Vitamin and Mineral Supplements - What, When & Why

We all have a pantry in our home filled with an assortment of vitamin and mineral supplements that we've accumulated over time. While some of these purchases may have been well-founded and professionally suggested, others are part of a miscellaneous collection of supplements we may not necessarily need, or understand. One way or the other, we consume these in a haphazard and unreliable schedule; when we remember rather than in a regimented pattern, and usually all at once.

There is, however, a science to taking these supplements - the time at which they are best absorbed, the combination of ingredients that support each other's function, and combinations that interfere with the intended benefit.

Here, we will break down a few commonly used supplements in terms of when and how to best take advantage of them, so your efforts truly produce the results you desire.

Remember to always consult your healthcare provider to test your vitamin and mineral status before starting a supplement routine and to see if the protocol will agree with you or if it is contraindicated based on your existing medical conditions or regime.

Before Breakfast

i.e. on an empty stomach. These particular supplements may interact with food or digestive enzymes and will be absorbed best first thing in the morning.


  • As a key component of hemoglobin (a molecule responsible for carrying oxygen throughout our body), low levels of iron can cause fatigue, lethargy, a weakened immune system (etc), and can be brought on by dietary deficiency, weakened absorptive capacity, and blood loss, just to name a few.

  • Best taken on an empty stomach with Vitamin C to aid absorption - fresh pressed orange juice or even just adding a little lemon to water will do the trick.

  • Avoid taking it with tea or coffee because the caffeine and tannins can affect absorption

  • Avoid with calcium as it inhibits iron absorption and the two reduce each other's uptake in the body so this is especially significant to follow if you have anaemia, osteoporosis, or conditions affected by the deficiency of either of these two substances. 

  • Avoid taking it at the same time as copper or zinc, as the three are absorbed through the same receptors and an excess of one nutrient crowds out the absorption of others.

  • Avoid the ferrous sulfate form as iron can cause constipation, and drink plenty of water early in the day as well as fiber in your next meal.

  • Iron from animal sources is much more absorbable than iron from plant foods like spinach beans or grains, because other factors in plant-based sources inhibit the update of iron, for example, the oxalic acid in spinach. For this reason, exogenous supplementation for vegetarians and vegans especially is generally a good idea.

Vitamin C

  • This is a water-soluble vitamin and antioxidant that boosts the immune system and energizes our cells, so taking it first thing in the morning primes your day in the most optimal way.

  • Best taken throughout the day in divided doses, but including one serving on an empty stomach sets your nutrient intake off to a great start, and aids absorption of iron as above.

B Complex

  • There are 8 different B-vitamins that make up the complex - 1,2,3,5,6,7,9,12. These are crucial for everything from red blood cell production, to nerve function, to eyesight, but are especially important for pregnant women to aid fetal brain development and reduce risk of birth defects, and in men to maintain testosterone levels which can decrease with age, and to help build muscle and strength.

  • Vitamin B is found in dairy, meat and seafood, dark leafy greens, whole grains, beans, nuts and seeds, avocados and citrus, yeast, etc. so unless you're eating a very limited diet or have trouble absorbing the vitamin due to conditions like inflammatory bowel disease, coeliac, HIV, alcohol dependence, rheumatoid arthritis, kidney disease, etc, you should be getting plenty in your diet without supplementation.

  • While a regulated supplement routine is unlikely to cause overdose, unnecessarily heavy supplementation can cause gastrointestinal upset, skin flushing and rashes, and even nerve damage so check with your physician whether it is right for you and then follow the recommended dose.

  • However, when you do take them since they are water-soluble they can be taken right before breakfast on an empty stomach or after a meal. Not too big of a difference in absorption either way.

  • Avoid taking at night as they can lead to restlessness and insomnia so it is better to take these in the morning on an empty stomach (unless you have a sensitive stomach in which case take these after a small meal)

  • B12 specifically - try to opt for a sublingual drop or liquid form of methylcobalamin rather than cyanocobalamin because it won’t have to go through a digestion process before absorption.


  • These are friendly bacteria that support out natural gut flora, but the research on when to take them is conflicting.

  • One theory suggests they are best taken on an empty stomach 30-60 minutes before meals to prevent interaction with digestive enzymes and harsh stomach acids which can destroy the live cultures, but other evidence also shows that healthy fats buffer stomach acids so taking the probiotics with a meal may offer increased protection to the live cultures.

  • Avoid probiotics warmed up or with a warm drink as the heat can destroy the live microorganisms. 

After Breakfast

These supplements are generally fat-soluble and therefore better absorbed with food 

Co-enzyme Q 10

  • This is a naturally occurring compound found in every cell, but especially in organs with high energy requirements like the heart and the brain. It is referred to as the biochemical spark plug because of its importance in the production of energy. 

  • Best taken with dietary fats (with or after a meal)

  • Avoid taking it at night to prevent any negative influences on sleep

  • Dietary fats can include healthy oils, flax seeds, chia seeds, avocado, fish, nuts, etc. These will also help you get the most benefit from foods rich in carotenoids (ex. yellow, orange, red produce) because the two make plant compounds like beta-carotene (which we convert to vitamin A) more available to our body.


  • Zinc is an essential mineral found in protein-rich foods like meat, seafood, nuts and seeds, and is used in the function of the immune and reproductive systems.

  • It is best taken in the late morning or afternoon with food as it can cause nausea if taken on an empty stomach.

  • Avoid taking it later in the day as it doesn't absorb well with calcium- we’ll get into this shortly.

Vitamin D

  • Vitamin D is synthesized in the body after exposure to sunlight, like our version of photosynthesis. It helps the body maintain muscle, bones, teeth, and the immune system. 

  • Being that it is fat soluble, it is best taken with dietary fats earlier in the day as it can have a negative influence on sleep.

  • One study found that consuming vitamin D with dinner (generally the heaviest meal of the day), increased blood levels of vitamin D by 50%, but because vitamin D disrupts the body’s production of melatonin and therefore sleep, it is better to have it after breakfast and avoid taking it later in the day.

After Dinner / Before Bed


  • Calcium is the most abundant mineral in the body and while it is heavily involved in the structure of bones and teeth, it is also used in nerve transmission and muscle function. 

  • Calcium supplements come in two forms - calcium carbonate and calcium citrate. Calcium carbonate is best taken with food as it is easier to absorb, but calcium citrate can be taken on an empty stomach.

  • Best taken at night with magnesium, or earlier in the day with vitamin D.

  • Avoid taking it too late after food to prevent the risk of developing kidney stones. Taking calcium and vitamin D with certain diuretics may increase the chance of kidney stones further.

  • Avoid taking it with iron, caffeine, or salty foods as these will impair absorption

  • Calcium can decrease the absorption of some medications (including thyroid medications and antibiotics) so as always, check with your healthcare provider first before adding this supplement to your regime.


  • Another abundant mineral in the body found in the bones and teeth and has a calming effect on the muscles and nervous system. 

  • Best taken in the evening about 2 hours before bed as magnesium aids sleep.

  • A 1:1 to 2:1 ratio of magnesium to calcium is ideal.


Disclaimer: This content is strictly the opinion of Dr. Mashal Khan and is for informational and educational purposes only. The information discussed is not intended to diagnose, treat, cure or prevent any specific disease or medical condition. It should not be used for or in the place of medical advice or treatment from a personal physician. All viewers of this content, especially those taking prescription or over-the-counter medications, are advised to consult their physicians before beginning any nutrition, supplement or lifestyle program and with specific health questions. Neither Dr. Khan nor the publisher of this content takes responsibility for possible health consequences of any person or persons reading or following the information in this educational content.

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