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 missed 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 on 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 can fight off illness. While this isn’t proven, many of the individual ingredients in multivitamins have been proven to enhance the immune system, helping you fight off illnesses – especially during times of stress.
3Multivitamins may help reduce infection in people with poor nutrition. One study looked at the effect of using a multivitamin supplement to fight infection in people who had a micronutrient deficiency (3).
The study found that daily supplementation reduced the incidence of patient-reported infection.
The problem with this study was that it was based on self reporting infection. Also, it only noticed changes in people who were already deficient in the vitamins.
A similar study, but this time in children in India found that multivitamin supplementation “decreased the incidence and severity of common infectious diseases” (4).
Again, you can see that this study found results in people with poor nutrition but did not see any difference in people with a healthy diet high in micronutrients.
4Multivitamin use may reduce depression, anxiety, and stress. A study in 2011 looked at the effect of multivitamin supplementation in older men.
The study found that taking multivitamins for a period of eight weeks led to a significant reduction in depression, stress, and anxiety, while also improving alertness and daily function (5). There was nothing to suggest that the results would be any different in women.
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 (6).
A study in 2000 found that multivitamins that were high in calcium, magnesium, and zinc were able to improve psychological well being in young men (7).
5Supplementing with multivitamins may slightly 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 (8).
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 3.4kg over a period of 26 weeks (9).
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 (10).
Despite all of these benefits above, the general consensus seems to be that multivitamins are unreliable and that they are ineffective at prevention of illness and disease. They have no effect on your mortality, and may even do more harm than good (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 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).
The study did mention that this may not have been down to the multivitamins though, but that people who took multivitamins were more likely to be healthy – which could itself be the cause.
10Multivitamin use might have a small protective benefit against cardiovascular. While we outlined numerous studies that found no significant effect of multivitamin use on mortality, that does not mean that it definitively does not. One study concluded that multivitamin use “may produce a modest protective benefit” (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 folic acid 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 folic acid during the early stages of pregnancy. Obviously, there are ways to increase folic acid through diet, but this does not always occur.
A study on 6,425 pregnant women in 2001 found that supplementation with multivitamin tablets that contained folate reduced the incidence of neural tube defects (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 positive were less likely to suffer from “adverse pregnancy outcomes such as fetal loss and low birth weight” when taking a multivitamin (27).
The study also found that multivitamin use can slow down HIV progression in people who are in the early stages.
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).
Usually 1-2 tablets 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 (35).
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 (unknown),
B9 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? Yes, the standard diet often lacks adequate nutrients to support optimal functioning in the human body. A multivitamin helps correct those deficiencies.
Is it better to take multivitamins in the morning or at night? It’s definitely better to take them in the morning, since certain vitamins (like vitamin C) are considered energy vitamins. Taking them at night can interfere with a good night’s sleep.
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? Any supplement is going to take a minimum of 2 to 4 weeks to begin to work before person feels them ‘kick in.’ If it’s a mineral, you’re looking at about 90 days before your deficiency is fully amended.
Do multivitamins give you more energy? Yes, research has clearly shown that B vitamins, like vitamin B6, vitamin B12, folic acid, 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.
The benefits of multivitamins do not seem to be well supported by evidence, there’s nothing that truly stands out. Prevention of eye deterioration seems like a useful benefit, but there isn’t much evidence to support it. 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, and most obese people are, 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.
A lack of nutritional education, and a lack of funds to afford the right type of foods needed for a healthy diet.
Multivitamins should be seen as a useful top up for people who have bad diets, but they will never replace good nutrition. If you are already eating healthily then a multivitamin is a waste of time and money. What’s worse, is that you may actually be at risk of exceeding your recommended dosage.
What’s interesting is that the more science tells people that multivitamins are 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 (36). People should stop seeing their daily multivitamin as an effective tool, and start analyzing how much they are spending per month on this product.
The only possible exception to this (other than people with bad diets) would be women who are attempting to get pregnant, or who are currently pregnant or breastfeeding.
The studies that showed the most potential all looked at multivitamins preventing premature births, and deformities. As usual, talk to your doctor before taking any supplement, but a multivitamin with added folic acid could be a very good decision.