Multivitamins were one of the first developed supplements (dating back to 1934) and are considered your nutritional insurance policy. Simply put, they plug any “nutrition holes” you might have due to diet, exercise, genetics, lifestyle and medication (1).
They are taken by millions of people every year, and are believed to be particularly effective at preventing illness. Some people see multivitamins as a way to stay healthy and live a long life.
A healthy diet that contains high levels of all essential vitamins and minerals will have little need for a multivitamin. However, someone with poor nutrition whether from a low-quality diet or from foods grown in nutrient-depleted soil, may benefit. In this article we will be looking specifically at the benefits of multivitamin use for women, while acknowledging benefits that affect both men and women.
1Multivitamins can prevent cancer. A 2012 study that looked at cancer prevention in men over a fourteen year period (1997-2011) found that daily multivitamin use “modestly but significantly reduced the risk of total cancer” (2).
2Multivitamins may fight off illness. While this hasn’t been shown with a multivitamin itself, many of the individual ingredients in multivitamins have been shown to enhance the immune system, improve sleep quality and support organs like the adrenal glands, helping you fight off illnesses especially during times of stress (3, 4).
3Multivitamins may help reduce infection in people with poor nutrition. One study from 2003 looked at the effect of using a multivitamin supplement to prevent infection in wide range of adults aged 45-65 (5).
The study found that daily supplementation reduced the incidence of patient-reported infection, especially in those with pre-existing diabetes and in those with poor nutrient intake from diet.
Another study found that 2 months of multivitamin use was able to reduce occurrence of infection in women with chronic fatigue syndrome, among other benefits (6).
4Multivitamin use may improve mood and reduce anxiety and stress. A study in 2016 looked at multivitamin supplementation’s effect on mood in older women.
The study found that taking multivitamins for a period of four weeks led to a daily reduction of perceived stress and mental fatigue (7).
A similar study in 2013 by Long & Benton found that multivitamin use improved perceived stress, mild psychiatric symptoms, and mood in healthy people 26. Particularly supplements that were high in B vitamins (8).
5Supplementing with multivitamins may improve memory. A 2012 study in the Journal of Alzheimer’s Disease found that regular supplementation with multivitamins had a significant effect on immediate free recall memory (remembering a list immediately after being told it for example), but not in any other cognitive tests (9).
6Multivitamins may help reduce body weight and body fat levels. A study in 2010 looked at the effects of a multivitamin on obese Chinese women. The study found that taking a multivitamin alone, without any exercise or nutrition interventions was enough to help the group drop an average of 8 pounds and induce reductions in waist circumference and fat mass over a period of 26 weeks (10). The placebo group showed a gain in fat mass and a reduced metabolism.
Their cholesterol also improved. Precision Nutrition’s Helen Kollias hypothesised that this was partly due to obese people being deficient in a number of micronutrients, and the weight loss was due to an improvement in gastrointestinal health, increased vitamin D, and an improved metabolism (11).
7Using a multivitamin may help protect eye health. A number of studies have found that multivitamin use has helped reduce the incidence of cataracts among older people. In 2014 a study by Zhao, Li, & Zhu found that there was sufficient evidence that multivitamins reduced the risk of age-related cataracts (12).
There is some debate about whether multivitamins can help prevent another condition, macular degeneration, in the elderly. This is a medical condition which can lead to blurred vision or blindness.
A Cochrane database system review in 2012 found that there was no evidence that multivitamin supplements could prevent age-related macular degeneration (13).
But an update in 2017 found that multivitamins could be effective at slowing down progression of macular degeneration – even if they could not prevent it entirely (14).
8Multivitamins can help fight vitamin D deficiency during winter months. Vitamin D is incredibly important for health, with many benefits attached to it.
But people in colder parts of the world can find themselves deficient during the colder months of the year. A study in the UK found that multivitamins that contained Vitamin D and fish oils were able to boost vitamin D levels and prevent hypovitaminosis D (15).
9Multivitamins containing Vitamin E may help to reduce hot flashes during menopause. This benefit is debatable, with some studies showing a reduction in hot flashes – such as a 1998 study looking at hot flashes in breast cancer survivors (16).
On the other hand, a study in 2004 found that multivitamin use led to a slight increase in hot flushes (17).
Both studies used a multi-factorial approach, looking at many different factors that can affect hot flash occurrence. Specific research is needed to isolate whether or not multivitamins have a direct effect on menopausal symptoms.
10Multivitamin use might have a small protective benefit against disease. While we outlined numerous studies that found no significant effect of multivitamin use on mortality, research is still ongoing. One study concluded that multivitamin use “may produce a modest protective benefit” against cardiovascular disease (18).
Again, this may be more pronounced in people with poor nutrition. A study in 2006 supports that theory, claiming that multivitamin use may “prevent cancer in individuals with poor or suboptimal nutritional status” (19).
11Multivitamins containing folate can help prevent neural tube defects in pregnant women. Neural tube defects are birth defects that affect the brain or spinal cord. An example of neural tube defects is spina bifida which is where a baby’s spine doesn’t develop properly in the womb.
This condition can be caused by a lack of folate, a B vitamin, during the early stages of pregnancy. Folic acid is the synthetic version of folate which is often added to processed and packaged foods. Obviously, there are ways to increase folate and folic acid through diet, but this does not always occur.
A study of nearly 18 million births in Brazil from 2001 to 2014 found that after a government-mandated fortification of flours with iron and folic acid, a significant reduction in the number of neural tube defects was seen (20).
The study also stated that supplementation of multivitamins with folic acid before pregnancy was advisable. So taking them while trying to conceive might be a good idea.
Sadly, the populations that are in the most need of multivitamins due to poor nutrition are also the least likely to use them, studies in America and in the United Kingdom have found that social and ethnic factors can determine whether a mother is likely to use multivitamins or not (21, 22, 23, 24).
A study in 2009 found that low-income adults were the least likely to take multivitamins (25).
12Multivitamin use may reduce premature births and low birth weights. A 1997 study by Bendich, Mallick, and Leader found that daily use of folic acid and zinc-containing multivitamins could reduce birth defects, low birth rate, and premature births (26).
The study claimed that increasing use among women could save $20 billion in hospital charges, through a reduction in birth complications.
13Multivitamin use in HIV/Aids patients who are pregnant can reduce birth complication risk. A study in 2007 by Mehta, and Fawzi found that pregnant women who were HIV-infected were less likely to suffer from “adverse pregnancy outcomes such as fetal loss and low birth weight” when taking a multivitamin (27). In addition, multivitamins containing vitamin A appear to be beneficial for HIV-positive children in reducing all-cause mortality.
The study also found that multivitamin use can slow down HIV progression in people who are in the early stages of the disease.
There are no real side effects to taking multivitamins as such, the main side effects come from accidentally taking too much of individual vitamins or minerals.
1Some studies seem to have found an increase in mortality rate for people who take multivitamins, but there is no causal link found. A study on men in the US found that there was a slight increase in the rate of prostate cancer deaths associated with multivitamin use, but this was only in men who took multivitamins and no other supplements (28).
Men who took multivitamins, as well as Vitamin A, C, or E supplements, did not have an increase in prostate cancer death.
A study on older women found that multivitamins containing iron led to a slight increase in mortality rate, but multivitamins containing calcium reduced mortality rate (29). Neither result has a causal link established, and it is impossible to draw any conclusions.
2Excessive Vitamin C supplementation can lead to diarrhea (30). This is unlikely to happen, as most multivitamins contain around 20-100mg per pill, while the tolerable upper limit of vitamin C is well over 2000. If you took a multivitamin alongside Vitamin C tablets or injections then you may be in trouble.
3Excessive Vitamin D supplementation combined with calcium can lead to kidney stones. A study into vitamin D and its effect on mortality rates, found that when you combine high levels of vitamin D and calcium together there is an increased risk of kidney stone formation, the study was performed on elderly women (31).
As you can see, the side effects of taking multivitamins are practically zero. Yes, there may be a risk of some unpleasant side effects if you combine multivitamin use with high doses of vitamins C or D, but that is not because of the multivitamin itself, that’s just poor dosing.
The evidence that multivitamins have a negative effect on health and increase mortality rate is even less convincing than the studies that found it had a positive effect.
4Multivitmains may not work as well as advertised. A study in 2009 on postmenopausal women found that “multivitamin use has little or no influence on the risk of common cancers, Cardiovascular Disease (CVD), or total mortality” (32).
Another study in 2010 found that multivitamin use had no significant effect on the outcome of patients with stage III colon cancer (33).
A 2011 study found that multivitamin use had no effect on mortality from all causes (including CVD and cancer) (34).
5Multivitamins containing non-methylated vitamins may not be ideal. It’s estimated that 40% of the world’s population carries at least one of the two variants on the MTHFR gene that codes for methylation, the process that converts vitamins to their usable forms. Different ethnicities have varying chances of a MTHFR variant. For example, it’s estimated that 6% of those of African descent have a double copy of one of the variants, 12-16% of North American Caucasians and 25% of Hispanics. Poor methylation of folate and B12 can lead to high homocysteine levels, B-vitamin anemia, and pregnancy complications among many other health issues (35). Though the research is unclear at this point, some functional medicine practitioners recommend taking methylated vitamins or avoiding synthetic vitamins like folic acid if you have these variants.
6Excessive biotin (vitamin B7) can alter lab results. The FDA released a statement warning the public about biotin found in supplements marketed for hair, skin and nails, B complex and prenatal vitamins could alter a variety of lab tests (36). This could significantly affect whether or not you are diagnosed with a condition and what treatment is started.
Usually 1-2 tablets, capsules or gummies per day is enough for most individuals.
However, because multivitamins are a combination of vitamins (plus some minerals) it is impossible to give a recommended dosage, other than saying take one serving per day. However, we can look at the individual recommended dosages for the different vitamins. All recommended doses come from NHS guidelines from the UK (37). Recommendations from the National Institute of Health (NIH) for the United States may differ. For example, the NIH recommends 4700mg potassium daily, not 3500mg.
Vitamin C (40mg per day)
B1 (0.8mg per day for women), B2 (1.1mg per day for women), B3 (13.2mg per day for women)
B5 (<200mg per day), B6 (1.2mg per day for women), B7 (0.03mg),
B9 folate/folic acid (200mcg per day), B12 (1.5mcg per day)
Vitamin A (0.6mg per day for women), Vitamin D (2000-4000iu per day in winter)
Vitamin E (3mg per day for women), Vitamin K (1mcg per kg of bodyweight).
Potassium (3,500mg per day), selenium (0.06mg per day for women)
Iodine (0.14mg per day), zinc (7mg per day for women)
Calcium (700mg per day), iron (14.8mg per day for women aged 19-50 and 8.7mg for women aged 50+)
Manganese (<4mg per day), and magnesium (270mg per day for women).
Are multivitamins necessary? Factors like nutrient-depleted soil, poor food quality and unhealthy food choices can lead to inadequate nutrient intake to support optimal functioning in the human body. A multivitamin may help correct those deficiencies. Research has shown that there does seem to be more benefit for those with current health conditions and with poor diets. So yes, for the majority of people, it appears multivitamins are necessary.
Is it better to take multivitamins in the morning or at night? The answer is it depends on the multivitamin formulation. B vitamins and some herbs are considered energy nutrients. Taking these vitamins at night may interfere with a good night’s sleep. Vitamins A, D, E and K are fat-soluble vitamins meaning they are better absorbed in the presence of fat. Taking your multivitamins with your breakfast or dinner is ideal. Sometimes the best time of day is the just the time you remember!
Should you take multivitamins on an empty stomach? No, they should be taken with food to maximize digestion.
How long does it take a vitamin to work? It depends on the supplement or specific nutrient but most will take a minimum of 2 to 4 weeks to begin to work before the person feels them ‘kick in.’ Vitamin deficiencies also begin to correct around this time. If it’s a mineral, you’re looking at about 90 days before your deficiency is fully amended (assuming your absorption is not compromised).
Do multivitamins give you more energy? Yes, research has clearly shown that B vitamins, like vitamin B6, vitamin B12, folate, thiamine and niacin support the energy metabolism process.
Do multivitamins cause acne? It is possible that multivitamins can cause acne – specifically the ones containing biotin.
Do multivitamins make you fat? No they will not make you fat. In fact they may do the opposite. However, watch out for multivitamins that have added sugars, the amount may surprise you!
The benefits of multivitamins do not seem to be well supported by evidence, however, the risks appear minimal when dosage is not excessive. Prevention of cataracts is indeed a valuable benefit, but there isn’t much evidence to support the use of multivitamins for prevention of other eye diseases. Multivitamins don’t appear to cause an increase or a decrease in mortality rate, and don’t affect cardiovascular disease, cancers, or any metabolic diseases.
It is a sad fact that the people who are most in need of them, usually the very poor, are the least likely demographic to take them. When you are following a micronutrient deficient diet, commonly seen in those who are eating a highly processed diet, there does seem to be some benefits to taking multivitamins, but they aren’t huge.
One issue that seems to occur is that many studies compare multivitamins to good diets, which are already high in vitamins. Comparing a diet that was filled with junk food, to a similar diet plus a multivitamin may produce more interesting results, and would reflect the issue that many people have.
Multivitamins should be seen as a useful top off for people who have bad diets, but they will never replace a good diet. If you are already eating healthy then a multivitamin is less likely to be of value. What’s worse, is that you may actually be at risk of exceeding your recommended dosage.
Despite the published research that multivitamins are largely ineffective and unhelpful, the more the public seems to buy them.
The National Products Association in America (a supplement trade organization) is a $30 billion industry (38). People should stop seeing their daily multivitamin as an effective tool, and start analyzing how much they are spending per month on this product, especially if it is replacing healthy food.
The exceptions to this (other than people with bad diets) would be women who are attempting to get pregnant, or who are currently pregnant or breastfeeding. Other exceptions include those who take certain medications that can lead to nutrient deficiencies (like in the case of statins and CoQ10) and those with malabsorption diseases.
As usual, talk to your doctor before taking any supplement, but a multivitamin appears to have minimal risks. While a multivitamin may be able to address nutrient deficiencies, a balanced, healthy diet provides far more confirmed benefits.