What is malnutrition?
Malnutrition is the deficiency, excess or imbalance of energy and or nutrients in our body. Malnutrition can refer to both undernutrition and overnutrition, and can be nutrient specific (for example, a vitamin deficiency or an excess of a particular micronutrient). Overnutrition, or when energy/food intake exceeds energy expenditure (physical activity), leads to fat accumulation and overweight and obesity. The latter are associated with increasing the risk of developing non-communicable diseases such as type 2 diabetes, cardiovascular disease and certain cancers.
Malnutrition occurs more commonly in two groups: 1) infants, particularly from low- and middle-income countries, and in 2) the elderly. It has been estimated that up to 10% of older adults living in the community suffer from malnutrition, and this increases to 40% when considering those in hospital (Kaiser et al. 2010). Undernutrition causes a reduction in physical and psychological health and greater risk of disease, including longer stays in hospital should hospitalisation occur.
Malnutrition in older adults
Older adults are at greater risk of being malnourished because of several predisposing factors and the main cause of malnourishment in older adults is the reduction in the intake of food (and therefore individual, important nutrients). This reduced energy intake may result from a combination of physiological as well as social factors. For example, as we age, we feel less hungry or tempted by food. The loss of appetite results from physiological alterations, such as to levels of hormones involved in the regulation of appetite (e.g. the “hunger hormone” ghrelin) and to disturbances in the sense of smell and taste. Some older adults may also suffer from difficulties swallowing foods, known as ‘dysphagia’ which puts them off eating. Polypharmacy (the use of multiple medications) is more common in the elderly, and some of these medicines may have side-effects including nausea and loss of appetite which further promote malnutrition (via reduced food intake). The elderly are more likely to also suffer from tooth loss and have dentures, which affects the amount and type of foods they may eat. For example, those who relied more heavily on meat as a source of protein and B vitamins may no longer be able to chew such food. Social factors are also important and contribute particularly to undernutrition, for example eating less because they are living on their own or live far away from a supermarket.
Gut health and malnutrition
A primary example of a gastrointestinal disease which increases the risk of malnutrition is inflammatory bowel disease (IBD) i.e. Crohn’s disease and ulcerative colitis (UC) and is one of the main causes of weight loss in patients with this disease. It is estimated that 65-75% of Crohn’s disease patients and up to 62% of individuals with UC experience malnutrition (Scaldaferri et al. 2017). As our guts are pivotal in digesting foods and absorbing the nutrients from them, it won’t come as a surprise to hear that diseases in our guts will affect our risk of malnutrition.
Below are examples of some of the symptoms of Crohn’s disease and/or UC that can contribute to malnutrition:
• Nausea and abdominal pain may reduce appetite
• Bleeding may lead to iron deficiency, and ultimately anaemia, and loss of protein
• Diarrhoea is linked to malabsorption of nutrients and dehydration
The role of the gut bacteria
The bacteria that live in your gut (named the gut microbiota) play a role in health and disease, at least in part by regulating the digestion of particular foods e.g. dietary fibre, absorption of nutrients and elimination of waste products. The types (diversity) and number (abundance) of gut bacteria change as we age, and this can lead to alternations in our gastrointestinal tract (Salazar et al. 2017). As well as changes occurring naturally with age, the gut microbiota may be modified by environmental and lifestyle factors including stress, physical activity and diet. These alterations to the gut microbiota can impair the metabolism and absorption of foods and have more systemic effects, such as reducing immune function and promoting inflammation. Changes to the ratio of ‘good’ to ‘bad’ bacteria and a reduction in the abundance and diversity of the gut bacteria have also been implicated in obesity (a consequence of overnutrition).
Protein malnutrition is an inadequate intake of energy from protein. The incidence of this increases with age and is associated with frailty, sarcopenia and risk of mortality. During ageing, there is a reduction in muscle mass, occurring from around the age of 30 and at rates of up to 5% per decade, known as sarcopenia. Although muscle loss cannot be reversed, this process can be ameliorated by making sure that we eat diets sufficiently high in protein and by being physically active, particularly undertaking resistance training or using weights. Protein malnutrition is one of the main causes of a reduction in the immune system in the elderly, as well as a reduction in the intake of vitamins e.g. C and D (Delafuente 1991).
Malnutrition in the form of excess energy intake coupled with inadequate protein intake and low muscle mass and strength relative to their size (particularly increased fat mass) can lead to sarcopenic obesity (Stenholm et al. 2008). As already described, age-related changes in body composition, including an increase in fat accumulation, occur. The energy balance can also be tipped to favour weight gain due to a reduction in physical activity and in basal metabolic rate with ageing.
Iron deficiency and anaemia
Iron deficiency is the most common nutrient deficiency worldwide and occurs in up to 20% of elderly men and women in the UK (Mukhopadhyay and Mohanaruban 2002). It can result from insufficient intake of protein and iron (e.g. that found in animal products) and/or gastrointestinal disorders that lead to reduced absorption of iron and other minerals. Iron-deficiency anaemia is the most common type of anaemia and is associated with an array of side effects, such as tiredness and shortness of breath, and has particularly debilitating consequences in the elderly e.g. frailty, cognitive impairment and increased risk of falls.
Other common micronutrient deficiencies in the elderly
In the UK, Public Health England advise for the supplementation with Vitamin D during the winter months (British Nutrition Foundation). This is particularly relevant to older adults as our ability to produce vitamin D from sunlight reduces with ageing, and they also tend to expose themselves less to sunlight. Vitamin D and calcium are important for maintaining bone health and deficiencies of these have been linked with an increase in the risk of falls and fractures. Alongside folate, other B vitamins (e.g. B12 and B6) are important for metabolism, including helping with the breaking down and release of energy from foods and transporting nutrients around the body, and a low status may increase the risk of having a stroke and developing dementia.
Treatments for malnutrition
The treatments for malnutrition differ depending on the type of malnutrition and the specific nutrient(s) that the person is deficient in, as well as the predisposing factors or causes of the malnutrition. In older adults with undernutrition, high-calorie foods, particularly in ‘drink’ form to overcome any issues with chewing or swallowing foods, are commonly used. These may focus particularly on certain macronutrients e.g. protein, or micronutrients e.g. vitamin B12. In more extreme cases, feeding may be done directly into blood (parenteral nutrition) or into the stomach (enteral nutrition) via tubes.
The best way to prevent malnutrition is to eat a balanced and diverse diet throughout the lifecourse, and ensure that you drink enough water. In particular, maintaining an adequate protein intake, and undertaking physical activity (particularly incorporating weights into training), will promote the preservation of muscle mass and healthy ageing.
Take home message
We should be able to get sufficient intake of energy, macronutrients (e.g. protein) and micronutrients (vitamins and minerals) from living a healthy lifestyle and eating a balanced diet. However, in some cases, individuals may need to take dietary supplements. For example, women are advised to take folic acid during pregnancy, we are recommended to supplement with vitamin D during the winter months and supplements are often prescribed to those suffering from chronic gastrointestinal diseases. In such cases, it is advised to seek expert opinions from a Dietitian.
This blog post was written by Dr. Fiona Malcomson BSc (Hons) MRes PhD a Research Associate at Newcastle University with a PhD in Molecular Nutrition. Her primary research interest is exploring the relationships between diet and lifestyle factors, and ageing, and markers of large bowel health and of bowel cancer risk. Her research investigates the underlying mechanisms behind these relationships. Fiona is passionate about breaking down complicated science so it’s accessible for everyone and contributing to evidence-based nutritional and lifestyle public health recommendations through her research. You can find her on Instagram @Fiona.Malcomson and twitter @FionaMalcomson
British Nutrition Foundation. Nutrition through life: Older adults.https://www.nutrition.org.uk/nutritionscience/life/older-adults.html?start=3
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