When it comes to the most-talked-about nutrient, protein, the majority of questions concern our consumption and whether we’re getting enough of it per day. We get it, gym culture has made large swathes of society more active than ever, fuelling people’s thirst for knowledge in all things muscle. And when it comes to muscle, protein is important.
The macronutrient works within every cell of your body and is essential for our muscle growth, strength, and repair. It doesn’t matter how much you bench press from the off, if you’re not getting enough protein in your diet then you’re not going to see improving results.
Not enough protein in your diet reduces lean body mass, muscle strength, and function. It can also cause muscle cramping, weakness, and soreness. Your body will take protein from muscle tissue and use it as energy to support other vital body functions when protein is low.
This is not good. It eventually leads to muscle wasting and atrophy. So even if you’re not a regular gym bunny, it pays to make sure you’re getting enough protein per day to keep your body working the way it should.
How Many Grams Of Protein Do You Need Per Kilogram Of Body Weight Then?
The science on this simple question is mixed. Our view is based on a review of the science.
If you are an active person or are looking to lose body fat while preserving lean mass or to gain lean mass, a daily intake of 1.2–2 grams protein per kilogram of bodyweight a day is about right and supported by the current literature.
Below we’ll summarise some of the science and recommendations that helped us arrive at these numbers.
At the low end of the scientific literature 60–75g of protein a day is suggested as sufficient according to an early study from Kent State University.
A later study in 2000 from The University of Western Ontario, argues for more protein consumption than that, placing its estimates at around 1.6–1.8g per kg of bodyweight, while a 2004 study suggests a whopping 3.0g per kg of bodyweight.
Depending on your bodyweight this is a range of around 60 to 250g per day. As you can see, this is quite a spread and most studies note that the right amount depends on your activity levels. As with most things in nutrition, there’s no simple answer.
Coming To A Conclusion
To look into this there are a couple of good reviews of the literature out there. The first is the position taken by the American College of Sports Medicine which states 1.2 to 1.7g per kg in a day.
The other is the stand taken by the International Society of Sports Nutrition on protein and exercise which states: “Protein intakes of 1.4–2.0 g/kg per day for physically active individuals is not only safe but may improve the training adaptations to exercise training”
Our recommendation is therefore based on a review of these two trusted reviews – 1.2 to 2.0g of protein, per kg of body weight, per day.
Remember, for most people up to 2g/kg per day is going to be sufficient but it really depends on the nature of the sport or exercise. Resistance, strength, and power-based exercise which relies on muscle hypertrophy will be at the high end (over 2g/kg perhaps) whereas endurance-based exercise may be at the lower end (approximately 1.2–1.4g/kg per day).
Muscle Protein Synthesis In Women
Do note that the majority of recommendations about protein are based on male studies, and generalised to women, a point stressed in the work of physiologist Dr. Stacy Sims.
The female hormones, oestrogen and progesterone, have different effects on muscle protein synthesis. When it comes to hormonal changes, men do not have the same peaks and troughs as women, nor do these hormones work in the same way or produce the same levels (men have very low levels of oestrogen for example).
Intake requirements may differ depending on where you are in your menstrual cycle. Both oestrogen and progesterone are generally low during the first half of your cycle. Levels of the latter hormone generally rise in the second half though. Progesterone has a catabolic effect on protein metabolism meaning it breaks down muscle, and so you may need to up your protein intake during this period.
Similarly, a decline in oestrogen levels during menopause is linked to decreased muscle mass and bone strength, and so for this reason, post-menopausal women should eat more protein. For women over 50, The Mayo Clinic recommends 1.5 grams of protein per kg of weight.
Quality Versus Quantity
Also remember that not all protein sources are created equal. Proteins are made out of smaller molecules called amino acids, which are linked together to form long protein chains. These are then folded into complex shapes.
Some amino acids can be produced by your body like glutamine and asparagine for example (it pays to top these up sometimes by consumption). You have to get the others through your diet though. These are what we call essential amino acids.
That’s why as well as following your protein consumption by mass, you should also look at whether your protein sources are complete with all nine of these essential amino acids (this list on the 12 of the best vegan protein sources offers a good range of examples). So, eat smart, and enjoy your gains.