Lactating women in developing countries have been reported to have significantly lower human milk ascorbic acid output than do women in industrialized countries. Human milk ascorbic acid content varies with maternal intake of ascorbic acid. Generally, lower maternal dietary intake of ascorbic acid and more pronounced seasonal variation in consumption of ascorbic acid-rich foods such as fruit and vegetables, have been identified as major reasons for the low human milk ascorbic acid content of women living in resource-poor areas. As a result of the large differences in the content of ascorbic acid in human milk between lactating women in different settings, the intake of ascorbic acid in exclusively breastfed infants varies widely. The aims of the present study were to compare human milk ascorbic acid content of European and African lactating women, and to evaluate the influence of an ascorbic acid supplement (1000 mg/d) in both study populations. In African women, the researchers also evaluated the influence of a lower dose of ascorbic acid as a supplement (100 mg ascorbic acid/d) as well as the effect of regular consumption of fresh orange juice, served 1 to 5 times per week (approximately 100 mg ascorbic acid/serving) for 6 weeks. African women with relatively low human milk ascorbic acid content (<40 mg/kg) were enrolled into the longitudinal intervention studies.
Apparently healthy, lactating women with apparently healthy infants older than 1 month, were recruited in Zurich, Switzerland, and in Abidjan, Cote d'Ivoire. To evaluate the effect of increased intake of ascorbic acid in women with different baseline ascorbic acid milk content, African women were recruited on the basis of an initial screening study. African women with milk ascorbic acid content <40 mg/kg were enrolled into studies 2, 4, and 5. All women enrolled into studies 2 to 5, were asked to not change their dietary habits or general lifestyle and to not consume ascorbic acid supplements (unless provided by the investigators), throughout the study.
Five separate studies were implemented. Study 1 was a screening study to evaluate ascorbic acid in human milk collected from European and African women. One sample of human milk was collected from each woman. Study 2 was designed to evaluate the influence of an additional intake of 1000 mg ascorbic acid/d for 10 consecutive days in European and African women. One sample of human milk was collected every day from each woman. In study 3, a group of European women consumed 1000 mg ascorbic acid/d for 5 consecutive days and were followed for 35 days after discontinuation of the supplement. Three samples of human milk were collected during the 5-day supplementation. Additional samples were collected twice per week during the next 35 days. The influence of a smaller dose of ascorbic acid (100 mg ascorbic acid/d) for 10 consecutive days was evaluated in African women in study 4. One sample of human milk was collected every day from each woman. Finally, in study 5, a dietary intervention was implemented to evaluate the influence of 1, 3, or 5 servings of fresh orange juice (approximately 100 mg ascorbic acid/serving) per week for 6 consecutive weeks, in African women. Samples of human milk were collected weekly during the supplementation (1 sample per week from the women receiving 1 serving of orange juice per week, and 2 samples per week from the women served 3 or 5 servings of orange juice per week).
Study 1
Human milk ascorbic acid content was significantly lower in the African women than in the European women.
Study 2
Intake of 1000 mg ascorbic acid/d for l0 days resulted in significantly increased human milk ascorbic acid content in both the European and the African women. In 10 European women, human milk ascorbic acid increased from 60 [+ or -] 12 mg/ kg at baseline to 70 [+ or -] 16 mg/kg after intake of a cumulative dose of 10 000 mg ascorbic acid. Corresponding values for the 18 African women in this study were 19 [+ or -] 16 and 60 [+ or -] 11 mg./kg. In the African women, ascorbic acid content increased significantly from day to day during the first few days of the intervention. However, after intake of a cumulative dose of 4000 mg ascorbic acid, no further increase in ascorbic acid content was observed. In the European women, no significant day-to-day increase was observed.
Study 3
Human milk ascorbic acid content increased from 70 [+ or -] 11 to 82 [+ or -] 11 mg/kg after intake of 1000 mg ascorbic acid/d for 5 days in 17 European women. After discontinuation of the supplementation, human milk ascorbic acid content was not significantly different from baseline for the first time after 21 days.
Study 4
Human milk ascorbic acid content increased from 17 [+ or -] 6.5 to 36 [+ or -] 8.0 mg/kg in 11 African women after intake of 100 mg ascorbic acid/d for 10 days. Study 5
Mean ascorbic acid content per serving of orange juice (180 g) was 105 mg. Baseline milk ascorbic acid content was significantly higher in the African women served one glass of orange juice per week (23 [+ or -] 5.3 mg/kg) than in the women consuming 3 servings of orange juice per week (16 [+ or -] 6.0 mg/ kg). Baseline milk ascorbic acid was not significantly different in the African women consuming 5 servings of orange juice per week (21 [+ or -] 4.3 mg/kg) than in the women consuming 1 or 3 servings per week. At the end of the study; human milk ascorbic acid content was 26 [+ or -] 7.1 mg/kg (1 serving/wk), 32 [+ or -] 6.9 mg/ kg (3 servings/week), and 46 [+ or -] 6.2 mg/kg (5 servings/week). Changes in human milk ascorbic acid content were not significantly different from zero in the women consuming one serving of orange juice per week, whereas human milk ascorbic acid content was significantly different from zero in the other 2 intervention groups at the end of the study.
Mean human milk ascorbic acid content was approximately 50% lower in the African women (31 mg/kg; n = 171) than in the European women (63 mg/kg; n = 142) in the present study. These results provide additional information on the significant difference in human milk ascorbic acid output in women living in different settings. A striking difference between the 2 study populations was noted when evaluating the distribution of the data: 29% of the African women had very low human milk ascorbic acid output--20 mg/kg to 29 mg/kg--whereas, none of the milk samples expressed by European women had such low ascorbic acid content. The importance of ascorbic acid intake on human milk ascorbic acid content was clearly shown in the subsequent intervention studies in both study populations.
In conclusion, ascorbic acid supplementation with a relatively high dose of ascorbic acid (1000 mg/d for 10 days) increased human milk ascorbic acid output in both European and African women. Although significant, however, the overall effect was modest in well-nourished European women in contrast with the 3-fold increase in mean human milk ascorbic acid content observed in African women. These results indicate that human milk ascorbic acid content is regulated and is in agreement with previous observations. With lower doses of ascorbic acid, in the form of dietary supplements or as ascorbic acid-rich fruit juice, human milk output can be doubled in African women with relatively low human milk ascorbic acid content at baseline. The results from this study highlight the importance of encouraging regular consumption of ascorbic acid-rich foods by lactating mothers, to ensure adequate human milk ascorbic acid output.
S. Daneel-Otterbech, L. Davidsson, R. Hurrell. Ascorbic acid supplementation and regular consumption of fresh orange juice increase the ascorbic acid content of human milk: studies in European and African lactating women. Am J Clin Nutr; 81(5): 1088-1093 (May, 2005). [Correspondence: L. Davidsson, Laboratory for Human Nutrition, Institute of Food Science and Nutrition, Swiss Federal Institute of Technology, PO Box 474, CH-8803, Ruschlikon, Switzerland. E-mail: lena.davidsson@ilw.agrl.ethz.ch]
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