Category: Nutrition Evidence

The Tanrub Journal · Vitamins & supplements · Sources checked 11 October 2026

1. Where targeted supplements have a clear role

Folic acid when planning pregnancy

Folic acid supplements help prevent neural tube defects, which affect the developing brain and spine. For Australian readers, the practical guidance matters more than a single percentage from an older overseas trial.

NSW Health recommends 400 micrograms of folic acid daily from at least one month before pregnancy through the first three months of pregnancy. Some people need a different amount, so discuss your circumstances with a doctor or midwife. Do not take several general multivitamins to reach a higher folic acid dose: that also increases the other ingredients.

Pregnancy advice covers more than folic acid. NSW Health also recommends iodine during pregnancy planning, pregnancy and breastfeeding, with medical advice before iodine supplementation if you have a thyroid condition. A pregnancy-labelled product is not automatically the right choice for every person.

Vitamin B12 when intake or absorption is inadequate

People eating vegan diets need reliable B12 sources from fortified foods or supplements. Some vegetarians, older adults and people with gastrointestinal conditions or previous stomach or intestinal surgery are also at increased risk of deficiency.

B12 deficiency can cause anaemia and neurological problems; neurological symptoms can occur without anaemia. Getting a deficiency assessed and treated matters. A clinician can decide which tests, treatment and follow-up are appropriate. These points come from the NIH Office of Dietary Supplements fact sheet.

Correcting inadequate B12 is different from taking extra B12 to improve memory or energy when levels are already sufficient. The evidence does not support treating B12 as a general performance booster.

AREDS2 for particular stages of age-related macular degeneration

The AREDS2 vitamin and mineral formula is a specific eye-disease intervention, not an ordinary multivitamin or a way for the general public to prevent age-related macular degeneration (AMD).

The National Eye Institute explains that the original AREDS formula reduced progression to advanced AMD by about 25% over five years in the studied population. AREDS2 supports replacing beta-carotene with lutein and zeaxanthin, particularly because beta-carotene supplements increase lung-cancer concerns for smokers and former smokers.

The often-quoted 26% figure applies to a subgroup with low dietary lutein and zeaxanthin intake, not to everyone taking AREDS2. Benefit depends on disease stage; people without AMD or with early AMD did not benefit in these trials. An eye-care professional should advise on suitability.

An analysis of existing AREDS/AREDS2 data, published online in 2024 also suggested slower movement of geographic atrophy towards the centre of the retina in some eyes with late dry AMD. This was a post hoc analysis, so it should not be presented as a new trial proving that supplements prevent all late-stage vision loss.

2. Multivitamins and memory: promising, with limits

The COSMOS trial programme tested a daily multivitamin-mineral formulation in older adults.

COSMOS-Clinic and its 2024 pooled analysis found small improvements in some cognitive tests. In the in-person substudy, episodic memory improved, while the overall cognition estimate narrowly included no effect. Executive function and attention did not significantly improve.

The pooled analysis found small improvements in overall cognition and episodic memory in 5,203 non-overlapping participants. The analysis excluded overlapping participants. These were three substudies within one trial programme; replication in separate trials and with other formulations would strengthen confidence.

“Two years less cognitive ageing” is an age-equivalent interpretation of a small test-score difference, not evidence that participants became younger. The findings also do not establish equal benefits in younger adults or from every multivitamin formulation.

A COSMOS-Mind analysis of clinical outcomes did not find a significant reduction in mild cognitive impairment or probable dementia over three years. The study had limited statistical power, with only 14 adjudicated dementia cases. Improved test scores should therefore not be described as proven dementia prevention; this small number of events also means the study cannot rule out a longer-term effect.

Funding context: COSMOS received public and industry support, including NIH and Mars Edge funding, with multivitamin and placebo tablets donated by Pfizer Consumer Healthcare (now Haleon). This is relevant context when assessing product-specific findings, rather than a reason on its own to dismiss a randomised study. The investigators’ funding statement gives details.

3. Vitamin D: prevention and deficiency are different questions

VITAL randomised 25,871 US adults—men aged at least 50 and women aged at least 55—to vitamin D3, omega-3, both or placebo. The vitamin D intervention was 2,000 IU daily; this describes the research, not a recommended dose for readers.

The main VITAL report found no significant reduction in invasive cancer or major cardiovascular events with vitamin D. Its fracture study also found no significant reduction in total, non-vertebral or hip fractures over a median 5.3 years.

Participants were not selected for vitamin D deficiency, osteoporosis or low bone mass. The results therefore do not establish that treating diagnosed deficiency is unnecessary, or replace a clinician’s bone-health plan.

The autoimmune finding needs context

A prespecified VITAL ancillary study found fewer confirmed autoimmune diseases in the vitamin D group: 123 cases versus 155 with placebo. The hazard ratio corresponded to a 22% relative reduction, but the observed proportions were approximately 1.0% versus 1.2%—a small absolute difference.

A 2024 follow-up added later-confirmed cases and two years of observation after supplementation ended. With the additional cases, the vitamin D estimate during the randomised period was no longer statistically significant (hazard ratio 0.85; 95% confidence interval 0.70–1.04). At seven years, there was also no clear benefit (0.98; 0.83–1.17). This weakens a general autoimmune-prevention claim.

A blood test is not a routine prerequisite for everyone

The Endocrine Society’s 2024 guideline advises against routine vitamin D testing in generally healthy adults without an established reason for testing. It also suggests against supplementation beyond recommended dietary intakes for most healthy adults younger than 75.

The guideline makes different conditional recommendations for certain groups, including adults aged 75 or older, pregnancy and high-risk prediabetes. This is international guidance, not an individual Australian prescription. Ask your clinician whether your circumstances warrant supplementation or testing, rather than assuming everyone needs either.

For Australian readers, the RACGP also advises against routine vitamin D screening, while supporting testing in appropriate high-risk groups. Healthdirect explains assessment and treatment of deficiency. A doctor can decide whether you need a test or supplement.

4. Heart disease, cancer and longevity

The USPSTF’s 2022 recommendation found insufficient evidence to judge the overall balance of benefits and harms of multivitamins, or most single or paired nutrients, for preventing cardiovascular disease or cancer.

“Insufficient evidence” does not mean that every possible benefit has been ruled out. It means the evidence does not justify a general prevention recommendation. This assessment concerns community-dwelling, nonpregnant adults; it does not cover known nutritional deficiencies or pregnancy needs.

The USPSTF recommends against beta-carotene and vitamin E supplements for preventing cardiovascular disease or cancer. That purpose matters: the recommendation should not be read as a direction to stop a clinician-advised AREDS2 formula or another specific treatment.

For longevity, a 2024 study of 390,124 US adults followed for more than 20 years found no association between daily multivitamin use and lower mortality. This was observational research, so it does not prove that multivitamins caused harm or settle every question about a particular product.

5. What the findings mean for different people

6. Practical checks before choosing a supplement

• Start with a reason. A diagnosed deficiency, dietary gap or clinician-advised indication is more useful than an “extra strength” label.
• Compare the full formula. Men’s, women’s and age-labelled products can differ, but their names do not establish your individual need.
• Review overlapping ingredients. Give your pharmacist or doctor a list of medicines and supplements. Combining a multivitamin with separate high-strength products can increase total intake.
• Check vitamin B6 across all products. The TGA warns that excessive supplemental B6 can damage peripheral nerves. B6 can appear in multivitamins, magnesium products and other formulas. If you develop tingling, burning or numbness, stop taking the supplement and seek medical advice.
• Read the Australian medicine label. The TGA explains AUST L, AUST L(A) and AUST R numbers. An AUST L number does not mean effectiveness was assessed before sale. Product type matters: not every nutrition product is a medicine.
• Use food and lifestyle foundations. A supplement can fill a specific gap; these studies do not show that it replaces a varied diet, physical activity or avoiding smoking.

The useful question: what do you need it for?

Targeted supplementation has an established place in healthcare. A daily multivitamin for every healthy adult has a narrower and less certain evidence base. Match the choice to your diet, life stage and clinical circumstances, and judge marketing claims against the outcome actually studied.

This article provides general information and is not personal medical advice. Discuss symptoms, suspected deficiency, pregnancy needs and medicine interactions with a qualified health professional.

Sources and scope

This is a focused overview of selected research and guidance, rather than a complete systematic review. References include original study reports or indexed abstracts and official health guidance. Findings from US trials may not transfer unchanged to Australian populations or products.

1. NSW Health: Folate and iodine.
2. NIH Office of Dietary Supplements: Vitamin B12.
3. National Eye Institute: AREDS/AREDS2 FAQs.
4. Keenan et al.: Geographic atrophy analysis, Ophthalmology, 2025 (online 2024).
5. Vyas et al.: COSMOS-Clinic and pooled cognition analysis, American Journal of Clinical Nutrition, 2024.
6. Sachs et al.: COSMOS-Mind clinical cognitive outcomes, Alzheimer’s & Dementia, 2023.
7. Manson et al.: VITAL cancer and cardiovascular outcomes, New England Journal of Medicine, 2019.
8. LeBoff et al.: VITAL fracture outcomes, New England Journal of Medicine, 2022.
9. Hahn et al.: VITAL autoimmune disease trial, BMJ, 2022.
10. Costenbader et al.: Autoimmune outcomes after VITAL, Arthritis & Rheumatology, 2024.
11. Endocrine Society: Vitamin D for the Prevention of Disease, 2024 guideline.
12. USPSTF: Vitamins for cardiovascular disease and cancer prevention, 2022.
13. Loftfield et al.: Multivitamin use and mortality, JAMA Network Open, 2024.
14. TGA: How are vitamins regulated in Australia?
15. RACGP: Vitamin D testing.
16. Healthdirect: Vitamin D deficiency.
17. TGA: Are you unknowingly taking too much vitamin B6? (2026).
18. Mass General Brigham: COSMOS findings and funding disclosure.