AUTHORITY NUTRITION

Do Multivitamins Actually Work? The Surprising Truth

Written by Hrefna Palsdottir, MS on October 4, 2015

Multivitamins are the most commonly used supplements in the world.

Their popularity has increased rapidly in the past few decades (1, 2).

Some people believe that multivitamins can improve health, make up for poor eating habits or even reduce the risk of chronic diseases.

But what does the science say about multivitamins? Do they actually work? This article takes an evidence-based look.

Multivitamins are supplements that contain many different vitamins and minerals, sometimes along with other ingredients (3).

There is no real standard about what constitutes a multivitamin, and their nutrient composition varies by brand and product.

They go by several different names, including multivitamins, multiminerals, multis, multiples or simply vitamins.

They are available in many forms, such as 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.

Multivitamins are available in pharmacies, large discount stores, supermarkets and from various online retailers.

Bottom Line: Multivitamins are supplements that contain many different vitamins and minerals. They are available in various forms.

There are 13 vitamins and at least 16 minerals that are essential to health.

Many of them participate in enzymatic reactions in the body, or function as hormones, signalling molecules or structural elements.

The body needs these nutrients for reproduction, maintenance, growth and regulation of bodily processes.

Multivitamins may contain many of these vitamins and minerals, but in varying forms and amounts. They can also contain other ingredients like herbs, amino acids and fatty acids.

Because dietary supplements are not regulated, multivitamins may contain higher or lower levels of some nutrients than the label states (4).

In some cases, they may not even contain all of the nutrients that are listed. There have been many cases of fraud in the supplement industry, so it is important to purchase from a reputable manufacturer.

Also, the nutrients in multivitamins may be derived from real foods or created synthetically in laboratories.

Bottom Line: Multivitamins may contain herbs, amino acids, and fatty acids in addition to vitamins and minerals. Label fraud is common, and the amount of nutrients can vary.

Heart disease is the most common cause of death worldwide (5).

Many people believe that taking multivitamins can help prevent heart disease, but the evidence is not clear.

Results from observational studies on multivitamins and heart disease are mixed. Some studies have found a reduced risk of heart attacks and death, while others have found no effects (6, 7, 8, 9).

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 reduction in heart attacks or strokes, and no reduction in mortality (10).

A recent study found that among women, but not men, taking a multivitamin for at least three years was linked to a 35% lower risk of dying from heart disease (11).

Bottom Line: Several observational studies have found multivitamin users to have a lower risk of heart disease. However, several others have found no connection. Overall, the evidence is mixed.

The evidence behind multivitamins and cancer risk is also mixed.

Some studies have found no effect on cancer risk, while others have linked multivitamin use to increased cancer risk (6, 8, 12, 13).

One review looked at results from 5 randomized, controlled trials (the gold standard of research) with a total of 47,289 participants.

They found a 31% lower risk of cancer in men, but no effect in women (14).

Two observational studies, one on women and the other on men, linked long-term multivitamin use with a reduced risk of colon cancer (15, 16).

The Physicians' Health Study II also found that long-term, daily multivitamin use reduced the risk of cancer in men with no cancer history. However, it had no effect on the risk of death during the study period (17).

Bottom Line: Some studies have linked multivitamin use to reduced risk of cancer. However, other studies find no benefit, and some have even found an increased risk.

Multivitamins have been studied for several other purposes, including brain function and eye health.

Brain Function

Several studies have found that multivitamin supplements can improve memory in older adults (18, 19, 20).

Supplementation may also improve mood. This makes sense, because many studies have found links between poor mood and nutrient deficiencies (21, 22, 23, 24).

Additionally, a few more studies have found that multivitamin supplements can improve mood or reduce depressive symptoms (25, 26).

However, other studies have found no changes in mood (27).

Bottom Line: Some studies link multivitamin supplementation to improved memory and mood. However, other studies have found no changes in mood.

Eye Health

Age-related macular degeneration is a leading cause of blindness, worldwide (28).

One study found that taking antioxidant vitamins and minerals may slow down its progression. However, there is no evidence that they prevent the disease from developing in the first place (29, 30).

There is also some evidence that multivitamins can reduce the risk of cataracts, another very common eye disease (31).

Bottom Line: Antioxidant vitamins and minerals may help slow down the progression of diseases that cause blindness.

More isn't always better in nutrition.

Although high doses of some vitamins and minerals are fine, others can be seriously harmful.

Vitamins are categorized into two groups, based on their solubility:

  • Water-soluble: Excess amounts of these vitamins are expelled by the body.
  • Fat-soluble: The body has no easy way to get rid of these, and excess amounts may build up over long periods of time.

Examples of fat-soluble vitamins include vitamins A, D, E and K.

Vitamins E and K are relatively nontoxic. However, vitamin A and vitamin D can exceed the body's storage capacity, with toxic effects.

Pregnant women need to be especially careful with their vitamin A intake, as excess amounts have been linked to birth defects (32).

Vitamin D toxicity is extremely rare, and is unlikely to happen from multivitamin use. However, vitamin A toxicity does occur from time to time (33, 34, 35).

If you eat a lot of nutrient-dense foods and then add a multivitamin on top of that, you can easily exceed the recommended daily intake of many nutrients.

Smokers should avoid multivitamins with large amounts of beta-carotene or vitamin A. It may increase the risk of developing lung cancer (36).

Minerals may also be harmful in high-dose supplementation. For example, high doses of iron can be downright dangerous for people who don't need it (37, 38).

Additionally, faulty production often causes multivitamins to contain much larger amounts of nutrients than they are supposed to (39).

Bottom Line: Taking large doses of certain nutrients can have harmful effects. This is more likely to occur if you take a high-potency multivitamin on top of a nutrient-dense diet.

There is no evidence that multivitamins should be recommended for everyone.

In fact, chances are that they can cause harm in some individuals.

However, there are certain groups that may benefit from supplementing their diet with vitamins and minerals.

These include:

  • The elderly: Vitamin B12 absorption decreases with age, and elderly people may also need higher amounts of calcium and vitamin D (40, 41).
  • Vegans and vegetarians: These people are at high risk of vitamin B12 deficiency, since this vitamin is only found in animal foods. They may also be lacking in calcium, zinc, iron, vitamin D and omega-3 fatty acids (42, 43).
  • Pregnant and breastfeeding women: Pregnant and breastfeeding women should talk to their doctor about this. Some nutrients are needed, while others (like vitamin A) can cause birth defects in large amounts (32).

Others may benefit from taking multivitamins as well. This includes people who have had weight loss surgery, are on low-calorie diets, have a poor appetite or don't get enough nutrients from food alone for some reason.

Bottom Line: Some individuals may need higher amounts of certain vitamins or minerals. This includes pregnant and breastfeeding women, elderly individuals, vegetarians, vegans and others.

Multivitamins are not a ticket to optimal health.

In fact, the evidence that they improve health for most people is weak and inconsistent. They may even cause harm in some cases.

If you have a nutrient deficiency, then it is much smarter to supplement with only that specific nutrient. Multivitamins contain large amounts of everything, most of which you don't need.

Additionally, taking a multivitamin to "fix" a poor diet is a bad idea. Eating a balanced diet of real food is much more likely to ensure good health in the long term.

Whenever possible, you should meet your nutrient needs with whole, single-ingredient, nutritious foods — not supplements.

An evidence-based nutrition article from our experts at Authority Nutrition.

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