Allschoolabs Nutrition Center ? Windmill Daily Vitamin with Iron and Beta-Carotene Compare to One-A-Day Essentialamp;reg; and Save100 Tablets Windmill Daily Vitamin with Iron and Beta-Carotene formula provides you with a nice assortment of vitamins and 18 mg of iron per tablet. If you compare the Windmill Daily Vitamin with Iron and Beta-Carotene formula to the One-A-Day Essentialamp;reg; formula, you will find out that the two formulas are almost identical; however, Windmill does not use artificial colors, flavors, or preservatives.