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Do You Really Need Protein Shakes?

Testosterone is the primary male hormone. It is responsible for increasing muscle mass and strength, boosting libido and virility, and decreasing the risk of long-term illness. It is important when beginning a weight lifting plan to do everything you can to optimize your levels in order to accelerate your progress.

Protein is by far the most popular macronutrient in gym circles. The industry is now filled with ‘proteinized’ foods that promise muscle building effects, and it’s pretty common for regular gym goers to supplement protein shakes too. It is an almost ritual-like aspect of weight lifting.

But do you really need protein shakes? Can they affect T levels?

In this article we’ll take a look. This is what we’ll cover:

  • Why do you need this macronutrient?
  • Do you really need protein shakes?
  • Can protein affect T levels?

Why Do You Need Protein?

Protein is a macronutrient that has a number of functions. Whilst it’s probably best known for its role in growth, maintenance and repair of body tissues, it also has a number of other important functions too.

It is involved in the regulation of some hormones and enzymes, transportation and storage of different molecules, and production of antibodies as well.

It is therefore important to get enough of this nutrient in the diet. Current recommendations suggest around 0.8g/lb for a sedentary person but more recent studies suggest that intakes as high as 3.5lb may be suitable for those who wish to optimize athletic performance [1].

Although these amounts can be met with natural foods, many fitness enthusiasts still choose to supplement with protein shakes. But do you really need them and is there any additional benefit to using them? Read on to find out…


Key Point: Protein is best known for its role in growth, maintenance and repair of body tissues. It also helps to regulate some hormones and enzymes as well as produce antibodies.

Do You Need Protein Shakes?

Protein shakes can come from a number of different sources including pea and soy but the most popular of course is whey – a type of protein found in dairy products.

Manufacturers of supplements often cherry pick studies to show that shakes either before or after training are beneficial for promoting muscle gains.

Although these studies do exist [2], they are few and far between and the majority don’t back up these claims. For example, a study published in the American Journal of Clinical Nutrition [3] found that even after a 12-week weight training program, supplementing 20g of protein after each session caused no further increases in muscle size. 

It seems unlikely that you ‘need’ to take protein shakes, but ultimately they provide a convenient source of the macronutrient in order to achieve the recommended daily amount – this may be useful for those who struggle to obtain it from food for whatever reason.

However, you need to be aware that whilst protein is an important building block for muscle, it can also have a negative effect on T levels.

Typically, shakes are taken throughout the day in order to keep levels ‘topped up’ to maximize muscle protein synthesis. However, a study by Hulmi et al [4] found that ingesting a 25g protein shake prior to strength training significantly decreased testosterone and growth hormone levels – both important hormones for muscle building.

So could protein really decrease testosterone levels? Let’s take a deeper look at the research…


Key Point: Protein shakes ingested prior to strength training might decrease testosterone and growth hormone levels.

The Protein and Testosterone Link?

A large proportion of T in the blood circulates bound to albumin and sex hormone binding globulin (SHBG). Only a small amount of testosterone (around 3%) is not bound to these compounds meaning that it is bioavailable, or ‘free’.

The higher the SHBG levels, the lower the available testosterone. Studies have shown that low protein diets are directly related to high SHBG levels, which of course is bad for optimal T levels [5].

But that doesn’t mean that more is better.

Some studies have found that high protein diets decrease testosterone in male strength athletes [6]. In one study, published in the Journal of Applied Physiology, 12 volunteers participated in a weight training program and had their diets monitored over a 17-day period.

The results showed that the amount of protein in the diet was a good indicator of pre-exercise T levels, and that higher protein levels were related to lower T both before and after exercise.

Similar results were seen in a group of older men after taking 15g of protein before and after a weight training session [7]. In this study, the impact of protein was to reduce both free and total T levels.

Research has also shown that high protein diets can elevate cortisol levels – the stress hormone that can decrease T levels.

A study published in Life Sciences [8] found that when volunteers ate a low protein diet (10% of total calories) and high carb diet for 10 days, their T levels increased, but when the group switched to a high protein diet (44% of total calories) their T levels dropped by 36% and cortisol increased. 

Soy-based shakes have also been found to blunt testosterone too. In a study conducted by William Kraemer and colleagues [9], 14-day soy supplementation was found to decrease testosterone, although it did not affect SHBG levels.

The take home message from these studies is that protein does not boost T levels and may possibly have a negative impact when taken in excess. 


Key Point: Excessive amounts of protein may have a negative effect on your T and SHBG levels.

Summary – Should You Use Protein Shakes

Protein is an important macronutrient that is involved in a number of regulatory processes. Whilst it is achievable to obtain the daily amounts of this nutrient through normal diet, many fitness enthusiasts choose to supplement with shakes such as soy and whey.

Research shows that excess protein may decrease testosterone concentrations as well as increase the hormone SHBG – this can also have a negative impact on T levels.

In the absence of any concrete evidence of the need to ingest protein quickly after exercise, and it’s potential effects on testosterone, we would suggest avoiding protein shakes and instead optimize muscle building by focusing on foods and supplements that can boost anabolic hormones.


  1. Phillips, SM et al. Dietary protein for athletes: from requirements to optimum adaptation. J Sports Sci. 2011; 29 Suppl 1: S29-38
  2. Cribb, PJ et al. Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy. Med Sci Sports Exerc. 2006; 38(11): 1918-25
  3. Verjijk, LB et al. Protein supplementation before and after exercise does not further augment skeletal muscle hypertrophy after resistance training in elderly men. Am J Clin Nutr. 2009; 89(2): 608-16
  4. Hulmi, JJ et al. Protein ingestion prior to strength exercise affects blood hormones and metabolism. Med Sci Sports Exerc. 2005; 37(11): 1990-7
  5. Longcope, C et al. Diet and sex hormone-binding globulin. J Clin Endocrinol Metab. 2000; 85(1): 293-6
  6. Volek, JS et al. Testosterone and cortisol in relationship to dietary nutrients and resistance exercise. J App Physiol. 1997; 82(1): 49-54
  7. Hulmi, JJ et al. Androgen receptors and testosterone in men–effects of protein ingestion, resistance exercise and fiber type. J Steroid Biochem Mol Biol. 2008; 110(1-2): 130-7
  8. Anderson, KE et al. Diet-hormone interactions: protein/carbohydrate ratio alters reciprocally the plasma levels of testosterone and cortisol and their respective binding globulins in man. Life Sciecnes. 1987; 40: 1761-1768
  9. Kraemer, WJ et al. The effects of soy and whey protein supplementation on acute hormonal reponses to resistance exercise in men. J Am Coll Nutr. 2013; 32(1): 66-74