The Issue With Multivitamins

Published 16 March 2023

Should you take them for a vegan diet?

Caitlyn Adler

Caitlin Arnold is a vegan Accredited Sports Nutritionist, Strength & Conditioning coach and bodybuilder at Plant Forged Physique. Her passion is helping vegans achieve their health and fitness goals with evidence-based guidance and expertise.

When transitioning to a vegan diet, it’s important to know what micronutrients you need to thrive and how to get them adequately on a fully plant-based diet.

Vegans should give consideration to iron, zinc, calcium, omega-3s, B12, iodine and vitamin D in particular. And some people might consider a multivitamin as a potential solution.

However, consuming a multivitamin to meet these micronutrient needs at once might not be the best solution after all.

Irregular Dosing

Vitamin and mineral dosages in multivitamins are rarely standardised. Different products can have notably different micronutrient levels.

As a result, some may have micronutrients which are underdosed. For example, the RDI for calcium is 1000mg/day but most multivitamins only contain 20-100mg which is only 2-8% of what you’d need to consume. So you couldn’t necessarily guarantee you’d get all your calcium intake reliably from a multivitamin alone.

On the flip side – other multivitamins can have high levels of micronutrients which might be consumed in excess. As another example, the RDI for Vitamin A is 900 mcg for men and 700 mcg for women. Some multivitamins contain 1500 mcg of Vitamin A. Vitamin A is a fat-soluble vitamin which means it gets stored in your body’s cells. If it’s taken as a supplement more than advised, it can build up over a long period of time and potentially causing harm.

The RDI for calcium is 1000mg/day but most multivitamins only contain 20-100mg which is only 2-8% of what you'd need to consume.

Competing for absorption

Many multivitamins contain multiple nutrients which compete for absorption in the small intestine. For example, minerals like calcium, iron, and magnesium and zinc compete for absorption, as do certain vitamins like vitamin K and vitamin E.

When consumed simultaneously, the amount of vitamin and mineral absorbed is reduced. This lowers the effectiveness of the multivitamin and the guarantee that it will meet those micronutrient needs.

Competes for absorption with...

Limited additional health benefits

Studies into the effectiveness of multivitamins in reducing the risk of heart disease, cancer, and mortality have not shown any positive association – meaning, multivitamins won’t necessarily lead to additional or further health improvements.

A more effective solution

If taken correctly, it’s unlikely that taking a multivitamin would cause any harm. However, they’re not necessarily the micronutrient ‘insurance policy’ that they’re often made out to be.

First priority: Food-first

Focus on how you can include more of these micronutrients in your diet (see the Micronutrient Mini-series by Vegan Easy). The benefit of a ‘food-first’ approach is that you’re more likely to consume a wider-variety of micronutrients, food types, and macronutrients which have positive health outcomes.

Second priority: Individual micronutrients

For key vitamins and minerals (such as iron, zinc, calcium, omega-3s, B12, iodine and vitamin D for vegans) it’s going to be more effective to supplement with the appropriate dosages of individual micronutrients.

Food first | Individual micronutrients

If you’re conscious of getting enough micronutrients on a vegan diet, then it’s important to assess if you’re deficient or at risk of a nutrient deficiency. Consulting your doctor and getting a blood test is usually the best way to determine your nutrient status. And then you can work with a dietitian or nutritionist to ensure adequate micronutrient intake moving forward.


  • Micronutrients to consider – iron, zinc, calcium, omega-3s, B12, iodine and vitamin D.
  • Some multivitamins may have micronutrients that are underdosed. Others can contain high levels of micronutrients which might be consumed in excess.
  • Many multivitamins contain several micronutrients which compete for absorption, reducing the total amount absorbed by the body
  • Solution:
    • Use the ‘food-first’ approach to incorporate a wide variety of micronutrients in your diet.
    • If you need to supplement, take individual micronutrient supplements.
  • Consult a medical practitioner to assess your nutrient levels


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