As clinicians, we always ask our clients what nutritional supplements they take, or we often recommend them.  An important aspect of taking supplements is knowing when and with what to take them.  For example, B vitamins on an empty stomach can cause nausea, or some oil soluble vitamins (A, D, E, K) will not be absorbed as well without some dietary fat.   In other cases, two nutrients compete for absorption so eating them together isn’t always the best way to absorb them. So with this blog, we thought we’d give you some highlights about the “how to” in taking some common supplements.  


  • Minerals
    • Iron
      • The best non-constipating forms are glycinate, bis-glycinate and gluconate.
      • Do not take at the same time as dairy or calcium as they compete with each other.  If they are in a multi-vitamin/mineral together, that’s okay.  
      • Best taken with vitamin C to enhance absorption.  Foods with vitamin C such as citrus, tomatoes, kiwis, etc. are the best.
      • Your needs for an iron supplement are based upon your diet and your iron stores and may vary.
    • Calcium
      • Calcium carbonate is a cheap and common calcium supplement but it is not the most absorbable form and must be taken with food as it requires the production of extra stomach acid to be absorbed – ask your nutritionist for a better form for you.
      • Do not take at the same time as iron.
      • If taking larger doses, which we do not recommend, take separately from other supplements because it will reduce absorption of them.
    • Magnesium (watch for a future blog on this)
      • There are various forms of magnesium supplements, all differing in bioavailbility, meaning some are absorbed by the human body better than others.
      • Some forms cause quicker bowel movement and in larger amounts can cause loose stools.
      • If taking in larger doses (to help with constipation, for example), then take separately from other minerals.
      • Some forms cross the blood brain barrier.
      • Ask your nutritionist to help pick the best form for you.
    • Zinc
      • If taking 50 mg or more/day for more than 10 weeks, include copper in some supplemental form as well. Long-term copper supplementation however is not recommended without checking lab work, as copper can act as an oxidant in the body.
  • Fish oil/ omegas
    • Best taken with a meal because the fat/oil from the meal will help the omegas cross the intestinal lining.


“The amount of fat in a fish oil supplement is only about 1 gram. While that might help a little, studies which have shown increased absorption of fat-soluble vitamins have involved taking them with foods or meals containing fats. Most meals provide at least 5 grams of fat (the amount of fat in a single egg, for instance), while a tuna wrap with mayo can have 40 grams.”¹


  • Oil soluble vitamins
    • Vitamins A, D, E and both K1 and K2 are also best taken with food, as they are absorbed better with dietary fat.
    • Vitamin D absorbs better when taken with dinner than with breakfast – up to 50% more!
    • If taking vitamin K, take at a different meal from the other oil soluble vitamins.
    • Taking vitamin D with a meal increases absorption by 32% to 57% compared to taking it with just water. The bigger (and fattier) the meal, the better — at least for absorption!²
  • Fiber
    • There are two types of fiber, soluble and insoluble. Soluble fiber dissolves in water and gels in the digestive tract. Soluble fiber helps control cholesterol and supports heart health. It bulks up stools and allows them to more easily move through the digestive tract as the muscles of the intestines can move bulky stools more easily than small, hard ones.  Insoluble fiber does not dissolve in water and moves through the digestive tract unchanged, as humans do not digest fiber. Insoluble fiber aids digestion and helps relieve constipation as well.
    • Most fiber supplements contain a mix of both soluble and insoluble fiber.
    • Best to take away from other supplements. Fiber can bind to nutrients and reduce their absorption.
  • B vitamins
    • Many of the B vitamins can cause nausea on an empty stomach.  Therefore take with food
    • B vitamins, most of which are water soluble, are ideally taken at intervals throughout the day because they don’t last very long in the body
    • Bright yellow urine is a by-product of some B vitamins.  It does not mean you are “peeing out” your vitamins and have poor absorption.
    • Do not take single B vitamins.  They work in harmony.  Even if you are taking a single vitamin, like thiamin (B1), make sure your multi has the full complement of B vitamins as well.
    • Some people have a common genetic variant called MTHFR and may need the ‘methylated’ form of B12 and/or folate.  For more information ask your nutritionist.
  • Other points to consider
    • Some vitamins do not contain what the label says they do, either they contain way more or way less of an ingredient than what is stated. For this reason, look for a label that states the product has been third-party tested. A couple examples of labels to look for that involve third-party testing are NSF, USP, or CL.  We only recommend professional line supplements, so the ones we sell are the best quality available.
    • Make sure to look at ‘inactive ingredients’ to look for possible irritants (ex: soy, gluten).
    • Many liquid, chewable, and gummy vitamins are often missing important nutrients or contain lower amounts of nutrients than their encapsulated counter-parts.  They also often contain a lot of extra, non-nutritive ingredients like food dye, sugar, and other additives.

These are just a few of the most common things to consider when taking vitamins and nutrition supplements.  Some medications can also inhibit the absorption of nutrients and vice versa.  The above may seem complicated, but your nutritionist can help answer further questions and sort out a supplement schedule with you.


1,2 Consumer Labs, accessed 2/5/2018.