Multivitamins - Are They Worth It?
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13 essential vitamins
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Vitamin A
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Vitamin B
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Thiamine (B1)
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Riboflavin (B2)
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Niacin (B3)
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Pantothenic acid (B5)
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Pyroxidine (B6)
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Biotin (B7)
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Folate (B9)
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Cobalamin (B12)
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Vitamin C
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Vitamin D
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Vitamin E
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Vitamin K
Fat soluble
Vitamin A, D, E and K
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Vitamin D: sun
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Vitamin K: dark green vegetables
Water soluble
Vitamin B and C
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Vitamin C: citrus fruits
vitamin functions and sources found here
Multivitamins have been the craze for the last few decades, commonly used as a supplement in the desire to improve overall health.
Many people consider it a primary prevention of chronic diseases as it can fill the gaps in our diet. Some people may even believe that it can make up for poor diets, increase nutrient intake, reduce the risk of chronic diseases and improve health.
However, they can carry health risks as there are no standard scientific definition and regulation on the components and concentrations of dietary supplement products. Therefore, multivitamin composition varies from brand to brand and safety and effectiveness are not verified before they are marketed (1, 2).
Many chronic diseases share common risk factors that can be modified by nutrients. In theory, antioxidants can reduce oxidative damage, folate and B vitamins can regulate DNA methylation, vitamin D and calcium regulates bone metabolism, iron for maintenance of healthy red blood cells, and other nutrients regulate cell differentiation, proliferation, and growth (3).
The body requires a wide spectrum of vitamins and minerals to carry out sophisticated functions. If a tablet contains all these nutrients that are essential for our health, won't it reduce our risks of chronic diseases and improve our mortality?
Vitamins
Components
Many multivitamin formulas contain many different vitamins, minerals and sometimes with other ingredients.
There are 13 vitamins and at least 16 minerals that are essential to health (4).
Multivitamins are generally tailored to age, sex, and a more specific nutritional requirement.
Calcium and magnesium are rarely included at 100% of the DRV as the pill would be too large.
Bioavailability
Vitamins and minerals come in different forms in real food, which range in their ability to be absorbed by the body (bioavailability). Vitamin E has 8 different forms but supplements usually contain only one.
The biological effects of a nutrient depend on its bioavailability. This depends on the type of nutrient presented in the gastrointestinal tract, the presence of other competing chemicals (phytates and chelating agents) that can bind to the nutrient and make it unavailable for absorption.
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High calcium intakes can reduce the absorption of minerals (zinc and magnesium).
Minerals
Synthetic or natural
More than 95% of vitamin supplements are synthetically produced (5). It is natural to presume that natural forms of vitamins are automatically better than their synthetic counterparts. However, not all-natural vitamins are better than synthetic forms and not all synthetic forms are harmful.
For example, synthetic folic acid is better absorbed than folate from natural sources (6).
However, for some other nutrients, there is a difference in efficacy between natural and synthetic forms.
Vitamin E has different forms (alpha-, beta-, delta- and gamma tocopherols, and alpha-, beta-, delta-, and gamma-tocotrienols) and the synthetic form allows you to only obtain an effective dose of half the dosage reported on the label.
Natural vitamin C is accompanied with bioflavonoids which allow better absorption and hence, increases bioavailability by 30% (7).
Cardiovascular disease and Cancer
Heart disease is the leading cause of death worldwide (8).
A 2012 meta-analysis found that taking multivitamins had zero impact, neither good nor bad, on mortality risk (9).
There were no increased risk or lower risk in the groups with multivitamin/mineral supplement use. However, total mortality was 9% lower among those who received beta-carotene, selenium, and vitamin E in the Linxian trial (10).
In some studies, it was even found that specific supplementation of vitamin E and beta-carotene may be associated with an increase in all-cause mortality (11, 12, 13, 14, 15).
Supplementation with beta-carotene in smokers and asbestos workers increased the risk of lung cancer by 28% and was associated with a 17% higher risk of mortality compared with smokers taking a placebo (16).
Regular supplementation of vitamin E above 400 IU/day is suspected to increase the risk of all-cause mortality (17).
A 2006 systematic review from the Annals of Internal Medicine concluded that there simply is not enough proof that multivitamins are beneficial to preventing cancer or chronic diseases outside of populations that are dealing with malnourishment (18).
Another systematic review in 2013 came to a similar conclusion, finding that vitamin and mineral supplements had limited evidence in preventing cancer and cardiovascular diseases (19).
A study in the same year also concluded that oral multivitamins did not statistically significantly reduce the events of heart problems in people that previously experience myocardial infarctions (20).
On the other hand, a study found an association between multivitamin use for more than 3 years and reduced cardiovascular disease risk and mortality risk for women (21).
To conclude: overall, observational studies observed multivitamins had no effects or were clinically insignificant in reducing the risk of cardiovascular disease and cancer. However, some studies have found vitamin E and beta-carotene supplementation led to an increased risk of cancer and all-cause mortality and hence, it is best to consult with a health professional before taking these supplements.
Other benefits
Research also suggests it does not improve cognitive function, prevent respiratory tract infections, or prevent any infections for that matter (22, 23).
No difference was found in cognitive performance in a 12 year follow up study (24).
Long-term use of multivitamins was associated with reduced risk of age-related cataracts, the main cause of loss of vision among the elderly population (25, 26, 27).
In addition, it may slow down the progression of age-related macular degeneration (AMD) (28).
Safety Issues
By looking at the nutritional values on the back of the multivitamin bottle, many of these nutrients contain more than 100% of the recommended daily value (RDV).
Vitamins are important compounds that are essential to our bodies. If a deficiency occurs, cells and enzymes might not be able to work properly, and would be prone to diseases. Therefore, the reason for taking multi-vitamin supplements is usually to prevent any vitamin deficiencies. Historically, supplementation led to the remediation of nutrient deficiencies but the cumulative effects of supplementation have raised safety concerns about exceeding upper levels (UL).
Tolerable upper intake level (UL) indicates the maximum amount of specified nutrients that you can take without risking negative health effects. The UL for water-soluble vitamins are typically higher than fat-soluble vitamins as excess can be excreted in the urine. However, fat-soluble vitamins will be stored in the body and can accumulate over time eventually causing toxicity or other health problems.
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During pregnancy or prior to pregnancy, taking excessive vitamin A (retinol) can increase the risk of birth defects in infants.
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As mentioned, smokers should avoid multivitamins that provide excessive amounts of beta-carotene or vitamin A as they are associated with an increased risk of lung cancer (29).
Deficiencies
People always assume that they have deficiencies when they actually do not. Many people believe that they need more vitamin B12, but in fact, only 3% of US and UK adults suffer from vitamin B12 deficiency (30). On top of that, it is simple to get vitamin B12 eating fortified grains or meats.
Granted, there are more common deficiencies, especially with those who consume the typical Westernised diet. Poor diets, while energy-rich like the Westernised diet is deficient in certain vitamins and minerals. It is important to note that nutrient deficiency can occur in both people who are overweight and underweight.
The analysis from NHANEs 2007 to 2010 indicated that 94% intake for vitamin D, 88% for vitamin E, 52 % for magnesium, 44% for calcium, 43% for vitamin A, and 39% for vitamin C were below the estimated average requirement (EAR) in the US (31).
Meanwhile, in the UK, 16% of women are iron deficient and more than 10% of the population have low levels of vitamin and vitamin B6 (32).
The problem is that most multivitamins would not give you enough of these.
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Take calcium, for example, where the optimal amount is roughly 700mg for most adults, most multivitamins only provides 50mg.
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In many cases, companies provide poor versions of these nutrients, such as magnesium oxide, which is the cheapest version of magnesium and is poorly absorbed by the body.
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Sometimes, multivitamins do not even have these nutrients entirely. When dealing with deficiencies, it is better off to supplement the specific vitamin or mineral. For instance, if you lack zinc and magnesium, ZMA supplements are the way to go.
Who should take them?
Although results are mixed and multivitamins do not appear to reduce the overall mortality risk, multivitamins might benefit certain population groups.
Post-menopausal women
Several studies demonstrate that calcium increases bone mineral density but on its own. Vitamin D in combination with calcium seems to decrease the risk for fractures in postmenopausal women (33).
Pregnant women
Women who lack folic acid during pregnancy should supplement it directly. 400 mcg/day of synthetic folic acid is recommended for the first trimester (12 weeks) (34). Taking sufficient amounts in during the first month of pregnancy reduces the risk of neural tube defects in newborn (35, 36).
The elderly
Multivitamins can be beneficial to the elderly since the risk of nutritional deficiencies increases with age (37). Vitamin B12 from dietary supplements may be beneficial as the elderly are less able to absorb the naturally occurring vitamin B12 from food.
Vegans
Vegans and vegetarians without an adequate intake of meat and dairy products should ensure their intakes of vitamin B12 are adequate. Remember supplementation depends on the nature of the diet.
Infants
The American Academy of Paediatrics recommends that infants receive 400 IU/day of vitamin D after birth until they are weaned to consume at least 1000 mL/day of vitamin D to prevent vitamin D deficiency (38).
Low economic status households
Multivitamins could also benefit those with lower household incomes as it could be difficult to afford a diverse variety of fruits, vegetables, legumes, and whole grains, yet they are the ones who are least likely to buy them (39).
When choosing multivitamins, people should find one that is tailored to their age, gender, medical history and health state.
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Infant: Vitamin D and iron
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Children: Vitamin A, Vitamin D, calcium
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Men: little to no iron
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Elderly: more calcium, vitamin D and B12
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Prenatal: no vitamin A (retinol)
Why are sales soaring?
Although multivitamin supplements technically have all the micronutrients that you need to be combined into one pill, it may not be as promising as it is.
In the U.S., half of the American population take vitamins of some form propelling it into a $37 billion dollar industry (40). With such controversy surrounding multivitamins, why are the sales increasing every year?
This is due to simple marketing. You can simply say, "Take this pill containing all the nutrients essential to improve your health and fix all your problems" and who wouldn't want that (41)?
Take home message
To clarify, micronutrients are most definitely important for our health. Our body requires them to function. But, the only time supplementation becomes effective is when faced with deficiencies especially in certain population groups e.g. infants, the elderly, pregnant women, etc. (42).
And of course, it is always better to acquire nutrients from a balanced diet of whole-foods rather than taking supplements.