The Gluten-Free Diet

By Alex Boynay

Section 1: What is the Gluten-Free Diet?

Section 2: Sample Diet Plan

Section 3: What Do the Studies Show?

Section 4: Key Findings

Section 5: References

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Section 1: What is the Gluten-Free Diet?

Section 2: Sample Diet Plan

Breakfast (298 calories)

2/3 cup gluten-free oats in water, with ½ cup raspberries, 1 tbsp. sliced almonds, and 1 tsp. drizzle of honey

A.M. Snack (50 calories)

2 medium carrots

Lunch (315 calories)

Tuna and white bean spinach salad

P.M. Snack (47 calories)

½ apple

Dinner (501 calories)

1 serving roast salmon, ½ cup cooked brown rice, ¾ cup steamed broccoli

Section 3: What Do the Studies Show?

With the gluten-free diet there is a lot of variability in the results of the studies. Most of the studies are focused on celiac patients. In many cases, there are severe consequences for celiac patients who do not follow a strict gluten-free diet, in particular individuals who are also diabetic. Recently, the diet has become popularized for the general population. There are many factors to consider with this diet, it does has some negative side effects but in some cases it does appear to promote weight loss, lower the risk of some diseases, and is able to lower LDL levels in the body.

    There are several biological markers to test the impact of the gluten-free diet on the body. These include cortisol levels, blood glucose, and the ratio of LDL/HDL. Cortisol has several different effects on the body, it can be used to help control blood sugar levels, regulate metabolism, reduce inflammation, it’s involved in the breakdown of lipids, and it’s involved in regulating blood pressure (Talbott, 2007). One study found that celiac patients that followed a strict gluten-free diet had reduced cortisol levels, where not adhering to the diet could result in hypercorticism (Esposito, 2018), which results in the formation of a benign tumour that stimulates the production of cortisol. Blood glucose levels indicate the presence of glucose in the blood, where high levels can lead to diabetes. Gluten-free foods typically had a higher glycaemic index (Saadah et al., 2004), which results in higher levels of glucose in the blood. Accordingly, gluten-free foods had larger area under the curve (blood glucose) compared to their counterparts, with the exception of pasta and gluten-free pasta (Berti et al., 2004).  A study on kids with type I diabetes and the celiac disease found a significant increase in BMI and insulin dosage (Saadah et al., 2004). So there are important considerations for diabetics on the gluten-free diet. Another important biological marker is HDL/LDL which relates to cholesterol. High amounts of LDL in the body can lead to the buildup of fatty deposits which can damage arteries and contribute to heart disease. One study investigated the effects of a gluten-free vegan diet on patients with rheumatoid arthritis, which resulted in changes that are possibly atheroprotective and reduce inflammation, they also found a decrease in LDL and ratio of LDL/HDL, as well as increased anti-PC IgM and IgA (Elkan et al., 2008), which are antibodies. IgA plays a role in immune function of mucous membranes and IgM is one of the first antibodies produced at the sign of infection.

    The gluten-free diet can also be examined based on its ability to prevent certain diseases, including diabetes, cancer, cardiovascular disease, and fatty liver disease. While there was a study mentioned previously regarding diabetic coeliacs, there may be some evidence to support the gluten-free diet being a preventative measure. One such example is a study done on rats and measuring amounts of microflora in their gut. The rats on the gluten-free diet were less likely to develop diabetes than the control, they also had lower levels of commensal microflora in their gut, which was lower in the nondiabetic mice than the diabetic mice (Hansen et al., 2005), which is possibly through immunological means as suggested in the study. There weren’t as many other results on this topic, so while this study is on rats it would be interesting to see future studies on humans, with respect to diabetes prevention. The gluten-free diet has a more significant impact on cancer prevention in celiacs, as an older study found that celiac individuals, who did not strictly adhere to the gluten-free diet, had an increased risk of cancer in all sites (Holmes et al., 1989). Whereas another study found that gluten-free foods are typically deficient in dietary fibers, as well as some other vitamins and minerals which can play a role in cancer prevention (Vici et al., 2016). However, a careful diet or supplemental vitamins and minerals (ex. daily vitamin tablets) could help the latter. One study examined the risk of death associated with celiac patients based on small-intestine histopathology, they found that the two highest causes of death were from cardiovascular disease and malignancies (Ludvigsson et al., 2009). The latter relates to the study by Holmes et al., which found an increased risk of cancer in celiac patients who didn’t stick to the gluten-free diet. In terms of cardiovascular disease, there were some risk factors associated with it that were found in 14% of CD subjects on the gluten-free diet in one study (Norsa et al., 2013). The most common of these include high fasting triglycerides, elevated blood pressure and high concentrations of calculated LDL cholesterol , while a very little percent was found with insulin resistance (Norsa et al., 2013). This conflicts with the previous study that found that the gluten-free diet resulted in lower levels of LDL. In terms of fatty liver disease, there were no direct studies testing the ability of the gluten-free diet to prevent fatty liver disease. However, one found that this disease is typically associated with insulin resistance and hyperinsulinemia (Marchesini et al., 1999). Another study found that the gluten-free diet helps reduce insulin resistance by increasing expression of PPAR-gamma, insulin receptor, GLUT-4 and adiponectin (Soares et al., 2012). Given the factors described associated with the disease and the results of the study, suggest  that the gluten-free diet may be able to reduce the risk of developing fatty liver disease. While there is some contradictory evidence, it does appear that the gluten-free diet does have some preventative measures, however most of these studies were on celiac patients, so there is little direct evidence for general use.

    There is also some contradictory evidence in terms of weight loss with the gluten-free diet. One short term study found there was no positive or negative effect to athletic performance and general well-being of athletes on the gluten-free diet, however this was only on a seven day trial. A longer study might produce different results, but they were variable. One found that 80% of patients on the gluten-free diet for 2 years gained some weight with 50% being overweight or obese, while another found weight loss in obese or overweight patients on the gluten-free diet (Scaramuzza et al., 2013). Another found that gluten-exclusion can provide benefits to not only celiac patients, but others suffering chronic disease like obesity. By slowing down weight gain through the reduction of visceral adiposity and adipocyte size. These in turn can improve insulin resistance. Excess adiposity, inflammation and insulin resistance is correlated with macrophage infiltration through release chemokines that recruit macrophages. Both of these negative influence insulin signalling. They found that the gluten-free diet resulted in lower concentrations of pro-inflammatory cytokines and adipokines, in part through lipid mobilization and oxidation in adipose tissue (Soares et al., 2012). These results were confirmed in another test that found CD patients on a strict diet had a lower BMI, fat mass and lean mass than the control patients (Bardella et al., 2000).

    Overall, there is a lot of variety in the results of the gluten-free diet with a lack of studies on non-celiac individuals. However, there is more developing evidence as to the benefits of gluten-free diet in chronic diseases, such as obesity. However, as the gluten-free diet may lack full nutrient value then there should be careful monitoring to ensure that the daily intake requirements are met to support normal function and be a preventative measure. Gluten-free foods do typically have a higher glycemic index, but a strict diet does appear to show results in lowering BMI, reducing adiposity, and insulin resistance. There is also the factor of taste, as gluten-free foods may not taste as appearing so patients in the study may have preferred healthier options. This could be beneficial in not over consuming foods, there will be less incentive. As well as gluten-free foods typically being more expensive. There are many pros and cons, but with more research the gluten-free diet could show some promise.

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Section 4: Key Findings

Biological Markers

Cortisol: When following a strict gluten-free diet, celiac patients had lower cortisol levels than those that did not. Not following the diet may result in hypercorticism in rare cases (Esposito, 2018).

Blood glucose: Area under blood glucose curve higher for gluten-free foods than their counterparts, with the exception of pasta and gluten-free pasta (Berti et al., 2004). Also, gluten-free foods typically had a higher glycaemic index (Saadah et al., 2004).

HDL/LDL: Decrease in LDL and ratio of LDL/HDL, as well as increased anti-PC IgM and IgA (Elkan et al., 2008).

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Disease Prevention

Diabetes: Gluten-free diet resulted in fewer rats developing diabetes and they had lower levels of commensal microflora in the gut, which was lower in nondiabetic mice than diabetic mice. This is possibly through immunological means, as celiac disease is an autoimmune disorder (Hansen et al., 2005).

Cancer: Gluten-free foods typically are deficient in dietary fibers, as well as some other vitamins and minerals which play a role in cancer prevention (Vici et al., 2016). An older study found an increase in cancer in all sites in celiac patients who did not strictly adhere to a gluten-free diet or who partook in a normal diet (Holmes et al., 1989).

Cardiovascular disease: Several factors associated with cardiovascular disease were found in 14% of CD subjects on the GFD (Norsa et al., 2013). A study examining the risk of death associated with Celiac patients based on small-intestine histopathology found two highest causes of death were from cardiovascular disease and malignancies (Ludvigsson et al., 2009).

Fatty liver disease: Fatty liver disease is typically associated with insulin resistance and hyperinsulinemia (Marchesini et al., 1999). The gluten-free diet helps reduce insulin resistance by increasing expression of PPAR-gamma, insulin receptor, GLUT-4 and adiponectin (Soares et al., 2012). This suggests that the gluten-free diet may be able to reduce the risk of developing fatty liver disease.

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Weight Loss

Short term: A 7-day study found no significant changes in overall well-being of athletes partaking in the gluten-free diet (Lis et al., 2015).

Long term: Variety of results. One study found that 80% patients on GFD for 2 years gained some weight with 51% being overweight or obese. While another study found weight loss in obese or overweight patients on the GFD (Scaramuzza et al., 2013).

Effects of Physical Activity on Diet: A 7-day study found no positive or negative effect to the athletic performance and overall well-being of athletes (Lis et al., 2015).

Body composition/lean muscle mass: CD patients on a strict diet had a lower BMI, fat mass, and lean mass than the control patients (Bardella et al., 2000).

Section 5: References

Ann-Charlotte Elkan, Beatrice Sjöberg, Björn Kolsrud, Bo Ringertz, Ingiäld Hafström, Johan Frostegård. Gluten-free vegan diet induces decreased LDL and oxidized LDL levels and raised atheroprotective natural antibodies against phosphorylcholine in patients with rheumatoid arthritis: a randomized study [Internet]. Arthritis Research & Therapy. BioMed Central; 2008. Available from: https://arthritis-research.biomedcentral.com/articles/10.1186/ar2388

Association of nonalcoholic fatty liver disease with insulin resistance [Internet]. NeuroImage. Academic Press; 1999. Available from: https://www.sciencedirect.com/science/article/pii/S0002934399002715

Esmeralda Capristo, Giovanni Addolorato, Geltrude Mingrone, Andrea De Gaetano, Aldo V Greco, Pietro A Tataranni, Giovanni Gasbarrini; Changes in body composition, substrate oxidation, and resting metabolic rate in adult celiac disease patients after a 1-y gluten-free diet treatment, The American Journal of Clinical Nutrition, Volume 72, Issue 1, 1 July 2000, Pages 76–81, https://doi.org/10.1093/ajcn/72.1.76

Esposito S, Miconi F, Savarese E, et al. Physiolgic hypercortisolism at onset of celiac disease in a girl: A case report. Medicine (Baltimore). 2018;97(36):e12160.

Gaesser, Glenn A. et al. Gluten-Free Diet: Imprudent Dietary Advice for the General Population? Journal of the Academy of Nutrition and Dietetics , Volume 112 , Issue 9 , 1330 – 1333

Gluten free diet and nutrient deficiencies: A review [Internet]. NeuroImage. Academic Press; 2016 . Available from: https://www.sciencedirect.com/science/article/pii/S0261561416300887

Gluten-free diet reduces adiposity, inflammation and insulin resistance associated with the induction of PPAR-alpha and PPAR-gamma expression [Internet]. NeuroImage. Academic Press; 2012. Available from: https://www.sciencedirect.com/science/article/pii/S0955286312002264

Hansen, A. K., Ling, F. , Kaas, A. , Funda, D. P., Farlov, H. and Buschard, K. (2006), Diabetes preventive gluten‐free diet decreases the number of caecal bacteria in non‐obese diabetic mice. Diabetes Metab. Res. Rev., 22: 220-225. doi:10.1002/dmrr.609

Holmes GK, Prior P, Lane MR, et al. Malignancy in coeliac disease–effect of a gluten free diet. Gut 1989;30:333-338.

Lis, Dana & Stellingwerff, Trent & Kitic, Cecilia & Ahuja, Kiran & Fell, James. (2015). No Effects of a Short Term Gluten free Diet Performance-D.Lis2015.

Ludvigsson JF, Montgomery SM, Ekbom A, Brandt L, Granath F. Small-Intestinal Histopathology and Mortality Risk in Celiac Disease. JAMA. 2009;302(11):1171–1178. doi:10.1001/jama.2009.1320

Maria Teresa Bardella, Clara Fredella, Luigia Prampolini, Nicoletta Molteni, Anna Maria Giunta, Paolo A Bianchi; Body composition and dietary intakes in adult celiac disease patients consuming a strict gluten-free diet, The American Journal of Clinical Nutrition, Volume 72, Issue 4, 1 October 2000, Pages 937–939, https://doi.org/10.1093/ajcn/72.4.937

Norsa L, Shamir R, Zevit N, et al. Cardiovascular disease risk factor profiles in children with celiac disease on gluten-free diets. World J Gastroenterol. 2013;19(34):5658-64.

Packer SC, Dornhorst A, Frost GS. The glycaemic index of a range of gluten‐free foods [Internet]. The Canadian Journal of Chemical Engineering. Wiley-Blackwell; 2002 [cited 2019Mar7]. Available from: https://onlinelibrary.wiley.com/doi/full/10.1046/j.1464-5491.2000.00356.x

Saadah OI, Zacharin M, O’Callaghan A, et al. Effect of gluten-free diet and adherence on growth and diabetic control in diabetics with coeliac disease. Archives of Disease in Childhood 2004;89:871-876.

Scaramuzza AE, Mantegazza C, Bosetti A, Zuccotti GV. Type 1 diabetes and celiac disease: The effects of gluten free diet on metabolic control. World J Diabetes. 2013;4(4):130-4.

Talbott SM. The cortisol connection: why stress makes you fat and ruins your health. Almeda, CA: Hunter House; 2007.