Do Multivitamins Work? The scientific evidence behind multivitamins
Multivitamins are the most commonly used supplements in the world. Their popularity has increased rapidly in the past few decades.
Some people believe that multivitamins can improve health, compensate for poor eating habits, and even reduce your risk of chronic diseases. However, you may wonder if these supposed benefits are true.
This article examines the scientific evidence behind multivitamins.
What are multivitamins?
Multivitamins are supplements that contain many different vitamins and minerals, sometimes alongside other ingredients.
As there’s no standard for what constitutes a multivitamin, their nutrient composition varies by brand and product.
Multivitamins are also called multiminerals, multis, multiples, or simply vitamins.
They’re available in many forms, including tablets, capsules, chewable gummies, powders, and liquids.
Most multivitamins should be taken once or twice a day. Make sure to read the label and follow the recommended dosage instructions.
What do multivitamins contain?
Thirteen vitamins and at least 16 minerals are essential to your health. Many of them aid enzyme reactions in your body or function as signalling molecules or structural elements.
Your body also needs these nutrients for reproduction, maintenance, growth, and regulation of bodily processes. Multivitamins may offer many of these vitamins and minerals — but in varying forms and amounts. They may also contain other ingredients like herbs, amino acids, and fatty acids.
Keep in mind that the nutrients in multivitamins may be derived from real foods or created synthetically in laboratories.
Multivitamins and heart disease
Heart disease is the leading cause of death worldwide. Many people believe that taking multivitamins can help prevent heart disease, but the evidence is mixed.
Some studies suggest that multivitamins are correlated to a reduced risk of heart attacks and death, while others show no effects. For more than a decade, the Physicians’ Health Study II investigated the effects of daily multivitamin use in over 14,000 middle-aged, male doctors. It found no reductions in heart attacks, strokes, or mortality.
A more recent study revealed that among women — but not men — taking a multivitamin for at least 3 years was linked to a 35% lower risk of dying from heart disease.
Multivitamins and cancer
The evidence regarding multivitamin use and cancer risk is also mixed. Some studies suggest no effect on cancer risk, while others link multivitamin use to increased cancer risk.
One review examined 5 randomized, controlled trials in 47,289 people. It found a 31% lower risk of cancer in men who took multivitamins but no effect in women.
Two observational studies, one including women and the other including men, tied long-term multivitamin use to a reduced risk of colon cancer.
The Physicians’ Health Study II noted that long-term, daily multivitamin use reduced the risk of cancer in men with no cancer history. Still, it had no effect on the risk of death during the study period.
Do multivitamins have any other health benefits?
Multivitamins have been studied for several other purposes, including brain function and eye health.
Several studies have found that multivitamins can improve memory in older adults.
These supplements may also improve mood. Research reveals links not only between poor mood and nutrient deficiencies but also between multivitamins and better mood or reduced depression symptoms.
However, other studies reveal no changes in mood.
Age-related macular degeneration is a leading cause of blindness worldwide.
One study found that taking antioxidant vitamins and minerals may slow its progression. However, no evidence suggests that these compounds prevent the disease in the first place.
All the same, some evidence indicates that multivitamins may reduce your risk of cataracts, another very common eye disease.
Multivitamins may be harmful in some cases
Dosage is an important factor to consider when taking multivitamins. Although high doses of some vitamins and minerals are fine, high amounts of others can be seriously harmful.
The appropriate dosage often depends on solubility, for which vitamins are categorized into two groups:
- Water-soluble. Your body expels excess amounts of these vitamins.
- Fat-soluble. As your body has no easy way to get rid of these, excess amounts may accumulate over long periods of time.
Fat-soluble vitamins include A, D, E, and K. While vitamins E and K are relatively nontoxic, vitamins A and D can have toxic effects if overconsumed.
Pregnant women need to be especially careful with their vitamin A intake, as excess amounts have been linked to birth defects.
Vitamin D toxicity is extremely rare and unlikely to develop from multivitamin use. However, vitamin A toxicity is more common.
If you take multivitamins and eat a lot of nutrient-dense foods, you can easily exceed the recommended daily intake of many nutrients.
Smokers should avoid multivitamins with large amounts of beta carotene or vitamin A, as these nutrients may increase your risk of lung cancer.
Minerals may also be harmful in high doses. For example, too much iron can be dangerous for people who don’t need it. Another risk is faulty production, which may cause multivitamins to harbor much larger amounts of nutrients than intended.
Who should take a multivitamin?
Multivitamins aren’t right for everyone.
Certain populations may benefit from multivitamins, including:
• Older adults. Vitamin B12 absorption decreases with age. Older adults may also need more calcium and vitamin D
• Vegans and vegetarians. As vitamin B12 is only found in animal foods, you’re at a higher risk if you follow a plant-based diet. You may also be lacking in calcium, zinc, iron, vitamin D, and omega-3 fatty acids
• Pregnant and breastfeeding women. These women should consult their healthcare provider, as some nutrients are good and others harmful. For example, excess vitamin A can cause birth defects
Other people who may benefit from multivitamins include those who’ve undergone weight loss surgery, are on low-calorie diets, have a poor appetite, or don't get enough nutrients from food alone.
The bottom line
Multivitamins are not a ticket to optimal health.
If you have a nutrient deficiency, it’s best to supplement with that specific nutrient. Multivitamins pack many nutrients, some of which you don’t need.
Additionally, you shouldn’t take a multivitamin to fix a poor diet. Eating a balanced diet of fresh, whole foods is much more likely to ensure good health over the long term. However, taking a good quality Multivitamin is a great way to supplement your diet if it is difficult to get all nutrients your body needs through food alone.
- Chris Price