What is ONS (Oral Nutritional Supplements)?
ONS are pre-packaged, energy and nutrient-dense medical nutrition products—available as liquids, powders, desserts, or bars—designed to supplement dietary intake when regular food alone cannot meet nutritional requirements. 1
Definition and Classification
ONS are classified as "foods for special medical purposes" (FSMPs) under EU legislation and must be used under medical supervision. 1 They are developed to provide concentrated energy and nutrients in forms including:
- Ready-to-drink liquids (also called "sip feeds") 1
- Powders that can be prepared as drinks or added to foods 1
- Cremes, desserts, and bars 1
Types of ONS
Nutritionally Complete ONS
These products contain balanced macro- and micronutrients, including essential amino acids, essential fatty acids, and micronutrients that reflect dietary recommendations. 1 They can serve as the sole source of nutrition for prolonged periods, though they are typically used to supplement regular diet. 1
Nutritionally Incomplete ONS
These are disease-specific formulations modified to contain certain nutrients in higher amounts while lacking or having insufficient amounts of others. 1 They are adapted for specific conditions such as diabetes, pressure ulcers, cirrhosis, cancer, renal failure, and pulmonary disease. 1
Clinical Indications and Evidence
When to Use ONS
Older persons with malnutrition or at risk of malnutrition should be offered ONS when dietary counseling and food fortification are insufficient to increase dietary intake and reach nutritional goals. 1
Specific populations that benefit from ONS include:
- Hospitalized older adults: ONS improve dietary intake, body weight, and lower risk of complications and readmission (Grade A recommendation) 1
- Post-discharge patients: ONS improve dietary intake, body weight, and lower risk of functional decline (Grade A recommendation) 1
- Persons with dementia and malnutrition: ONS should be offered to improve energy and protein intake and maintain nutritional status (Grade A recommendation) 1
Dosing Recommendations
ONS offered to older persons with malnutrition should provide at least 400 kcal/day including 30 g or more of protein/day. 1 The American College of Nutrition recommends ONS as the first-line intervention when artificial nutrition is indicated. 2
Important Limitations
ONS should NOT be used in persons with dementia to correct cognitive impairment or prevent further cognitive and functional decline (Grade B recommendation, 100% consensus). 1 Multiple RCTs using MMSE as the cognitive assessment tool showed no beneficial effects on cognitive outcomes. 1
Clinical Effectiveness
ONS have well-established clinical effects and cost-effectiveness. 1 In hospitalized malnourished older patients, specialized ONS improve handgrip strength, which correlates with improved nutritional status and activities of daily living. 3 In residents requiring texture-modified diets, ONS significantly increase energy, protein, carbohydrate, and fat intake, helping meet protein requirements though energy targets may still fall short. 4
Practical Considerations
Patients may require supervision and support when consuming ONS, particularly those with dementia. 1 Compliance depends on product, context, and person-related factors—community-dwelling persons take ONS to prolong independence, while care home residents focus on quality of life improvements. 5 The majority of users consume ONS based on physician or dietician prescription due to trust in professional advice. 5