Vitamin A studies in rural Philippine communities

Vitamin A deficiency is a public health problem in many non-industrialized nations. In the Philippines, the 2003 National Nutrition Survey (FNRI-DOST) showed that 40.1 percent of children between the ages of six months and five years, 36.0 percent of school-aged children, 17.5 percent of pregnant women, and 20.1 percent of lactating women have plasma vitamin A (retinol) levels that are below normal values. Vitamin A deficiency can result in anemia, reduced resistance to infection, impaired cellular differentiation, xerophthalmia, and ultimately, blindness and death. The World Health Organization estimates that about 140 million children worldwide are subclinically vitamin A deficient, and that 250,000 to 500,000 vitamin A-deficient children become blind every year, with half of them dying within 12 months of losing their sight.

During the past 10 years, I have been very fortunate to be able to obtain research grants to conduct vitamin A studies in rural Philippine communities. It all started when in 1995, a Request for Proposals (RFP) was sent out by the International Atomic Energy Agency (IAEA), one of the agencies within the United Nations Organization. Based in Vienna, Austria, the IAEA is known for its role in monitoring the safe usage of radioactive materials as an energy source, and more recently, for its role in searching for weapons of mass destruction in Iraq. What many do not realize is that the IAEA serves other functions as well such as, for example, conducting and/or supporting studies on the application of stable isotopes in health-related research. The IAEA has a Nutritional and Health-Related Environmental Studies Section in a Division of Human Health, and it was this section that sent out the RFP "to study the development and application of isotopic techniques in studies of vitamin A nutrition." A stipulation of the RFP was that researchers from developed and developing countries would have to team up, as the field work should be done in the developing country, and laboratory analyses, in the developed nation. This was the opportunity I had dreamed about – to be able to conduct research studies in the Philippines. But who should I team up with? As an undergraduate student at UST, I studied Chemistry and it was only in graduate school when I focused on Biochemistry and Nutrition that I started paying attention to Public Health Nutrition studies. Dr. Florentino Solon of the Nutrition Center of the Philippines (NCP) came to mind. An internationally known public health nutritionist, he is a contributor of articles to the Sight and Life Newsletter, a publication from Basel, Switzerland dedicated to vitamin A studies and projects worldwide. We have never met, but after a flurry of e-mails, we became the team and settled into the task of writing a successful grant proposal to the IAEA. Thus begun my first research collaboration with the NCP which took me to the backroads of Barangay Santa Elena in Santo Tomas, Batangas and Barangay Hukay in Silang, Cavite – a journey to be repeated in the coming years with other vitamin A studies in other rural Philippine communities.

Before any human research study can be initiated, for the protection of study participants, the protocol undergoes review by an institutional review board. All our studies were rigorously reviewed and approved by not one, but two, review committees – the Ethical Review Board of the Philippine Council for Health Research and Development, and the Tufts University-New England Medical Center Human Investigation Review Committee.

The long-term objective of all our studies in the Philippines is the alleviation and eradication of vitamin A deficiency. The specific main objective in Santa Elena and Hukay was to determine whether ingestion of locally available fruits and vegetables that are rich in provitamin A carotenoids can improve the vitamin A status of malnourished schoolchildren. At that time, there was some controversy regarding the bioefficacy of plant foods for vitamin A use because other investigators have reported no improvement in vitamin A status in lactating women with increased green leafy vegetable intake. The assessment methods used by these investigators may not have the sensitivity to evaluate changes in vitamin A status in response to an intervention. By using stable-isotope-dilution methodology, our data showed an improvement in total-body stores of vitamin A in schoolchildren fed fruits and vegetables for 10 weeks.

Stable isotopes are used as tracers in metabolic research studies and are safe to ingest. Unlike radioactive isotopes which undergo spontaneous disintegration and emit radiation, stable isotopes do not disintegrate (thus, are "stable"), do not emit radiation, and in fact are naturally present in small amounts in the body. Because of their low abundance in the body, small amounts of compounds tagged with 13C or 2H (deuterium) can be introduced into the body and used as tracers. For example, a vitamin A molecule in which four hydrogen atoms (1H) are replaced by four deuterium atoms is a stable isotope of vitamin A (i.e., tetradeuterated vitamin A) and when ingested, it mixes with the body’s vitamin A pool. When there is sufficient vitamin A in the body, the ratio of deuterated to non-deuterated retinol in serum is low since there is plenty of vitamin A in the body to "dilute" the labeled vitamin A molecules ingested. By using a number of assumptions regarding the efficiency of absorption and storage of the tracer dose, the difference in retinol isotopic ratios in liver versus serum, the half-life of vitamin A turnover in the body, and the liver to body weight ratio, the serum retinol isotopic ratio can be used in a mathematical equation to provide a numerical estimate of total-body vitamin A stores and of liver vitamin A concentrations.

My second study with the NCP was conducted in Barangays Malabanan and Palsara in Balete, Batangas with funding from the US Department of Agriculture Foreign Agricultural Service. In this study, we aimed to determine the vitamin A requirements of elderly people. Very few vitamin A studies have been done among the elderly; previous studies were mostly conducted in children, and pregnant and lactating women. Using the deuterated-retinol-dilution (DRD) technique, we found that elderly people are also vulnerable to vitamin A deficiency; 14.5 percent of the study participants had low liver vitamin A levels, even though none had serum vitamin A values that are considered low. These data, together with our previous and subsequent data, confirm that stable-isotope-dilution methodology is a powerful tool for assessing vitamin A status. By determining the usual dietary vitamin A intakes of those with adequate versus those with low liver vitamin A, we estimated that vitamin A intakes of about 500 and 400 micrograms daily by elderly men and women, respectively, are advisable for maintaining adequate vitamin A reserves in liver. As examples, 100 grams of malunggay can provide about 645 micrograms of vitamin A, and 100 grams of kamote leaves, about 323 micrograms.

My third study in the Philippines is being funded by the US Department of Agriculture National Research Initiative. In this study, we continue to explore factors influencing the bioefficacy of plant sources of vitamin A. Specifically, this study, the field work of which was conducted among schoolchildren in Barangays Banawang and Overland in Bagac, Bataan, aims to understand the influence of amounts of dietary fat on carotenoid bioavailability and on the bioconversion of plant provitamin A carotenoids into vitamin A. The children were fed standardized vegetable-containing meals three times daily, for five days a week, for nine weeks in their schools; the meals differed only in the amounts of dietary fat they contained. Data analyses are currently in progress and will provide other information such as the vitamin A requirements of this age group, interactions between vitamin A and iron, effect of carotene-rich meals on the prevalence of anemia, and influence of parasitic infections on vitamin A status and iron status.

These studies in the Philippines have contributed substantially to what is now known regarding the use of stable-isotope-dilution methodology (i.e., DRD, as well as a shortened procedure called three-day DRD) in vitamin A studies. The DRD procedure has become the "gold standard" for biochemical assessment of vitamin A status; it is useful for assessing a wide range of status, from deficiency to sub-toxicity. It is the best method available for monitoring the effectiveness of vitamin A intervention programs.

In all our studies in these rural Philippine communities, we make every effort to design the protocol to be as non-invasive as possible (with only the minimum number of blood draws at baseline and at post-intervention), and to provide a benefit not only to the study participants, but also to the community. For example, during the screening phase, the study physician conducted a physical examination of all children whose parents gave their consent, regardless of whether the child would decide to participate in the study or not; those found to have abnormalities were treated or referred to the local clinic for follow-up. Tests for intestinal parasitic infections were done routinely, and those found to have worms were treated. Blood pressure measurements were available to the parents and the community. The studies among the children were designed to be food-intervention studies which provided nutritious meals and/or snacks for nine to 10 weeks at the schools, and employed local residents to assist with meal preparation and clean-up. After the study, some schools were left with a renovated room (the study kitchen/dining area) with running water. The children were provided with school supplies. The elders were given a physical exam, including an electrocardiogram and other medical tests not part of the research agenda. As a result of the tests, several were identified to have tuberculosis and received treatment for it. Medical and nutritional advice was available to everyone.

Our studies in Santa Elena, Hukay, Malabanan, Palsara, Banawang, and Overland have given the research work that I do an added significance that is both profound and special, and I am very thankful. It has been a privilege and a pleasure working in all these places.

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The author is a scientist at the Jean Mayer USDA Human Nutrition Research Center at Tufts University, Boston, Massachusetts, USA, and can be reached via e-mail at [email protected]. She has a Doctor of Science degree from Harvard University. She is a member of the Philippine Academy of Science and Engineering.