A whole grain is a grain of any cereal and pseudocereal that contains the endosperm, germ, and bran, in contrast to refined grains, which retain only the endosperm.
Eating whole grains is part of a generally healthy diet and is associated with a lower risk of several chronic diseases.
In a study from Tufts University, scientists found middle- to older-aged adults who ate at least three servings of whole grains daily had smaller increases in waist size, blood pressure, and blood sugar levels over time compared to those who ate less than a one-half serving per day.
They examined how whole- and refined-grain intake over time impacted five risk factors of heart disease: Waist size, blood pressure, blood sugar, triglyceride, and HDL (‘good’) cholesterol.
The team used data from the Framingham Heart Study Offspring Cohort, which began in the 1970s to assess long-term risk factors of heart disease.
They examined health outcomes associated with whole- and refined-grain consumption over a median of 18 years. The 3,100 participants from the cohort were mostly 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, across four categories of reported whole grain intake, ranging from less than a half serving per day to three or more servings per day.
They showed that for each four-year interval, waist size increased by an average of over 1 inch in the low-intake participants, versus about ½ inch in the high-intake participants.
Even after accounting for changes in waist size, average increases in blood sugar levels and systolic blood pressure were greater in low-intake participants compared to high-intake participants.
The researchers also examined the five risk factors across four categories of refined-grain intake, ranging from less than two servings per day to more than four servings per day.
Lower refined-grain intake led to a lower average increase in waist size and a greater mean decline in triglyceride levels for each four-year period.
The findings suggest that eating whole-grain foods as part of a healthy diet delivers health benefits beyond just helping us lose or maintain weight as we age.
In fact, these data suggest that people who eat more whole grains are better able to maintain their blood sugar and blood pressure over time. Managing these risk factors as we age may help to protect against heart disease.
The greatest contributor to whole-grain intake among participants was whole-wheat bread and ready-to-eat whole-grain breakfast cereals. The refined grains came mostly from pasta and white bread.
The difference in health benefits between whole and refined grains may stem from the fact that whole grains are less processed than refined grains.
Whole grains have a fiber-rich outer layer and an inner germ layer packed with B vitamins, antioxidants, and small amounts of healthy fats.
Milling whole grains removes these nutrient-dense components, leaving only the starch-packed refined grain behind.
If you care about nutrition, please read studies about how diets could help lower high blood pressure, and 4 types of eating disorders you need to know.
For more information about nutrition, please see recent studies that green tea could strongly reduce blood pressure, and results showing people with diabetes should consider taking this vitamin.
The study was conducted by Nicola McKeown et al and published in the Journal of Nutrition.
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