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[5 min read] Vitamin and mineral supplements: What GPs need to know

Step into the supplement aisle of your pharmacy and you will see row after row of bottles, capsules, powders, and drinks. The options are endless, but is there really any benefit?

Vitamins and minerals are micronutrients the body requires from food for proper functioning. Vitamin and mineral supplements are the most popular dietary supplements used by populations worldwide (1-3), and are important contributors to total daily intakes. Despite this enthusiasm, most randomised clinical trials of vitamin and mineral supplements have not shown clear benefits when used in primary care for the prevention of diseases unrelated to nutritional deficiencies.

For the general population, the bottom line is that supplements do not replace a well-balanced diet. Clinicians should counsel patients on the many benefits of obtaining vitamins and minerals from food rather than supplements, as they are better absorbed by the body and are often less expensive (4). These nutrients are also accompanied by many complex micronutrients that supplements cannot replicate, such as antioxidants, flavonoids, and carotenoids, which work together to keep us healthy. Food sources of key vitamins and minerals include:

  • Vitamin D: Oily fish such as salmon and tuna, egg yolks, cheese, fortified cereals and milks
  • Iron: Red meat, chickpeas, beans, lentils, green leafy vegetables
  • Calcium: Dairy products such as milk and cheese, firm tofu

Patients should work with their primary care doctor or dietitian to get a sense of what is missing from their diet and what dietary changes could be considered before turning to supplements.

When are supplements needed?

Supplementation can play an important role in medical nutrition plans for high-risk groups who cannot meet their nutritional requirements through diet alone. These include people with medical conditions that affect nutrient absorption or metabolism, or conditions which can be treated with certain nutritional supplements. Patients who have had weight-loss surgery require various supplements including A, D, and B vitamins, calcium, and iron, among others. Those with gut conditions – like Crohn’s disease, chronic diarrhoea, or ulcerative colitis– may have similar requirements.

Adults diagnosed with osteoporosis or other bone health issues may benefit greatly from extra calcium and vitamin D, depending on the quality of their diet. Supplementation may also be warranted in healthy people at certain life stages such as during pregnancy and older age, and those following a vegan or vegetarian diet (5).

Choosing and using supplements

Like any medicine, vitamin and mineral supplements can have side effects or interact with other medicines in unwanted ways. When reviewing medications, clinicians should ask patients about the use of supplements or complementary medicines to avoid potential interactions. Another risk is the potential of overdose. More is not always better, and some supplements provide much more than the recommended dosage, which can be dangerous.

Learn more about vitamin and mineral supplements in the online Professional Diploma Program in Medical Nutrition.


Lynette Law, Provisional Accredited Practising Dietitian

See more recent research.


  1. Skeie G, Braaten T, Hjartåker A, Lentjes M, Amiano P, Jakszyn P, et al. Use of dietary supplements in the European Prospective Investigation into Cancer and Nutrition calibration study. European journal of clinical nutrition. 2009;63(4):S226-S38.
  2. O’Brien SK, Malacova E, Sherriff JL, Black LJ. The prevalence and predictors of dietary supplement use in the Australian population. Nutrients. 2017;9(10):1154.
  3. Kang M, Kim D, Baek Y, Moon S, Jung H, Song Y, et al. Dietary supplement use and its effect on nutrient intake in Korean adult population in the Korea National Health and Nutrition Examination Survey IV (2007–2009) data. European journal of clinical nutrition. 2014;68(7):804-10.
  4. Rautiainen S, Manson JE, Lichtenstein AH, Sesso HD. Dietary supplements and disease prevention—a global overview. Nature Reviews Endocrinology. 2016;12(7):407-20.
  5. Manson JE, Bassuk SS. Vitamin and Mineral Supplements: What Clinicians Need to Know. JAMA. 2018;319(9):859-60.

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