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  • Writer's pictureDr Gabi Clinic

Is the key to Djokovic’s success his change in diet?

When a World Number 1 Novak Djokovic attributes his 2011 tennis season, when he won “ten titles, three Grand Slams, and forty-three consecutive matches” to a recent change in diet, people stop to listen to the ingredients that went into making this tennis champion.1

In his book, Serve to Win, Djokovic describes himself as collapsing during matches, double-faulting during critical points and having to retire during tournaments. His book outlines the suspected diagnosis of gluten intolerance given by nutritionist Dr Cetojevic, which I did find somewhat curious and interesting…

“With the bread against my stomach, my arm struggled to resist Cetojevic’s downward pressure. I was noticeably weaker”.1

How on earth could the pathophysiology behind gluten intolerance lead to this reaction? What Djokovic is describing is something called kinesiology muscle testing and is a known, although seemingly scientifically unproven way to test for allergens. A positive kinesiology test would be holding the allergy provoking food in one hand (in this case gluten-containing bread) and resulting in muscle weakness in the other arm. We have been unable to find robust scientific foundations to explain how this test works.

That said, for Djokovic, his blood test for gluten antibodies was positive, supporting the kinesiology result.2 Antibodies are proteins made by the body in response to substances the body deems are foreign, with the role of binding and labelling the substance which then triggers an immune reaction.

His book gives general advice for everyone not just people with specific gluten intolerance. But is a gluten-free diet only beneficial to those with gluten-intolerance or is it a healthier alternative for everyone?

With celebrities and athletes, like Djokovic, Kourtney Kardashian and Miley Cyrus, advocating gluten-free diets, as well as the increase in the variety of gluten-free products in shops, a gluten-free diet does have somewhat ‘trendy’ connotations.

So, what is gluten?

Gluten is a protein processed from wheat and other related grains like barley and rye.3 It’s elastic properties mean that it a useful component in pasta and bread, soy sauce, and can also-interestingly-be found in lipsticks and Play-Doh.4

A gluten-free diet is the recommended diet for people with certain conditions such as coeliac’s disease. In this condition, eating gluten causes the body to attack its own cells in the digestive tract, specifically, the small intestine- leading to impairment of nutrient absorption.5 Coeliac disease can be associated with nutritional deficiencies, a blistering rash and an increased risk lymphoma and small bowel cancer.6 The symptoms of coeliac disease include having a swollen stomach, diarrhoea, foul-smelling stools, and, specifically in children generalised weakness, lethargy and lack of weight gain.7

A gluten-free diet is also recommended for those with non-coeliac gluten sensitivity (NCGS) (like Djokovic) and wheat allergy.8 NCGS is a relatively new subtype of gluten intolerance whereby consumption of gluten leads to similar symptoms of coeliac disease but without damage to the intestinal wall.9 On adopting a gluten-free diet the symptoms go away.10 Symptoms of NCGS are quite non-specific and can affect different parts of your body. A few examples are headaches, tiredness, joint pain, eczema, abdominal pain, bloating and diarrhoea.6 As the symptoms can vary person to person it is a condition which is often self-diagnosed without medical advice.10 It is important to note that the diagnosis of NCGS cannot be made until coeliac disease and wheat allergy have been eliminated.10 Therefore if you are experiencing symptoms it is best to go seek medical advice before making changes to your diet.

Studies show people with autoimmune conditions such as psoriasis or lupus may benefit from a gluten-free diet but further research is needed in this area.3 Most importantly there is established evidence stating that a gluten-free diet is beneficial for those with thyroid disease, particularly, Hashimoto’s thyroiditis.11 Hashimoto’s is an autoimmune condition in which the body destroys the thyroid gland (this gland produces a very important hormone called thyroxine which is required for multiple processes in the body). Gluten can make this autoimmune process even worse because it contains a protein called gliadin which is a similar molecule to the tissue of thyroid gland.12 The body detects the presence of gliadin as it enters the blood from the gut due to leaky gut syndrome (explained further on in the article).12 Once detected, the body reacts to it in a similar way to how it reacts to the thyroid gland, worsening the symptoms of hypothyroidism.12 Look out for another blog article where we discuss this in more detail.

Let’s debunk some gluten-free diet myths that do not apply to people with coeliac’s disease, NCGS or thyroid disease.

1) “A gluten-free diet can lead to weight loss”

Our research could not find evidence to support this.

The above statement is also dependent on what type of gluten-free diet you lead. Based on the literature it is not purely the lack of gluten itself which is exerting weight loss effects, rather other components. A study in Australia found that gluten products in core food categories have overall similar nutritional profiles to gluten-free foods.13 Therefore it is dependent on the types of gluten-free foods you opt for: eating very fatty gluten-free foods will have similar implications to that of eating fatty non-gluten free foods. People with a gluten-intolerance may be encouraged to opt for foods which are naturally gluten-free rather than gluten-free bread, pasta and cereal products which may contain increased fat and sugar.6

2) “A gluten-free diet is a healthier alternative”

Eating high amounts of gluten can lead to leaky gut also known as intestinal permeability even in those who do not have coeliac’s disease.11 Gluten has glue-like properties and can cause the release of an inflammatory protein called zonulin which causes gaps to form in the lining of the gut leading to food particles leaking into the bloodstream.11 These proteins do not belong in the bloodstream and cause an immune response which in turn leads to systemic inflammation. However, evidence shows eating no gluten at all can lead to vitamin deficiencies in iron or folate as gluten-containing bread and cereals are often fortified with vitamins.9 Balance is key so it could be worth trying a low gluten approach. This alone is not the magic answer to leading a healthier life.

3) “A gluten-free diet will improve my athletic performance”

If you have the coeliac disease it may. In this condition, the tiny projections of the small intestine (called villi) are destroyed. As the role of these villi is to increase the surface area of the small intestine for absorption of nutrients, destruction of it results in impaired absorption of vitamins including iron, b12 and folate.5 Following a gluten-free diet prevents this from happening, allowing absorption of nutrients which are important in increasing athletic performance.

Our research was unable to find solid proof of a gluten-free diet improving athletic performance for those without a gluten intolerance.

Purpose Print Summary

The bottom line is that research shows gluten can cause inflammation and intestinal permeability (leaky gut). If you think you may have a gluten allergy or intolerance it is worth discussing this with your doctor and having a coeliac’s disease test. They may recommend further investigations above this. If you have already excluded gluten from your diet this test may not pick up the disease. Once an obvious disease is excluded some people may want to try 4 weeks without gluten and then reintroduce it to their diet to see if symptoms return if they do a low gluten diet option may be an especially relevant good option going forward. Being completely gluten-free can be restrictive with financial and psychosocial implications but is life-transforming for people with established coeliac’s disease.

Going completely gluten-free it is not a decision to take lightly and is always best implemented with the support of a dietician. Choosing to reduce (not completely stop) gluten intake is an easy, safe lifestyle change people can make to their diet help reduce intestinal permeability yet still get the nutrition they need.


[1] Serve to Win: The 14-Day Gluten-Free Plan for Physical and Mental Excellence - Novak Djokovic - Google Books. (n.d.). Retrieved December 6, 2019, from to win&f=false

[2] Tennis Champ Djokovic Talks Game-Changing Gluten-free Diet - (n.d.). Retrieved December 6, 2019, from

[3] Gaesser, G. A., & Angadi, S. S. (2012). Gluten-Free Diet: Imprudent Dietary Advice for the General Population? JAND, 112, 1330–1333.

[4] Trede, I. (2019). CU Scholar The American Gluten Craze: Its Origins, Persistence, and Impacts on the Safety of Gluten-Free Boulder Restaurant Foods The American Gluten Craze​ : Its Origins, Persistence, and Impacts on the Safety of Gluten-Free Boulder Restaurant Foods. In History of Science. Retrieved from Technology, and Medicine Commons, Public Health Commons website:

[5] Harris, M. M., & Meyer, N. (2013). GO GLUTEN-FREE. ACSM’s Health & Fitness Journal, 17(1), 22–26.

[6] Newberry, C., McKnight, L., Sarav, M., & Pickett-Blakely, O. (2017, November 1). Going Gluten-Free: the History and Nutritional Implications of Today’s Most Popular Diet. Current Gastroenterology Reports, Vol. 19.

[7] Fasano, A., & Catassi, C. (2001). Current approaches to diagnosis and treatment of celiac disease: An evolving spectrum. Gastroenterology, 120(3), 636–651.

[8] Gaesser, G. A., & Angadi, S. S. (2012). Gluten-free diet: Imprudent dietary advice for the general population? Journal of the Academy of Nutrition and Dietetics, 112(9), 1330–1333.

[9] Going gluten-free just because? Here’s what you need to know - Harvard Health Blog - Harvard Health Publishing. (n.d.). Retrieved November 3, 2019, from

[10] Czaja-Bulsa, G. (2015, April 1). Non-coeliac gluten sensitivity - A new disease with gluten intolerance. Clinical Nutrition, Vol. 34, pp. 189–194.

[11] Does Gluten Cause Thyroid Conditions? - Dr Izabella Wentz. (n.d.). Retrieved December 6, 2019, from

[12] Why gluten needs to go if you have Hashimoto’s | Dr Mark Hyman. (n.d.). Retrieved January 2, 2020, from

[13] Y Wu, J. H., Neal, B., & Trevena, H. (2015). Are gluten-free foods healthier than non-gluten free foods? An evaluation of supermarket products in Australia. British Journal of Nutrition.

Aditi Rajgopal - Purpose Print Team

Disclaimer: Information in our blogs are as accurate and a comprehensive as possible. This is general advice and should not be used as a substitute for the individual advice readers might receive from consulting their own doctor. For other medical professionals reading, it is advised to use your own clinical judgement when interpreting the information and deciding how to best apply this to the treatment of their patients. Please see our terms and conditions page for further information on this.

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