Impact of Dietary Supplements on Postmenopausal Serum Biomarkers Explored

Dietary supplements, particularly vitamin B12, fish oil, and flaxseed oil, have been shown to significantly elevate serum biomarkers in postmenopausal women, according to a study presented at the American Society for Nutrition (ASN) 2025 Annual Meeting on June 11, 2025. The research, led by Hannah T. Baillie, MS, RD, a PhD candidate at the University of Washington, Seattle, involved a controlled feeding study with 153 participants from the Women's Health Initiative.

The findings revealed that women who consumed vitamin B12 supplements exhibited a 58% increase in serum levels of the vitamin compared to nonusers (p < .001). Additionally, those who took fish oil or flaxseed oil supplements saw their serum concentrations of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) rise between 38% and 46% compared to nonusers (p < .0001). Conversely, the study found no significant correlation between lutein and zeaxanthin supplements and serum concentrations of these nutrients (p = .72).

Baillie emphasized the importance of measuring serum nutrient levels to assess the efficacy of supplements. She noted that while many participants were on multiple supplements—one individual reported taking 18 per day—the study revealed issues with nutrient absorption, especially concerning lutein and zeaxanthin. This suggests that the effectiveness of certain supplements may be compromised, highlighting the need for more robust clinical inquiries into dietary supplement use among older adults.

Dr. Christine M. Sager, an assistant professor at East Tennessee State University, remarked that the study's short duration and limited sample size prevent sweeping generalizations regarding supplement intake. However, she pointed out that the findings align with clinical observations where elevated serum B12 levels are common among patients who take B vitamins.

The study raises critical questions about dietary supplement labeling and the accuracy of nutrient content claims, which can lead to inconsistencies in reported nutrient intake. Baillie acknowledged this limitation, stating that discrepancies between label claims and actual content can hinder the assessment of total nutrient intake.

To ensure optimal health outcomes, Baillie advocates for healthcare professionals to inquire about not only the supplements their patients consume but also the dosages and timing of intake. The study's implications extend to future research, which should focus on diverse populations and the potential safety and efficacy of intravenous vitamins.

The research was supported by the National Cancer Institute and the National Heart, Lung, and Blood Institute, with no reported financial conflicts from the researchers involved. As dietary supplements continue to be prevalent among older adults, the findings underscore the necessity for ongoing research to clarify the health impacts and optimal usage of these products in clinical settings.