People often choose multivitamins as a one stop shop to cover all their nutritional bases, so they don’t have to think about which vitamins and minerals to take. Multi-vitamins are a great option to:

• • Simplify a supplement routine – especially for those who don’t like numerous pills
  • Helpful for those with no current health issues
  • Beneficial for general health maintenance

However, how do you know which multivitamin to choose (especially since not all multivitamins are made equal) and what about absorption? 

One concern that some people have is the minerals that are included in multivitamins and whether or not they compete for absorption. The answer is, yes, minerals in multivitamins can compete for absorption in the digestive tract, mainly from shared transport pathways and chemical interactions. There are several factors that impact absorption competition, including dosage, formulation, and ratio balance.

Key examples of mineral competition are between: 1. calcium, zinc, and iron; 2. zinc and copper; and 3. iron and manganese.

1.Calcium (Ca), Zinc (Zn), and Iron (Fe)

• • • • • These minerals are divalent cations (ions with a +2 electrical charge, e.g., Ca²⁺, Zn²⁺, Fe²⁺) and share similar absorption mechanisms in the small intestine, particularly via DMT1 (Divalent Metal Transporter 1).
        • High doses of one mineral (e.g. calcium) can inhibit the absorption of the others (e.g. iron or zinc) and vice versa.

 

2. Zinc and Copper (Cu)

• • • • • Zinc supplementation can reduce copper absorption by increasing the production of metallothionein, a protein in intestinal cells that binds copper and prevents its absorption.
        • This can potentially lead to copper deficiency with long-term high-dose zinc supplementation (higher than 40 mg/day). 
          • • Copper deficiency is rare, however some medications, such as thiazide diuretics, used to treat high blood pressure, can lead to zinc loss in the urine, causing deficiency. People with low copper levels might have brain and nervous system issues, including numbness and weakness in the limbs. Another common symptom is fatigue, as when copper levels are low, the body has trouble absorbing iron, which could lead to iron deficiency anemia. This can be managed by eating a copper rich diet. Other symptoms can be frequent sickness, brittle bones, problems with memory and learning.

 

3.Iron and Manganese (Mn)

• • • • • Both iron and manganese compete for absorption via DMT1. Excessive iron may impair manganese uptake.

 

Knowing these key interactions, what are the implications for multivitamins?

1.Formulation Matters: Some multivitamins use chelated forms of minerals (e.g. iron bisglycinate, magnesium citrate) to improve absorption and reduce competition. Chelated minerals are bound to compounds like amino or organic acids, which helps your body uptake the mineral. I find it is best to take a multivitamin that takes these conflicts into consideration.

2.Dosage Timing: Spacing out when you take conflicting minerals (e.g. take iron in the morning and calcium at dinner) can improve overall absorption.

3.Ratio Balance: Manufacturers often adjust mineral ratios to minimize interference (e.g. adding copper alongside zinc).

Here is a comparison chart of multivitamins from professional brands commonly prescribed by Naturopathic Doctors:

Product	Ca (mg)	Mg (mg)	Zn (mg)	Cu (mg)	Fe	Mn (mg)	Chelated Form – yes or no?	Competition Risk
Cyto‑Matrix Multi matrix (Daily dose 4 capsules)	160	80	10	—	—	9	Yes	Minimal – low-dose, no Fe/Cu
Bioclinic BioFoundation-G™ (Daily Dose 3 tablets)	50	100	7.5	0.51	—	2.4	Yes	Low – Moderate Zn & Cu, chelated
NFH Multi SAP (Daily Dose 3 capsules)	125	100	15	1.5	—	1.5	Yes	Low–Moderate – Zn/Cu ratio ~10:1
Metagenics PhytoMulti (Daily dose 2 tablets)	—	80	15	1	—	0.5	Yes	Low – chelated, low doses, no Cu
Designs for Health Complete Multi (Daily dose 4 capsules)	100	200	15	—	—	1	Yes	Low–Moderate – no Cu/ Fe, chelated

 

Mineral Interactions Breakdown

Calcium vs. Magnesium

• All products use chelated mineral forms.
• Doses (≤200 mg Ca, ≤200 mg Mg) remain low‑moderate — little competition.

 

Zinc–Copper–Iron Triad

• Cyto‑Matrix / Designs: no Cu or Fe → negligible Zn-related competition.
• Bioclinic / NFH: Zn and Cu included in balanced ratios; moderate potential risk but mitigated by chelation.
• Metagenics: 15 mg Zn + 1 mg Cu in citrate forms — low risk
• None include iron, eliminating iron-related competition.

 

Manganese & Miscellaneous Minerals

• Mn levels (0.5–5 mg) are low in all listed brands except CytoMatrix, which has a moderate amount (9 mg); and the chelated forms minimize transporter competition (e.g., via DMT1).
• Other trace minerals (selenium, chromium, molybdenum, iodine) are present in safe, low doses across formulas.

Drugstore/Grocery Store Brands Comparison

Product	Ca (mg)	Mg (mg)	Zn (mg)	Cu (mg)	Fe (mg)	Mn (mg)	Chelated Form – yes or no?	Competition Risk
Centrum Women (Tablets)	400	64	8	0.9	7.5	5	No – Oxides/sulfates/carbonate	Moderate – iron plus zinc/copper
Centrum Men (Tablets)	300	84	11	0.9	6	5.5	No – Oxides/sulfates/carbonate	Moderate – iron plus zinc/copper
One A Day Women Multivitamin Tablets (Bayer)	130	42	8	1.35	18	–	No – Oxides/carbonate	Moderate – High – higher iron & zinc
One A Day Men Multivitamin Tablets (Bayer)	210	120	11	0.9	–	2.3	No – Oxides/carbonate	Low – Moderate – zinc and copper (less than 10:1 ratio), no iron
Webber Naturals Most Complete Multi Women	100	50	10	0.75	7.5	2.5	Cu and Mn chelated, others not	Moderate – zinc, copper and iron interactions
Webber Naturals Most Complete Multi Men	100	50	15	0.75	6	2.5	Cu and Mn chelated, others not	Moderate – zinc, copper and iron interactions
Jamieson 100% Complete Multi Adults	175	50	3	1	10	–	No – oxides/carbonates/sulfates	Moderate – presence of iron, zinc and copper

Mineral Interactions Breakdown of Drugstore/Grocery Store Brands Comparison

1.Iron–Zinc–Copper Triad

• • All listed products provide iron, along with zinc and copper.
  • This combination creates the highest potential for mineral competition, especially when doses are moderate to high (e.g. 7–18 mg iron, 7–11 mg zinc, ~0.5–1 mg copper).
  • Zinc and iron compete for intestinal absorption via DMT1, while zinc over-supplementation can reduce copper absorption via metallothionein induction.

 

2.Calcium & Magnesium

• • Present in low to moderate amounts; interaction at these levels is minimal.
  • Absorption of Ca and Mg is largely independent of iron/zinc/copper competition.

 

3.Manganese & Other Trace Minerals

• • Mn (typically 2–5 mg) is low enough that any transporter competition is unlikely.
  • Other trace minerals in these formulas (selenium, chromium, iodine, molybdenum) are typically at low safe levels.

 

4.Form of Minerals

• • These drugstore brands most often use inorganic forms like oxides, carbonates, and sulfates.
  • Such forms tend to have lower bioavailability and greater competition than chelated forms found in professional-grade formulas.

 

Practical Tips

• To reduce competition, consider separating supplemental iron and mineral-rich meals by 2–3 hours.
• Taking with food (especially with vitamin C) enhances iron absorption and reduces GI irritation.
• For those particularly concerned about absorption or competition, clinician-grade chelated formulas (like Cyto‑Matrix, Metagenics, Designs, etc.) offer lower interaction potential are recommended.

Can multivitamins move the needle?

One of Dr. Chris, ND concerns with multivitamins is that they have low doses of essential minerals which are safer for absorption competition, but they are not enough to “move the needle” on a specific health concern. Selenium supplementation, for example, is indicated for thyroid disease, both hypothyroidism and hyperthyroidism, but the trace amounts in the multivitamins would not have significant impact on disease management. 

Another example is the iron content in multivitamins – they are quite low (none in professional brands, or 6- 18mg in drugstore brands) compared to heme iron supplements which tend to have much more (up to 36mg) and minimal competition if timed appropriately with other supplementation. Low iron levels are implicated in depression, anxiety and other mental health conditions, so to ensure iron supplementation is effective enough to address health concerns, we need to go beyond multivitamins.

Final Thoughts & Recommendations

The supplement world is complex and the minerals contained inside the bottles are equally complex. Multivitamins from professional brands that are recommended by naturopathic doctors are thoughtfully formulated: they all use chelated forms and do not include iron, thus significantly decreasing the risk of nutrient absorption competition. As you venture out to shop at the drugstore or online for your next multivitamin, keep the points reviewed above in mind!

1.For virtually zero mineral competition, choose Cyto‑Matrix Multi matrix

2.For well-rounded daily coverage with minimal competition, Bioclinic, NFH, Metagenics, or Designs for Health are all excellent

3.Chelated minerals + no iron across all professional products largely avoid absorption conflicts. This is not the case for drug store brands.

4.If you ever need to take additional iron or calcium, space it apart from your multivitamin to prevent interactions.

We recommend seeing a naturopathic doctor who can guide your health to taking supplements that you need for your specific health concerns. You don’t want an “off the shelf” and “one-size fits all” approach to your number 1 asset: your health! You want a precision approach that is customized to your individual needs. That is why choosing naturopathic medicine is the best investment you can make for your health!

References

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Keen, C. L., & Zidenberg-Cherr, S. (1996). Manganese. In: Ziegler EE, Filer LJ, eds. Present Knowledge in Nutrition. 7th ed. Washington, DC: ILSI Press.

Li, Y., Cheng, Y., & Tang, N. (2024). Unraveling the Intricate Interplay: Iron and Zinc’s Regulatory Mechanisms on Calcium Bioavailability During Intestinal Absorption. Food Reviews International, 41(2), 345–372. https://doi.org/10.1080/87559129.2024.2401431

Raman, R. (2020, May 20). Chelated minerals: Types, benefits, and recommendation. Healthline. https://www.healthline.com/nutrition/chelated-minerals

Rolić, T., Yazdani, M., Mandić, S. et al. Iron Metabolism, Calcium, Magnesium and Trace Elements: A Review. Biol Trace Elem Res 203, 2216–2225 (2025). https://doi.org/10.1007/s12011-024-04289-z

Sandström, B. (2001). Micronutrient interactions: effects on absorption and bioavailability. British Journal of Nutrition, 85(S2), S181–S185. https://doi.org/10.1079/BJN2000312

Turnlund, J. R. (1998). Human whole-body copper metabolism. The American Journal of Clinical Nutrition, 67(5), 960S–964S. https://doi.org/10.1093/ajcn/67.5.960S

U.S. Department of Health and Human Services. (n.d.). Office of dietary supplements – manganese. NIH Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Manganese-HealthProfessional/

https://www.mayoclinic.org/drugs-supplements-zinc/art-20366112

https://www.healthline.com/nutrition/copper-deficiency-symptoms#TOC_TITLE_HDR_2

https://pmc.ncbi.nlm.nih.gov/articles/PMC5307254/

https://pmc.ncbi.nlm.nih.gov/articles/PMC10788288/#:~:text=We%20hypothesize%20that%20young%20adult,thereby%20reducing%20risk%20for%20depression.