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Ask a Medcan dietitian: Do I need to take a vitamin supplement?

Review this list with your registered dietitian

high angle view of vitamins and pills

With so many nutrition theories out there, it’s easy to get confused, especially when it comes to nutrition supplements.

Taking a daily multivitamin wards off cancer (untrue), vitamin C treats the common cold (possibly, for certain people), vitamin B12 helps repair DNA (true), multivitamins make up for a bad diet (nope!), and so on. Turns out, you can’t believe everything you hear. Taking supplements that you don’t need can be unhelpful, even harmful.

At Medcan, we believe it’s important to reach for whole foods first to meet daily nutrient needs. These foods deliver plenty of other beneficial ingredients, too, including fibre and phytochemicals. Sometimes, though, that’s not practical or possible. That’s when a supplement can fill the void.

Here’s what you need to know to determine if a certain nutrition supplement is right for you (as always, we recommend that you consult a registered dietitian to review your current diet and to discuss foods and supplements that can bridge gaps).

Haphazard eaters, low-calorie dieters

If you’re prone to skipping meals or you eat a low-calorie diet, it can be difficult to meet daily requirements for certain vitamins and minerals.

Depending on which kind of diet you follow (e.g., low-carbohydrate, gluten-free, vegan, keto), you could be missing out on certain nutrients, including vitamin D, iron, folate, calcium, magnesium, iodine and omega-3 fatty acids.

A broad-based multivitamin and mineral supplement, or for some people a specific nutrient supplement can help cover your needs.

For women: Folic acid, iron

Women of childbearing age are recommended to take a multivitamin that provides 0.4 mg of folic acid in order to prevent neural tube defects, birth defects that affect a developing baby’s brain and spinal cord. Spinal cord defects occur during the first month of pregnancy, so it’s important to take a multivitamin for at least two to three months before becoming pregnant and then throughout pregnancy and breastfeeding.

Iron requirements increase during pregnancy; most prenatal multivitamins provide 27 mg of iron, the daily requirement during pregnancy.

Menstruating women, who need 18 mg of iron each day, may also benefit by taking a multivitamin and mineral supplement with iron.

Vegan diet reinforcement

Taking a daily multivitamin and mineral can help vegans prevent nutrient deficiencies. Vitamin B12 for example, needed to make red blood cells, repair DNA and keep your nerves working properly, is found only in animal foods and foods that are fortified with this vitamin (e.g., plant-based beverages, soy products). Nutritional yeast is also a good source of B12.

Taking a multivitamin that contains 5 to 10 mcg of B12 helps vegans ensure they’re meeting their daily B12 requirements.

Vegans have higher daily iron requirements than meat-eaters do since the type of iron in plant foods, called non-heme iron, is harder to absorb than heme iron found in meat.

Iodine, a mineral that’s needed for proper thyroid function, is another reason why vegans should take a one-a-day supplement. The nutrient is found mostly in dairy and seafood; adults need 150 mcg per day.

Older adults: B12

Adults over 50 should pay extra attention to vitamin B12. That’s because absorption of B12 from foods relies on an adequate release of stomach acid (hydrochloric acid). It’s estimated that as many as 30 per cent of older adults have atrophic gastritis, a condition that reduces the stomach’s ability to release acid.

It’s recommended that older adults get the majority of their B12 each day from a supplement, such as a multivitamin or B Complex, or fortified foods.

If your vitamin B12 level is low, you may need to take a separate B12 supplement to bring it to the sufficient range; speak to your doctor or dietitian about the right type of B12 supplement for you.

Drugs that deplete nutrients

Certain medications can deplete nutrients and increase the risk of deficiency if you take them long term.

Proton pump inhibitors (e.g., Losec, Tecta, Nexium, Prevacid), used to treat ulcers in the stomach and esophagus and GERD (gastroesophageal reflux disease), reduce the production of stomach acid. In doing so, they can interfere with nutrients that need adequate stomach acid to be absorbed from food, including B12 and magnesium.

Metformin, a drug that helps control blood sugar, also interferes with vitamin B12 absorption.  Research suggests that people taking Metformin for three years or longer are at risk for B12 deficiency,

If you are taking these medications long-term, bolstering your diet with nutrient-rich foods and taking a daily supplement can help prevent a deficiency.

Wondering if you need to take a certain nutrition supplement? Consult a Medcan registered dietitian who will assess your diet, medical history, medications and lifestyle to determine what’s right (and what’s not) for you. Medcan also offers a range of high quality professional brand nutrition supplements for purchase at reception. 

Have more questions?  Reach out to me by email or book a session with a registered dietitian at Medcan by phone (416) 862-1553  or email

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