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Do's and Don'ts for Different Vitamins

By Dr. Mehmet Oz and Dr. Mike Roizen, MDs

When it comes to combining vitamins, it pays to know which may block each other from doing their good work and which may amplify their effects.

Fat-soluble vitamins A, D, E, and K:

  • Absorption is improved if you take fat-soluble vitamins with a meal that contains healthy fats. One study found that taking vitamin D with your largest meal of the day increases your blood level by 50%.
  • Vitamin A may be better absorbed when taken with vitamin E, but Johns Hopkins University research shows doses of vitamin E over 400 IU a day are associated with a higher risk of all causes of death — maybe because most vitamin E supplements contain just one of the eight forms of vitamin alpha-tocopherol. Make sure you buy vitamin E containing mixed tocopherols, or at least the one most experts think is beneficial: gamma topherol.

Water-soluble vitamins C and the Bs (B6, B12, biotin, folate, niacin, pantothenic acid, riboflavin, and thiamine):

  • Take water-soluble vitamins on an empty stomach with a glass of water.
  • Excessive doses of vitamin B6 can produce peripheral neuropathy, especially if your levels of B12, B2, and B9 are low.
  • Vitamin C increases absorption of iron from supplements and food.

Increase your vitamin intake with fresh fruits and veggies, oily fish, nuts, and seeds. Twice daily take half a multivitamin/multimineral that delivers the recommended levels of nutrients, not mega-doses. A balanced intake is what you're aiming for.

Get a blood test to check for vitamin deficiencies, then follow your doctor's advice.