Protein Intake for Healthy Subjects

Overseen By Mahroukh Rafii, BSc

Age: Any Age

Sex: Any

Trial Phase: Academic

Sponsor: The Hospital for Sick Children

Must not be taking: Acetaminophen, Steroids

Disqualifiers: HIV, Diabetes, Cancer, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: Unknown

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial explores whether consuming more protein than currently recommended can boost the body's production of an antioxidant called GSH, which protects cells from damage. Participants will follow special diets with varying protein intakes to observe the effects on antioxidant levels in their blood. The trial seeks healthy school-aged children, young adults, and older adults who are generally healthy and willing to adhere to a specific diet and undergo blood draws. As an unphased trial, participants contribute to groundbreaking nutritional research that may enhance health guidelines.

Will I have to stop taking my current medications?

If you are taking medications that affect GSH (an antioxidant) or protein metabolism, like acetaminophen or steroids, you will need to stop taking them to participate in this trial.

What prior data suggests that varying protein intakes are safe for healthy individuals?

Research shows that adjusting protein intake is generally safe for healthy individuals. Studies have found that increased protein consumption can aid in building muscle and strength. For adults engaging in weightlifting or resistance exercises, higher protein intake can enhance body composition and fitness.

However, caution is advised with very high protein consumption. The risks of protein constituting more than 20-23% of daily calories remain unclear. Nonetheless, no strong evidence suggests that moderate protein increases are harmful.

Overall, healthy individuals tolerate protein well, with most not experiencing serious side effects. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about varying protein intakes because it explores how different levels of protein consumption can impact overall health in ways not fully understood yet. Unlike standard nutritional guidelines that suggest fixed protein amounts, this approach studies personalized protein intake levels to optimize health benefits. By examining these variations, scientists hope to uncover insights into protein's role in metabolism, muscle maintenance, and overall wellness, potentially leading to more tailored dietary recommendations in the future.

What evidence suggests that varying protein intakes might be effective for increasing GSH synthesis rates?

Research shows that increasing daily protein intake can slightly enhance muscle size and leg strength in healthy adults. This trial will examine different protein intakes to evaluate their effects. Studies have found that protein supplements can strengthen and enlarge muscles, particularly when combined with weightlifting or resistance exercises. However, consuming more protein does not significantly affect body weight or fat during activities like running or cycling. For older adults, protein can also help manage hunger. These findings suggest that more protein may aid muscle growth and strength, but effects can vary based on activity level and age. ^{2 6 7 8 9}

Who Is on the Research Team?

Glenda Courtney-Martin, PhD

Principal Investigator

Academic &Clinical Specialist

Are You a Good Fit for This Trial?

This trial is for healthy children over 22 kg, young adults aged 19-40 with a BMI under 25, and older adults aged 60-90 in good health with normal blood markers. Participants must be willing to have their diet and protein intake controlled and provide consent. Those on weight loss diets, with recent significant weight loss, chronic diseases affecting metabolism or unwilling to have blood drawn are excluded.

Inclusion Criteria

Healthy school-aged children

Body weight ≥ 22 kg

No history of anemia

Exclusion Criteria

You have lost a lot of weight in the past month.

You have lost a lot of weight in the past month or are following a diet to intentionally lose weight.

You have a long-term illness or recent sickness that affects how your body processes certain substances. This includes conditions like HIV, diabetes, cancer, liver or kidney disease, and having a cold or flu.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Adaptation

Participants consume low protein foods plus a milkshake drink for adaptation

2-3 days for children and young adults, 3 days for old adults

In-person visits at SickKids

Study Day

Participants consume hourly protein drinks or milkshake diets and special cookies

1 day

In-person visit at SickKids

Follow-up

Participants are monitored for safety and effectiveness after treatment

up to 24 months

What Are the Treatments Tested in This Trial?

Interventions

• Varying protein intakes

Trial Overview The study aims to understand how different levels of protein intake affect the production of Glutathione (GSH), an important antioxidant in our cells. Healthy participants will consume diets formulated with varying amounts of protein to see if higher intakes boost GSH synthesis rates in red blood cells across different age groups.

How Is the Trial Designed?

Group I: Protein intake Experimental Treatment 1 Intervention

Varying protein intakes.

Who Is Running the Clinical Trial?

The Hospital for Sick Children

Lead Sponsor

Trials

724

Recruited

6,969,000+

Published Research Related to This Trial

Protein supplementation in healthy older adults can lead to suppressed appetite ratings in acute studies, but overall energy intake (EI) may actually increase when considering the energy content of the protein supplements.

Longitudinal studies showed that while protein intake increased significantly, there was no significant difference in daily energy intake between protein and control groups, suggesting that protein supplementation can help boost protein consumption without negatively affecting overall appetite.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The Impact of Protein Supplementation on Appetite and Energy Intake in Healthy Older Adults: A Systematic Review with Meta-Analysis. Ben-Harchache, S., Roche, HM., Corish, CA., et al.[2023]

The Dietary Reference Intake (DRI) recommends a protein intake of 0.8 g/kg/day for adults, but athletes may require more due to their higher activity levels, although this is not officially recognized in the RDA.

Higher protein diets (30%-35% of total energy) have been shown to promote greater weight loss and fat loss while preserving lean muscle mass compared to lower protein diets, making them beneficial for both athletes and individuals aiming for weight reduction.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dietary protein for athletes: from requirements to metabolic advantage. Phillips, SM.[2022]

Higher protein intake, specifically between 1.2 to 1.6 g/(kg·day), is associated with better health outcomes, including prevention of age-related muscle loss (sarcopenia) and improved weight management.

Increased protein consumption enhances satiety and supports athletic performance by aiding muscle recovery, with no evidence linking high protein diets to kidney disease or negative effects on bone health.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Protein "requirements" beyond the RDA: implications for optimizing health. Phillips, SM., Chevalier, S., Leidy, HJ.[2022]

In a study involving 84 hospitalized patients at nutritional risk, a novel protein-supplemented food service significantly increased the percentage of patients meeting their protein requirements (66% in the intervention group vs. 30% in the control group).

The intervention group also had a higher mean intake of energy and protein per body weight compared to the control group, indicating that the protein-supplemented food service effectively improved nutritional intake in these patients.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Positive effect of protein-supplemented hospital food on protein intake in patients at nutritional risk: a randomised controlled trial. Munk, T., Beck, AM., Holst, M., et al.[2014]

Short-term oral protein-energy supplementation in moderately malnourished elderly patients significantly increased dietary intake (energy by 32% and protein by 65%) and fat-free mass (FFM) by 1.3 kg, indicating its efficacy in improving nutritional status.

The study highlights the importance of using Dual energy X-ray absorptiometry (DXA) to assess changes in FFM, as other methods like bio-impedance analysis and anthropometry did not accurately reflect these changes, suggesting a need for larger studies to confirm these findings.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Nutritional status after short-term dietary supplementation in hospitalized malnourished geriatric patients. Bos, C., Benamouzig, R., Bruhat, A., et al.[2007]

A systematic review of 18 randomized controlled trials involving over 1300 older adults found that increasing protein intake may positively affect lean body mass, with some benefits for muscle strength when combined with physical exercise.

However, the evidence is insufficient to support significant health benefits from increased protein intake in older adults already consuming ≥0.8 g/(kg BW · d), particularly for outcomes like physical performance and bone health.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Health Effects of Increasing Protein Intake Above the Current Population Reference Intake in Older Adults: A Systematic Review of the Health Council of the Netherlands. Hengeveld, LM., de Goede, J., Afman, LA., et al.[2023]

The Recommended Dietary Allowance for protein is 0.8 g per kg of body weight per day for healthy adults, but higher intakes of 1.0 to 1.6 g per kg are recommended for those with varying levels of physical activity to support muscle growth and strength.

While long-term protein intake of up to 2 g per kg per day is considered safe, exceeding this amount may lead to health issues such as digestive and renal problems, highlighting the importance of both the quantity and quality of protein in the diet.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dietary protein intake and human health. Wu, G.[2016]

In a study of 62 hospitalized adults aged 65 and older, only 17 patients achieved the recommended protein intake of ≥1.2 g/kg, highlighting a significant gap in meeting nutritional guidelines for older adults.

The medium/high risk group, which received a protein-enriched diet, had an average intake of 1.2 g/kg, while the low-risk group only averaged 0.9 g/kg, suggesting that a protein-enriched diet may be beneficial for all older hospitalized patients, regardless of malnutrition risk.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Protein intake in hospitalized older people with and without increased risk of malnutrition. Vasse, E., Beelen, J., de Roos, NM., et al.[2019]

In a study of hospitalized patients at nutrition risk, combining a protein-enriched menu with individualized dietary counseling led to 92% of patients meeting over 75% of their energy requirements, compared to 76% in the historical intervention group.

The intervention group also showed a significant increase in mean energy and protein intake, with 31 kcal/kg and 1.2 g protein/kg, respectively, indicating that this combined approach is more effective than using a protein-enriched menu alone.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

From Evidence to Clinical Practice: Positive Effect of Implementing a Protein-Enriched Hospital Menu in Conjunction With Individualized Dietary Counseling. Munk, T., Bruun, N., Nielsen, MA., et al.[2018]

In a study of 2,853 mechanically ventilated ICU patients, higher protein and energy intake significantly reduced mortality and shortened time to discharge for high-risk patients, indicating the importance of tailored nutritional support in critical care.

For patients assessed as low-risk, increased nutritional intake did not show a significant impact on mortality or discharge times, suggesting that nutritional needs may vary based on individual risk levels.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Greater Protein and Energy Intake May Be Associated With Improved Mortality in Higher Risk Critically Ill Patients: A Multicenter, Multinational Observational Study. Compher, C., Chittams, J., Sammarco, T., et al.[2017]

A study involving 24 adults aged 50-75 found that short-term supplementation with 20 g of whey protein did not affect overall energy or nutrient intake, regardless of whether it was taken in the morning or evening.

The protein supplement also did not change self-reported hunger or appetite levels, suggesting that this approach could help older adults increase their protein intake without negatively impacting their overall diet.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Short-Term Protein Supplementation Does Not Alter Energy Intake, Macronutrient Intake and Appetite in 50-75 Year Old Adults. Tuttiett, ER., Green, DJ., Stevenson, EJ., et al.[2022]

In a study involving 51 older adults with sarcopenia, personalized protein supplementation significantly increased total protein intake to 1.55 g·kg-1·d-1 without negatively impacting regular dietary protein or energy intake.

The supplementation improved the distribution of leucine intake across meals, particularly at breakfast and dinner, ensuring that participants received adequate amounts of this important amino acid without altering their usual dietary habits.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Personalized Protein Supplementation Improves Total Protein, Leucine, and Energy Intake in (Pre)Sarcopenic Community-Dwelling Older Adults in the ENHANce RCT. Dedeyne, L., Dupont, J., Verschueren, S., et al.[2021]

Older adults need higher protein intake than currently recommended, specifically 1.0 to 1.3 g/kg/day, to help maintain muscle mass and strength, especially when combined with resistance exercise.

Research shows that increased dietary protein significantly benefits lean mass gain and leg strength in older individuals, highlighting the importance of tailored nutrition for improving physical function in this age group.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Protein Requirements and Recommendations for Older People: A Review. Nowson, C., O'Connell, S.[2023]

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC8978023/

Systematic review and meta‐analysis of protein intake to ... In conclusion, increasing daily protein ingestion results in small additional gains in LBM and lower body muscle strength gains in healthy adults enrolled in ...

2. pubmed.ncbi.nlm.nih.gov pubmed.ncbi.nlm.nih.gov/28698222/

A systematic review, meta-analysis and meta-regression of ... Dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults.

3. sciencedirect.com sciencedirect.com/science/article/abs/pii/S0022316625000240

Comparison of the Effectiveness of Protein ... The combined intervention of protein supplementation and resistance training significantly improved lean body mass (standardized mean difference [SMD]: 0.44; 95 ...

4. frontiersin.org frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1663860/full

Effects of protein supplementation on body composition ... Our meta-analysis results showed that protein supplementation had no significant effect on body weight and body fat during endurance training, while the effect ...

5. sciencedirect.com sciencedirect.com/science/article/pii/S2161831322001788

The Impact of Protein Supplementation on Appetite and ... This systematic review and meta-analysis aimed to determine the effects of protein supplementation on appetite and/or energy intake (EI) in healthy older ...

6. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC3730112/

Health effects of protein intake in healthy adults Vegetable protein intake was associated with decreased risk in many studies. Potentially adverse effects of a protein intake exceeding 20–23 E% remain to be ...

7. jissn.biomedcentral.com jissn.biomedcentral.com/articles/10.1186/s12970-017-0177-8

International Society of Sports Nutrition Position Stand: protein ... There is novel evidence that suggests higher protein intakes (>3.0 g/kg/d) may have positive effects on body composition in resistance-trained ...

8. bjsm.bmj.com bjsm.bmj.com/content/52/6/376

A systematic review, meta-analysis and meta-regression ... Summary/conclusion Dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults.

9. jn.nutrition.org jn.nutrition.org/article/S0022-3166(22)02189-7/fulltext

The Role of Protein Intake and its Timing on Body ... Increased protein intake has been suggested to improve gains in muscle mass and strength in adults. Furthermore, the timing of protein intake has been discussed ...