“Should Everyone Be Taking Vitamin Supplements? Evaluating Evidence, Risks, and Benefits”

Vitamin supplements are often promoted as an efficient way to compensate for dietary deficiencies. Yet, while the global market is valued at $32.7 billion (£24.2 billion), with over 74% of Americans and two-thirds of Britons reporting regular use, the science remains deeply contested. Some studies suggest supplements offer little to no health benefit, while others raise concerns about potential harm. This raises key questions: Who actually benefits from supplementation? Should vitamin use be universal, targeted, or avoided altogether?

Why Do People Take Vitamins and Minerals?

Vitamins and minerals are essential micronutrients that the body cannot synthesize and must obtain from food. Examples include vitamin A (critical for vision and skin health), vitamin C (immune function), vitamin K (blood clotting), and minerals such as calcium, magnesium, and potassium. Because they are needed only in small quantities, they are classed as micronutrients, distinct from macronutrients such as carbohydrates, proteins, and fats.

In principle, a balanced diet—rich in vegetables, fruits, grains, nuts, dairy, and fish—should meet these needs. Yet dietary surveys suggest many people fail to achieve this. Fast food and ultra-processed products often displace fresh, nutrient-dense meals. As Bess Dawson-Hughes of Tufts University observes, “The average American is eating half of the fruits and vegetables that are recommended. If you’re leaning in that direction, then you are probably missing out on some essential nutrients.”

The Case for and Against Multivitamins

Could multivitamins help bridge this gap? The answer is complex. Historically, enthusiasm for supplements surged in the 1970s, driven by claims such as Nobel laureate Linus Pauling’s belief that massive doses of vitamin C could prevent colds, cardiovascular disease, and even cancer. These claims have since been discredited, yet the practice of “mega-dosing” persists, particularly in influencer-driven supplement culture, despite limited regulation, unverified formulations, and a lack of randomized controlled trials (RCTs).

Excessive supplementation can be harmful. High levels of vitamin D have been linked to kidney damage, seizures, and even death. Excess vitamin A can cause blurred vision, dizziness, and, in extreme cases, coma. Vitamin E, in large doses, has been associated with an increased risk of hemorrhagic stroke due to its blood-thinning effects. Moreover, over-supplementation can disrupt the absorption of related nutrients, as with beta-carotene interfering with lutein uptake.

What Do Clinical Trials Show?

Early trials of antioxidant vitamins (beta-carotene, C, and E) showed no benefit in preventing cancer or cardiovascular disease. Some even revealed harm—for example, beta-carotene supplementation increasing lung cancer risk in smokers.

Vitamin D remains a notable exception. While technically a hormone synthesized in the skin through sun exposure, it is vital for bone health and may have broader effects. In northern latitudes with limited winter sunlight, supplementation is recommended. Results from JoAnn Manson’s VITAL trial, involving more than 25,000 U.S. adults, found that while vitamin D supplementation did not reduce overall cancer incidence, it was linked to a 17% reduction in cancer mortality, with even greater reductions among long-term users. It also showed promise in lowering rates of autoimmune diseases.

Yet evidence on vitamin D and bone health remains inconclusive. Some trials, such as VITAL and D-Health, showed no reduction in fractures, likely because many participants already had sufficient vitamin D levels at baseline.

Who Might Benefit?

Evidence suggests supplementation may be beneficial in specific groups:

• Older adults: Daily multivitamins may reduce cancer risk and cognitive decline, with trials such as Physicians’ Health Study II and COSMOS showing significant benefits in participants over 70.

• Pregnant women: Folic acid supplementation is proven to reduce neural tube defects.

• People with restricted diets: Vegetarians, vegans, or those consuming little fish may benefit from vitamin B12 or omega-3 supplements.

• Individuals with medical conditions: Disorders such as Crohn’s disease or medications like metformin can impair nutrient absorption.

• Elderly in care homes: Combined vitamin D and calcium supplementation has been shown to reduce hip fractures by up to 40%.

The Bottom Line

Most experts, including Manson and Dawson-Hughes, emphasize that for the majority, supplements are unnecessary when a balanced diet is achievable. Whole foods not only provide vitamins in more bioavailable forms but also deliver fiber and other beneficial compounds absent in pills. Importantly, “more is not better”: exceeding recommended daily allowances offers no benefit and can be harmful.

However, for certain populations—older adults, pregnant women, individuals with restricted diets, or those with absorption difficulties—a carefully chosen multivitamin or targeted supplement may act as a form of “nutritional insurance.” As Manson concludes, “Multivitamins are very safe, so if anyone has concerns about whether they’re getting an adequately healthy balanced diet, taking a multivitamin could be a reasonable safeguard.”

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