April 2011

Nutrient intake and anemia risk in the Women’s Health Initiative Observational Study.

Thomson, C.A., Stanaway, J.D., Neuhouser, M.L., Snetselaar, L.G., Stefanick, M.L, Arendell, L., Chen, Z.

The purpose of this study was to examine the relationship between nutrient intakes and the prevalence of anemia in postmenopausal women, while also looking at both the persistence and frequency of anemia. In the United States, it is not uncommon to find anemia in the older population. Anemia is linked to increased hospitalizations as well as mortality rates and it has been shown that nutrient-related anemia can be avoided in postmenopausal women.

Participants included 93,676 postmenopausal women of diverse ethnicities/races involved in the longitudinal, observational cohort study by the Women’s Health Initiative over a period of seven years. Ages ranged between 50 and 79 years and the participants were recruited by newspaper advertising or by mail. Women were excluded from the study if they had a history of CHF, MI, RA, lupus, any type of cancer, or medical condition with a life expectancy of less than three years.

Anemia was defined by the World Health Organization (WHO) as a hemoglobin concentration of less than 12.0g/dL in women. This study required data on hemoglobin levels at baseline and again at year three. Nutrition-related anemia consists of long-term inadequate intake of vitamin B-12, vitamin C, folate, iron, and protein. Inadequate intake of these nutrients among this population is commonly associated with reduced appetite, poor dentition, lack of/loss of intrinsic factor (IF), and decreased tolerance of milk/milk products. Anemia related to nutritional causes is usually a result of modifications to ones’ diet. Non-nutritional anemia is also common among elderly/aging women due to increased levels of pro-inflammatory cytokines, which decrease the bioavailability of iron. In addition, blood loss is another contributor that is common in the elderly population that is thought to be a major cause of microcytic anemia.

The researchers hypothesized that the occurrence, frequency, and persistence of anemia would be higher in postmenopausal women that reported low intakes of iron, vitamin B-12, and folate at the beginning of the study compared to the women with adequate consumption of these three nutrients according to the DRI’s after being controlled for contradicting factors. It was also hypothesized that participants with inadequate intake of these nutrients would also be at a higher risk for persistent and incident anemia by year three of the study. Incident anemia or newly diagnosed anemia was defined as a reduction in hemoglobin levels to lower than 12.0g/dL at year three of the study from baseline hemoglobin levels that were greater than 12.0g/dL. Persistent anemia was defined as women with baseline and year 3 hemoglobin levels of less than 12.0g/dL.

Participants’ dietary intake was collected at baseline and again at year number 3 of the study using a food frequency questionnaire (FFQ) that was created/validated by Fred Hutchinson Cancer Research Center. It was specifically designed to include food that corresponds with the nation’s food supply and portray ethnic and regional food choices. The FFQ included 122 food profiles and asked the participants to self-report portion sizes and frequency of the food they consumed based on their food intake pattern over the previous three months using a Likert scale. Nutrient intake was evaluated with the use of the Nutrition Data System for Research food and nutrient database. Dietary inadequacy of vitamin B-12, vitamin C, folate, iron, and animal/vegetable protein intake was defined as levels below the DRI’s for each nutrient based on recommendations for women about the age of 50 years. The use of supplemental vitamins or minerals was also examined using the nutrient database.

Statistical analyses were conducted and baseline characteristics were represented using the mean and standard deviations of the anemia group. To compare the baseline anemia group with the non-anemia group, t-tests and x² tests were conduction for both categorical and continuous variables. Unconditional logistic regression was used to examine the relationship between inadequacy of nutrient intake, the amount of anemia-related dietary inadequacy of micronutrients (at baseline), and number of servings of specific food groups (iron/folic acid fortified cereal, red meat intake, animal protein and vegetable protein intake, vitamin C, vitamin B-12, folate, and iron). Anemia-related nutrient inadequacies and ethnicity/race was examined to reveal differences among groups.

Results of the study revealed anemia was more prevalent in women greater than 63.5 years and current smokers, while it had an inverse relationship with income, education level, and body weight. BMI revealed a U-shaped curve associated with anemia risk. Race/ethnicity was also associated with anemia risk. Anemia was prevalent in 4.2% of Asians, 4.5% of non-Hispanic whites, 5.6% of Hispanic/Latinos, and 16.3% of African Americans (with Hgb less than 12.0g/dL). Multiple nutrient deficiencies showed a 21% greater risk for persistent anemia and participants with three or more deficiencies had a 44% higher risk for persistent anemia. Lower intake of the nutrients related to anemia were reported in women that were either newly diagnosed with persistent or incident anemia, but those that reported adequate or higher consumption of foods with folate, vitamin B-12, vitamin C, iron, red meat, etc. did not present with anemia. The use of supplemental vitamin B-12 and iron was much higher in the participants with anemia compared to the group without anemia, however multivitamin/mineral supplementation was not associated with reduction in anemia rates. The researchers concluded that this was one of the first longitudinal studies of its’ size to examine the associations between anemia and dietary intake among postmenopausal, aging, and multiethnic women.

Thomson, C.A., Stanaway, J.D., Neuhouser, M.L., Snetselaar, L.G., Stefanick, M.L, Arendell, L., Chen, Z. Nutrient intake and anemia risk in the Women’s Health Initiative Observational Study. Journal of the American Dietetic Association. 2011; 111(4): 532-541.

Related Article:

Bor, M.V., Lydeking-Olsen, E., Møller, J., Nexø, E. A daily intake of approximately 6 microg vitamin B-12 appears to saturate all the vitamin B-12-related variables in Danish postmenopausal women. American Journal of Clinical Nutrition. 2006; 83(1): 52-58. PMID: 16400049.