this does not result in a shortened life span and the consumption of additional antioxidants confers no additional increase in longevity. Taken together, the findings from the studies above suggest that additional antioxidants do not improve performance, do not appear to improve muscle tissue repair postexercise, and are not beneficial in terms of increasing life span in exercised rodents. Although the interactions between the immune system and ROS produced during exercise need further research, at this time it does not appear that additional antioxidants will enhance immune responses such as postexercise muscle tissue repair.