Metabolic

Eating whole grains can protect against heart disease

A study in middle to older adults suggests that whole grains can protect against heart disease.

Consumption of whole grains is associated with smaller increases in waist size, blood pressure, and blood sugar

Middle-aged adults who ate at least three servings of whole grains daily had smaller increases in waist circumference, blood pressure, and blood sugar levels over time compared to those who ate less than half a serving per day, according to new research.

The study by researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, published today (July 13, 2021) in the Journal of Nutrition, looked at how intake of whole grains and refined grains increased over time on five risk factors for heart disease Impacted: waist circumference, blood pressure, blood sugar, triglycerides and HDL (“good”) cholesterol.

Using data from the Framingham Heart Study Offspring Cohort, which began evaluating long-term risk factors for heart disease in the 1970s, the new study examined health outcomes associated with whole grain and refined cereal consumption over a median of 18 years. The 3,100 participants in the cohort were predominantly white and on average in their mid-50s at the start of data collection.

The research team compared changes in the five risk factors over four-year intervals in four categories of reported whole grain intake, ranging from less than half a serving per day to three or more servings per day. As per the American Dietary Guidelines 2020-2025, the recommended amount of whole grains is three or more servings per day. An example of a serving is a slice of whole wheat bread, half a cup of oatmeal, or half a cup of brown rice.

The results showed that for each four year interval:

  • The waist circumference increased an average of over 1 inch in the low intakes participants compared to about ½ inch in the high intakes participants.
  • Even after taking into account changes in waist size, the mean increases in blood sugar levels and systolic blood pressure were higher in the low-intake participants than in the high-intake participants.

The researchers also looked at the five risk factors in four categories of refined grain intake, ranging from less than two servings per day to more than four servings per day. Less refined grain intake resulted in a smaller mean increase in waist circumference and a larger mean decrease in triglyceride levels for each four-year period.

“Our results suggest that eating whole grains as part of a healthy diet offers health benefits that not only help us lose or maintain weight as we age. In fact, this data suggests that people who eat more whole grains may be better at holding their blood sugar and blood pressure over time. Dealing with these risk factors as we age can help protect against heart disease, ”said Nicola McKeown, senior and corresponding author and researcher on the Nutritional Epidemiology Team at the USDA HNRCA.

“There are several reasons that whole grains can help maintain waist size and reduce increases in other risk factors. The presence of fiber in whole grains can have a satiating effect, and magnesium, potassium, and antioxidants can help lower blood pressure. Soluble fiber in particular can have a positive effect on blood sugar spikes after a meal, ”said Caleigh Sawicki. Sawicki completed this work as part of her PhD while studying at the Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy at Tufts University and while working with the USDA HNRCA’s Nutritional Epidemiology Team.

Whole grain breads and ready-to-eat whole-grain breakfast cereals made the largest contribution to the whole grain intake of the participants. The refined grains came mainly from pasta and white bread. The difference in health benefits between whole grains and refined grains may be due to the fact that whole grains are less processed than refined grains. Whole grains have a fiber-rich outer layer and an inner germ layer that is filled with B vitamins, antioxidants, and small amounts of healthy fats. Milling whole grains removes these nutrient-rich components, leaving only the starchy refined grains.

“The average American consumes about five servings of refined grains a day, much more than recommended. So it’s important to think about ways to replace refined grains with whole grains later in the day. For example, you might consider a bowl of whole grain cereal instead of a white flour bagel for breakfast, replacing refined snacks, appetizers, and side dishes with whole grain options. Small incremental changes in your diet to increase your intake of whole grains will make a difference over time, ”McKeown said.

methodology

To measure daily grain intake, researchers used nutrition questionnaires that participants completed every four years from 1991 to 2014, resulting in a median of 18 years of data.

Nutritional assessment data were obtained from five study exams, and observations were included only when participants participated in at least two consecutive examinations with accurate nutritional data. Participants with baseline diabetes were excluded.

The statistical analysis was adjusted for factors that might affect the results, including other aspects of healthy eating. The limitations of the study include the fact that food consumption is self-reported and participants may overestimate or underestimate the intake of certain foods based on perceived social desirability. Due to the observation design, the study does not reflect a causal relationship.

Reference: July 13, 2021, Journal of Nutrition.
DOI: 10.1093 / jn / nxab177

Other authors of the study are Paul Jacques, Alice Lichtenstein, Gail T. Rogers from the USDA HNRCA and Jiantao Ma and Edward Saltzman from the Friedman School.

This work was supported by the USDA’s Agricultural Research Service, the General Mills Bell Institute of Health and Nutrition, and the National Heart, Lung, and Blood Institute of the National Institutes of Health (Framingham Heart Study). The authors are solely responsible for their content and do not necessarily represent the official views of the National Institutes of Health. Please refer to the study for information on conflicts of interest.

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