Oral Nutritional Supplements in Illness and Recovery

Oral nutritional supplements, often called ONS, are commercially prepared, nutrient-dense drinks or semi-solid products designed for people who cannot meet their calorie and protein needs through regular food alone. The clinical evidence behind them is stronger than many people expect: in malnourished hospitalized adults, ONS have been shown to cut 90-day mortality roughly in half and reduce hospital readmissions by a third or more. The benefits extend well beyond keeping weight on, reaching into wound healing, muscle preservation, pediatric growth, and even health-system economics.

Fewer Hospital Readmissions and Lower Mortality

The most striking evidence for ONS comes from studies tracking what happens after malnourished patients leave the hospital. A randomized trial in older malnourished adults compared a high-protein supplement containing the amino acid metabolite HMB against a placebo. The 90-day mortality rate was roughly half in the supplement group compared with placebo: about 5% versus 10%, with a number-needed-to-treat of about 20 to prevent one death. Patients taking the supplement also showed better nutritional status and gained more weight within the first month.¹

Readmission rates tell a similar story. At one U.S. academic medical center, malnourished patients who received ONS during their hospital stay had nearly 39% fewer 30-day readmissions than similar patients who did not receive them. Among cancer patients specifically, the reduction was even larger, approaching 46%.² A separate analysis of older hip-fracture patients found that those assigned to ONS had lower hospital readmission rates during follow-up: about 18% in the supplement group versus 44% in the control group when the analysis was restricted to participants who actually adhered to the protocol.³

These are not marginal differences. The consistent direction across different patient populations and study designs makes a persuasive case that for people who are genuinely malnourished or at nutritional risk, ONS after hospitalization carry real clinical weight.

Wound Healing and Surgical Recovery

Healing tissue demands extra protein, calories, and specific micronutrients. When a patient is malnourished, the body simply does not have the building blocks to close wounds efficiently. ONS formulated with arginine, zinc, and antioxidants have shown meaningful effects on pressure ulcers, which are common in long-term care residents who spend extended time in bed or wheelchairs.

In one study of long-term care residents with pressure ulcers, nine weeks of specialized nutritional support reduced ulcer area by about 53%, and one in five ulcers achieved complete closure within that period.⁴ A randomized trial comparing an enriched formula (with added arginine, zinc, and antioxidants) to a standard control formula found the enriched version shrank ulcer area by about 61%, versus 45% for the control. Patients on the enriched formula were roughly twice as likely to achieve a 40% or greater reduction in wound size at eight weeks.⁵

In surgical settings, the evidence follows a similar pattern. A systematic review found that supplements containing arginine and omega-3 fatty acids improved wound healing in head and neck cancer patients after surgery, reducing postoperative complications and shortening hospital stays.⁶ The takeaway for caregivers and patients is that standard protein shakes may not be enough when wound healing is the goal; formulas designed with wound-specific nutrients can outperform generic options.

Preserving Muscle During Bed Rest and Illness

One of the quieter dangers of hospitalization, injury, or prolonged illness is rapid muscle loss. Healthy older adults can lose significant lean body mass in as little as ten days of bed rest. This loss is not just cosmetic; it compromises the ability to stand, walk, and recover independence.

Two studies have examined whether specific nutrients can blunt this effect. In one trial, healthy older adults confined to bed for ten days received either HMB (a metabolite of the amino acid leucine) or a placebo. The placebo group lost an average of about 2 kg of lean body mass. The HMB group, by contrast, experienced essentially no loss.⁷ A related study in middle-aged adults tested leucine supplementation during bed rest. Leucine cut leg strength loss roughly in half, preserved muscle quality over two weeks, and slowed lean mass loss in the first week, though the protection faded somewhat by day fourteen.⁸

For people already diagnosed with sarcopenia (the age-related loss of muscle mass and function), the picture is more nuanced. A trial comparing an enriched ONS to a conventional control in sarcopenic, malnourished older adults found that both groups improved in strength and gait speed, and the enriched formula did not consistently outperform the control. The exception was a subgroup with mild-to-moderate sarcopenia and normal grip strength, where the enriched formula produced greater strength gains at 12 weeks.⁹ The lesson here is that ONS seem most protective when used early, before severe muscle wasting has set in, rather than as a late rescue.

ONS for Children With Faltering Growth

Oral nutritional supplements are not just for adults. Pediatric ONS are designed for children who are underweight, failing to gain weight at expected rates, or recovering from illness. The evidence in children, while smaller in volume than the adult literature, consistently points toward improved growth when ONS are added to the diet.

A systematic review and meta-analysis of trials in children with or at risk of faltering growth found that ONS use was associated with an extra 0.4 kg of weight gain and 0.3 cm of additional height compared with controls.¹⁰ These are modest-sounding numbers in isolation, but for a child who has stalled on a growth curve, that bump can represent the difference between catching up and falling further behind.

Energy density matters for younger patients. A pilot trial comparing an energy-dense pediatric ONS (2.4 kcal per mL) to a standard-density formula found that the denser product improved nutrient intake, growth, and, perhaps surprisingly, appetite.¹¹ A study of underweight children aged 5 to 14 with short stature confirmed this pattern: the concentrated formula produced significantly greater weight gain, improvements in BMI, and increases in IGF-1, a growth-related hormone, compared with a standard-calorie version.¹² The logic is straightforward: a child who can only tolerate small volumes benefits from packing more nutrition into each sip.

For children with diarrheal illness, the formulation specifics shift. A systematic review found that supplements high in zinc and fiber, along with products based on yogurt or lactose-free milk, had the best outcomes in managing diarrhea and supporting recovery.¹³

Appetite in Older Adults With Poor Intake

A common concern among caregivers is that giving someone a supplement drink will spoil their appetite for meals, creating a cycle where the supplement replaces food rather than adding to overall intake. The data suggest this worry is mostly unfounded. A meta-analysis of randomized trials in older adults with anorexia found that ONS increased overall energy intake, protein intake, and fat intake without significantly reducing appetite for meals. Body weight and BMI also improved. The analysis did find a modest improvement in overall appetite and consumption scores, though individual appetite dimensions like hunger or desire to eat did not change much on their own.¹⁴

In practical terms, this means ONS tend to add calories on top of whatever the patient is already eating rather than displacing meals. That said, the benefit depends on the patient actually drinking the supplement, which brings us to one of the most underappreciated barriers in nutritional care.

Why So Many People Stop Taking Them

Prescribing or recommending an ONS is one thing; getting a patient to drink it consistently is another. Adherence is a persistent problem, and the reasons are both physiological and sensory. In gastrointestinal cancer patients, the main reasons for dropping ONS include symptoms like early satiety, bloating, and diarrhea after consumption, along with taste changes that make the supplement unpleasant.¹⁵

A broader literature review identified several categories of factors that influence whether people stick with their supplement. Personal factors, including age-related sensory changes and overall motivation, shape how the product tastes and how willing the person is to keep drinking it. The product itself matters too: undesirable off-flavors often stem directly from the nutritional ingredients that make the supplement effective, creating a tension between palatability and potency that manufacturers constantly try to resolve.¹⁶

If you are caring for someone who dislikes their ONS, a few practical strategies can help: try different flavors or brands, serve the supplement chilled (cold masks off-notes better than room temperature), and offer it between meals rather than alongside food. Switching from a standard-volume product to a low-volume, energy-dense version can also help, because the patient has less liquid to get through.

Does Timing of Delivery Matter?

A popular approach in hospitals and care homes is called MEDPass, where a small amount of ONS is given alongside each medication round rather than as a standalone drink between meals. The idea is that integrating supplements into an existing routine will boost intake. A randomized trial testing this head-to-head with conventional between-meal delivery found no meaningful difference in energy or protein coverage, daily ONS intake, or 30-day mortality between the two approaches.¹⁷ A secondary analysis of the same trial confirmed that MEDPass was not superior regardless of patients’ nutritional risk level or baseline nutritional status.¹⁸

This is actually reassuring. It means you can fit supplements into whatever schedule works best for the patient or the care setting without worrying that you are sacrificing effectiveness. If someone responds better to small sips with their pills, that works. If they prefer a full serving mid-morning and mid-afternoon, that works too.

The Economic Case for ONS

Even for people who accept that ONS help patients recover, the cost question looms. Hospital supplements are not free, and insurance coverage varies. But the economics are more favorable than you might guess, because the biggest cost in healthcare is not the supplement itself; it is the hospital readmission it may prevent.

A U.S.-based economic model estimated that providing ONS to older malnourished patients after discharge would cost roughly $175 per patient per month. Across an estimated population of about 1.7 million older patients at nutritional risk, this would prevent an estimated 117,000 readmissions per year, saving roughly $1.9 billion after accounting for the cost of the supplements themselves. The cost per readmission avoided was about $2,500, and the cost per death avoided was about $4,400.¹⁹

In the UK, a separate analysis of malnourished care home residents found that ONS were cost-effective compared with dietary advice alone. The extra cost per quality-adjusted life year gained was about £11,000, well below the threshold typically considered a good use of healthcare resources. The probability of cost-effectiveness remained above 80% across sensitivity analyses.²⁰ For healthcare systems that are hesitant to pay for supplements, this is the argument that often changes minds: the per-patient cost of ONS is a rounding error compared to one avoided readmission.

Swallowing Difficulties and Texture-Modified Products

Many people who need nutritional support also have trouble swallowing, particularly after a stroke. Standard thin liquids can be dangerous for these patients because the fluid can slip into the airway before the swallow reflex activates. Texture-modified supplements, thickened with agents like xanthan gum, address this by slowing the liquid’s flow and giving the throat more time to close off the airway.

In post-stroke patients with swallowing dysfunction, a comprehensive management approach that included xanthan gum-based thickened fluids was associated with reduced risk of aspiration and aspiration pneumonia while maintaining adequate nutrition and hydration. Instrumental swallowing assessments confirmed improved function over time.²¹ If you are managing nutrition for someone with dysphagia, working with a speech-language pathologist to determine the right consistency is essential. The “right” supplement is not just about calories and protein; it is also about whether the person can safely get it down.

Specialized Medical Nutrition for Cognitive Decline

An emerging and somewhat surprising branch of ONS research involves products designed not for general malnutrition but for specific neurological conditions. One product, Souvenaid, contains a combination of omega-3 fatty acids, uridine monophosphate, choline, phospholipids, B vitamins, and antioxidants. The rationale is that these nutrients are precursors to the phospholipids that make up neuronal membranes and synapses, and that people with Alzheimer’s disease may have heightened requirements for them.

Two randomized controlled trials in patients with mild Alzheimer’s who were not yet on medication found that this nutrient combination improved memory performance. Electroencephalography data from one of the trials also suggested changes in brain connectivity, a marker that the supplement was affecting synaptic function rather than acting purely as a placebo.²² These products occupy an interesting regulatory gray zone. In the United States, they are classified as medical foods rather than drugs or dietary supplements, which means they are intended for use under medical supervision but do not go through the same approval process as pharmaceuticals. The distinction trips up patients and clinicians alike, and the regulatory framework continues to evolve.

The cognitive-health applications are still early-stage relative to the well-established evidence for malnutrition-related ONS. But they illustrate how far the concept of “nutritional supplement” has traveled from the original protein-and-calorie shake, and they are worth watching for anyone interested in non-pharmacological strategies for neurodegenerative disease.