More than 6,500 participants across randomized trials showed the strongest cardiometabolic gains at 60-100 grams of whole grains daily—about 4 to 6 servings.
High-certainty evidence tied that intake to lower body weight, waist circumference, total cholesterol and IL-6, while moderate-certainty evidence pointed to improvements in LDL cholesterol, triglycerides, systolic blood pressure and fasting glucose.
Some of the analyzed trials replaced refined grains with whole grains, suggesting the benefits may depend on substitution rather than simply adding whole grains to an otherwise unchanged diet.
An 8-week median trial length limits conclusions on whether the effects persist long term, and evidence remains thin for intakes above 140 grams a day.
The findings, published in the European Heart Journal, support pushing intake toward the upper end of current recommendations as most U.S. adults still fall short.