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Food supplements: Exploring our reasons for taking them

Food supplements: Exploring our reasons for taking them

Most people get enough vitamins and minerals from their diet, yet 30% of people on the island of Ireland report taking food supplements. This reseach examined why people are taking these supplements to help inform guidance to the public.


Food Supplements: Exploring our reasons for taking them (PDF 1.7MB, Opens in new window)

Executive summary

Aim and objectives

The aim of this research project was to explore why adults on the island of Ireland may or may not choose to take a food supplement, employing the Theory of Planned Behaviour to gain a better understanding of the personal, social and psychological factors that influence food supplements use in an adult population.

The objectives were to

  • Conduct a literature review of existing available data on food supplements use and associated factors from within the island of Ireland and internationally
  • Gain a better understanding of the personal, social and psychological factors that influence food supplements use in an adult population, employing the Theory of Planned Behaviour to define and measure these factors
  • Explore behaviours, beliefs, attitudes, knowledge and awareness of risk or safety in relation to food supplements among adults on the island of Ireland, identifying factors that motivate and predict food supplements use behaviour and intentions


A mixed study methods approach was used including

  • A review of relevant literature – that is, published scientific research.
  • A desk-based audit, or survey, of a sample of 13 newsletters from the French Agency for Food, Environmental and Occupational Health and Safety’s Nutrivigilance scheme. (“Nutrivigilance” refers to any system that aims to improve consumer safety by rapidly identifying and reporting possible adverse effects, such as rashes, headaches, stomach pain and so on, associated with the consumption of foods, including food supplements.)

Two stages of data collection and analysis to obtain a comprehensive understanding of food supplements use in adults on the island of Ireland. The results of the literature review were used to inform, or develop:

  • A qualitative elicitation study in the form of 4 online focus groups, made up of 39 participants in total. (An “elicitation” study aims to draw out
  • information that is not directly countable such as emotions and perceptions – the “qualitative” data.)
  • A quantitative study in the form of a cross-sectional, representative survey of 2,000 people. (“Quantitative” information is directly countable or measurable. A “cross-sectional” study captures data about a population from a single point in time.)

The Theory of Planned Behaviour was used to define and measure factors that influence food supplements use behaviour and intentions.

Key findings

Literature review

Food supplements play an important role in correcting nutritional deficiencies, maintaining an adequate intake of certain nutrients and supporting specific physiological (bodily) functions. In the United Kingdom and Ireland, current public health guidelines focus on food-based recommendations and only advocate (advise and support) the use of food supplements in specific circumstances (such as in pregnancy or during the winter months). Despite this, there is growing evidence of the widespread use of food supplements across the population, with dietary surveys from Ireland and the United Kingdom recording that 20 to 50 per cent of adults report regularly taking food supplements (depending on gender and age group and often increasing with age).

The regulation of food supplements poses a significant challenge due to the nature and diversity of the market, and there are growing fears over the potential risk of excess micronutrient intakes, particularly among vulnerable groups such as older adults and children. There is also concern that the population may view supplements use as a substitute for eating a healthy diet. The aim of the review was to critically analyse current evidence investigating consumer knowledge, attitudes and behaviours and to examine issues in relation to the safe and appropriate use of food supplements.

Systematic literature searches identified 36 relevant studies that were included in the review. Observational evidence (simply data collected from observing a study sample that is behaving naturally or that is self-reporting on its everyday behaviour) has identified key characteristics of supplement users, with higher reported use among females, older adults and those from a more advantaged socioeconomic (social and economic) background. Furthermore, the reasons for taking food supplements are often multifactorial with “general health improvement” being a common motivation. It is evident that food supplements are generally perceived as “low risk” by the people who take them. This review highlights the need for future work to increase consumer knowledge around the safe and appropriate use of food supplements for example, checking whether a supplement is truly necessary or beneficial for health, only taking the correct dose, and checking whether supplements are safe to use when also taking medications. The provision of targeted nutritional supplementation use advice is warranted.

Audit of a sample of the French Agency for Food, Environmental and Occupational Health and Safety’s Nutrivigilance newsletters (number 59 August 2019 to number 71 August 2020)

The audit of a sample of 13 newsletters from the French Agency for Food, Environmental and Occupational Health and Safety’s Nutrivigilance scheme provided an evidence-based insight into clinical cases of adverse events associated with the consumption of food supplements and other food products. During the timeframe of the audit, 170 adverse event cases were recorded (on average, approx. 13 per month), and two-thirds of these were classified as likely or very likely that the product direct caused the adverse event. Cases of adverse events were reported across a wide age range of adults (18-90yrs) with approx. 10% reported in children and often in children <5yrs. Varying degrees of severity of adverse events were noted, spanning many different bodily systems and conditions. Most common were gastrointestinal, allergic, hepatic and cardiovascular-related symptoms.

Findings from qualitative focus groups and quantitative survey
  • In the quantitative survey, almost half of the adults on the island of Ireland reported that they currently take food supplements (48 per cent).
  • A significantly higher proportion of food supplements users were female, aged from 35 to 49 years, from Ireland, with a more advantaged socioeconomic background, working full-time, married or living as married, living with a diagnosed physical health condition, vegetarian or vegan.
  • Among people who reported that they currently take food supplements, the mean or average number of supplements reported was 2.6 with a standard deviation (variation from the mean value) 1.7 above or below this number (on a range from 1 to 12 supplements used):
    • More than half of this group (60 per cent) were taking at least 1 food supplement (Vitamin D).
    • The top 3 food supplements reported by current users were vitamin D (60 per cent), multi- vitamin or mineral (41 per cent) and vitamin C (34 per cent). (Minerals are substances that occur naturally in the earth, for example calcium, iron, magnesium.) (Vitamins are substances which are found in food or can be eaten in the form of pills).
    • The majority reported daily use of food supplements (81 per cent).
    • Nearly a quarter (24 per cent) of current food supplement users had been taking a supplement for the last 6 months.
    • The majority of current users bought the supplements themselves (87 per cent).
    • Food supplements were most likely to be bought from a chemist or pharmacy (37 per cent).
    • Nearly half of all parents or those with children in their care (47 per cent) among the survey respondents reported currently giving food supplements to their child or children.
  • Parents, or those with children in their care, who were food supplements users themselves were 2.4 times more likely to give their child or children food supplements than parents who were not food supplement users.
  • Beliefs and attitudes · The top 3 forms of food supplements commonly referred to during focus group discussions were “tablets or capsules”, “sachets or powders” and “shakes or drinks”.
  • The terms “vitamin(s)” and “multivitamin(s)” were used by many people to mean any type of food supplement.
  • Qualitative data from focus groups suggested that adults:
    • Mainly held positive attitudes towards food supplements
    • Are commonly influenced by healthcare professionals, family or other food supplements users
    • Could identify more facilitators than barriers to the use of food supplements
  • Knowledge and awareness of risk and safety in relation to food supplements
  • Although there was better knowledge about food supplements among those who used them as against those who did not (mean, or average "knowledge" score of 2.64 as against 2.36, out of a possible score of 6), the difference was marginal and scores were low overall.
  • The level of consideration and thought given to the use of food supplements was high, with more than two thirds agreeing or strongly agreeing that they
    •  “Think carefully” about taking more than 1 supplement at a time
    •  “Think carefully” about taking supplements at the same time as taking medication
    •  “Always” check the correct dosage
  • Around 2 out of 5 adults perceived food supplements use to be “risk free” (37 per cent).
  • A small proportion (around 5 to 10 per cent) of respondents do not think carefully about taking more than 1 food supplement at a time or with medications, or do not check the correct dose.
Predictors of behaviour and intentions
  • The major determinants of behaviour (that is, use of food supplements) were being female, with higher socioeconomic status and having more positive intentions or attitudes towards supplements and their use.
  • Intentions towards food supplements use (in the next month) increases among females, younger adults, those with higher socioeconomic status, and those with more favourable pre-existing attitudes towards food supplements, higher subjective norms (more influencers/social pressure), more perceived behavioural control (a person’s belief in their ability to act or to change their environment) and more social pressure towards undertaking the behaviour.
  • Perceived health status was not associated with food supplements use or with the intention to use supplements.


  • Given the increasing proportion of the adult population reporting food supplements use (increased compared to previous estimates), more consumer education is needed to
    • Ensure consumer choice and behaviour is better aligned with the specific food supplements included in dietary guidance or recommendations
    • Increase the awareness of risks as against benefits
    • Ensure appropriate food supplement use.
  • Education (for example continuing professional development, online training courses / webinars, resources distributed to key point-of-care groups, through professional bodies) for all healthcare professionals will help to ensure current public health messages are supported at the point of care.
  • Updated guidance should be provided at common points-of-sale for food supplements (for example in pharmacies or on supermarket shelf-edges) to better inform consumers.
  • Development of a reputable online resource by relevant public health bodies that would become the “norm” for those looking to obtain accurate and reliable information on food supplements would be desirable.
Public health communications

Targeted public health campaigns on food supplements should

  • Promote clear and consistent messaging to consumers about food supplements use
  • Make clear what food supplements are specified in public health policy
  • Give hints and tips to help consumers get into the habit of only taking food supplements that are needed
  • Support consumers in making lower-cost choices when required, e.g. signposting to less expensive own-brand products
Monitoring and surveillance
  • Food supplements use on the island of Ireland should be monitored in the long term to assess changes in consumer behaviour over time in the context of current Government guidelines and to inform future public health policy.
  • An accessible system for identifying, reporting and monitoring of suspected adverse events, such as allergic reactions and poisonings, related to the use of food supplements is warranted to contribute to improved knowledge of food supplements and consumer safety.

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