We know that protein is an essential nutrient for health, but how much protein should we eat each day?

After water, there are more proteins in the body than any other compound.

It’s needed for a broad range of bodily functions including enzyme production, bone health, and tissue growth and repair.

It's one of the three macronutrients: protein, carbohydrates, and fats, and adequate intake is vital for good health.

Read this article for more information about the benefits of protein.

There’s no magic number for protein intake - the optimum amount for each individual depends on a variety of factors, including age, gender, weight, exercise regime, and health goals.

In this article, we'll look at what protein is, and learn about its many functions within the body. 

We'll also look at how protein requirements vary throughout our life, and the many different factors which affect our protein needs. 

Read on, to learn more about protein and how to determine the best intake for your needs.

Why is a recommended protein intake important?

 Proteins are made up of organic compounds called amino acids. Your body needs around 20 amino acids to do all of its daily protein business, and it can make some of these itself. However, there are nine essential amino acids which the body cannot make, so they must be obtained from your diet each day. These are:

• Histidine
• Methionine
• Phenylalanine
• Isoleucine
• Leucine
• Lysine
• Tryptophan
• Threonine
• Valine

Some protein foods contain all of these nine amino acids, but some plant-based protein foods only contain a few so it’s important to combine a wide variety of different protein sources each day if you’re vegan or vegetarian. 

The daily reference nutrient intake (RNI) for adults is around 0.6-0.8g of protein per kg of body weight each day(1), but this is just the bare minimum we need to keep our bodies functioning. Optimum protein intake can actually vary dramatically from person to person, depending on their age, lifestyle, gender, weight and fitness level.

                                                              We need to get 9 essential amino acids from protein sources in our diet every day

Protein for adults

The protein requirements for the ‘average’ adult are currently 0.8g of protein per kg of bodyweight. However, we’ve learned that there are many factors which can affect our protein needs, and our protein intake:

• Fitness/elite: If you’re an athlete, fitness fanatic, or even just take regular exercise, you’ll probably be aware that this will increase your protein needs. You’ll need more protein to support new muscle development, especially if you’re strength training, and for muscle repair and recovery following exercise. Depending on the amount of regular exercise you do, you should be consuming between 1.2 - 2g of protein per kg of body weight(2), though some elite athletes may need up to 3g per kg.  (2,3,4) Speak to your health professional for personalised recommendations.

• Pregnancy: Should pregnant women be eating for two (or more!)? Whilst it’s not necessary for women to double their food intake during pregnancy, it is true that their nutrient requirements do increase in the final two trimesters. The actual amount will still vary according to weight and activity level but as an average pregnant women should aim to eat around 1.1g per kg of protein daily, and ensure an intake of at least 60g of protein per day. (5,6)

• Restricted or exclusion diets: Our diet is a very important part of our life. With our individual likes, dislikes, food allergies/intolerances, medical conditions, weight and fitness goals, and moral considerations, it can be a highly personal, and often highly emotive, subject for us. It's particularly important to monitor protein intake when eating a restricted diet:
  • Weight loss: If we want to restrict our food intake to lose weight, it’s important to remember that diets are not just all about eating a certain number of calories. Your daily calories must still provide you with the nutrients you need and it's recommended that around 35% of your daily calorie intake should come from protein, though again, optimum intake will depend on your activity level and individual requirements. For tips on making every calorie count, read our article 28 Quick Ways to Cut Calories. There can be benefits to eating higher levels of protein when on a weight management diet, as protein can help to aid weight loss by balancing blood sugar and reducing cravings for sugary foods, and helping you to feel fuller for longer. (7)  Read our in-depth article for more detailed information about the relationship between protein and weight loss.
  • Vegetarian/vegan diets: In the UK there is a heavy reliance on animal products to supply protein, but globally, it is plant-based food sources which are the leading source of protein. (8) However, it might take a little more care to meet your needs, for example, plant-based milk alternatives will typically be much lower in protein than dairy milk. Also, plant-based protein sources don’t always contain all nine essential amino acids so it’s important to vary the foods you eat each day. Read this blog for more information about how to get enough protein as a vegetarian.
  • Food allergies, intolerances, or medical conditions: Protein sources such as nuts, fish, meat, dairy, soy, peanuts, or gluten, are among some of the most typically excluded food groups as proteins are usually the cause of allergic food reactions. Sometimes medical conditions like coeliac disease are the cause of food allergies. There are even some medications which can interact with certain foods and can therefore result in food restrictions.

You'll have an increased need for protein if you're training regularly

Whatever we do or don’t, can or can’t eat, if we restrict or exclude any major food groups, then it’s important to ensure that the restricted foods are replaced with other foods that offer the same nutritional value. The good news is that there are a multitude of protein sources to choose from, so you should always be able to meet your protein needs. If you’re on any sort of restricted diet and are unsure how to meet your nutrient requirements, then consult a nutrition professional, or subscribe to a healthy meal prep service so you know your meals are balanced and your protein needs are covered.

Protein requirements by age

Our protein needs don't stay the same over the course of our lives - age is also a factor in determining our daily protein requirements. Let’s take a look at some examples to see how our individual protein needs might change over the course of our life, from birth to old age.

• Protein for infants and children

As protein is needed for growth, it’s really important that children’s protein needs are met, but the amount they need to function is still relatively small compared to adults. Though teenagers and adults require more grams of protein each day, comparatively speaking children require more protein per kg of bodyweight: children age 4–13 years require 0.95g per kg whereas teenagers and adults 14–18 years and beyond require around 0.8g per kg. These figures are based on requirements for both growth and maintenance, but not physical activity.

This works out as these average intakes for children(1):

0-12mths - 12.5-13g

1-3 years - 13-15g

4-6 years - 15-20g

7-10 years - 20g

11-14 years - 20-30g

However, more recent research studies (9) suggest that these recommendations are too low, and that the RNI should be closer to 1.5g per day for children 6-10 years. These figures also don’t take into account a child’s activity level. Physical exercise increases the need for protein to replace amino acids and to develop and maintain increased muscle mass, and many parents of very active children want to know if they can give their children protein powders. Medical professionals tend to advise against this, as whilst child athletes may have a slightly increased need for protein, too much protein is equally not advisable for children. Overall, It’s important to ensure children are meeting their minimum protein requirements, but if your child is very active or you think they’re not developing as they should, speak to a doctor or health professional for more personalised advice before significantly increasing their daily protein intake.

• Protein for teenagers

The teenage years are a challenging time for kids, both physically and mentally. Protein requirements peak at around 0.8g per kg of bodyweight, remaining largely the same throughout adulthood. Protein needs also start to vary more according to gender.

Average daily RNIs for 15-18 years are 42.1g for males and 41.2g for females.(1).

This can be a time of extreme variations in physical activity and lifestyle. Typically teenagers have a low level of physical activity(10) but it’s also a time when many teenagers might start to take fitness, sports and games more seriously. They’re also likely to experiment with different lifestyle choices like extreme dieting or vegan/vegetarian diets. This is where, without proper care, they may start to fall short of their optimum protein intake. 

It’s also a very stressful time of life, with hormonal changes, dating, and exam pressures, and these stressors can also affect protein requirements. For more about the connection between protein and mental health, read our article Can protein help support mental health?

Our protein needs change over the course of our lives, and we need more protein in later life

• Protein for older people

Our activity levels often reduce as we get older, so you might think that older people need to eat less protein; however, the reverse is true. In fact, research (11,12) suggests that our protein needs increase as we age because protein turnover declines from 30% in normal adulthood to 20% by age 70, and that older people should be eating around 1.2g per kg of body weight daily, and at least 20g of protein at each meal. There are concerns that many older adults are not eating enough protein, as lack of exercise, dental issues, and medical complaints may affect appetite and eating patterns. 

Low levels of physical activity also lead to muscle loss, known as sarcopenia, in older adults, and this will be exacerbated by low protein intake, which can also affect skin health, immune function, and wound-healing and recovery from illness or injury. It is possible to rebuild muscle mass even after age 70, with exercise and adequate nutrition. However, it can be difficult for older people to shop for and prepare nutritious meals which contain enough protein for their needs, so it can be helpful for them to be subscribed to a healthy, balanced meal prep service.

Summary:

• Your body needs 9 essential amino acids from your diet each day
• Adults need around 0.6-0.8g of protein per kg of bodyweight each day, but your optimum individual protein requirements will vary depending on your age, weight and lifestyle.
• Pregnant women and older adults have an increased need for protein.
• If you’re on any form of restricted diet, then make sure you are replacing these foods with other types of protein.

If you enjoyed this article, take a look at these other articles on our website:

Can protein help support mental health?

Benefits of protein

Benefits of fibre in your diet

Protein and weight loss

References:

1. Protein - British Nutrition Foundation. Available at: https://www.nutrition.org.uk/healthy-sustainable-d... (Accessed: 17 November 2023).
2. Williamson E, Fung HJW, Adams C, West DWD, Moore DR. (2023) Protein Requirements Are Increased in Endurance-Trained Athletes but Similar between Females and Males during Postexercise Recovery. Med Sci Sports Exerc. ;55(10):1866-1875. doi: 10.1249/MSS.0000000000003219. Epub 2023 May 19. PMID: 37710376.
3. Thomas et al Nutrition and athletic performance. Medicine & Science in Sports & Exercise. 2016;48(3):543-568. doi:10.1249/MSS.0000000000000852
4. Jäger R, Kerksick CM, Campbell BI, et al. International society of sports nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. doi:10.1186/s12970-017-0177-8
5. Institute of Medicine . Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. National Academy Press; Washington, DC, USA: 2005.
6. Murphy MM, Higgins KA, Bi X, Barraj LM. Adequacy and Sources of Protein Intake among Pregnant Women in the United States, NHANES 2003-2012. Nutrients. 2021 Feb 28;13(3):795. doi: 10.3390/nu13030795. PMID: 33670970; PMCID: PMC7997328.
7. Leidy HJ, Tang M, Armstrong CL, Martin CB, Campbell WW. The effects of consuming frequent, higher protein meals on appetite and satiety during weight loss in overweight/obese men. Obesity (Silver Spring). 2011 Apr;19(4):818-24. doi: 10.1038/oby.2010.203. Epub 2010 Sep 16. PMID: 20847729; PMCID: PMC4564867.
8. Lonnie M, Hooker E, Brunstrom JM, Corfe BM, Green MA, Watson AW, Williams EA, Stevenson EJ, Penson S, Johnstone AM. Protein for Life: Review of Optimal Protein Intake, Sustainable Dietary Sources and the Effect on Appetite in Ageing Adults. Nutrients. 2018 Mar 16;10(3):360. doi: 10.3390/nu10030360. PMID: 29547523; PMCID: PMC5872778.
9. Hudson JL, Baum JI, Diaz EC, Børsheim E. Dietary Protein Requirements in Children: Methods for Consideration. Nutrients. 2021 May 5;13(5):1554. doi: 10.3390/nu13051554. PMID: 34063030; PMCID: PMC8147948.
10. van Sluijs EMF, Ekelund U, Crochemore-Silva I, Guthold R, Ha A, Lubans D, Oyeyemi AL, Ding D, Katzmarzyk PT. Physical activity behaviours in adolescence: current evidence and opportunities for intervention. Lancet. 2021 Jul 31;398(10298):429-442. doi: 10.1016/S0140-6736(21)01259-9. Epub 2021 Jul 21. PMID: 34302767; PMCID: PMC7612669.
11. Morris, S.; Cater, J.D.; Green, M.A.; Johnstone, A.M.; Brunstrom, J.M.; Stevenson, E.J.; Williams, E.A.; Corfe, B.M. Inadequacy of Protein Intake in Older UK Adults. Geriatrics 2020, 5, 6. https://doi.org/10.3390/geriatrics5010006
12. Chernoff R. Protein and older adults. J Am Coll Nutr. 2004 Dec;23(6 Suppl):627S-630S. doi: 10.1080/07315724.2004.10719434. PMID: 15640517.