Oral nutritional supplements

Definition and Scope
Oral nutritional supplements (ONS) are commercially formulated products designed to provide macronutrients (carbohydrates, proteins, fats) and micronutrients (vitamins, minerals) in a concentrated, easy-to-consume form. They are typically administered orally to individuals who are unable or unwilling to meet their nutritional requirements through normal diet alone. These supplements are used in a variety of clinical and non-clinical contexts, including malnutrition, chronic illness, recovery from surgery or trauma, and age-related anorexia.

ONS may be standard (polymeric), elemental (monomeric), disease-specific, or modular (single nutrient-focused). While not classified as drugs, they are regulated under food and nutrition legislation in most jurisdictions and may be prescribed or recommended medically as part of nutritional support therapy.

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1. Mechanism of Action and Purpose

ONS do not act pharmacologically in the traditional sense; instead, they:

• Prevent or treat malnutrition by correcting nutrient deficiencies

• Provide adequate energy and protein to maintain or restore lean body mass

• Support immune function, wound healing, and metabolic recovery

• Serve as adjuncts in patients with chronic disease, gastrointestinal disorders, or after surgery

Mechanistically, their benefit lies in nutritional bioavailability and enhanced nutrient absorption, especially when natural intake is compromised.

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2. Types of Oral Nutritional Supplements

Category	Description
Standard/polymeric	Contain intact proteins, complex carbs, and long-chain fats. Require digestion
Elemental/monomeric	Contain amino acids, simple sugars, and MCTs. Used in malabsorption
Semi-elemental	Partially hydrolyzed proteins and lipids; moderate digestibility
Disease-specific	Tailored for conditions like diabetes, CKD, liver failure, COPD, cancer
High-protein	For catabolic states, wound healing, sarcopenia
Immune-enhancing	Enriched with arginine, nucleotides, omega-3s, antioxidants
Fiber-enriched	Includes soluble/insoluble fiber to support GI health
Modular supplements	Single nutrients (e.g., protein powders, carbohydrate gels, MCT oil)

3. Commonly Used Oral Nutritional Supplements

Brand Name	Manufacturer	Indication
Ensure	Abbott	General supplementation, elderly, chronic illness
Boost	Nestlé Health Science	Malnutrition, cancer, aging
Fortisip	Nutricia	Disease-related malnutrition
Resource	Nestlé Health Science	Standard and disease-specific nutrition
Jevity	Abbott	Fiber-enriched nutritional support
Glucerna	Abbott	Diabetes-specific formulation
Nepro	Abbott	Renal nutrition (CKD, dialysis patients)
Oxepa	Abbott	Critically ill, pulmonary disease
Prosure	Abbott	Cancer-related cachexia
HMB-enriched	Various (e.g., Ensure Enlive)	Muscle preservation, sarcopenia

4. Formulations and Routes of Administration

• Liquids (most common) – ready-to-drink or powdered to mix with water/milk

• Puddings – for patients with dysphagia or altered texture requirements

• Powdered mixes – protein powders, fiber powders, carbohydrate boosters

• Capsules/tablets – used in specific micronutrient deficiencies (e.g., iron, vitamin D)

• Specialized gels or bars – useful for sports nutrition or modular approaches

All are administered orally, typically 1–3 times daily, depending on patient needs and clinical goals.

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5. Clinical Indications

Use Case	Indication
Geriatric nutrition	Age-related anorexia, frailty, falls prevention
Chronic illness	COPD, cancer, heart failure, kidney disease
Pre- and post-operative nutrition	Surgical patients with increased metabolic demand
Malabsorption syndromes	IBD, short bowel, pancreatic insufficiency
Wound healing	Pressure ulcers, burns, trauma
Neurological disease	Stroke, ALS, Parkinson’s (with swallowing difficulties)
Sports and recovery nutrition	Muscle recovery, endurance performance
Post-COVID cachexia or recovery	Restoration of lean mass and function
Eating disorders	Controlled refeeding strategies

6. Composition and Nutrient Content

Macronutrient	Range per serving
Energy	200–400 kcal (per 200–250 mL serving)
Protein	8–20 g (whey, casein, soy, pea protein)
Carbohydrates	20–45 g (maltodextrin, glucose polymers)
Fats	5–15 g (MCT, sunflower oil, canola oil)
Fiber	0–6 g (soluble and insoluble types)
Micronutrients	Complete RDA for 20+ vitamins/minerals

Some advanced formulations include:

• Omega-3 fatty acids (EPA, DHA)

• L-arginine, HMB (beta-hydroxy-beta-methylbutyrate) for muscle protection

• Prebiotics and probiotics for gut health

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7. Pharmacokinetics and Absorption

ONS do not exhibit pharmacokinetics in the classical sense but rely on:

• Gastrointestinal absorption

• First-pass metabolism of nutrients (especially amino acids and carbohydrates)

• Bioavailability depending on individual gut function, presence of food, or disease state

Patients with severe GI dysfunction (e.g., severe IBD, short bowel syndrome) may not fully absorb ONS and require enteral/parenteral support.

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8. Contraindications and Cautions

Condition	Consideration
Severe milk/soy allergy	Many ONS contain dairy or soy derivatives
Renal impairment	Protein and electrolyte content must be adjusted
Hepatic encephalopathy	Consider branched-chain amino acid (BCAA) formulations
Diabetes mellitus	Use low glycemic index products (e.g., Glucerna)
Phenylketonuria (PKU)	Avoid phenylalanine-containing formulations
Congestive heart failure	Monitor fluid load in high-volume liquid supplements

9. Adverse Effects and Tolerability

ONS are generally well-tolerated, but potential adverse effects include:

• Gastrointestinal: bloating, gas, diarrhea, or constipation

• Taste fatigue: long-term use may reduce adherence

• Hypersensitivity: rare allergic reactions to protein sources (whey, casein, soy)

• Hyperglycemia: in patients with impaired glucose tolerance or diabetes

• Hyperphosphatemia or hyperkalemia: especially in renal impairment if not tailored

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10. Monitoring and Outcome Assessment

Clinical benefit should be monitored through:

Parameter	Monitoring Guidance
Body weight and BMI	Monitor weekly or bi-weekly
Serum albumin/prealbumin	Reflects nutritional status (note: not always reliable in inflammation)
Dietary intake logs	Ensures compliance and sufficiency
Muscle mass and strength	Handgrip strength, lean body mass (DEXA/BIA)
Clinical function	Functional recovery (mobility, ADL independence)

11. Drug Interactions

Though generally safe, some considerations exist:

Drug	Interaction
Levothyroxine	Absorption may be impaired by calcium/iron in supplements
Ciprofloxacin, tetracyclines	Chelation with calcium or magnesium in ONS may reduce absorption
Warfarin	Vitamin K-containing ONS can affect INR
Phenytoin	Protein content may alter absorption
ACE inhibitors, ARBs	Monitor potassium if using potassium-rich ONS in renal patients

12. Dosing and Administration Guidelines

Population	Dosing Recommendation
Adults (general)	1–3 servings/day (200–250 mL/serving)
Elderly/frail	Start with 1–2/day; monitor GI tolerance
Post-surgery or burns	Higher protein demand: 2–3 servings/day
Renal disease	Adjust fluid and electrolytes; use renal-specific ONS
Children	Pediatric-specific formulations required

Best administered between meals to avoid appetite suppression and to optimize nutrient intake from natural meals.

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13. Examples of Disease-Specific ONS

Condition	Formulation Used
Diabetes	Glucerna, Resource Diabetic
Kidney disease	Nepro, Suplena
COPD	Oxepa (high-fat, low-carb)
Cancer cachexia	Prosure (with EPA), Resource Support
Sarcopenia	Ensure Enlive (HMB, vitamin D, high-protein)
IBD/malabsorption	Elemental formulas (e.g., Peptamen, Vital 1.5)

14. Clinical Guidelines and Recommendations

• ESPEN and ASPEN recommend ONS for patients at risk of or with existing malnutrition

• ONS should be used as part of a structured care plan involving a dietitian or clinician

• Must be combined with education, monitoring, and follow-up for effectiveness

• Cost-effectiveness proven in reducing hospital admissions, pressure ulcers, and mortality in malnourished patients

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15. Regulatory Status and Reimbursement

• Categorized as “food for special medical purposes” (FSMP) in EU and similar terms in U.S./Canada

• Require dietitian or physician prescription in some health systems for insurance reimbursement

• Quality and safety overseen by EFSA, FDA, or local food/drug authorities

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16. Future Trends and Innovations

• Personalized nutrition platforms integrating genomics and AI

• Plant-based ONS to meet vegan/vegetarian dietary needs

• Development of low-FODMAP and allergen-free formulations

• Use of bioactive peptides and functional ingredients (e.g., curcumin, collagen)

• Sustainable packaging and production methods in alignment with global health goals