Potentially eligible women of reproductive age (WRA) will be identified from existing community census records and will be listed sequentially. A random number generator will be used to select individual women from this list for possible participation in the Phase 1 studies. In cases where two or more WRA are selected from the same household (HH), one will be randomly selected for possible participation in the study and the other(s) will be replaced by a WRA from another HH, using the same random selection procedure. A member of the study team will then visit the homes of women who are selected for possible participation in Phase 1 to describe the study to them, assess their eligibility, and request their consent to participate. In particular, the data collector will present an initial disclosure statement concerning the screening interview and will then obtain descriptive information from verbally consenting women on their age, general health status, address, cell phone number (if available), and potential willingness to participate in the subsequent research studies. The data collector will review the women's health history and determine their eligibility for the Phase 1 study.

For women who found to be eligible to participate in the Phase 1 study, the field worker will describe the purpose of the study, the study procedures and related risks and benefits, the confidentiality of results, and the fact that participation is voluntary. After providing an opportunity for women to consult with family members and ask any questions to the research team, the field worker (in the presence of a neutral witness) will request written consent from the women to participate in the study. Additional questions will be asked of consenting women regarding their marital status, ethnicity, religion, educational level, and employment; and their housing characteristics (housing construction, water source, sanitary facilities, access to electricity and cell phone service); and selected HH assets.

All eligible, consenting women will be requested to report to the Chefe Donsa Health Center or one of the local health posts within the next one or two days following the initial screening interview for fasting blood collection, anthropometric assessment, additional interviews, and scheduling of subsequent home visits by the study team for full-day dietary observations to measure discretionary salt intake and folate intake and to initiate 24-hour urine collections to measure sodium and iodine excretion. The fasting blood specimens will be collected for a complete blood count and measurement of red blood cell (RBC) folate and serum folate, unmetabolized folic acid, vitamin B12, holo-transcobalamin, methyl malonic acid, other B vitamins, genetic polymorphisms that affect folate metabolism, thyroglobulin, glucose, insulin, retinol binding protein (RBP), ferritin, soluble transferrin receptor, C-reactive protein, and alpha-1 acid glycoprotein and to complete a malaria rapid diagnostic test (RDT). Serum retinol will be measured in a subset of 40 women to establish the relationship between serum retinol and RBP in the study population. Blood specimens may also be collected from a subset of 20 women for possible metabolomics assays and natural killer cell (immune function) assays. Women with a positive RDT and those subsequently found to have anemia (Hb\<13.2 g/dL, to adjust for altitude) will be referred to the local health facility for treatment. Additional interviews will be completed to assess the women's birth history, contraceptive use, and household food insecurity.

All women will participate in dietary assessments and 24-hour urine collections on one day within four weeks of enrollment, and a randomly selected sub-set of 40 women will complete these studies on a second day one-to-two weeks later. The purpose of the second set of studies is to allow for calculation of intra-individual variation in intakes and urinary sodium and iodine excretion, which is necessary to estimate the distribution of usual discretionary salt and folate intake and urinary sodium and iodine excretion of the study population. The dietary studies will involve a dietitian who will remain in the participant's home throughout the day to weigh all foods included in mixed dishes and to weigh the amounts served and consumed. Portions of each food will be collected to analyze these in the laboratory for sodium and selected nutrient contents. The investigators The investigators will also carry out HH salt disappearance studies over a period of one week using iodized refined salt provided by the project to determine the rate of salt utilization in relation to HH size. This information will be used to estimate the quantities of salt that we will need to deliver during Phase 2.