Multivitamin supplements are big business. Pharmacy and supermarket shelves groan under the weight of choice available to us. So, if you’re serious about your health, should you be taking one of these even if it is just as an insurance policy for a less-than-perfect diet? While multivitamins won't boost your health as much as what people believe, they do have the potential to be useful for certain groups of people. In this podcast, I’ll investigate the evidence for any health benefits of multivitamins and then tell you for which people they could prove useful and for whom they really are just a waste of money.
Are you someone who frequently takes a multivitamin-multimineral supplement as an insurance policy on your health? If so, you’re in good company. Estimates point to around one in 3 people being regular consumers of these supplements. Reasons for taking a supplement can vary: from health and wellbeing, a perception of a poor diet or even just out of habit are all common justifications.
But what is a multivitamin-multimineral supplement? To make things simpler, the term ‘multivitamin’ seems to be the collective term used here, but it is usually implied that such a supplement will contain some minerals too.
There is no standard regulatory definition of what nutrients or to what level a multivitamin must contain. One way to classify a multivitamin supplement is based on it containing most of the recognised essential vitamins and minerals at levels close to their recommended daily requirements. There is a lot of scope to work within here based on nutrient needs across the lifespan. That means formulations can be optimised for children, adults, men, women, pregnant women and older adults.
Just to show the breadth of what could define a multivitamin, some formulations can contain doses of some nutrients closer to the established tolerable upper intake level. Some formulations can also contain additional herbal ingredients, blurring the definition even more. And in the research field when looking at any health benefits of multivitamins, definitions are also broad. Some research uses a very low-bar definition that a multivitamin supplement is one contain just three or more vitamins and minerals. This is an important point as already it makes it hard to make blanket statements that multivitamins are or are not beneficial. It all will depend on what type of formulation you are looking at and importantly: the population group it is targeted for.
Are there health benefits?
So, are there health benefits from taking a multivitamin that the wider population may enjoy? In an ironic twist, people who take multivitamins tend to have higher micronutrient intakes from their diet than nonusers. And these same people are more likely to have a higher education level, higher incomes, lower body mass index and higher physical activity levels – all factors that are linked to better health. There is indeed some validity to the claim that many users of multivitamins sit within the ‘worried well’ group.
So, let’s investigate the research about multivitamins and health. Most of the studies here have been observational, which can only suggest an association, but cannot prove definitively if taking multivitamins do, or not do, have a health benefit. This is confounded further when you consider that people who take these supplements are more likely to have healthier diets and lifestyles. But if you look at the observational research as a whole, some suggest a benefit, some show adverse health problems and others no benefit. A very much a mixed bag indeed
One of the biggest observational studies looking at multivitamins and health involved over 160,000 postmenopausal women aged 50–79 years. They were all part of the Women’s Health Initiative study that explored health and risks for cancer, heart disease, and osteoporosis in postmenopausal women. Over 40 percent of women were taking a multivitamin supplement, yet over the 8 years of the study, there was no link between taking these supplements and the risk of developing cancer, cardiovascular disease, or dying earlier.
For heart disease, the most recent systematic review and meta-analysis of 18 observational studies involving over 2 million participants found no association between multivitamin supplementation and cardiovascular disease outcomes including mortality. And I’ll link to this study in the show notes. https://pubmed.ncbi.nlm.nih.gov/29991644
Randomised-controlled trials are superior for investigating any direct effects of multivitamins on health than observational studies. But, way back in 2006, a comprehensive review looking at only randomised-controlled clinical trials found that the use of multivitamins did not reduce the risk of any chronic disease.
More recently and published in 2012, The Physicians Health Study II looked at the benefit of multivitamins using a randomised-controlled trial design. Involving over 14,000 male physicians in the United States aged 50 years and older, there was no benefit seen from taking a broad-spectrum multivitamin in reducing the risk of major cardiovascular events, heart attacks, stroke, or cardiovascular-related deaths. Men taking the multivitamin also saw no benefit in their risk of dying earlier. In another analysis of the data from this same group of men, taking a multivitamin was however linked to an 8 percent lower risk of developing cancer, but there was no significant reduction in the risk of mortality from cancer.
Moving to the most recent research and assessment of the evidence in the field, a 2015 critical review of observational studies and randomised-controlled trials explored the efficacy of multivitamins in reducing the risk of chronic disease. And I’ll link to this study in the show notes. What did it find? The majority of scientific studies investigating the use of supplements in chronic disease risk reduction reported no significant effect. The review, however, did note prior research that suggested some benefit of multivitamins in reducing the risk of developing cancer in men, yet no strong evidence shows that women may benefit also benefit. On that topic of cancer and supplements, a comprehensive evaluation of the research field by the World Cancer Research Fund and the American Institute for Cancer Research recommended against the use of dietary supplements for cancer prevention because of the unpredictability of potential benefits and risks, as well as the possibility of unexpected adverse events. https://pubmed.ncbi.nlm.nih.gov/24941429
There is though some evidence that multivitamins that include high doses of antioxidants may help to reduce the risk of cataracts and age-related macular degeneration, but we are still waiting on higher-quality studies to confirm this. Use of high-dose antioxidants though is not without risk so may offset any eye-health benefit.
But multivitamins can help with deficiencies
It is not all negative news for multivitamins though. Taking a multivitamin supplement helps people obtain the recommended intakes of vitamins and minerals when they cannot meet these needs from food alone. And there are many situations where this is the case such as:
People more likely to have a poor food intake such as those on restricted diets or the elderly Women planning pregnancy where taking folic acid and other nutrients such as iodine, iron and vitamin D before and during pregnancy is well supported by scientific evidencePeople following a vegan diet where vitamin B12 deficiency can be an issuePeople who are chronic drinkers of alcoholPeople who have undergone bariatric weight-loss surgeryPeople with malabsorption problems such as coeliac disease, Crohn’s disease, cystic fibrosis or pancreatitis.Food is more than vitamins and minerals
All this discussion on multivitamin supplements can obscure the forest for the trees. Humans eat food and food is a complex source of vitamins, minerals and phytochemicals (plant chemicals), which all work together. Supplements tend to work in isolation and only contain a fraction of the nutrients that can be found in a diverse diet. Foods also contain vitamins in different forms. For example, vitamin E naturally occurs in 8 different forms, but supplements usually contain just one of these forms. Each of these forms has different levels of bioavailability and even activity.
There are over 8,000 different types of polyphenols found in fruits, vegetables, grains, legumes, tea and coffee. Polyphenols are linked to many health benefits, yet it is rare to find any of them in a broad-spectrum multivitamin. A brief reading about polyphenols on the Internet will bring up article after article highlighting that polyphenols are antioxidants and that explains their health benefits. They are much more than antioxidants. It should instead be about polyphenols and their multitude of benefits and actions in the body such as:
Regulating cell growth and deathSlowing down cancer cell proliferationAltering glucose responses and insulin sensitivityIncreasing activity of enzymes involved in removing harmful substances from the bodyDecreasing inflammation.That is a lot of potential health benefits to be gained from eating whole plant-based food and likely why most studies don’t show that multivitamins offer many health benefits. Food is much more than just essential vitamins and minerals.
What to look for in a supplement
If you do decide to take a multivitamin supplement, then what should you look for? Firstly, it should deliver close to the recommended daily intake for most of the vitamins and minerals. And I’ll link to these Nutrient Reference Values as they apply to Australia in the show notes, but they vary little from other similar countries. A level of 75 percent is a good baseline to work from. But a true multivitamin cannot hope to achieve this for all nutrients and still pack it all into a one-a-day pill. Calcium is a good example as the amount we need is so large – about 1 gram per day. https://www.nrv.gov.au
Choose a multivitamin tailored to your age, gender, and other characteristics such as if you are pregnant. Multivitamins for women usually contain more iron for example whereas those for seniors typically provide more calcium and vitamins D and B12.
Taking a basic multivitamin that provides nutrients at close to the recommended amounts is unlikely to pose a safety risk for healthy people. However, be aware that eating a diet high in fortified foods may mean it is possible to consume some nutrients at levels exceeding the upper level of intake.
Summary
Multivitamins have their use for people with vitamin and mineral deficiencies, but they don’t appear to offer many health benefits for the general population. If you feel that you could be lacking in certain vitamins and minerals, it may be better to look at changing your diet and lifestyle rather than reaching for supplements. If you need help, see your doctor or a dietitian.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.