Oral Nutritional Supplements (ONS)

Lifestyle Preventative Health and Medications > Oral Nutritional Supplements (ONS)

Oral Nutritional Supplements (ONS)

ONS are sterile liquids, semi-solids or powders that provide macro- and micronutrients. (1) It is usually prescribed to individuals who are unable to achieve their nutrient requirements through whole foods alone. These conditions include:

Malnutrition (2)
Recovering from conditions that increase nutrient requirements such as burns and surgery.(2)

On the other hand, a person might need to consume ONS as sole source of nutrition if he or she has dysphagia requiring tube feeding. Hence, they may be prescribed in an acute setting as short-term or in long-term chronic conditions.

To encourage intake or compliance, there are different flavours of ONS available. Adult supplementary formulas can be classified into many categories according to their nutrient profiles and indications. Some provide complete nutrition while others might be lacking in some nutrients or only provide certain nutrients. The table below shows the types of common formulas and their general characteristics.

Formula Type	General Characteristics
Polymeric formulas	Contain non-hydrolysed macronutrients (carbohydrate, protein, fat) Caloric density: 1 to 2kcal per millilitre (ml) Complete and balanced formulas. May be taken as the sole source of nutrition Some contain fibre to promote digestive health and bowel movement regularity
Disease-specific formulas
Diabetes/glucose intolerance	Lower content of carbohydrate and glycaemic index (GI) Added fibre Complete and balanced formulas. May be taken as the sole source of nutrition
Renal	Low in water in content Lower electrolytes such as sodium, potassium and phosphate Can be either high or low in protein contents for patients with or without dialysis respectively Caloric density: 1.8 to 2kcal per ml Complete and balanced nutrition for renal patients May be suitable for renal patients with significant electrolyte abnormalities
Pulmonary	Higher in calories and protein Lower in carbohydrate and higher in fat content Complete and balanced nutrition Not the first choice among all patients with pulmonary diseases, unless indicated
Cancer	Higher in calories and protein Added with omega-3 fatty acids (EPA) Not complete balanced nutrition Not the first choice among all patients with cancers. May be beneficial in patients with advanced cancer undergoing chemotherapy and at risk of weight loss or malnourished
Pre-digested/semi-elemental formulas	Contain pre-digested/hydrolysed macronutrients to optimise nutrient absorption Complete and balanced formulas May be suitable for patients with severe malabsorption and maldigestion but not for routine use
Hepatic	Higher in calories Lower in aromatic amino acids (AAAs) and higher in branch-chain amino acids (BCAAs) Lower sodium content Not complete balanced nutrition Not the first choice among all patients with liver diseases, unless indicated
Modular formulas	Come in single macronutrient (carbohydrate, protein, fat or fibre) Unable to rely as the sole source of nutrition as they are nutritionally incomplete
Fruit juice-like formulas or clear fluids	Suitable for patients on clear fluid diet Low residue Fat free Unable to rely as the sole source of nutrition as they are nutritionally incomplete

Note. Adapted from “New guidelines on nutrition support for the critically ill,” by Corrigan ML, 2016, Today’s Geriatr Med, 9(6):8-9 and “Enteral nutrition formula selection: Current evidence and implications for practice,” by Brown B, Roehl K, Betz Melanie, 2016, ASPEN Nutr in Clin Pract., 30(1):72-85.

The use of ONS may improve certain medical outcomes, for instance, reducing the length of stay in hospital, medical cost, hospital readmission rate, when they are used appropriately in certain medical conditions. (2) Upon initiation, there should be close monitoring done by the dietitians or doctors to monitor the effectiveness of ONS and to prevent any complications related to overfeeding such as biochemical derangements. Therefore, individuals should consult the dietitians for a thorough assessment and proper prescription before choosing ONS, especially the disease-specific formulas.

References
1. BAPEN. Oral Nutritional Supplements (ONS). 2016. http://www.bapen.org.uk/nutrition-support/nutrition-by-mouth/oral-nutritional-supplements. Assessed February 18, 2017.
2. McClave SA, Taylor BE, Martindale RG, et al. Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: Society of Critical Care Medicine (SCCM) and American Society for Parental and Enteral Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr. 2016;40(2):159-211.
3. Corrigan ML. New guidelines on nutrition support for the critically ill. Today’s Geriatr Med. 2016;9(6):8-9.
4. Brown B, Roehl K, Betz Melanie. Enteral nutrition formula selection: Current evidence and implications for practice. ASPEN Nutr in Clin Pract. 2016;30(1):72-85.

Take home messages:

Use fiber supplementation first, prior to using long term laxatives
Drink plenty and stay hydrated when using laxatives
Avoid stimulant laxatives if possible.
If you continue to have problems with constipation, please consult your doctor. Constipation maybe a warning sign of a more serious problem such as hypothyroidism, colon cancer or diabetes, amongst others.