A concerted effort in the Dietary Guidelines to reduce intake of certain food groups, including enriched grains, may have unintended and undesirable public health consequences for children, according to research published recently in the Journal of the Academy of Nutrition and Dietetics. The 22-page study offered a rare look into and strong endorsement of the value of the fortification and enrichment of foods in the American diet. It also affirmed the dominant position of grain-based foods as the leading source of micronutrients in the American diet.
“Despite the large nutrient contributions made by fortified foods, they are not always among the foods targeted by recommendations to increase intakes, and sometimes, as in the case of refined grain foods and juice drinks, reduced intakes might even be recommended,” the researchers said. The study went on to cite data indicating that yeast bread/rolls and pizza were among the top five sources of total and added thiamin, niacin, riboflavin, folate and iron for children between the ages of 2 and 18.
“There is some overlap between major food sources of micronutrients and major sources of components targeted for reduction, and care should be taken so that following dietary advice (to limit macronutrient intake from certain foods, for example) does not have an unintended effect of reducing intake of key micronutrients,” the researchers said.
The admonition was among conclusions of the study, “Fortified Foods are Major Contributors to Nutrient Intakes in Diets of U.S. Children and Adolescents.” The study was published by a team led by Louise A. Berner, a professor of food science and nutrition at California Polytechnic State University, San Luis Obispo, Calif. Other contributors to the study were from the Schools of Medicine and Friedman School of Nutrition Science and Policy at Tufts University in Boston; the Office of Dietary Supplements at the National Institutes of Health in Bethesda, Md.; and Food and Nutrition Database Research, Inc.
The researchers sought to understand the impact of fortification on nutrient adequacy among U.S. children and adolescents and to rank food sources of added nutrient intake. The study also looked into concerns of excess intake of certain nutrients because of fortification.
Absent fortification, the diets of many children and adolescents led to inadequate intake of numerous micronutrients, especially among older girls, the study said. The researcher said the data could be important in putting “dietary advice into a practical context.”
The researchers based their conclusions on findings in NHANES, a continuous nationally representative population based survey. Specifically, the 2003-04 and 2005-06 What We Eat in America data were used, focusing on children between the ages of 2 and 18. Nutrient intakes from food sources and dietary supplements were determined using 2 days of 24-hour dietary recall data, along with dietary supplement questionnaire data. Parents completed responses for children aged 2 to 5, and assisted children aged 6 to 11.
“The impact of fortification on the percentages of children having intakes less than the Estimated Average Requirement and more than the Upper Tolerable Intake Level was assessed by comparing intakes from intrinsic nutrients to intakes from intrinsic plus added nutrients,” the researchers said.
The researchers separated the sources of nutrients added by enrichment or fortification from naturally occurring (intrinsic) nutrients in 56 food groupings eaten by NHANES participants. Data on 7,250 children were gathered.
Nutrient inadequacy was most rare for children ages 2 to 8 and most common for females between the ages of 14 and 18.
Among the 10 food groups identified as categories in the study, grain-based foods dominated as the leading source of micronutrients. Grain-based foods ranked first among food groups for 8 of the 11 nutrients — folate, iron, thiamin, riboflavin, niacin, vitamin B6, vitamin B12 and zinc. Vitamins A, D and C were the three nutrients in which grain-based foods were not the top source for children. Other food categories were vegetables; fruits; dairy products; eggs, legumes, nuts and seeds; fats and oils; desserts and sweets; beverages; and other foods.
Excluding the nutrient contribution from fortification, 25% to 100% of participants would have had inadequate intake of vitamins A, D, E, folate and calcium. Among females aged 14 to 18, 23% to 92% additionally would have had inadequate intake of thiamin, riboflavin, niacin, vitamin B6, vitamin C, phosphorus, magnesium, iron and zinc.
“Among most subgroups, the percentages having usual intakes above the upper limit were very low or zero for most nutrients, even when considering total intakes from food plus supplements,” the researchers said.
The latter aspect of the study reflected the researchers observation that, despite the documented success of fortification in eliminating nutrient deficiency diseases such as rickets and pellagra, fortification has been characterized as risky.
This scrutiny is due to “concerns it could lead to overconsumption of nutrients.”
Zinc was an example of a nutrient in which overconsumption was found based on guidelines established by the Institute of Medicine. The overconsumption was limited to children ages 2-8. The U.L. was exceeded even when fortified foods and supplements were excluded, i.e., “considering only the zinc intrinsic to food.” Other nutrients sometimes exceeding the U.L. were niacin and folate, especially when supplements were considered.
The researchers suggested the intake above the U.L. was not necessarily cause for worry.
“The intakes might not be truly of public health concern if the U.L. established for children are set too low,” the study said. “Questions about the quantification of the U.L. remain because of lack of evidence of any adverse effects, even though many children have usual intakes above the U.L. for nutrients such as zinc; because of a lack of data on specific hazard identification relevant to children; and because the extrapolation of adult U.L. values to children on the basis of body weight is controversial and can be fraught with error.”
The authors said the study is not part of a large body of knowledge regarding the micronutrient contribution in children’s diets of various foods sources.
They suggested the number of so-called “shortfall nutrients” flagged in the Dietary Guidelines of Americans could be much larger but for the benefits of fortification.
“For these children and adolescents, fortification added noticeably to intakes of iron and each of the shortfall vitamins identified in 2010 Dietary Guidelines for Americans reports, except for vitamin E, and shifted the prevalence of inadequate intakes lower,” the study said “If it had not been for added nutrients, thiamin, riboflavin, niacin, vitamin B-6, and zinc might also have been considered ‘shortfall nutrients’ in older children, particularly girls.”
The researchers said their findings highlighted potential benefits of further fortification, a recommendation that appeared to reinforce a flour milling industry exploration of adding vitamin D to wheat flour.
“As a Food and Nutrition Board committee concluded, one of the guiding principles to justify discretionary fortification is documentation of dietary inadequacy, a criterion that is met for several of the nutrients mentioned,” the researchers said. “This presents an opportunity for selective fortification with nutrients such as vitamin D and calcium. However, it is an ongoing challenge to improve intakes of target populations without potentially exposing others to excessive amounts.”
Beyond their observation that recommendations to cut intake of refined grain products such as bread, ready-to-eat cereal and pasta could lead to inadequate micronutrient intake, the researchers went even further to suggest cutting fruit drinks and indulgent grain-based foods could have adverse effects.
“Data show fruit drinks/-ades were major sources of total and added vitamin C, and the ‘cake, cookies, quick bread, pastry, and pies’ group was among the top five or six sources of added enrichment nutrients,” the authors said.
While the Dietary Guidelines Advisory Committee models the substitutions of enriched grains with whole grains, the modeling assumes consumer behaviors around intake of whole grains, fruits and vegetables that have not matched reality. Even with the committee’s assumptions, certain nutrient deficiencies were expected, the researchers said.
“Modeling showed that by replacing all grains with whole grains, without including fortified whole grain products such as ready-to-eat cereals, the dietary pattern would contain inadequate levels of folate and iron, and lower (but still adequate) levels of thiamin, niacin, and riboflavin,” the researchers said. “These careful scenarios assumed that other recommended components of U.S.D.A. patterns (such as recommended servings of fruits and vegetables) were in compliance with food guidance. From the public health standpoint, shifts in intake of fortified foods, and any resultant nutrient intake changes, should be monitored. In addition, modified enrichment/ fortification strategies might help optimize alignment of food-based and nutrient-based dietary guidance.”
The authors viewed the results as a strong validation of food fortification.
“Without added nutrients, a high percentage of all children/adolescents would have inadequate intakes of numerous micronutrients, with the greatest inadequacy among older girls,” the researchers said. “Fortification reduced the percentage less than the Estimated Average Requirement for many, although not all, micronutrients without resulting in excessive intakes. Data demonstrated the powerful influence of fortification on food-source rankings,” they said.
The research for the paper was funded in part by the Fortification Committee of the North American branch of the International Life Sciences Institute. I.L.S.A. “provides a forum to advance understanding of scientific issues related to the nutritional quality and safety of the food.” The group sponsors research programs, educational seminars and workshops, and publications.A potential conflict of interest statement noted that two of the four authors, including Dr. Berner, were supported, in part, under consulting contracts with the I.L.S.A. No potential conflict of interest was reported by the other authors.