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Don’t be green when it comes to adult nutrition

By Irish Pharmacist - 01st Feb 2024

A good diet is vital for immunity, safer pregnancy, lowering the risk of suffering many diseases, and longevity, writes Damien O’Brien

Nutrition is the intake of food to meet the body’s dietary needs and it is essential for good health. Nutrition impacts the development process of each individual at every stage of their life cycle from conception to death, but this article focuses on nutrition in adulthood. Good nutrition is vital for immunity, safer pregnancy, lowering risk of many diseases and longevity. Inadequate nutrition can lead to lowered immunity, increased susceptibility to disease, impaired physical development, impaired mental development and reduced productivity. Malnutrition encompasses undernutrition and overnutrition. Undernutrition is defined as a lack of nutrients, with overnutrition defined as a surplus of nutrients in the diet. Both can cause many health problems and present a significant morbidity and mortality burden.

What is good nutrition?

Good nutrition for an adults encompasses a diet where macronutrients are consumed in appropriate proportions to allow energetic and physiological requirements to be fulfilled, without excess intake. In addition to this, a good nutritional diet will provide sufficient micronutrients and hydration to meet physiological requirements of the body. Macronutrients include carbohydrates, fats and proteins, which supply the energy necessary for the cellular processes required for daily functioning. Micronutrients are the vitamins and minerals, which are required in small amounts for normal growth, development, metabolism and physiological functioning.

Additionally, water is the principal component of the body – accounting for the majority of lean body mass and total body mass. Water provides essential hydration for the body, as well as carrying micronutrients and electrolytes. Furthermore, water can provide up to 20 per cent of the recommended daily intake of minerals such as calcium and magnesium.

Non-communicable diseases (NCDs) are one of the leading causes of death and disability in the world. NCDs include many diseases including certain cancers, cardiovascular disease, respiratory disease, diabetes, obesity and cognitive impairment. Although several environmental and genetic factors contribute to the risk of developing NCDs, modifiable lifestyle-related factors, including nutrition, contribute to this risk. The rise observed in chronic NCDs in recent years has a causal link to dietary patterns that are characterised by high levels of processed food, saturated fats, refined grains, salt and sugars, while lacking in fruits and vegetables. There are several health benefits associated with good nutrition in adults and include:

  • Longer life;
  • Healthy skin, teeth, eyes and muscles;
  • Boosts immune system;
  • Supports healthy pregnancy and breastfeeding;
  • Strengthening of bones;
  • Lowers risk of cardiovascular disease, type 2 diabetes and certain cancers;
  • Improves functioning of the digestive system;
  • Maintaining a healthy body mass.


Malnutrition is a significant problem globally. Undernutrition occurs when the body does not obtain sufficient macronutrients and micronutrients required for normal functioning of the body. Overnutrition occurs when the body obtains excessive nutrition. Both of these can cause big health-related issues. Undernutrition causes depletion of fat and muscle mass, while it can also affect cardiac, respiratory and gastrointestinal function. Furthermore, it can reduce the immune system and impair wound healing. Overnutrition often leads to an individual being overweight or obese, which has proved to be a huge burden for health systems in recent years. Obesity is a risk factor for many conditions including certain forms of cancer, type 2 diabetes and cardiovascular disease.


Carbohydrates, proteins and fats are the macronutrients required for cellular processes in the body. They each have a unique set of properties that has an influence on an individual’s health. They all play a vital role in the body and adequate nutrition involves an appropriate intake of all these macronutrients.


Proteins are large molecules that are an agglomeration of one or more amino acid chains. The defining characteristics of protein, from a nutrition point of view, is the amino acid composition. Amino acids are linked by peptide bonds. These peptide bonds are hydrolysed in the stomach by hydrochloric acid and protease enzymes, to allow the absorption of essential amino acids. Protein is an essential nutrient in the human body for growth and maintenance of body cells. They are the major structural component of all body cells and are the one of the building blocks of body tissue.

Furthermore, protein is also a fuel source – providing four kilocalories (kcal) or 17 kilojoules (kJ) per gram. Meat, fish, eggs and dairy products are all excellent sources of protein, while plant protein sources include nuts, seeds, legumes, grains and some fruits and vegetables. Adequate dietary protein intake is vital for maintenance of lean body mass throughout adulthood. Brittle nails and hair are often the first sign of a protein deficiency. Other signs can include feeling weak or hungry, mood changes and muscle weakness. Deficiency in protein also leaves an individual prone to stress fractures of the bones. Studies have suggested that increasing daily protein intake can significantly reduce decline in physical functioning in older adults. This reduces the age-related loss of muscle strength and function, as well as reducing the likelihood of developing mobility limitations, which underlines the importance of sufficient protein intake in adults.


Carbohydrates are simple sugars, occurring as monosaccharides or chains of connected monosaccharides, to form disaccharides, oligosaccharides or polysaccharides. The bonds of these chains are either hydrolysed in the digestive tract or are resistant to this hydrolysis, as in the case of dietary fibre. Carbohydrates have numerous important functions in the body. First, they are the primary source of energy in the diet – providing 4kcal or 17kJ of energy per gram. Carbohydrates also are a component of important co-enzymes and genetic material in the body. Dietary fibre is important in maintaining the function of the digestive system. Grains, legumes, fruits and vegetables are all good sources of dietary carbohydrates. Wholegrains are preferred over processed grains, due to the higher fibre and micronutrient content in wholegrains. Various studies have shown a corelation with increased intake of wholegrains and a reduced risk of cardiovascular disease, diabetes, certain cancers, respiratory disease and infectious disease. Studies have suggested that an over-ingestion of simple and refined carbohydrates can affect mood, alertness and cause fatigue. Furthermore, excessive carbohydrates can put individuals at increased risk of developing metabolic syndrome and other metabolic disorders, including type 2 diabetes mellitus.


Fats are composed of glycerol and fatty acids. Fats are a dense source of energy in adults – providing 9kcal or 38kJ per gram. Additionally, fats have an important structural and metabolic role in the body. Furthermore, they are important for the storage of fat-soluble vitamins. Dietary sources of fats include meat, dairy products, eggs, oily fish, nuts and seeds. Four categories of dietary fats exist – monounsaturated fats, polyunsaturated fats, saturated fats and trans fats, with most food sources containing a mix of these categories of fats. Unsaturated fats are associated with a reduced risk of cardiovascular disease and mortality. Meanwhile trans fats and, to a lesser degree, saturated fats are associated with an increased risk of cardiovascular disease and mortality. Omega-3 and omega-6 are essential fatty acids that must be obtained from dietary sources. Some evidence suggests that omega-3 fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have health benefits including cardioprotection, reducing inflammation, improving insulin resistance and preventing cognitive decline. Excessive intake of dietary fat is linked to obesity and problems related to obesity. Additionally, high consumption of fats is considered a risk factor for cardiovascular disease.


Vitamins A, D, E and K are fat soluble vitamins, which means they are easily stored in fat upon absorption. Vitamins B and C are water soluble vitamins, which are not as easily stored in the body and can be eliminated via excretion.

Vitamin A is essential for cellular differentiation, immune function and vision. It can be obtained from the diet from animal sources such as meat, fish and dairy products or from plant sources such as colourful fruits and vegetables. Vision problems is a common manifestation of deficiency. Vitamin A can be toxic if ingested in very large quantities and it is also teratogenic.

The B vitamins are a diverse range of vitamins that are vital in cell metabolism and red blood cell synthesis. There are many B vitamins, including thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9) and cobalamin (B12). Dietary sources of B vitamins include meat, dairy products, eggs, spinach and legumes. The different B vitamins have slightly different functions and therefore, deficiency in the different vitamins can lead to different conditions. Thiamine deficiency can lead to beriberi, which is characterised by heart failure, oedema and dyspnoea. Deficiency of riboflavin can result in cheilosis and corneal vascularisation, while niacin deficiency can lead to pellagra – characterised by diarrhoea, dermatitis and dementia. Deficiency of pantothenic acid is characterised by dermatitis, alopecia and adrenal insufficiency. Reduced dietary ingestion of pyridoxine can result in anaemia, convulsions and peripheral neuropathy, while biotin deficiency can cause muscle pain, heart problems and anaemia. Folate deficiency can lead to neural tube defects during pregnancy and deficiency of cobalamin can lead to pernicious anaemia. Toxicity is rare due to the water solubility of B vitamins, with large doses sometimes causing transient adverse effects including insomnia, restlessness and nausea.

Vitamin C is essential for wound healing, formation of bones, collagen growth, boosting the immune system and absorption of iron. It is found in citrus fruits, berries and other fruits and vegetables. Deficiency can cause scurvy, poor wound healing, bleeding gums and loss of teeth. It is generally well tolerated but ingestion of large doses can cause gastrointestinal pain, headache and skin flushing.

Vitamin D is essential for the maintenance of serum calcium concentration within the normal physiological range for musculoskeletal health. Vitamin D can be obtained through dietary consumption from oily fish, meat, liver, eggs and dairy products. Additionally, it is produced in the skin on exposure to sunlight. Vitamin D deficiency can lead to osteomalacia.

Vitamin E acts as an antioxidant and is important in protecting cells from oxidative stress and regulating immune function. It is found in a wide range of food including nuts, seeds, fish and vegetables. Deficiency of vitamin E can cause issues with the nervous system, but it is very rare and usually only observed in individuals with fat absorption problems.

Vitamin K is essential in maintaining normal coagulation in the body. It is obtained in the diet from green, leafy vegetables, as well as meat and dairy products. Dietary deficiency is also rare with vitamin K, with deficiency usually as a result of malabsorption or pharmacological inhibition. Deficiency can lead to reduced blood clotting, increased bleeding and increased prothrombin time.

There are also several minerals required by adults, in varying quantities, to perform a range of physiological functions to maintain health. These minerals can be ingested from dietary sources or various supplements are available. Iron is vital in red blood cell formation, while calcium is important for bone and dental health. Chloride and sodium are important for regulation of body fluids and electrolyte balance. Magnesium is required for enzyme and muscular function, while potassium is vital in regulating heartbeat and the nervous system. Iodine is important for thyroid function and metabolism.

Role of pharmacist

Community pharmacists are one of the most accessible healthcare professions. The role of the pharmacist is expanding, with opportunities to reduce pressure on the healthcare system. Due to the accessibility and knowledge of pharmacists, they can play a prominent role in disease prevention through patient education on modifiable behaviours, including nutritional intake.

First, pharmacists can counsel patients on vitamin and mineral supplements. They can take a medical history including symptoms, medical conditions and medication being taken. Based on this, pharmacists can give evidence-based advice for the indication, dosing, monitoring and potential adverse effects of supplementation, or refer to another healthcare professional if necessary for further investigations.

The use of oral nutritional supplements (ONS), both over the counter and on prescription, is common, with many different brands with different nutritional content available. These are useful to increase energy and micronutrient intake for patients that may be suffering with undernutrition, particularly in elderly patients or patients recovering from illness. Pharmacists are ideally placed to counsel patients on the appropriate use of these supplements. Additionally, patients with compliance issues can be identified by the pharmacist. These issues could be resolved by changing the patient to a similar product or referring to a dietitian for review if necessary.

Pharmacists also have an important role in identifying potential food-drug and vitamin-drug interactions. There are many food-drug and vitamin-drug interactions that can lead to poor clinical outcomes for the patient. This harm can be due to the effect of the drug being increased, decreased or a new effect being produced. Pharmacists can help in the identification of these interactions due to their drug knowledge and access to patient medication records. Patients that may be most at risk include older patients, use of multiple medications, use of multiple supplements, renal or hepatic impairment and use of medication with a narrow therapeutic index. The pharmacist may be able to determine if the supplement is necessary or if another supplement would be more suitable to limit exposure to potentially harmful drug interactions. l

References upon request






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