Multivitamins

https://www.ncbi.nlm...pubmed/31502930
Multivitamin/Multimineral Supplement Use is Associated with Increased Micronutrient Intakes and Biomarkers and Decreased Prevalence of Inadequacies and Deficiencies in Middle-Aged and Older Adults in the United States.
Regular MVM use (≥16 days/month) increased the proportion exceeding the tolerable upper intake level of folic acid. Vitamin B6 deficiency in MVM non-users was common and increased with age.

https://www.ncbi.nlm...pubmed/31382793
Multivitamins and Nutritional Adequacy in Middle-Aged to Older Americans by Obesity Status.
Multivitamin use (sporadic and consistent) also increased the proportion of individuals who exceeded the tolerable upper intake level for folic acid to 8%-10%.

https://www.ncbi.nlm...pubmed/30589152
Analysis of oral dietary supplement use in rural older adults.
Researchers found that 83% of the rural older adults used oral dietary supplements in addition to their prescribed medications. Participants took additional single-dose vitamins along with their multivitamin; 57% took vitamin D, 52% took calcium, 15% took vitamin C and 13% took additional potassium and vitamin E. Participants also used oral dietary supplements with medications that had a potential for interaction.