Although multivitamins are often promoted as general health boosters, researchers at Mass General Brigham note that earlier studies were too small or inconsistent to detect subtle physiological effects.
To address those gaps, the large-scale COSMOS trial, which follows adults who entered the trial without hypertension, examined whether daily multivitamin use influences long-term health outcomes.
How the trial was conducted
The team analyzed results from 8,905 participants who received either a multivitamin or a placebo over several years.
More than 1,500 participants also completed both clinic and home blood-pressure measurements, a method the researchers say provides a more reliable picture of day-to-day variation than self-reported readings alone.
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Overall, the trial did not show that multivitamins reduced the incidence of new hypertension.
However, two groups showed different responses.
Adults with poorer diet quality experienced a modest improvement in blood-pressure outcomes when taking a daily multivitamin.
Participants who started the study with normal blood pressure also showed slight downward trends over roughly two years.
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Why these subgroup trends matter
Even minor shifts can reveal which populations may benefit from supplementation.
According to the researchers, individuals with nutritional gaps may respond more readily to added micronutrients, while those with healthy baseline readings may experience additional stability.
Senior investigator Howard Sesso stresses that multivitamins are not a universal solution.
Their value, he notes, depends on individual dietary patterns and cardiovascular risk profiles.
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Sources: Mass General Brigham, American Journal of Hypertension og COSMOS.
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