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Frequently asked questions about nutrition

Nutrition and fitness: your questions answered
A piece of paper pinned to a cork board with Nutrition and Fitness: Your Questions Answered written on it.

Dr Maria O’Sullivan, Associate Professor in Human Nutrition, and Deirdre O’Connor, Postgraduate Research Assistant have put together some answers to the most common questions people have with regards to nutrition. Click on each of the following links to read more information.


Nutritional advice is so confusing. Who can I trust to give me the best evidence based advice?

Deirdre O’Connor

Choosing the right person to seek help and advice from about your diet can be a confusing task. Unfortunately, there are many people claim who claim to be experts in nutrition, yet have very limited knowledge and offer no protection to the public. The following points may help clarify the difference between a Dietitian, Nutritionist and a Nutritional Therapist and more.


Dietitians have a minimum qualification requirement of a BSc (Hons) in Human Nutrition & Dietetics or BSc (Hons) in related biological science with a two year post graduate university diploma in Dietetics. Dietitians apply knowledge of food, nutrition and other related disciplines such as biochemistry, physiology and behavioural science to promote health, prevent disease and aid in the management of illness. Dietitians are uniquely qualified to help translate the latest scientific research into practical and impartial nutrition advice for clients and are qualified to work with healthy and sick people in a broad range of settings.

The Irish Nutrition & Dietetic Institute is the professional organisation for clinical nutritionists/dietitians in Ireland. Dietitians work across all age groups and in a great variety of organisations and settings including acute and community services within the HSE (the health services in Ireland), private practice, the food industry, education, research and the media. CORU is Ireland’s multi-profession health regulator and is responsible for regulation of health and social care professions (HSCPs) under the Health and Social Care Professional’s Act, 2005, in Ireland. Dietitians have public protection as their mandate. Dietitians are held accountable for their conduct and the care they provide both through the regulation process and also through membership of INDI). All members of The INDI are bound to comply with the code of ethics and professional practice.


Nutritionists and Public Health Nutritionists in Ireland have BSc (Hons) or MSc in Public Health Nutrition, Human Nutrition or Nutritional Science. They are qualified to provide information about food and healthy eating and often work in roles including public health, health improvement, health policy, local and national government as well as in education and research. Those who possess a degree in Public Health Nutrition often work with government bodies to promote health eating for the general population. Unfortunately, the term “Nutritionist” can also be used by those who do not hold a BSc (Hons) degree in Nutrition from an accredited university or any type of formal qualification as this title is not protected by law in Ireland. However, those who hold the appropriate qualifications can register with the UK Voluntary Register of Nutritionists (UKVRN). This, is a UK register, there is no register of Nutritionists in Ireland, but many Irish nutritionists register with this body to show that their qualification is of a high standard.

Nutritionists do not give direct health-related advice to individuals with known medical conditions, unlike dietitians, as they are not trained in clinical practice.

Nutritional Therapists

Nutritional Therapists can acquire their qualification from many courses of differing lengths and standards and they are not eligible to register with the UKVRN. Nutritional therapists generally provide nutritional advice in private settings and some may offer nutritional tests such as food intolerance testing or hair analysis which are not evidence-based within conventional medicine. While many are knowledgeable and well-meaning, some may also offer treatments such as supplements, detox diets, and food exclusions for which there is little robust scientific evidence, and may prove to be harmful to those with underlying medical conditions.

Diet Experts, Nutrition Gurus and beyond…

There exist many other individuals who can style themselves as ‘diet experts’ or ‘nutrition experts’ etc. sometimes with many letters after their name. Some may have no more qualifications than an interest in food. This is largely a self-regulated industry where anyone can set up and practice, meaning there is no real protection or standard of guidance for consumers. Do not be afraid to ask your source of nutrition information about their past training to ensure the information you receive is up to date, safe and correct.

Protected Titles (in Ireland)

Unfortunately anyone can call themselves a Nutritionist in Ireland at present. In 2013, the title of Clinical Nutritionist / Dietitian was protected by law in Ireland thus ensuring high standards of practice are maintained in addition to the appropriate university qualifications.

Take Home Tips:

  • Check with your local health authority about what the (local) regulations are regarding the use of titles such as Dietitian or Nutritionist etc.
  • Do not be afraid to ask your source of nutrition information about their past training and qualifications to ensure the information you receive is up to date, safe and correct. Nutrition is an evolving science and bona fide experts strive to communicate the most up-to-date research findings that have been published in peer-reviewed articles.
  • Remember that someone else’s personal experience (e.g. weight loss in the past) is never equivalent to the university training of a dietitian and could sometimes be harmful, especially if you have an underlying medical condition for which the advice is not appropriate.
  • As Maria said in her video, if you have received advice about your diet that seems too good to be true, it probably is. Always question over-simplistic advice.
  • For online guidance regarding nutrition, always seek information from your Government bodies (e.g. Foods Standards Agency in the UK, the Food Safety Authority of Ireland, the Centre for Disease Control and Prevention in the US) or from highly regulated professional organisations, for example the Irish Nutrition & Dietetic Institute, the British Dietetics Association.
  • If you have a medical condition and are concerned about aspects of your diet, speak to your GP or local public health nurse about getting a referral to see a Registered Dietitian for a one-to-one consultation.

INDI and BDA give some in depth information about Dietitians, Nutritionists and more here and here.

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What are the sources of vitamin D and B12?

Maria O’Sullivan

The main source of vitamin D is from the action of sunlight on the skin. However, if you live at Northern latitudes such as Ireland, UVB rays are only sufficiently strong to make vitamin D from about April to September. During this time, about 15-20 min exposure to sunlight, on arms a few times a week is sufficient for vitamin D-making. Food sources are few, but include oily fish, egg yolk and fortified foods (e.g. some milks and cereals) (read more about this in Step 3.9).

Vitamin B12 is required for red blood cell formation and a healthy nervous system. The vitamin is present in a variety of foods, but mainly meat, fish, eggs and dairy products and some fortified products (e.g. milk, soya milks, cereals). Those who do not consume animal products may be at risk of deficiency (vegan diets) or those with poor or low dietary intake, which may include older adults. The area of B12 is a highly active area of research, particularly how this vitamin may be involved in brain health and cognition.

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Is organic produce healthier than its non-organic counterparts?

Deirdre O’Connor

Organic food is the product of an agricultural or aqua-cultural system of farming that places a strong emphasis on environmental protection and animal welfare. While organic and non-organically produced food may appear very similar, the systems of farming involved in their production can be very different. The term “organic” means different things to different people. For some, it means produce that is healthier, or more nutritious. For others, it could signify eco-friendly, or even tastier. It brings with it connotations of clean, good, or… even more expensive foods.

The question of whether organic food is different to non-organic food with respect to nutritional content or quality is still a matter of furious public and scientific debate. While the farming systems used can differ substantially, organically grown food is nutritionally identical to conventional food and there is no definitive data to date that has reported distinguishable differences between the end-products of organic farming and their non-organically produced counterparts – in terms of taste or nutritional content. Moreover, there is no recognised scientific test that exclusively differentiates between the nutrient content of organic and non-organic produce.

Organic produce is subject to the same stringent food safety regulations as all food consumed, distributed, marketed or produced in Ireland. The presence of certain pesticide residues, growth promoters or genetically modified material in a food product, could indicate that the food was not produced to organic standards, however, organic produce is not devoid of pesticides. EU legislation denotes that organic farming can involve the use of a limited number of naturally occurring pesticides, as opposed to synthetic ones. As with all produce, pesticide residues that are found on organic produce must not exceed accepted safety limits and each pesticide used must be authorised for use. The difference between organic pesticides and regular pesticides is not that big. In fact, although organic pesticides come from natural sources, and are not processed, they sometimes contain the exact same substances as regular pesticides. Organic pesticides pose the same health risks as non-organic ones. In Ireland, the top 2.5% of consumers of any crop will have pesticide intakes at levels between 0.1 -10% of the safe exposure dose established by the World Health Organisation.

From a price point of view, “organic” has become a synonym for luxury, and is a marketing dream. The higher price of organic produce does not necessarily mean it is a higher quality product. The organic industry is booming in Ireland, and organic food can be up to 47% more expensive than non-organic varieties. Of course, organic food is more expensive to produce than regular food, but a recent study in the Proceedings of the National Academy of Sciences in the US found that it is merely 5-7% more expensive to produce.

Organic animal farming is without a doubt more ethical and can offer better life conditions for the animals. Organic principles and regulations are also designed to ensure that animals are treated as humanely as possible. There are strict rules on the way in which animals are housed, guaranteeing a degree of comfort for the animals. However, organic crop production can be considerably different. The most discussed environmental advantage of organic foods is that they don’t have any chemical pesticides. As described above, this is not true. A 2010 study found that some organic pesticides can actually have a worse environmental impact than conventional ones. In addition, because organic produce must be maintained as strictly non-GMO, sometimes more liberal application of these naturally occurring pesticides (pesticides nonetheless) is necessary, as the genetic strain of the crop in question may be less robust and less resistant to microorganisms etc. than its genetically modified counterpart. Several studies have shown that entire environmental impact of organic crops is just as big (and sometimes bigger) than conventional farming. Research at Oxford University analysed 71 peer-reviewed studies and observed that organic products are sometimes worse for the environment. Organic milk, cereals, and pork generated higher greenhouse gas emissions per product than conventional ones but organic beef and olives had lower emissions in most studies.

In many cases organic products require less energy, but take up more land. For example, organic wheat production requires less energy than conventionally farmed wheat, but requires more land. A recent study, published by the University of Oregon found that in the US, because organic agriculture is now done mostly by big corporations, and not local producers, and the lower yields combined with the intensive use of machinery means that overall, in terms of emissions and pollution, organic agriculture is usually worse than conventional.

My take on the debate:

For me, organic foods raise more questions answers. As a trained scientist, I don’t believe organic food to be bad for you, but rather, to date there is no definitive empirical evidence to suggest that it is better for you, or indeed the environment, than conventional produce. Of course, this will vary depending on geographic location. Buying and eating healthy, sustainable food is of critical concern of us all. In my opinion, in an Irish context, if you want healthier foods and to minimize your environmental impact, you should buy local – whether organic or not, and more importantly, in season. In Ireland, local produce is cost competitive with supermarkets, and fruit and vegetables that are in season will be fresher, and cost less in terms of CO2 emissions (factoring in transport and storage time) and contribute to support local producers and economies.

Ultimately, it is a matter of personal choice (and budget). Try to keep in mind that just because something is branded as healthy and eco-friendly, this doesn’t necessarily make it so. The globalization of food production and trade mean that it can be quite a tangled web to un-weave to understand exactly how much of an environmental footprint the food you buy truly has.

The nutrition and health aspects of organic food have been explored in many studies, and there is still minimal evidence that organic foods confer discernible health benefits to humans in comparison to non-organic foods. The scientific community is still waiting for a well- designed, strictly controlled study that provides the evidence to confirm the perceived positive health benefits associated with organic food.

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Hydration: how much water should I be drinking daily?

Deirdre O’Connor

The truth is, how much water you should drink each day – depends on you, the individual. Everyone’s fluid needs are dynamic and should be tailored accordingly. Factors such as gender, environmental conditions, level of heat acclimatization, exercise or work intensity, age, and even diet need to be considered.

Regular drinks are necessary to replace fluid lost during the day. Water is a major constituent of the body and has many functions including transporting nutrients and compounds in blood, removing waste-products that are then passed in urine. Water regulates the body’s temperature and without enough water, people can quickly become dehydrated. When dehydrated, the first thing you will notice is increased thirst and a dry, sticky mouth. Other side effects can include tiredness, poor concentration, headaches and even dizziness or light headedness. Drinking enough is vital to maintain good health in the short and long term, for example, for the prevention of constipation, kidney stones and urinary tract infections. Good hydration can also prevent other conditions, such as chronic renal disease.

It sounds complicated, but paying attention to your body’s natural cues, including thirst and urination frequency and colour, is a simple and effective place to start. When you drink fluids, you stop you feeling thirsty before you are completely rehydrated. Older people, in particular, need to be careful to drink enough as in many, the sense of thirst decreases with age. Therefore keeping an eye on the colour of your urine is truly the best indicator of hydration; if you are drinking enough water your urine should be a straw or pale yellow colour.

Generally speaking, most dietary guidelines recommend adult women and men take on between 1600ml-2000ml per day, or 8-10 cups of water (1 cup = 200ml) per day. This is about right. Drinking at regular intervals throughout the day is the best way to ensure you stay hydrated. As stated above, your urine is the best indicator of your personal hydration status. Keep an eye on the colour of your urine; if it is dark, you need to drink more water.

Water is the best drink for hydration. It replaces fluids without adding extra calories or stimulants. People can also get a lot of fluid from the foods they consume too, such as fruit and vegetables (e.g. example, cucumber, celery, iceberg lettuce, tomatoes radishes, bell peppers and many more are full of water). While fruit juices and diet soft drinks also provide fluids, they should be kept to a minimum as they can be harmful to teeth and can be high in sugar and artificial additives. Tea and coffee also contribute to fluid intake and can be a good way of keeping older adults well hydrated. However, if you drink a lot of tea and coffee, you need to be aware of the amount of caffeine you are consuming, as excessive amounts of caffeine can have a diuretic effect. Caffeine is a stimulant which can be mildly addictive and high intakes should be avoided. Decaffeinated and herbal teas are a good alternative.

Older people are vulnerable to dehydration and they may have difficulties accessing drinks. Fear of incontinence may also mean that some elderly people restrict their fluid intake and it is important to be cognisant of this. Older dehydrated people are at particular risk of urine infections and falls and should closely monitor how much they drink during hot weather. Having regular drinks throughout the day will help you stay well hydrated, especially when it is hot or if you are exercising and regularly monitoring your urine output should help to gauge how well hydrated you are.

For more information on healthy eating guidelines in Ireland, click here.

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Do I need to take Vitamin and Mineral Supplements?

Maria O’Sullivan

Most recommendations, agree that adults do not need to take vitamin and mineral supplements, or multivitamin products (unless specifically indicated on an individual basis by a health professional); The World Cancer Research Fund (WCRF), for example, are very strong on their message on this for cancer prevention – the advice is not new, and perhaps may sound mundane, but ’eat food not supplements’ and aim to get your vitamin and minerals through a varied healthy diet. Their website is a source of good source of well-evidenced simple diet and lifestyle messages for health: See:

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Do I need to take vitamins for bone health or for osteoporosis?

Maria O’Sullivan

One area of concern is maintaining bone health through adulthood, and both physical activity and adequate vitamin D and calcium are important here. Adults, in Ireland for example, would tend to be prescribed a vitamin D and calcium supplement if osteoporosis is detected or earlier signs of osteoporosis were noted. Some recommendations on vitamin D vary, in Ireland a low dose supplement of vitamin D is actually recommended (10µg per day for people aged 51 years and over) – Ireland and other northern countries don’t get enough sunlight to make vitamin D especially from November to March/ April. We are actually studying much higher doses of vitamin D 3 in adults aged 65+, to see if it may be associated with better brain health and muscle function, but that is still very much really at a research level, and cannot yet recommend these higher doses. See these guidelines for more information.

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So it’s all just moderation and fruit and veg then?

Maria O’Sullivan

The ‘moderation message’ often seems like a ‘common sense’ or a less exciting message. And it is not going to make the headlines like the next new fad. If anything the science highlights even more so that moderation along with Mediterranean and plant-rich type diets seem to have multiple benefits including newer aspects such as promoting positive effects on gut flora (microbiome) as well as preventing common chronic diseases. The evidence now, for example, also shows that diet and lifestyle approaches aimed at preventing cardiovascular disease are also strategies for promoting brain health and cognitive function – the adage of “heart and mind – what’s good for the heart is good for the brain”. But along with all the other lifestyle approaches, such as exercise, social activities and engagement.

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  • If there is any message, it is beware of fads, follow credible information sources and ask questions. We also highlighted that food is an important part of social activities and engagement. And, next week (Week 4) is all about ‘being engaged’.
© Trinity College Dublin
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