I need some help in taking the decision to use the supplement. I am trying to build my body but couldn't get a better result even after 6 months of continuous training, when asked my fellow trainer he told me that I was lacking power and needed to take protein supplements in order to build bigger muscles.

Also I have heard people say that using supplements to build your body might have some residual effect on the organs of our body. Is this really true?

Do protein supplements have any side-effects?

  • 7
    In order to thank him, you might want to consider marking his answer as correct.
    – G__
    Aug 9, 2011 at 4:09
  • Ioannis Delimaris, “Adverse Effects Associated with Protein Intake above the Recommended Dietary Allowance for Adults,” ISRN Nutrition, vol. 2013, Article ID 126929, 6 pages, 2013. doi:10.5402/2013/126929@hindawi.com/journals/isrn.nutrition/2013/126929
    – user10402
    Aug 5, 2014 at 20:10

2 Answers 2


Unfortunately, the bulk of protein study centers around its efficacy (or usefulness), not harmful side effects. That said, excess protein (beyond what the body needs to build muscle) is broken down in the kidneys to become glycogen. Drinking plenty of water facilitates this process and makes your kidneys happy. However, if your kidneys are not functioning normally, an excess of protein can be dangerous for you.

Now, based on a Consumer Reports study on available protein powders there are other harmful chemicals that are present in higher densities than they would be in naturally occurring food. These are things like cadmium, arsenic, etc. The numbers in the chart represent the load of the chemicals in 3 servings of the protein. The protein maker's response calls the study into question saying that the CR report had an agenda.

All that said, there are a couple reasons for not building more muscle:

  • You did not do enough work to cause the body to adapt (see Practical Programming by Rippetoe and Dr. Kilgore [book])
  • The body's adaptive systems did not have the resources required to hyper-compensate. (see same resource)

Your trainer believes that the problem you are facing is the second bullet point. In essence your body needs sufficient protein, calories and rest in order to build the muscle required to do more work.

Underweight (by weightlifting standards) lifters will constantly run into this problem. Protein powders are simply one way to get that extra protein and in many cases calories. Another way is the "Gallon of Milk a Day" (GOMAD) approach which will have the same effect for probably less money and fewer risks of having too much of the disagreeable heavy metals found in the CR report. NOTE: if you do GOMAD, don't do it for longer than 8 weeks at a time. You will also retain water, which will go away after you start drinking a gallon of water a day instead of the milk.

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    I've seen that chart on dangerous metals in protein powders before. I've always wondered why the more expensive protein powders have a lower dangerous metals to protein ratio than the cheap powders. I thought that by paying more, you're paying for less fat/cholesterol/carbs and faster absorbing protein. Why should you have to pay more to not get poisoned? Promoting the safeness of the powder has not been a marketing point of any supplement company as far as I know.
    – JoJo
    Aug 2, 2011 at 16:37
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    Has to do with the processing and quality control. The more expensive powders go through stricter quality controls and gets you a better protein. Until the CR report, no one even questioned the amount of dangerous metals in protein powders. Aug 2, 2011 at 17:05
  • I would point out that the CR report is somewhat skewed, in that not all samples of the protein supplements tested produced anomalous results, and not all protein supplements were tested. It's somewhat alarmist, designed to get people to buy the magazine/article.
    – JohnP
    Sep 10, 2012 at 15:06
  • There is an wonderful sites who review supplements for living : labdoor.com and consumerlab.com ! They also measure the quantity of metals too !! I guess the cheap ones have more poison because the filtering is more expensive...anyway this is a thing FDA should enforce a maximum level for this substances
    – Freedo
    Jun 18, 2015 at 16:18

On the other hand we may wonder what are the side effects of taking supplementary protein , assuming the guaranteed quality of the product.

I will draw your attention to this study published at July 2013 and examined the side effects of this supplement on so many different aspects. This paper answers following questions

Research questions

The research questions were formulated in cooperation with other relevant expert groups. The effects or associations marked with * should be reviewed in cooperation with or in the relevant expert groups (e.g. infants and children, elderly, pregnant and lactating women).

  1. What is the dietary requirement of protein and protein of different dietary sources for adequate growth, development, and maintenance of body functions, mainly based on N-balance studies?
  2. What is the association and what are the effects of different intake, timing, and frequency of protein and protein of different dietary sources, while considering the intake of other energy-giving nutrients at the same time, on: well-established markers or indicators of functional or clinical outcomes, such as serum lipids, glucose and insulin, blood pressure (BP), body composition, and bone mineral density (BMD)? functional or clinical outcomes including

    -pregnancy* or birth outcomes*, growth, development, and sarcopenia

    -cardiovascular diseases, weight outcomes, cancer, type 2 diabetes (T2D), fractures, renal outcomes, physical training, muscular strength, and mortality

  3. Does intake and dietary source of protein (including vegan diet) affect the lactation/milk production in Nordic countries in relation to lactation duration, infant's need, and growth?

As you'll find out reading the answers for these questions specially regards to adverse effects of protein supplements on Kidney, the results are evaluated as inconclusive.

Assuming the trustworthiness of the paper and hoping it's not bypassed or secretively funded by a supplement company I was relieved that not any significant/major side effect found in this level on a healthy adult.

Reference> Health effects of protein intake in healthy adults: a systematic literature review

Pedersen, Agnes N., Jens Kondrup, and Elisabet Børsheim. "Health effects of protein intake in healthy adults: a systematic literature review." Food & nutrition research 57 (2013).

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