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PUBLICATION FOR INDUSTRY & HEALTH PROFESSIONALS
Dietary Protein: Dairy and Sleep How much, for whom, and how often? Dairy and Sleep from folklore to science
Volume 18, Issue 1 | August 2026
from folklore to science
Volume 13, Issue 2 | August 2021
Editorial
Protein is firmly in the spotlight, shaping conversations around ageing, sports nutrition, weight management, and sustainable healthy diets. At Warm milk before going to bed is a the same time, there is conflicting tradition that has been passedtodown information about how much eat through generations as and the best sources. a practice to facilitate a restful night’s sleep. In this edition of DN Forum, we review As with other bedtime routines, the latest evidence on dietary protein Warm milk befo it may be the ritual thatcourse, helps requirements acrossitself the life tradition that ha to induce anticipation of sleep. looking at the recommendations, protein through genera quality, sustainability, and emerging Also, drinking milk before falling topics asbe GLP-1 medications. asleepsuch could associated with to facilitate a re soothing, early childhood memories It highlights the importanceAs of that evoke calmness. However,with it is other be considering protein within the context may be the rit also believed that naturally it occurring of whole dietary patterns, and the components in milk can support the the an to induce need to balance nutrient adequacy process of sleep. goals. with environmental
Editorial
Volume 13, Issue 2 | August 2021
Editorial
Summary Points •
Protein is a fundamental macronutrient, essential for body growth and repair. While protein recommendations for healthy adults are well established, there is increasing interest in whether higher intakes may benefit specific populations.
Summary Points •
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with higher requirements. Animal source proteins are deemed ‘higher biological value’ based on the number of amino acids present, but may have a higher environmental footprint.
Summary Points
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DN Forum
Volume 18, Issue 1 | August 2026
Dietary Protein: How much, for whom, and how often? INTRODUCTION
Dr Anne Nugent
Protein is one of the fundamental macronutrients essential for life, deriving its English name from the Greek ‘proteios’ meaning prime or primary. At its simplest level, protein is needed for energy and to help the body grow and repair itself. Dietary deficiency typically arises from inadequate dietary intakes of protein, or of food in general, or is associated with increased demands usually associated with disease state1. Protein is comprised of 20 building blocks or amino acids, each with varying structures and shapes which influence their end function, nine of these amino acids cannot be made by the human body and therefore are deemed essential within our diets (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine) 2. Although dietary intakes in Ireland and Western countries are generally deemed to be ‘adequate’, protein is currently, a ‘hot topic’ or key nutrient of interest. There is much debate about both quantity and source (quality) of protein in our diets and how much exactly we must consume for optimal health depending on our life stages and activity level.
School of Biological Sciences/ Institute for Global Food Security, Queen’s University Belfast. Visiting Associate Professor, Institute of Food and Health, School of Agriculture and Food Sciences, University College Dublin
This DN Forum will review the evidence in relation to dietary protein intake in terms of quantity and quality as relevant for differing population groups. It will also critique the concept of a ‘protein gap’ and the debate surrounding protein sources whether from animal or plant foods or supplements.
PROTEIN RECOMMENDATIONS: HOW MUCH? An essential nutrient in our diets, dietary proteins are the main source of nitrogen and essential amino acids which are used for a broad range of nutritional and biological functions by the body, primarily linked to growth, repair and maintenance2. Dietary recommendations for protein have been established by numerous agencies with the numerical values for adults ranging from 0.75g to 0.83g/kg body weight (bw) / day3-5, with adaptations for key life stages e.g. early life or pregnancy/lactation and sometimes for older adults. For a 70kg adult, this translates to dietary intakes from approximately 53 to 58g of protein per day. While individual recommendations exist for the essential amino acids6, in practice the emphasis is often on total protein rather than individual amino acids, as total protein intakes are typically adequate and such guidance is difficult to implement in practice7,8.
In Ireland, dietary protein recommendations for the general population, as issued by the Food Safety Authority of Ireland, adhere to the European Food Safety Authority (EFSA) dietary reference value for protein, which set the population reference intake at 0.83g/kg bw/ day (loosely translating to 58g for a 70kg adult)4,9. The FSAI also recommended that older adults at risk of frailty, sarcopenia, and undernutrition eat at least 1.0-1.2 g/kg bw/day to keep muscle mass9. Beyond that, there are no other specific recommendations for other subgroups for whom protein may be of interest e.g. very active adults or athletes. Against this background, there is a significant degree of debate concerning dietary protein recommendations, primarily with the ethos that for certain population groups, higher dietary protein intakes are needed and that there is a ‘gap’. For example, expert groups recommend a higher intake of 1.0-1.2g/kg bw/day for healthy older adults, and even 1.2-1.5g/kg bw/ day for older adults who are malnourished or at risk of malnutrition10,11. Meanwhile for athletes intake recommendations have been tailored by type of sport. For example, the Australian Institute of Sport suggest an intake of 1.2-1.7g/kg bw/day for those participating in moderate-intensity, endurance, and team sports and 1.2-2.0 g/kg bw/day for athletes focusing on strength, power, and resistance12 (see Table 1). These guidelines are considerably higher than those proposed for the general population.
ESSENTIAL AMINO ACIDS
Dietary Protein: How much, for whom, and how often?
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Table 1. Summary comparison of dietary protein recommendation (g/day) for a 70kg adult as recommended by select issuing bodies in comparison to available data on dietary intakes in comparable cohorts in Ireland. Values are presented as indicative rather than exhaustive or comprehensive Recommended Dietary Protein (g/day)
Dietary intakes (g/day)4
Ireland (FSAI) 19
58
82
UK (PHE)2
53
76
Ireland (FSAI) Healthy 9
70-84
75
UK (PHE) 2
53
67
Ireland (FSAI) acute/chronic disease9
84-105
Per 70kg adults Adults 18-64y
Adults>65y
Athletes Moderate intensity, endurance or team12
84-119
Strength, power and resistance12
84-140
Perhaps it is not surprising that consensus has not been reached for recommended dietary intakes for protein for all population groups given that protein’s role is so central to such a wide range of body functions not limited to muscle and bone tissue, cellular structures and signalling, and tissue repair and growth. A key challenge for protein, as with most other nutrients, is the methodology and ethical considerations which have underpinned the establishment of dietary requirements. The primary method upon which dietary protein recommendations have been calculated remains the ‘nitrogen balance’ method which is determined as the single amount of protein needed to maintain nitrogen equilibrium or balance in healthy adults not gaining or losing weight (i.e. attaining a balance between food nitrogen intake minus nitrogen excreted in urine, faeces, sweat, skin, hair, and other miscellaneous ways)6,14. However, arguments suggest lack of sensitivity of the assessment, for example the method does not account for protein source or quality, that it is limited to only nitrogen balance and no other function of physiological relevance, e.g. age, lean body mass, as well lack of accuracy and sensitivity15. Furthermore, most studies used to underpin dietary requirements are based on estimations in adults (often males) and therefore an additional step (factorial method) is
Less characterised in representative samples but limited study suggests adequacy e.g. intakes of 114 in Gaelic players13 then needed to calculate or regress requirements to account for physiological conditions such as growth, pregnancy or lactation4. Although other methods (staple isotope or indicator amino acid oxidation) have been proposed for determining protein requirements, to date, dietary recommendations still rely on balance studies16. Against this setting, expert groups have issued the above mentioned more tailored (higher) recommendations for age and activity arguing the need to account for physiological changes with age and for benefits for skeletal muscle and lean mass outcomes (optimal health) beyond nitrogen balance9,11,15 (see Table 1). Concerns relating to higher protein intakes and insulin sensitivity, bone or kidney health are not fully understood due to a lack of available data15. Other guidance suggests spreading intakes across the day rather than at a single meal, whilst also eating enough dietary protein at a single eating occasion, to stimulate new functioning proteins, including that of the muscle (termed muscle protein synthesis) 17-19. The final set of recommendations typically relate to consumption of animal versus plant sources of proteins. The arguments here typically relate to choosing plant source proteins (beans, pulses, legumes) for health and environmental benefits versus animal source proteins (meats, dairy)20. Animal source proteins are deemed
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Volume 18, Issue 1 | August 2026
‘higher biological value’ based on the number of amino acids present, but may have a higher environmental footprint15. Evidence shows that animal derived proteins produce a greater anabolic response per protein dose compared to plant proteins, due to their higher content of essential amino acids21 linking in with the above recommendation of spacing intakes across the day19. Hence, current consensus would suggest greatest potential benefits from adhering to relevant guidance whilst considering protein type (animal vs plant), and quality sources, with a further recommendation of moving to more personalised guidance based on sex, age, health, and activity levels2,15.
Dietary Intakes: Dietary protein intakes for Ireland generally reveal adequacy. For example, the most recent national food survey for Ireland (NANS II) reports usual daily intakes of protein for adults of 82g/day and for older adults >65y of 75g/day or on average 18% of total energy22. More detailed analysis combining both NANS II with
the Northern Ireland cohort of the comparable food survey (the National Diet and Nutrition Survey, NDNS) for 19-64 year olds showed a combined intake of protein for this cohort contributing 17% of total energy intake, with 77% of participants meeting the 0.83g/kg bw/day recommendation23. When intakes were ranked into thirds (tertiles), the difference in protein intake was 7.8% of total energy (21.2 vs 13.4% total energy) with higher protein consumers being slightly older, having a slightly higher BMI and higher intakes of many nutrients (e.g. fibre, calcium, zinc, sodium, iron, folate, vitamins A, C, D, B12 ) and with lower intakes of carbohydrate, total fat and saturated fat. Key differences in food intake between the groups were higher intake of whole milk, chicken and chicken dishes, beef and beef dishes, and fish and fish dishes by those with the higher protein intakes23. Analysis focusing on the essential amino acids also reveals adequacy, both in older adults using older survey data (year 2008-2010)24 and as part of the combined NANS/NDNS cohort.25
Food Sources: As indicated above, at a population level, the main foods contributing to dietary protein intake relate to animal source foods (e.g. meats and dairy) but the contribution of cereal products also merits mention with breads, bread products, and breakfast cereals contributing approx. 15% of daily protein intake– protein is not just about animal source foods22 (see Figure 1). This is important when assessing the environmental impact of our dietary choices where, for Ireland, meat and their alternatives (27-44%), eggs, dairy and dairy alternatives (29-52%), and starchy staples (10-20%) are the main contributors to greenhouse gas emissions across all population groups 26, yet also main contributors to dietary protein. Currently, contributions from plant based proteins such as beans, legumes, and pulses is much lower and falls within the ‘other’ category.
Figure 1. Sources of protein in Irish adults as extracted from the National Adult Nutrition survey II
Sources of protein in Irish adults as extracted from the National Adult Nutrition survey II 35
32 33
30
19-64y
25
>65y
20 15 10 5
0
11 11
9
14
12 7 8
7 2
5 4
4 4
4 4
4
6
3 3
12
Dietary Protein: How much, for whom, and how often?
www.ndc.ie
Protein in healthy sustainable diets: The need to move food consumption to more sustainable diets, e.g. decreasing greenhouse gas emissions, to improve both human and planetary health is unquestionable27. Emphasis is often on animal source foods but such foods are key sources of, not just protein, but many key nutrients which are often shortfall in our diets, including calcium, iron, folate, vitamin B12, and for starchy cereals, fibre.28 Hence, animal source foods remain recommended in sustainability updates for national food based dietary guidelines in countries such as Sweden, Denmark and the Netherlands (for review see Sinclair et al.29), with concurrent increased recommendations for plant source foods. This is supported by modelling of national food survey data for the island of Ireland as part of the Protein I project30, which created hypothetical healthy sustainable diets whilst minimising changes from current intakes to ensure acceptability – in all diets consumption of some animal source foods such as dairy and meat were retained, albeit with limited amounts and greater intake of plant based protein foods.31 A recent randomised controlled trial here in Ireland (MyPlanetDiet), compared the impact on environmental and health outcomes of adhering to either personalised advice based on the existing food pyramid or proposed sustainable healthy eating guidelines in healthy Irish meat consuming adults over 12 weeks32. Both intervention arms successfully reduced greenhouse gas emissions (10-33%) but the sustainable healthy intervention resulted in higher prevalence of inadequate intakes of several micronutrients, especially among women (calcium, riboflavin, zinc, vitamins B6, B12, i.e. nutrients naturally present in animal source, and protein rich, foods)33,34. Separately, there is increasing evidence of the environmental footprint of discretionary foods reported to account for 17-32% of environmental impact in analysis of purchase decisions by over 22,000 Finnish consumers35, similar to that of Australian consumers36 and suggested for Ireland37, foods of course not needed for dietary adequacy. Collectively, this reminds us that our foods are not just single nutrients, e.g. protein or micronutrients, but a complex matrix of multiple nutrients and that by consuming nutrient and protein rich foods in their diets, people can better achieve adequate intakes of multiple nutrients28.
How can different populations consume more protein? It is noteworthy that the above studies are typically in healthy adults and not in the cohorts who may choose or be asked to increase their protein intakes – i.e. older adults or very active adults (athletes). Here, accounting for total dietary patterns, food source and meeting rather than exceeding intakes may be wise. Dietary patterns, such as a protein-enriched Mediterranean diet, have improved nutritional status in at-risk older adults (MNA score) and dietary quality (protein, fibre, selenium, iron, and vitamin D) after just three months38. While, for athletes, education tools have been developed to highlight how environmental impact is influenced by volume of food, training load, sex, and animal/plant protein balance39,40. While dietary (protein) supplements, may be proposed as a potential alternative for athletes or very active adults, in general such supplementation may not be needed if foods are used appropriately and their use should ideally be considered along with advice from a sports nutritionist to create a clear plan of how they can meet requirements and influence performance41. More is not always more. Consideration may also be needed regarding the value of third party testing42. Of greatest benefit with respect to dietary protein intake and
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impacts for skeletal health (muscle protein synthesis) is simply from balancing patterns of protein intake across the day – patterns for Ireland typically reveal skewed intakes with the lowest intakes at breakfast43. Furthermore, it has been shown a nutrition intervention targeting supplemental dairy protein intake at breakfast and lunch (0.17 g kg−1 protein/~12 g protein per meal) was successful in increasing lean body mass (LBM) over 24 weeks in Irish adults aged 50–70 years even in the absence of exercise training44 .
Consideration of GLP-1 agonist medications Beyond this, other population groups keen to maximise protein intakes include those on weight loss regimes, including use of GLP-1 agonist medications. Indeed, ensuring adequate intake of protein rich foods is recommended whilst taking GLP-1 medication to preserve muscle mass alongside some strength activites45. Suggested practical advice includes eating protein rich foods first where appetite is small45. In contrast, limited evidence from the US, shows that GLP-1 users under consume protein rich food groups, such as dairy produce, resulting in inadequacies in
Volume 18, Issue 1 | August 2026
intakes of key nutrients such as calcium, magnesium, potassium, choline, and vitamins A, C, D, and E46. As GLP-1 use increases, and is anticipated to increase further, careful consideration is needed regarding appropriate guidance and messaging about protein rich foods from both animal and plant source foods46. On one hand, greater environmental benefits (reductions in greenhouse gas emissions) are suggested from use of GLP-1 medications, than those gained from switching to electric vehicles or adopting a vegetarian diet (simply through reduced volumes of foods needed and consumed)43. On the other hand is the clear need to include protein rich animal source foods (typically associated with higher environmental footprints) to ensure nutrient adequacy among users47. More in-depth research is needed to characterise and understand this new area, whilst also recognising the potential for less-controlled recreational GLP-1 use within many population groups, including younger females, older adults, and athletes, such as body builders48.
Dietary Protein: How much, for whom, and how often?
www.ndc.ie
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CONCLUSION Protein is a critical nutrient, supporting our general health and integral to multiple body functions. Despite general perception, dietary protein intakes for the adult population are typically adequate but careful consideration is needed for some subgroups, e.g. older adults, active adults (athletes), and GLP-1 users. While sustainability and environmental considerations remain important, the value of animal source foods, including dairy, in contributing to total protein intakes (and that of other key nutrients) should not be overlooked, particularly in instances where higher dietary intakes are recommended. Above all is the reality that protein foods are rarely eaten alone and it reminds us of the commonality that all protein rich foods should form part of healthy eating encompassing other key food groups too.
References Bhutta ZA, Dewraj HL (2002) Protein, Deficiency. In Encyclopaedia of Human Nutrition, 2nd ed., pp 8286 [ B Caballero , editor], California: Elsevier.
Protein intake and exercise for optimal muscle function with aging: recommendations from the ESPEN expert group. Clin Nutr 33, 929–936.
2. Maleky F, Ahmadi L (2025) Adhering to recommended dietary protein intake for optimizing human health benefits versus exceeding levels. RSC Adv. 15,9230-9242.
12. Australian Institute of Sport. https://www.ausport. gov.au/ (Accessed July 2026)
1.
3. Public Health England (2016) Government Dietary Recommendations. Government Recommendations for Energy and Nutrients for Males and Females Aged 1-18 Years and 19+ Years. https://assets.publishing.service.gov.uk/government/ uploads/system/uploads/attachment_data/ file/618167/government_dietary_recommendations. pdf (Accessed on 3.7.2026) 4. European Food Safety Authority Panel on Dietetic Products, Nutrition and Allergies (2012). Scientific Opinion on Dietary Reference Values for protein. EFSA Journal 10(2),2557 5. Food and Agriculture Organisation & World Health Organisation (1991) Protein quality evaluation. Report of the joint FAO/WHO expert consultation, FAO Food and Nutrition Paper No. 51, 66 pp. Bethesda. 6. Institute of Medicine (2005) Dietary Reference Intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. National Academies Press, Washington. 7.
Rodriguez NR, Miller SL (2015) Effective translation of current dietary guidance: understanding and communicating the concepts of minimal and optimal levels of dietary protein. Am J Clin Nutr 101, 1353S–1358S.
8. Rodriguez NR (2015) Introduction to protein summit 2⋅0: continued exploration of the impact of highquality protein on optimal health. Am J Clin Nutr 101, 1317S–1319S. 9. Food Safety Authority Ireland (2021) Scientific recommendations for food-based dietary guidelines for older adults in Ireland. https://www. fsai.ie/getmedia/c0610e7f-9bfa-457a-9dca3f97149e43a1/scientific-recommendations-forfood-based-dietary-guidelines-for-older-adults-inireland.pdf?ext=.pdf (Accessed July 2026) 10. Bauer J, Biolo G, Cederholm T et al. (2013) Evidencebased recommendations for optimal dietary protein intake in older people: a position paper from the prot-age study group. J Am Med Dir Assoc 14, 542–559. 11. Deutz NEP, Bauer JM, Barazzoni R et al. (2014)
13. McCrink CM, McSorley EM, Grant K et al. (2021) An investigation of dietary intake, nutrition knowledge and hydration status of Gaelic Football players. Eur J Nutr. 60,1465-1473. 14. Wolfe RR, Cifelli AM, Kostas G et al. (2017) Optimizing protein intake in adults: interpretation and application of the recommended dietary allowance compared with the acceptable macronutrient distribution range. Adv Nutr 8, 266–275 15. Kanter MM, Aaron S, Austad SN et al. (2026) Examining widely held propositions on human dietary protein needs and benefits: a critical review of the science that shapes both the data and our understanding of an essential macronutrient. Crit Rev Food Sci Nutr. Published online May 8, 2026. DOI: 10.1080/10408398.2026.2658728 16. Morgan PT, Witard OC, Højfeldt G et al. (2025). Dietary protein recommendations to support healthy muscle ageing in the 21st century and beyond: considerations and future directions. Proceedings of the Nutrition Society. 84, 245-258. 17. Moore DR, Robinson MJ, Fry JL et al. (2009) Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am J Clin Nutr. 891,161-168 18. Witard OC, Jackman SR, Breen L et al (2014). Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. Am J Clin Nutr 99, 86-95. 19. Jäger R, Kerksick CM, Campbell BI, et al (2017) International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 14, 20. 20. FSAI (2011) Scientific Recommendations for Health Eating guidelines in Ireland. https:// www.fsai.ie/getmedia/26b9d220-237e-4b2eb7de-fa0dbcf2a664/healthy_eating_guidelines_ report_2011.pdf?ext=.pdf (Accessed on 3.7.2026) 21. Berrazaga I, Micard V, Gueugneau M et al. (2019) The Role of the Anabolic Properties of Plant- versus Animal-Based Protein Sources in Supporting Muscle Mass Maintenance: A Critical Review. Nutrients. 11,1825.
22. Irish Universities Nutrition Alliance (IUNA) (2024) National Adult Nutrition Survey II: Summary Report. Available at https://irp.cdn-website.com/46a7ad27/ files/uploaded/NANS_II_Summary_Report_ (May_2024).pdf. [Accessed on 3.7.2026]. 23. Griffin H, Nugent AP, McNulty BA et al. (2024) Characterising dietary protein intake in Irish adults on the island of Ireland. Proc Nut Soc. 83 (OCE2):E207. 24. Burke A, O’ Sullivan E, Giblin L et al. (2026) Amino Acid Intakes and Dietary Sources in a Nationally Representative Sample of Older Adults in Ireland: Findings from the National Adult Nutrition Survey (NANS). Nutrients. 18(3),487 25. Griffin H (2026) Modelling the nutritional impact towards more sustainable dietary protein intakes. PhD Thesis, Queen’s University Belfast. 26. Kirwan LB, Walton J, Flynn A et al. (2023). Assessment of the Environmental Impact of Food Consumption in Ireland—Informing a Transition to Sustainable Diets. Nutrients, 15(4), 981. 27. Food and Agriculture Organisation and World Health Organisation (2019) Sustainable healthy diets: guiding principles. Available at: https://www. who.int/publications/i/item/9789241516648 (accessed July 2026) 28. Phillips SM, Fulgoni VL 3rd, Heaney RP et al (2015) Commonly consumed protein foods contribute to nutrient intake, diet quality, and nutrient adequacy. Am J Clin Nutr. 101,1346S–1352S. 29. Sinclair M, Combet E, Davis T et al (2025). Sustainability in food-based dietary guidelines: a review of recommendations around meat and dairy consumption and their visual representation. Ann Med. 57, 2470252. 30. Brennan L, O’Gorman, A, Barth S et al. (2022) An innovative food system approach to diversifying protein intake: Protein-I: Shared Island sustainable healthy nutrition. Nutr Bull, 47 (4), 516–523. 31. Griffin H, McNulty B, Wright D et al. (2025) Creating healthy and sustainable diets whilst minimising change from current diets: a linear programming approach. Journal of Nutritional Science. IUNS, Paris. 32. Davies KP, Gibney ER, Leonard UM, et al. (2024) Developing and testing personalised nutrition feedback for more sustainable healthy diets: the MyPlanetDiet randomised controlled trial protocol. Eur J Nutr. 63(7),2681-2696. 33. Davies KP, Gibney ER, Leonard UM, et al. (2025) Sustainable diets reduce diet-related greenhouse gas emissions and improve diet quality: results from
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the MyPlanetDiet randomized controlled trial. Am J Clin Nutr. 122(4),962-971.
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34. Leonard UM, Davies KP, Lindberg L, et al. (2025) 39. Reguant-Closa A, Roesch A, Lansche J et al. (2020). The Environmental Impact of the Athlete’s Plate Impact of sustainable diets on micronutrient intakes and status: outcomes of the MyPlanetDiet Nutrition Education Tool. Nutrients, 12(8), 2484. randomized controlled trial. Am J Clin Nutr. 40. Baroni L, Pelosi E, Giampieri F et al. (2023) The 1. Matricciani L, Bin YS, Lallukka T et al . (2018) J Pharmacol Sci 124, 320-35. Questionnaire: a new tool for assessing and 122(5),1275-1288. VegPlate for Sports: A Plant-Based Food Guide for Rethinking the sleep-health link. Sleep Health
24 weeks beyond habitual intakes increases wholebody lean tissue mass in healthy older adults. J Nutr 146, 65–69.
with Subjective Memory Decline enrolled in the PROMED-EX trial. Proc Nut Soc 83(OCE4):E269.
managing sleep in elite athletes. Br J Sports
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