Clinical Evidence Library for Surgeons

Featured research

The strongest evidence, at a glance.

These studies evaluated specific interventions, not the finished GlowWell program.

The physiological problem

Hidden nutritional deficits.

Peer-reviewed estimates suggest that 40% to 65% of patients facing major surgery meet the clinical criteria for malnutrition before their first incision — a metabolic deficit that is rarely identified or managed. Among older adults, this deficit is particularly widespread and is associated with longer length of stay and poorer postoperative outcomes.

In a single-institution cohort of 456 elective surgical patients who underwent formal clinical nutritional assessment, 44% met malnutrition criteria. Only 20% of those were underweight, and only 38% had a low serum albumin — meaning standard screening markers miss the majority of malnourished patients, leaving nutritional risk undetected before major surgery.

Perioperative malnutrition is perhaps the least often identified surgical risk factor and is among the most treatable.

40–65%

of major-surgery patients meet malnutrition criteria before incision (Williams 2019)

44%

of 456 elective patients met criteria on formal assessment (Portuondo 2020)

20%

of those malnourished patients were underweight

38%

of those malnourished patients had low serum albumin

Browse by surgery type

Evidence for your specialty.

Open a specialty to see its professional guidance and every study in the library, strongest designs first, each linked to the original publication.

Browse by clinical outcome

What outcomes has preparation been studied against?

Every effect size comes from the cited publication. Forest plots show the reported estimate and 95% confidence interval; values left of the dashed line favor the prepared group.

Browse by preparation strategy · Part A

Nutritional optimization, and where PREP™ fits.

First, what the published literature actually tested. Then each component of PREP, with the kind of evidence behind it named plainly.

What the research evaluated

Defining validated "nutritional optimization"

Oral Nutritional Supplements (ONS): High-protein, nutrient-dense formulas (e.g., whey protein providing 10–20 grams of amino acids per serving) used to meet increased protein needs during the perioperative period.
Immunonutrition Formulas: Supplements containing arginine, omega-3 fatty acids, glutamine, and nucleotides. A meta-analysis of 37 RCTs (3,793 patients) found immunonutrition reduced length of stay by 1.94 days (95% CI −3.0 to −0.87) and infectious complications (OR 0.58; 95% CI 0.47–0.72) in gastrointestinal cancer surgery.
Protein Targets: ESPEN recommends about 1.5 g/kg/day for surgical patients (roughly 0.7 g per pound). ASPEN/SCCM recommends 1.2–2.0 g/kg/day for critically ill patients.
Micronutrient Support: Vitamin C, vitamin A, and zinc are required co-factors for collagen synthesis and wound healing.

The optimal duration of preoperative nutritional preparation is 7 to 21 days, depending on the degree of nutritional risk.

How to read the table

Three kinds of evidence, kept separate

Nutrient physiology The nutrient's established role in normal body function.
Studied intervention The ingredient appeared in an intervention that was tested in surgical patients. Dose, format, and companion ingredients differed from PREP.
Outcome data · other formulas Clinical outcomes were measured for a different product category. Those results do not transfer to PREP.

PREP has not been evaluated in a clinical outcomes trial. It is designed to deliver nutrients that the perioperative literature focuses on, in a format patients will take daily.

Research category	In each PREP serving	What the library contains	Evidence type

†These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Browse by preparation strategy · Part B

The READY Method™: daily preparation actions, mapped to the literature.

READY organizes surgical preparation into 14 pillars across five steps: Rebuild. Energize. Align. De-Stress. You. Each preparation category below links to the studies in this library that examined it.

Preparation category	READY pillars	What the research examined	Studies in this library

Clinical guidelines & professional societies

What do professional organizations recommend?

Published guidance organized by clinical topic. Each card names the organization, the document, its year, and links to the source.

The gap between evidence and practice

The barriers are logistical, not clinical.

Despite this consensus, only 31.5% of surgical departments worldwide have a formal prehabilitation program. The barriers are logistical — unawareness among healthcare professionals and patients, inability to offer personalized programs, and complex logistics — not clinical. Yet adherence among patients who do enroll is 79% (95% CI 70–88%), based on a meta-analysis of 105 trials with 4,941 patients.

31.5%

of surgical departments have a formal prehabilitation program (Bezmarević 2026)

79%

adherence among enrolled patients, 105 trials (Berrio-Valencia 2025)

Surgery-Conscious by Design™

Evidence matters. So does perioperative safety.

Published evidence for prehabilitation does not mean every supplement is appropriate before surgery. Here is how GlowWell approaches ingredient selection and surgical-team review.

Ingredient transparency

Exact amounts for every ingredient. No herbal ingredients. No proprietary blends.

Deliberately left out, for now

Omega-3s have real evidence in surgical nutrition, including as part of immunonutrition formulas, and the 2021 SPAQI consensus recommends continuing fish oil around surgery. Because PREP is used across many types of surgery, and some surgeons still ask patients to stop omega-3s, especially before fine superficial dissection, we left them out. We will revisit this as the evidence develops. PREP also contains no nucleotides and is not designed to be a complete immunonutrition formula.

Built for team review

Patients are encouraged to share the Clinical Ingredient Passport with their surgical team before starting PREP. It lists every ingredient and dose on one page.

Perioperative consideration	How PREP addresses it
Bleeding & blood pressure	No omega-3, vitamin K, or herbal extracts. L-arginine is the only ingredient in PREP on the SPAQI supplement hold list. That is why PREP stops 24 hours before surgery.
Fasting	PREP is not a clear liquid and is not a preoperative carbohydrate-loading drink. No PREP on the day of surgery. Follow your institution's fasting and carbohydrate-loading protocol.
Pregnancy	PREP has not been evaluated in pregnancy.
Immunonutrition	Do not combine PREP with an ERAS immunonutrition formula.
Allergens	Contains milk (whey protein isolate).
Kidney function	Contains 300 mg magnesium and 160 mg potassium per serving. Review for patients with renal insufficiency.
Herpes simplex	Contains 7 g L-arginine. Review for patients with a history of recurrent herpes outbreaks.
Medication interactions	Every ingredient and dose is listed on the Clinical Ingredient Passport for medication reconciliation.

Download the Clinical Ingredient Passport

Using PREP before and after surgery

A simple schedule your team can follow.

Individual surgical-team instructions always take precedence.

14 days beforeStart one serving a day alongside the READY Guide's 14-day preparation countdown.
24 hours beforeLast serving. L-arginine is on the SPAQI supplement hold list, so PREP stops 24 hours before surgery.
Surgery dayNo PREP. It is not a clear liquid and is not a preoperative carbohydrate-loading drink.
After surgeryResume once the surgical team clears the patient for oral intake. The READY Guide's 7-day recovery tracker continues the plan.

Who this applies to

Nutritional risk is common, and often invisible.

In 456 elective surgical patients, 44% met malnutrition criteria on formal assessment, yet only 20% were underweight and only 38% had low albumin.
Surgery raises protein needs for every patient. Guidelines target about 1.5 g/kg/day around surgery.
The strongest outcome data come from patients at nutritional risk, older adults, and major abdominal, oncologic, or cardiac surgery. The ACS Strong for Surgery checklist flags patients who should also see a dietitian: BMI under 19, unintentional weight loss of more than 8 lbs in 3 months, poor appetite, or inability to take food by mouth.

PREP gives every patient a simple daily way to support protein and micronutrient intake through the surgical window.†

Protein in context

PREP adds to dietary protein. It does not replace it.

At about 1.5 g/kg/day, a 70 kg patient needs roughly 105 g of protein a day. One PREP serving provides 15 g of whey protein. The READY Guide helps patients reach the rest through food.

For adults.
PREP has not been evaluated in pregnancy.

Supplement Facts PREP Supplement Facts panel

Full Supplement Facts panel, as printed on the PREP label.

THE TARGETS YOUR PATIENTS FOLLOW

Daily READY Guide targets, open to your amendment.

These are the general targets printed in the READY Guide. The Guide tells patients that their surgical team's instructions always override these targets, so adjust any of them for your patient.

READY PILLAR	GUIDE TARGET	COMMON REASONS TO ADJUST
R · Strength (P1)	2+ short sessions (15–20 min) of strength and resistance work per week	Weight-bearing or lifting restrictions; cardiac limits
R · Cardio (P2)	120 minutes of moderate exercise per week	Cardiac or pulmonary disease; orthopedic limits
R · Steps and movement (P6)	5,000+ steps a day, if safe	Mobility limits; fall risk
E · Protein (P7)	At least 0.7 g per pound per day (about 1.5 g/kg)	Kidney or liver disease
E · Water (P8)	Ounces equal to half of body weight in pounds	Heart failure; kidney disease; any fluid restriction
E · PREP	One serving daily; last serving 24 hours before surgery	See the perioperative considerations table
A · Clean habits (P9)	Avoid nicotine, vaping, cannabis, and alcohol	Heavy alcohol use: patients are told not to stop suddenly and to ask for a safe plan
A · Medication plan (P10)	Review all medications and supplements; follow the team's instructions	Anticoagulants, insulin and GLP-1 medications, antihypertensives
A · Breathing (P11)	10 deep breaths, 3 times a day	Your incentive spirometry or inspiratory muscle training protocol
D · Sleep (P12)	7–9 hours a night	Sleep apnea and CPAP use
D · Brain activity (P13)	15 minutes a day of puzzles, reading, or brain games	None typical
D · Calm practice (P14)	One calming activity daily: breathing, stretching, or quiet time	None typical

One-time milestones before surgery: know the surgery plan and arrival instructions; complete a medication and supplement review; know the pain management plan; set a gut and bowel regularity plan; check for illness or new symptoms; write down questions for the surgical team.

The evidence behind GlowWell

How the research informs our program.

PREP™ Nutrition

Provides targeted nutrients
Supports normal muscle, tissue, and metabolic function†
Exact ingredients and amounts disclosed
Reviewed for perioperative considerations

READY Method™

Provides daily preparation actions
Addresses movement, nutrition, sleep, risk reduction, and recovery planning
Research-informed preparation framework
Adapted to the treating team's instructions

Fuel without a plan is just a shake. A plan without fuel is just advice.

Explore the Complete GlowWell System

For surgeons & surgical practices

Great surgery deserves a prepared patient.

You focus on the surgery. We help patients prepare for it.

20,000+patients guided through surgery by Dr. Long

Board-certified anesthesiologist

Former Medical Director of a Perioperative Surgical Home

GlowWell combines targeted nutrition with a structured preparation guide to help patients take an active role in the days before and after surgery.

ReviewRead the Clinical Ingredient Passport and the READY Guide your patients will follow.

RecommendPoint patients to a preparation plan that matches the guidance in this library.

ConnectDirect-to-consumer right now. Register your interest for when wholesale orders open.

Review the Program for Your Patients Alert Me When Wholesale Orders Open Contact Dr. Cherie Long

What your patients hear from me

Dear Patient,

I am the anesthesiologist you will likely meet for the first time on the morning of your surgery—when you are in a hospital gown, your belongings in a plastic bag, trying to stay calm while the pre-op room buzzes around you. I will only have a few brief minutes with you before we roll back into the operating room.

If I could sit down with you before that hectic moment—back when you still have time to prepare—I would tell you a truth the medical system rarely explains clearly:

There is a profound difference between being cleared for surgery and being ready for it.

Being cleared means your labs are baseline safe, your heart looks stable enough, and you present no immediate anesthesia risk. Being ready is a different standard—how well your body can withstand the physical and metabolic stress that is coming, not just on the table, but in the critical days and weeks afterward.

Most people don't realize the athletic-level stress surgery places on the body. It demands a surge from your immune system. It forces you to fast, then rebuild tissue while exhausted. It triggers hypermetabolism that breaks down lean muscle for fuel. It can unsettle your gut and digestion. When patients feel depleted and drained afterward, it is not because they did something wrong. It is because no one ever taught them how to prepare their body for the journey.

I see this every day. Some patients come through smoothly; others face prolonged setbacks. The difference often isn't age or luck—it is nutrient reserves: the muscle, protein stores, and metabolic resilience you bring in with you. Standard clearance doesn't measure them, but they are what matters most. And here is the good news: you have far more control over them than anyone tells you. Even if surgery is weeks away. Even—especially—if you are anxious.

That is why I founded GlowWell—to take the science of the operating room and turn it into something that empowers you before surgery day. PREP is my answer to the gap I see daily: patients cleared for surgery but not prepared for it. It is a targeted formula designed to supply the protein, carbohydrates, and micronutrients that support your muscles, immune defenses, and digestive comfort through your surgical window.

You don't need to be an elite athlete, have perfect labs, or have months of time. You need a targeted nutritional and preparation plan—built by an anesthesiologist who has spent years in the operating room seeing firsthand what supports the body under stress. You deserve better than "nothing to eat or drink after midnight, see you in pre-op."

You cannot control every variable of an operation. But you can control the body and the reserves you bring into it. And that choice matters more than anyone ever tells you.

With you on the journey,
Dr. Cherie Long
Anesthesiologist and Founder, GlowWell

Do your own evidence review

Check the evidence with your favorite AI tool.

These are prompts we suggest putting into OpenEvidence or another clinical AI tool. AI answers can contain errors, so confirm them against the original publications.

Perioperative safety of the ingredients

Review the perioperative safety of an oral nutrition drink containing, per serving: whey protein isolate 15 g, L-arginine 7 g, L-glutamine 5 g, vitamin C 500 mg, zinc 25 mg, vitamin A 900 mcg RAE, vitamin D3 75 mcg (3,000 IU), selenium 100 mcg, copper 1 mg, thiamin 12 mg, riboflavin 10 mg, niacin 25 mg, pantothenic acid 50 mg, vitamin B6 15 mg, biotin 300 mcg, folate 500 mcg DFE, vitamin B12 500 mcg, choline 100 mg, magnesium 300 mg, potassium 160 mg, sodium 334 mg, inulin 1.5 g, and a postbiotic 340 mg. It is taken once daily, with the last serving 24 hours before surgery and none on the day of surgery. Are there clinically significant concerns for bleeding, anesthesia, blood pressure, or blood glucose at these doses? Cite sources.

Supplement hold list

According to the 2021 SPAQI consensus statement on perioperative management of dietary supplements, which of these ingredients should be held before surgery, and for how long: whey protein isolate 15 g, L-arginine 7 g, L-glutamine 5 g, vitamin C 500 mg, zinc 25 mg, vitamin A 900 mcg RAE, vitamin D3 75 mcg (3,000 IU), selenium 100 mcg, copper 1 mg, thiamin 12 mg, riboflavin 10 mg, niacin 25 mg, pantothenic acid 50 mg, vitamin B6 15 mg, biotin 300 mcg, folate 500 mcg DFE, vitamin B12 500 mcg, choline 100 mg, magnesium 300 mg, potassium 160 mg, sodium 334 mg, inulin 1.5 g, and a postbiotic 340 mg?

Protein targets around surgery

What daily protein intake do ESPEN, ASPEN, and ASER/POQI recommend before and after elective surgery? What is the evidence for preoperative oral nutritional supplements? Give effect sizes and full citations.

Evidence in your specialty

What is the evidence that preoperative nutrition and prehabilitation affect outcomes in [your specialty] surgery? Give effect sizes with 95% confidence intervals and full citations.

Which patients benefit most

Which validated tools screen for malnutrition risk before elective surgery, and which patients benefit most from preoperative nutritional optimization? Cite guidelines and studies.

Complete research index

All clinical studies and guidelines.

A searchable, filterable reference collection. A surgeon who wants the short version can read the specialty cards. A researcher or medical director who wants the complete bibliography can use this index.

Evidence considerations

Reading this evidence.

The studies in this library evaluated specific nutritional, exercise, and psychological interventions. PREP and the GlowWell® Surgical Readiness System were not studied in them, and their results should not be read as results for PREP.
Certainty varies across the literature. Several pooled estimates combine different program designs or rest on low-certainty evidence, and some findings are observational. Benefits are most consistent in patients at nutritional risk and in major abdominal and oncologic surgery; breast and arthroplasty evidence is mainly functional and observational.

The science behind surgical readiness.