(HMT) Relationship between vitamins and infections By s. Emmanuel E.

THE RELATIONSHIP BETWEEN VITAMIN A AND INFECTION, 

              E.G HIV INFECTION AND FERTILITY.

 INTRODUCTIONhttps://www.google.com.ng/www.blogger.com

Vitamin A deficiency has been shown to alter immune and haematological status in infected subjects. Malnutrition remains an endemic problem in many African countries which has been recently complicated by the impact of infections.  Malnutrition is known to affect micronutrient status and more so in infected persons.  Research studies observed that several vitamins especially vitamin A are critical in fighting HIV infection.  This is because these vitamins (vitamin A inclusive) are utilized by the immune system and important organs to attack infectious pathogens hence, the need to examine relationship between vitamin A and  infected person, e. g HIV person.

Vitamins appear to have considerable clinical importance in HIV infection.  Research and observational studies have shown that certain vitamins are frequently deficient in HIV-infected patients^1,2.  Vitamin deficiency appears to be related to altered immune and haematological status in the infected patients¹.  A number of vitamins including vitamin A may enhance (and their deficiency impair) the immune response in HIV-infected patients².  Of the micronutrients, the role of vitamin A in HIV infection has received prominent attention.  This is because of its well-known role in affecting child morbidity and mortality, as well as early observations that vitamin A status was associated with increased risk of mother-to-child-transmission (MTCT) of HIV³, progression to AIDS^{4, 5, 6}, adult survival^{1, 3, 4}, infant morbidity⁷ and mortality⁸.

Vitamin A has been recognized as a likely potential co-factor (micronutrient) in HIV progression and disease expression⁹.  HIV positive persons may be at particular risk for vitamin A deficiency for some reasons.  These include chronic and recurrent infections, chronic inflammatory conditions, poor intake, diarrhoea with or without malabsorption^{9, 10}.  Vitamin A has remarkable positive effects including established roles in haematopoiesis, the maintenance of epithelial integrity and optimal function of the immune system. 

We aim to examine the role of vitamin A, vitamin A in HIV infection, its deficiency in relation to HIV infection, consequences of its deficiency and the benefits of vitamin A supplementation in HIV persons.

Role of Vitamin A

Vitamin A is a fat-soluble substance and can be ingested either preformed (retinal) or synthesized within the body from ingested plant carotenoids¹¹.  The best known function of vitamin A is in the visual process where, as 11-cis-retinal, it serves as the photosensitive chromophoric group of the visual pigments of rod and cone cells of the retina ^{8, 9, 10, 11}.  Vitamin A has a clear vital role in the differentiation of epithelial cells.  It is documented that vitamin A deficient individuals experienced replacement of normal mucus-secreting cells by cells that produce keratin, particularly in the conjunctiva and cornea of the eye, the trachea, the skin and of ectodermal tissues^{8, 9, 10, 11}. 

Vitamin A is also necessary for reproduction.  For example, rats maintained with retinoic acid grow well and appear healthy, but lose reproductive ability (male show impaired spermatogenesis and females abort and resorb their feotuses).  Studies show that injection of retinal into the testis restores spermatogenesis, indicating that vitamin A has a direct role in that organ¹³.  Vitamin A is important in supporting immune competence.  Vitamin A-deficient animals and humans are typically more susceptible to infection than are individuals of adequate vitamin A nutrition. Epidemiological studies have found that low vitamin A status is frequently associated with increased disease incidence and mortality rates^{8, 9, 10, 11}.

Vitamin A status in HIV Infection

The impact of HIV infection on vitamin A status has been examined in a number of studies.  Mean serum retinal levels for HIV positive adults fall within the normal range.  However, a significant number of persons (although in the minority) have retinal levels below 1.05 µmol/L, the cut-off for biochemical deficiency^{2, 12}.  In a micronutrient survey of 112 asymptomatic homosexuals, Baum et al ² found biochemical vitamin A deficiency in 16%.  Although the authors stated that the proportion of individuals with multiple vitamin deficiencies increased over-time, no data were provided to follow-up vitamin A status changes with HIV disease progression.  Their observations could not be explained by decreased vitamin A intake since none of the study subjects consumed less than the recommended daily allowance (RDA) for vitamin A.  Similar report have also been documented by the same group in a study where they examined 100 homosexuals and 42 heterosexual individuals with HIV infection ⁹. 

Bogden et al ¹² studied a smaller number of subjects (N=30) at various stages of HIV infection.  The result showed that the mean serum retinal level was normal and 12% were biochemically deficient in vitamin A.  Although the total number of subjects in this study is relatively small, the data suggest an association between HIV infection and vitamin A and is consistent with deterioration of vitamin A status with advancing HIV infection.

Vitamin A deficiency in HIV Infection

Some populations are at increased risk for vitamin A deficiency.  These groups include intravenous drug users, alcoholics, the homeless and persons with chronic diseases.  HIV-infected persons are disproportionately represented in these risk groups¹⁰.  Besides, several characteristics of HIV infection are likely to increase the demand for and decrease the supply of this vitamin.  These include chronic and repeated acute bacterial or viral infections, decrease oral intake (due to oral thrush, mental status changes), active liver disease (impaired storage) and decreased intestinal absorption^{10, 13}.

Vitamin A deficiency has been said to be rare in developed countries.  However, the prevalence of hyporetinaemia in HIV-1 infected individuals in industrialized countries has risen to 29%.  In developing countries, up to 60% of HIV-infected women are hyporetinaemic.  In such women, the relative risk of peri-natal transmission may be increased more than fourfold¹⁴.  According to Watson ¹⁵ vitamin A deficiency is associated with decreased CD4 T-cell production, depressed cellular immunity and reduced humoral response to protein antigens.  In a study by Karter (1995) on “Vitamin A deficiency in non-supplemented patients with AIDS”; sixty eligible patients with AIDS provided serum samples that were analyzed for retinal content.  Exclusion criteria included current use of vitamin supplements.  Past dietary intake was determined using a standardized food intake frequency questionnaire.  The prevalence of hyporetinaemia was 22%.  There was a positive association between serum retinal status and dietary intake but 27% of those with adequate intake had serum retinal levels below the normal range.  These findings suggest that regardless of intake, patients with AIDS may represent a population at considerable risk of vitamin A deficiency.  Vitamin A deficiency is strongly associated with iron deficiency anaemia¹⁵.  Hemosiderosis of the liver has been found at autopsy in children who die with vitamin A deficiency suggesting the inability to mobilize hepatic iron stores underlies the associated anaemia¹⁵.  The disruption of iron metabolism has also been reported in HIV positive persons and anaemia is an early and consistent finding in HIV infection¹⁰.  Severe anaemia requiring transfusion has been reported in advanced HIV infection.  Hemosiderosis has also been reported in few cases in HIV infection.  Factors contributing to this include direct infection of erythrocyte precursors in the bone marrow, chronic infections and decreased production of erythropoietin^{16, 17, 18}.  In animals deprived of vitamin A, there is disruption of mucosal surfaces with loss of cilia and disintegrated microvilli in the respiratory, gastrointestinal tracts, vagina and salivary glands.  The effects of vitamin A on the vagina mocusa raise the possibility that changes in vitamin A status may influence heterosexual and peri-natal transmission of HIV^{15, 16, 19}.  The evidence that vitamin A deficiency impairs normal immune function comes from several sources.  These include animal studies with experimental depletion and repletion, in vitro studies of human immune cell function with supplemental retinoids and field studies of deficiency ^{20, 21, 22, 23}. 

Although the immunological impact of changes in vitamin A status has been less studied in man, retinoids have been found to influence a wide range of human immune cell functions in vitro.  These include proliferation of thymocytes, B-cells, T-cells and the production of a number of cytokines^{24, 25, 26}.  Vitamin A-deficient children respond poorly to tetanus toxoid, are found to have low CD4+/CD8+ ratios and suffer increased infection-related mortality.  Vitamin A repletion is associated with increased CD4+ counts and CD4+/CD8+ ratios as well as improved antibody production ^{3, 26}.

Consequences of Vitamin A deficiency in HIV Infection

The consequences of vitamin A deficiency resulting from HIV infection are potentially severe.  Watson¹⁹ examined a population group of 53 HIV-sero-negative and 126 HIV-sero-positive subjects in a cross-sectional study of vitamin A status.  Two of the 53 HIV-1 sero-negative (3.7% and 19 of the 126 sero positive subjects (15.1%) had serum vitamin A levels <1.05 µmol/L.  There was a strong association between low serum retinal levels and absolute CD4 counts for both sero-positive and sero-negative subjects. The mean follow-up was 22.8 months during which time 15 subjects died from AIDS-related causes.

Kaplan-Meier product limit estimates for subgroups stratified by vitamin A status (above or below 1.05 µmol/L) revealed that individuals with vitamin A deficiency had significantly decreased mean survival time by the log-rank test (P<0.0001).  The adjusted odds ratio for serum retinal as an independent predictor of mortality was 4.3 compared to 10.0 for CD4+ cell counts <200 mm³.  Increased infant mortality has also been observed in children born to HIV positive mothers with vitamin A deficiency ⁸. These findings suggest strongly that vitamin A status is an important co-factor in HIV progression.

Vitamin A supplementation in HIV infection

The potential role for vitamin A as an adjuvant therapy in HIV-infected populations is very relevant especially in the developing world.  In these settings, the risk of vitamin deficiency is great and the range of available treatments for HIV infection is limited.  The cost of a bimonthly 200,000 IU capsule of vitamin A compares well with other form of interventions in HIV infection. While this may not be a panacea, the demonstration of a beneficial effect of vitamin A supplementation in HIV infection may offer hope of treatment where there is currently none^{15, 19}.

In a study of 288 HIV-positive homosexual men in Baltimore, dietary and supplemental intake of vitamin A (9000-20000 IU/day was associated with slower progression to AIDS during a seven-year follow-up^{15, 19}.  Kennedy ²⁹ examined the effects of vitamin A supplementation during pregnancy and early lactation on maternal weight among HIV-1 sero-positive South African women.  The author observed a benefit on maintenance of post-natal weight in vitamin A deficient women.  It was concluded that in a population for whom anti-retroviral therapy is not readily available or accessible, the finding that vitamin A improve post-partum weight lends some hope to a relatively inexpensive treatment.  Vitamin A could thus be used for helping to ameliorate some weight loss that is common during HIV infection.

According to Nimmagadda¹⁴, vitamin A supplementation may be especially useful in adjunctive therapy for HIV-infected pregnant women who live in the developing world.  Vitamin A supplementation of women during pregnancy improved vitamin A status of mothers and of their infants³⁰.  It has also been demonstrated from recent studies that vitamin A supplementation during pregnancy enhanced the concentration of retinal levels in breast milk³⁰.  Coutsoudis et al (1995) carried out a double-blind randomized controlled trial of vitamin A supplementation on children of HIV-positive mothers in Durban, South Africa. It was demonstrated from the study that 28% of the supplemented group had reduction in the incidence of prolonged diarrhoea and 77% had reductions in hospital admissions for diarrhoea.  Benefits from vitamin A supplementation include not only improved health and welfare for individuals and family, but also improved chances of prolonged survival for HIV infected persons^29-31.  In Tanzania, vitamin A supplementation of HIV-infected children reduced all-cause mortality by 63% among HIV-infected children aged six months to five years and was associated with a 68% reduction in AIDS-related deaths and a 92% reduction in diarrhoea-related deaths^{31, 27}.  To date, despite demonstrated associations between vitamin A deficiency and HIV infection, there is no clear evidence yet that vitamin A supplementation can positively alter HIV vertical transmission or disease progression in adults.  It is known that good nutrition and a healthy diet may help prolong the period of time between HIV infection and onset of secondary infections commonly attributed to progression to AIDS. This is because of the relationship between nutritional status and immune system function and integrity.

Further research is urgently needed on the nutritional management of HIV/AIDS especially that on vitamin A supplementation especially in the African countries, where HIV is spreading rapidly, where malnutrition is endemic and resources for the management of both HIV and malnutrition are extremely constrained. Studies are needed to determine the efficacy and safety of micronutrient supplements for improving nutritional status, preventing disease progression and delaying AIDS-related mortality in populations that are endemically deficient and may also experience chronic food insecurity.

Vitamin A and Fertility

Vitamin A is an important vitamin to help boost both male and female fertility. There are few things more powerful in the world than the desire to have a child and there are only a few sadder feelings than what couples experience when faced with infertility. However, what for some may seem like the end of the world could be easily overcome with a few major but valuable changes in their lifestyle – like a healthy daily dose of vitamin A. Here are the four basic principles of a vitamin A rich diet:

Decrease coffee & alcohol

Increasing the daily intake of vitamin A is the first step in fighting infertility, the second one involving that all the foods and drinks that do not allow the proper assimilation of vitamin A be eliminated. Besides the deficiency of vitamin A, fertility may be inhibited by the excessive consumption of coffee, alcohol and unhealthy foods. It is therefore important for all the negative influences in one’s diet to be eliminated, in order to create the premises for conceiving a child.

Vitamin A & male fertility

Vitamin A is one of the most important elements for any living organism allowing the proper functioning of various organs, but also playing an important part in the fertility process. The men who have a diet low in vitamin A have their sperm cells stuck together instead of them acting individually. This way, the sperm cells are inhibited and cannot reach the uterus and, from there, the egg. It is like having glued thousands of people together and none of them can move faster than the other. To increase female and male fertility, a daily intake of 200 up to 1000 mg is recommended for at least one month. Because it is almost impossible to get this amount only from food, one can take supplements rich in vitamin A, fertility being thus restored to normal within a relatively short period of time. This fact is backed up by some recent studies performed in various medical centers, where an improvement with more than 80 % of the pregnancy success rate was noticed.

Do not overdo it

As with any good thing, too much of it can have the opposite effect, so, women who want to get pregnant must avoid the overdoses of vitamin A. The vitamin excess dries the internal secretions from the vagina, slowing down the movement of the egg. The amount of vitamin A found in fruits and vegetables, plus the one present in the prenatal vitamins is sufficient for a healthy woman.

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