Oral Nutritional Supplement – Definition and Uses

What Are Oral Nutritional Supplements?

Oral nutritional supplements (ONS), commonly known as nutritional drinks or medical nutrition drinks, are specially formulated liquid, semi-liquid, or creamy products used in clinical nutrition therapy. They are designed to deliver a concentrated source of macronutrients and micronutrients in an easily consumable form. ONS are prescribed or recommended when a person is unable to meet their daily nutritional requirements through regular meals alone.

Types and Composition

Oral nutritional supplements are available in a wide range of formulations tailored to specific medical needs:

• High-calorie ONS: Provides a large number of calories in a small volume, ideal for patients with severely reduced appetite.
• High-protein ONS: Contains an elevated protein content, particularly beneficial for wound healing, muscle wasting, or post-surgical recovery.
• Diabetes-specific ONS: Features a modified carbohydrate profile designed for patients with diabetes mellitus.
• Renal-specific ONS: Has reduced levels of phosphorus, potassium, and protein, suitable for patients with chronic kidney disease.
• Complete/balanced ONS: Can serve as the sole source of nutrition, covering all essential nutrient requirements.

When Are Oral Nutritional Supplements Used?

ONS are recommended by physicians and dietitians across a wide range of clinical conditions, including:

• Malnutrition or risk of malnutrition
• Unintentional weight loss and cachexia (severe muscle and fat wasting)
• Swallowing difficulties (dysphagia), where solid food is difficult or unsafe to swallow
• Chronic diseases such as cancer, inflammatory bowel disease (Crohn's disease, ulcerative colitis), or COPD
• Pre- and post-operative nutritional optimization
• Elderly patients with reduced appetite or increased nutritional demands
• Neurological conditions such as dementia or stroke

Benefits of Oral Nutritional Supplements

Compared to other forms of medical nutrition support such as enteral tube feeding or parenteral nutrition, ONS offer several advantages:

• They can be consumed orally, supporting natural digestion and gut function.
• They are available in a variety of flavors, making long-term use more manageable.
• They do not require invasive procedures such as nasogastric tube placement.
• They can supplement regular meals or serve as a complete nutritional replacement depending on clinical need.

Usage and Dosage

The quantity and frequency of ONS intake is determined individually by a physician or registered dietitian. As a general guideline, 1 to 3 servings per day are commonly recommended, depending on the individual caloric needs and degree of nutritional deficit. ONS should be sipped slowly and, where possible, used in addition to regular meals rather than as a complete replacement. They may be consumed chilled or at room temperature according to personal preference.

Potential Side Effects and Considerations

Oral nutritional supplements are generally well tolerated. However, some individuals may experience:

• Nausea or bloating, especially when consumed too quickly
• Diarrhea, particularly with high-fat formulas or in cases of lactose intolerance (lactose-free options are available)
• Taste fatigue with long-term use (switching between flavors is recommended)

ONS are classified as Foods for Special Medical Purposes (FSMP) and are subject to strict regulatory standards within the European Union regarding composition, labeling, and safety.

References

1. Arends J. et al. – ESPEN Guidelines on Nutrition in Cancer Patients. Clinical Nutrition, 2017.
2. Volkert D. et al. – ESPEN Guideline on Clinical Nutrition and Hydration in Geriatrics. Clinical Nutrition, 2019.
3. World Health Organization (WHO) – Malnutrition Fact Sheet, 2021. Available at: https://www.who.int