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Dr. David Killilea, a researcher at the University of California, San Francisco, is analyzing samples of wheat kernels, flour, and bread to determine their vitamin content.
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Credit: Holly Duden, UCSF
Chicago (July 1, 2024) — What does whole wheat have that refined flour doesn’t? New research reveals where nutrients are lost (and sometimes gained) along the journey from farm to fork, as well as key differences in nutrient content.
Previous studies have assessed the nutrients present in different crops and foods, but this new study is one of the first to link the two together by tracking how processing and baking affect the nutrient composition at each stage.
The researchers reported that refined wheat flour and bread made with refined wheat flour had nearly three-quarters less key minerals than whole wheat. Additionally, milling and baking significantly reduced the amounts of other nutrients, including vitamin E, in both refined and whole wheat products compared to raw wheat kernels.
“Tracking nutritional content from farm to fork is key to assessing whether agricultural products are actually contributing to the diet,” said David Killilea, PhD, a researcher at the University of California, San Francisco. “Our experimental approach revealed that both milling and baking have significant effects on multiple nutrient levels in flour and bread.”
Kirillia will present his findings at NUTRITION 2024, the American Academy of Nutrition’s flagship annual meeting, taking place in Chicago from June 29 to July 2.
The Dietary Guidelines for Americans recommend that at least half of your total grain intake be whole grains, but research shows that most people do not meet this recommendation. This study reveals stark differences in the nutritional value of refined and less refined wheat products and highlights the importance of a diet rich in whole grains.
“Whole grains play an important nutritional role in the Western diet and we strongly support promoting whole grain intake,” said Kirilia. “Processes that increase the nutrient density of wheat-based foods should be encouraged, while processes that decrease the nutrient density should also be understood.”
For the study, researchers obtained raw wheat kernels from a single farm, milled the kernels to produce three types of flour, and cooked bread with the flour. At each stage, they assessed the content of major minerals (calcium, magnesium, phosphorus, potassium), trace minerals (copper, iron, molybdenum, zinc), carotenoids (compounds similar to vitamin A), and vitamin E.
The three flour types were whole wheat flour (stone milled), regenerated whole wheat flour (roller milled), and refined white flour (roller milled to remove the bran and germ).
In the two types of whole wheat flour, the content of major minerals changed little from kernel to flour to bread, but the content of some trace minerals actually increased during processing. In refined flour and bread, major minerals were reduced by up to 72% and trace minerals by up to 64% compared to wheat kernel.
Regardless of the type of flour used to make the bread, each processing step significantly reduced the vitamin E content. Ultimately, breads made with all flour types contained less than one-fifth the vitamin E found in wheat grains. Baking the flour into bread also reduced the carotenoid content, with all breads containing less than one-quarter the carotenoids found in wheat grains.
Next, the researchers plan to study how different farming and processing methods affect the nutrient density of wheat and wheat products. Because deficiencies in vitamins A and E are major health issues in the U.S., the researchers will focus in particular on whether fermentation and other processes can help preserve the vitamin content of wheat products.
Kirilia The study will be presented at the Food Science and Nutrition session on Monday, July 1, from 2:12 to 2:24 p.m. CDT at McCormick Place.Abstract; Presentation details).
Please note that although the abstracts presented at NUTRITION 2024 were evaluated and selected by an expert committee, they have not undergone the peer review process typically required for publication in a scientific journal. Therefore, the presented research findings should be considered provisional until a peer-reviewed publication has been published.
About NUTRITION 2024
NUTRITION 2024 is the flagship meeting of the American Academy of Nutrition and the premier educational event for nutrition professionals worldwide. NUTRITION brings together laboratory scientists, clinicians, population health researchers, and community intervention investigators to identify solutions to today’s greatest nutrition challenges. Our audience also includes undergraduate, graduate, and medical students who are emerging leaders in the field. NUTRITION 2024 will be held in Chicago from June 29 to July 2, 2024. https://nutrition.org/N24 #Nutrition2024
About the American Society for Nutrition (ASN)
ASN is the preeminent professional organization for nutrition researchers and clinicians worldwide. Founded in 1928, the Society brings together top nutrition researchers, health care professionals, policy makers, and industry leaders to advance nutrition knowledge and applications. ASN publishes four peer-reviewed journals and provides education and professional development opportunities to advance nutrition research, practice, and education. Since 2018, the American Society for Nutrition has produced NUTRITION, the world’s leading annual conference for nutrition professionals. http://www.nutrition.org
For more breaking news from NUTRITION 2024, visit https://www.eurekalert.org/newsroom/nutrition2024/home
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