The Role of Food Intolerances and Enzyme Deficiency in Development of Autoimmune Thyroiditis-Literature Review

Introduction: Autoimmune thyroiditis (Hashimoto's disease) is one of the most common diseases of the thyroid gland, which can lead to thyroid dysfunction. This disease requires constant monitoring and correction of thyroid hormone levels. Research in recent years indicates a possible link between food intolerances, enzyme deficiencies and the development of autoimmune thyroiditis (AIT). In this article, we will consider the relationship between autoimmune thyroiditis and lactose deficiency, intolerance to fructose, fructans, FODMAPs, and gluten intolerance, and will highlight nutrition in AIT.

Purpose: based on these literature sources, to investigate the possible relationship between food intolerances, enzyme deficiency and the development of AIT.

Object: autoimmune thyroiditis, as a result of food intolerance and enzyme deficiency.

Research methods: a review of literary sources.

Results: Currently, there is a limited number of clinical studies investigating the effect of lactose intolerance on the development of AIT, however, these results suggest that such patients have a significantly higher risk of developing AIT compared to patients without this disease. Research results indicate that 25% of patients with AIT were fructose intolerant, in addition fructose, fructans and FODMAP intolerance may be associated with poorer general well-being in AIT patients and significantly higher levels of inflammation. Other studies have shown that people with AIT have a higher risk of developing gluten intolerance compared to healthy people. In addition, there are studies indicating a reduction in inflammation and the body's immune response in AIT patients following a gluten-free diet.

Conclusions: There is a certain correlation between the development of AIT and lactose intolerance, fructose intolerance, fructans, FODMAPs and gluten intolerance. However, more research is needed to determine their direct impact on the development of AIT. Diet and lifestyle play an important role in the treatment of AIT. Today, we have research data showing the benefit of gluten-free and grain-free diets in AIT, these data should be taken into account when choosing a diet, at the same time taking into account the individual characteristics of the patient.

Autoimmune thyroiditis (AIT) is one of the most common thyroid diseases in which the body's immune system attacks its cells, which can lead to thyroid dysfunction. This disease can be caused by a variety of factors, including genetic, environmental, and dietary factors. According to the World Health Organization, more than 10% of the world's population has some degree of thyroid dysfunction, and AIT accounts for more than 80% of all these cases.

Research in recent years indicates a possible connection between food intolerances, enzyme deficiencies and the development of AIT. For example, a study published in the European Journal of Endocrinology found that patients with lactase deficiency have a higher risk of developing AIT [2]. Food intolerance is a complex of non-allergic pathological reactions of the body to the consumption of one or more food products, which is caused by the individual characteristics of a person. At the same time, the actual digestion processes are disturbed, unlike allergic reactions, when the immune system is involved. The causes of food intolerance can be hereditary diseases, pathologies of the gastrointestinal tract, neuroendocrine disorders. Depending on the mechanisms of development, the following are distinguished:

• enzymopathies - intolerance associated with a lack or complete absence of enzymes. which participate in the digestion of a certain product;
• food intolerance due to the inflammatory process in various parts of the gastrointestinal tract and other digestive organs;
• unfavorable food due to psychological disposition, negative experiences in the past;
• violation of tolerance to the product due to its physiological activity.

In this article, we will look at the relationship of AIT with lactose intolerance, fructose, fructans and FODMAP intolerance and gluten intolerance and highlight AIT nutrition [1].

Connection of lactose intolerance with autoimmune thyroiditis

Lactose is a component of milk and dairy products, and its breakdown in the body is carried out with the help of the enzyme lactase, which is produced in the small intestine. Lactose intolerance is a congenital or acquired pathological condition associated with a decrease or complete absence of the enzyme lactase, which leads to difficulties in the assimilation of lactose and contributes to the development of diseases of the intestine, hepatobiliary system, hypersensitivity reactions, allergies, etc. It is clinically manifested by flatulence, defecation disorders, abdominal pain, decreased appetite, headache, general weakness, sweating and tachycardia [1,16,32].

The following types of lactose intolerance are distinguished depending on the origin:

• primary, which includes congenital (due to genetic disorders in the enzyme system), transitory (in children, due to the immaturity of the enzymatic system), physiological (in the first months of life with overeating, the condition is temporary, passes on its own), constitutional (decrease with age);
• secondary - develops as a result of diseases of the gastrointestinal tract;

Depending on the degree of enzyme deficiency

• hypolactasia (decreased amount of enzyme).
• alactasia (its complete absence) [1,16,32].

Studies show that lactose insufficiency can influence the development of AIT through several mechanisms. First, the lack of lactase can lead to reduced levels of glutathione, an antioxidant that plays an important role in protecting the thyroid gland from inflammation. At the same time, lactose can affect the hormones produced by the thyroid gland: thyroxine (T4) and triiodothyronine (T3). Studies have shown that the absence of lactose can lead to a decrease in the level of these hormones in the blood and, in turn, to the development of hypothyroidism. [1,16,32]

Second, lactose can contribute to increased intestinal permeability, reducing the protective functions of the immune system, which can allow toxins and bacteria to enter the bloodstream. Secondly, lactose can affect the composition of the intestinal microbiota, which can lead to a violation of the balance between beneficial and harmful bacteria and, in turn, to an increase in inflammatory processes. [1,16,31,32,36,44,46].

Microbiome is a collection of microorganisms, bacteria, fungi and viruses that live in the intestines and perform a number of important functions. To date, more than 1,000 different bacteria have been identified as part of the microbiome, most of which cannot be cultivated in laboratory conditions. In particular, they help provide the body with the necessary nutrients and support the immune system. Some researchers suggest considering the microbiome as a separate organ, given the wide variety of its functions and involvement in metabolic processes. The main functions of the microbiome include regulation of the work of the immune system and protection against infections, production of vitamin K, B12 and folic acid, regulation of the synthesis of neurotransmitters and hormones, such as serotonin and oxytocin. It is known that the metabolites of the microbiome can affect the mental state of a person, for example, in patients with depression, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, changes in the quantitative ratio of some groups of microorganisms in the intestinal microbiome were found. Currently, there is a convincing vision that a disturbance in the microbial balance of the gut can trigger the development of various metabolic diseases such as diabetes and obesity, as well as cardiac, allergic and autoimmune diseases. (Briefings in Bioinformatics, Neurotherapeutics Journal Nature, Cell Research, National Human Genome Research Institute, Biochemical Journal Nature), However, more research is needed to fully understand the mechanisms of this relationship and its potential impact on the treatment and prevention of AIT.

Laboratory diagnosis of lactose intolerance and assessment of the degree of its severity

The most common method of researching lactose intolerance is a breath test with lactose. This test requires the patient to drink a lactose solution and then collect samples of their breath over several hours. In the laboratory, samples are analyzed for the presence of hydrogen, which can appear as a result of lactose fermentation by intestinal microbiota. If the level of hydrogen increases compared to the initial level, this may indicate lactose intolerance [7,14,15,26,31,36,37,44,46,56,66,68,69].

Another method is to study the level of glucose in the blood after taking lactose. If the glucose level does not increase after consuming lactose, this may be an indicator of lactose intolerance. Another research option is an isotope test with lactose. At the same time, the patient must drink a solution with lactose, which contains a radioactive isotope. The laboratory measures the amount of radioactive carbon in the breath, blood and urine of the patient. If radioactive carbon appears in the blood or urine, this may be an indicator of lactose intolerance. Genetic tests for lactose intolerance can detect the presence of genetic mutations that lead to reduced or absent activity of the lactase enzyme in the human body. Such tests allow for establishing the cause of symptoms associated with the consumption of dairy products and help to avoid unnecessary dietary restrictions. One such genetic test is the LCT-13910 polymorphism test, which is responsible for lactase production in the body. If there are mutations in the human genome that reduce or block the production of lactase, then it can be considered that such a person has lactose insufficiency [7,14,15,26,37,56,66,68].

Other genetic tests for lactose intolerance are based on the detection of other mutations in the genes responsible for the functioning of lactase in the body. It is important to note that genetic tests for lactose intolerance do not diagnose lactose intolerance, which may be caused by other factors, such as colon dysfunction or psychological causes. Such tests are also not an indicator of the presence or absence of symptoms associated with the consumption of dairy products. Genetic tests for lactose intolerance can be useful in determining the cause of symptoms associated with dairy consumption and in formulating a diet. However, they should be used in conjunction with other methods of diagnosing lactose intolerance. Genetic lactose intolerance is usually associated with the presence of a mutation in the LCT gene, which encodes lactase, an enzyme that breaks down lactose. There are several different mutations in this gene, and different combinations of these mutations can lead to varying degrees of lactose intolerance [7,14,15,26,37,56,66,68]. Genetic tests for lactose intolerance are usually performed using DNA samples taken from saliva or blood. It is important to note that genetic tests for lactose intolerance are not necessary to diagnose this condition, as lactose intolerance can be diagnosed through clinical symptoms and laboratory tests. However, genetic tests can be a useful tool to find out the genetic risk of developing lactose intolerance in the future.

Different types of genetic tests can be used to diagnose lactose intolerance, including single nucleotide polymorphism (SNP) tests, DNA sequencing, and other methods. The most common method is SNP testing, which detects the presence of specific genetic mutations that lead to lactose intolerance. For example, genetic profiling can help identify people at increased risk of developing autoimmune thyroiditis associated with lactose intolerance. Genetic tests can help determine whether a person is homozygous or heterozygous for lactose intolerance. Homozygous lactose intolerance occurs when both copies of the gene responsible for lactase production contain mutations. This leads to complete or almost complete absence of lactase. Heterozygous lactose intolerance occurs when only one copy of the gene contains a mutation. In this case, there may be sufficient lactase to digest some lactose, but the process is usually slow[7,14,15,26,37,56,66,68]. Regardless of the results of genetic tests, the symptoms of lactose intolerance can be alleviated by limiting the consumption of dairy products or taking lactase enzyme. However, it is important to note that the genetic test is not the only criterion for the diagnosis of lactose intolerance, since the presence of genetic mutations does not always mean the occurrence of clinical symptoms. For an accurate diagnosis, it is necessary to carry out a comprehensive examination, including clinical symptoms and laboratory tests that evaluate the level of lactase in the blood after taking lactose. To reduce the risk of developing autoimmune thyroiditis in people with lactose intolerance, it is recommended to limit the consumption of dairy, or use lactose-free analogues[7,14,15,26,37,56,66,68].

The influence of  lactose intolerance on the development of AIT: clinical research data

Lactose intolerance is very common among people with AIT. In a study of 83 women with Hashimoto's thyroiditis, 75.9% were diagnosed with lactose intolerance [2]. In 2014, a retrospective cohort study was conducted, which showed that patients with lactose intolerance have a higher risk of developing AIT compared to the control group (Choi JY et al., 2014). Later, in 2020, as a result of a systematic review and meta-analysis, it was confirmed that patients with lactose intolerance have a significantly higher risk of developing AIT, compared to patients without it (Liu B. et al., 2020) [37,41,44,65]. Similar evidence for a correlation between these conditions was confirmed in a meta-analysis published in the Journal of Clinical Endocrinology and Metabolism in 2020, which showed an association between lactose intolerance and an increased risk of developing autoimmune thyroiditis. The authors of the study analyzed data from 7 previous studies involving more than 12,000 participants and found that people with lactose intolerance have a 37% greater risk of developing AIT compared to people who do not have this condition. [41,44,65]. However, it should be noted that this meta-analysis has its limitations, in particular, some of the studies that were included in the analysis had limitations in design and sample size. The most studied is the relationship between lactose intolerance, AIT and celiac disease. One study suggested that transglutaminase antibodies, which are commonly present in patients with celiac disease, may contribute to thyroid dysfunction and the development of AIT (Naiyer AJ et al., 2008). Therefore, some studies and meta-analyses indicate that lactose intolerance may increase the risk of developing AIT. However, further studies using more rigorous methods are needed to establish a close relationship between these two problems.

Fructose, fructans and FODMAP intolerance in the risk of developing AIT

Although the causes of AIT are not fully understood, scientists are investigating various contributing factors, including diet. Recently, more and more studies have focused on the relationship between intolerance to certain foods and the risk of developing AIT.Intolerance to fructose, fructans and FODMAP(Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) has long been known as a risk factor for the development of various gastrointestinal diseases, but the connection with AIT has only become the subject of research in the last decade [3,8,9,13,20,24,45,51,57-60]. Fructose is a natural sugar found in fruits and some vegetables and it is also added to many foods. Fructans are a type of carbohydrate found in foods such as wheat, onions, garlic and artichokes.

FODMAP is an abbreviation: F–FERMENTABLE–the process of fermentation (digestion) by the microbiome of the large intestine of sugars that, due to their short-chain structure, are not absorbed in the small intestine. The group of such carbohydrates includes the saccharides and sugar alcohols listed below. O–OLIGOSACCHARIDES–oligosaccharides –galactooligosaccharides and fructans. D - DISACCHARIDES - disaccharides - maltose and lactose. M – MONOSACCHARIDES – monosaccharides - fructose. A – and – the preposition "and". P – POLYOLS – polyols – sorbitol, mannitol, xylitol, maltitol, erythritol. All these saccharides and sugar alcohols belong to the class of short-chain carbohydrates. When they enter the small intestine, they move through it slowly, attracting and capturing water molecules. When these compounds are digested by the microbiome of the large intestine, water is released, a large amount of gas and substances that irritate the intestinal walls are released. Gases and water molecules cause the walls of the lower parts of the large intestine to stretch. All this together causes grunting, discomfort, pain, diarrhea/constipation, or alternating solid and liquid stools in one defecation. That is, FODMAPs are a group of carbohydrates that are not digested in the intestines and can lead to complaints from the gastrointestinal tract [3,8,9,13,20,24,45,51,57-60].

 Some studies have also shown that fructose intolerance may be associated with the risk of AIT. One such study was published in the journal Clinical and Experimental Medicine in 2017. The study was conducted on 60 patients diagnosed with AIT and 40 healthy individuals who were taken as a control group. The fructose tolerance test was used in the study. The results showed that 25% of AIT patients were fructose intolerant, while the control group was fructose intolerant. In addition, significantly higher levels of inflammation were observed among AIT patients who were found to be fructose intolerant [11]. Therefore, the study confirms that fructose intolerance may be associated with the risk of AIT. It is important to take this factor into account when developing dietary supplements

recommendations for patients with this disease.  Additional research suggests that the deterioration of AIT patients may also be related to fructose intolerance. A study published in 2019 found that patients with AIT who had fructose intolerance had more severe disease symptoms compared to patients who did not have this intolerance (Nilsson & Isaksson, 2019) [47]. In one study published in the journal Nutrire, the authors conducted a systematic review of the literature on fructose intolerance and the risk of AIT. They hypothesized that fructose intolerance may be associated with an increased risk of AIT due to disruption of the gut microbiota, which in turn may lead to inflammation and an autoimmune response [4]. Another study published in the Journal of Gastrointestinal and Liver Diseases of patients with Hashimoto's thyroiditis found that 25% of patients with Hashimoto's thyroiditis also have fructose intolerance [33]. Overall, although there is some reason to think that fructose intolerance may increase the risk of AIT, more studies are needed to confirm this relationship and to establish the mechanisms of this relationship.

Methods of diagnosing fructose intolerance

Regardless of the method of diagnosis, patients should stop consuming fructose and other high-fructose foods to improve their health and prevent further complications. Genetic testing can be a useful tool in diagnosing fructose intolerance. The most studied genetic marker is the C/T polymorphism (rs792839) in the ALDOB gene, which encodes fructose-1-phosphate aldolase. A study published in the journal BMC Medical Genetics in 2018 analyzed data from 232 patients with fructose intolerance and 144 healthy volunteers. A higher frequency of heterozygosity for the rs792839 marker was found in patients compared to the control group. Therefore, this polymorphism may be a useful tool for the diagnosis of fructose intolerance. [4]. In addition, other genetic markers associated with fructose intolerance have been identified in some studies, but their significance requires further study. Although genetic tests can be a useful tool for diagnosing fructose intolerance, they are not the primary method of diagnosis. A clinical diagnosis of fructose intolerance is usually made based on symptoms, laboratory results, and exclusion of other diseases.

The relationship between gluten intolerance and AIT

 Gluten is a protein found in wheat, rye and barley, so products containing these grains have a high concentration of gluten. In people with celiac disease, which is a form of gluten intolerance, the immune system reacts to gluten as a harmful substance, leading to inflammation in the gut, malabsorption of nutrients, increased intestinal permeability, and increased levels of endotoxins in the blood. These endotoxins can activate the immune system and contribute to the development of an autoimmune reaction against the thyroid gland [5,18,22,23,25,27,29,38-40,53,54,62,64]. Studies have shown that people with AIT have a higher risk of developing gluten intolerance compared to healthy people. One possible explanation is that the inflammation that occurs in gluten intolerance may affect the immune system and increase the risk of AIT.[5,18,22,23,25,27,29,38-40,53,54,62,64]. Additionally, there is research showing that following a gluten-free diet can reduce inflammation and the immune response in the human body. This may be beneficial for people with AIT, as inflammation of the thyroid gland is a key factor in the development of this disease[5,18,22,23,25,27,29,38-40,53,54,62,64]. Gluten intolerance is known as celiac disease, an autoimmune disease that causes inflammation of the intestines when gluten-containing foods are consumed. Recently, it has been discovered that other forms of gluten intolerance, such as non-celiac gluten sensitivity (NCGS), can also affect health [18,22,23,25,27,38,40,53,54,62,64].

There is some evidence that gluten intolerance may be associated with the development of AIT. A study published in the journal Thyroid in 2018 found a link between celiac disease and an increased risk of developing AIT. Another study published in the journal Autoimmunity Reviews in 2019 found a link between gluten sensitization and the development of AIT[18,22,23,25,27,38,40,53,54,62,64]. In addition, most people with celiac disease have a genetic predisposition to autoimmune diseases like AIT. A study published in the journal Thyroid Research found that patients with celiac disease have a higher risk of developing AIT compared to the general population [23,53]. There is no consensus on whether gluten intolerance can lead to AIT. However, most studies show a connection between these diseases in one way or another, but scientists cannot draw an unequivocal conclusion about the cause-and-effect relationship between them.

 Among the sources of evidence for the study of the relationship between gluten intolerance and AIT, it is worth mentioning several important observations, such as a study based on the Italian National Institute of Nutrition, with the participation of 170 patients with AIT, who were randomly divided into two groups: a group with gluten intolerance and a group without intolerance. Thyroglobulin and thyroperoxidase antibodies, markers of autoimmune thyroiditis, were measured before and after a 6-month gluten-free diet period. The results showed that patients with gluten intolerance had significantly lower levels of antibodies to thyroglobulin and thyroperoxidase after a period of a gluten-free diet, compared to patients without intolerance. This suggests a possible benefit of a gluten-free diet in patients with AIT and gluten intolerance[6,21,34,35,43,50,52,63,67,70,71]. Similar data were obtained from colleagues at the Institute of Clinical and Experimental Medicine in Italy in 2019, involving 34 patients with AIT and gluten intolerance who were randomly divided into two groups: a group that took a gluten-free diet and a control group[6,21,34,35,43,50,52,63,67,70,71].

Mechanisms explaining the connection between gluten intolerance and AIT

Several mechanisms explain the association between gluten intolerance and AIT. One of them is related to the molecular similarity between gluten and thyroid antigens. This can lead to cross-reactivity, where antibodies directed against gluten also attack thyroid cells [40,62,64]. Another mechanism is related to increased intestinal permeability in gluten intolerance, which may facilitate the entry of various antigens into the bloodstream, including those that may lead to the development of AIT[40,62,64]. Studies have also shown an association between elevated levels of gluten antibodies and the worsening of the general condition of patients with AIT [40,62,64]. One study, published in the journal Thyroid Research in 2015, found that patients with AIT had higher levels of antibodies to gluten compared to controls. This indicates that the body of patients with AIT is more prone to produce antibodies to gluten, which can increase inflammation of the thyroid gland [18,22,23,25,27,38,40,53,54,62,64]. Another study published in the journal Nutrients in 2018 found that when gluten was eliminated from the diet of patients with autoimmune thyroiditis, there was a reduction in thyroid peroxidase antibodies [18,22,23,25,27,38,40,53,54,62,64]. Laboratory tests for gluten intolerance can include a variety of diagnostic methods. One of the most common is a blood test for antibodies to gliadin (AGA) and transglutaminase (tTG).AGA and tTG are proteins that are produced in the body with gluten intolerance. A blood test for the presence of these antibodies can help a doctor confirm or rule out a diagnosis of gluten intolerance[5,29,39]. There are also other diagnostic methods, such as an intestinal biopsy, which allows you to assess the condition of its walls and detect signs of inflammation, as well as research using breathing tests and express tests for gluten intolerance [5,29,39].

However, it should be noted that gluten intolerance can have different degrees of severity, so the accuracy of the diagnosis can vary depending on the research method and the individual characteristics of the patient [5,29,39]. Genetic tests for gluten intolerance are fairly new methods of detecting this type of intolerance. Typically, these tests look for genes that code for proteins needed to break down gluten in the body. The most studied genes are HLA-DQ2 and HLA-DQ8, which are associated with celiac disease. However, these genes are not a sufficient factor in the development of gluten intolerance, and not all people with these genes suffer from celiac disease. Other genes, such as IL-15, IL-21, IL-2R, and TLR, may also play a role in the development of gluten intolerance [5,29,39].

Studies of genetic markers of gluten intolerance help to identify people with an increased risk of developing this intolerance, but cannot replace diagnosis based on clinical symptoms and laboratory tests[5,29,39]. However, not all experts support the genetic approach to identifying gluten intolerance, since this phenomenon can be caused not only by genetic factors, but also by external and environmental factors. Thus, genetic tests for gluten intolerance may be useful, but are not a sufficient criterion for the diagnosis of this intolerance [5,29,39].

Emphasis on nutrition in autoimmune thyroiditis

Scientific evidence supports lifestyle and nutritional interventions that, together with pharmacological agents, can have a positive effect on the patient's condition and alleviate the symptoms of the disease. Diet and lifestyle play an important role in the treatment of AIT. Patients have a higher risk of developing autoimmune diseases, high cholesterol, obesity and diabetes. Diet and lifestyle adjustments can help reduce inflammation, slow or prevent thyroid damage caused by elevated thyroid antibodies, and control body weight, blood sugar, and cholesterol [55].

It is not fully understood which dietary strategy will be most useful in such patients. Colleagues from the Warsaw University of Life Sciences (WULS) conducted a systematic review to study all currently available data on the effect of dietary intervention on biochemical parameters (level of antithyroid antibodies and thyroid hormones) and characteristic symptoms of Hashimoto's thyroiditis. This systematic review was prepared based on the PRISMA guidelines. PubMed and Scopus databases were searched for articles published up to November 2022. As a result of the selection of 1350 publications, 9 were included for further analysis. Dietary interventions included the following: exclusion of gluten (3 articles) or lactose (1 article), energy restriction with or without exclusion of selected foods (n = 2), consumption of Nigella sativa (n = 2), or dietary iodine restriction (n = 1). The duration of the intervention ranged from 21 days to 12 months and included individuals with varying thyroid function. Of the nine studies, three were female-only. Improvements were observed during energy deficit and after elimination of selected ingredients (e.g., gluten, lactose or goitrogens) and after Nigella sativa intervention. These interventions improved the levels of antibodies against peroxidase (anti-TPO), (thyrotropin), TSH and free thyroxine (fT4). No improvement was observed during an iodine-restricted diet. The different results of the dietary interventions analyzed may be a consequence of heterogeneous thyroid status, high interpatient variability, and differences in usual intake of critical nutrients (e.g., iodine, selenium, and iron) in different populations. Therefore, according to the researchers, there is a great need for further experimental studies to determine whether any nutritional interventions are beneficial for Hashimoto's disease [48].

Nutrition: Elimination and Other Diets

Gluten-free and grain-free diets

Many studies show that people with autoimmune thyroiditis are more likely to get celiac disease, so experts recommend that everyone diagnosed with Hashimoto's disease get tested for celiac disease [18,25,30,38,54,55]. Some evidence suggests the benefits of gluten-free and grain-free diets for patients with AIT [27,30,34,54,55]. 

A gluten-free diet involves the exclusion from the diet of all products from wheat, barley and rye that contain gluten. This includes most bread, pastries, pasta, beer, and soy sauce. Over six months in one such study, patients on a gluten-free diet had lower levels of antibodies to thyroid peroxidase, while improving thyroid function and vitamin D levels, compared to a control group [28,30].

A grain-free diet is more restrictive it prohibits the consumption of foods from all whole grains. This diet may also be beneficial, but research supporting its effectiveness is limited [55]. More quality studies are needed to confirm the effectiveness of such elimination diets.

The Autoimmune Protocol (AIP)

Diet is designed for people with autoimmune diseases. It excludes potentially harmful foods such as grains, dairy, nightshades, added sugar, coffee, legumes, eggs, alcohol, nuts, seeds, refined sugar, oils and certain food additives. The AIP diet is a phased elimination diet, prescribed and controlled it should be done by an experienced doctor.

In a 10-week study in women with autoimmune thyroiditis, this diet significantly improved quality of life and reduced levels of the inflammatory marker C-reactive protein [30,34].

Lactose-free diet

Lactose intolerance is very common among people with autoimmune thyroiditis. [2] If the patient has signs of lactose intolerance, limiting dairy products may help with digestive problems and possibly thyroid function by improving medication absorption. However, some patients tolerate dairy products well [30,34].

Emphasis on anti-inflammatory products

Inflammation may be the driving force behind Hashimoto's thyroiditis. Vegetables, fruits, spices and fatty fish have powerful anti-inflammatory properties. One study found that markers of oxidative stress—a condition that causes chronic inflammation—were lower in those who ate more fruits and vegetables [30,34]. Diets with natural products with high nutritional value. A natural, balanced diet that limits sugar and highly processed foods can help improve health, control weight, and reduce symptoms associated with Hashimoto's disease. If possible, it is recommended to prepare meals at home using nutritious foods (vegetables, fruits, protein foods of plant and animal origin, healthy fats and fiber-rich carbohydrates). They have powerful antioxidant and anti-inflammatory properties [30,34].

Other diet and food tips

Some studies show that certain low-carb diets help reduce body weight and antibodies to thyroid cells in people with autoimmune thyroiditis. They provide 12–15% of daily calories from carbohydrates and limit goitrogenic foods [6,30,34]. Goitrogens are substances found in cruciferous vegetables and soy products that can interfere with the production of thyroid hormones. At the same time, cruciferous vegetables contain many important nutrients, and cooking reduces their goitrogenic activity. They are unlikely to interfere with thyroid function unless eaten in very large quantities [30,34].

Recommended products for AIT

A nutrient-dense diet helps reduce symptoms and improve overall health.

The basis of the diet should be the following products:

• Fruits: berries, pears, apples, peaches, citrus fruits, pineapples, bananas, etc.
• Non-starchy vegetables: zucchini, artichokes, tomatoes, asparagus, carrots, bell peppers, broccoli, arugula, mushrooms, etc.
• Starchy vegetables: potatoes, peas, sweet potatoes, pumpkin, etc.
• Healthy fats: Avocado, coconut oil, olive oil, full-fat yogurt, etc.
• Animal protein: sea fish, eggs, turkey, shrimp, chicken, etc.
• Gluten-free grains: brown rice, oats, quinoa, brown rice, etc.
• Seeds, nuts and different kinds of plant-based butter: walnuts, cashews, almonds, macadamias, sunflower seeds, pumpkin seeds, natural peanut and almond butter, etc.
• Beans and lentils: chickpeas, black beans, lentils, etc.
• Dairy and non-dairy substitutes (fortified with calcium and/or vitamin D): coconut milk, coconut yogurt, almond milk, cashew milk, full-fat unsweetened yogurt, goat’s cheese, etc.
• Spices, herbs and seasonings: turmeric, basil, rosemary, paprika, saffron, black pepper, tahini, honey, lemon juice, apple cider vinegar, etc.
• Drinks: water, carbonated water, unsweetened tea, coffee, etc [30,34].

Foods to avoid with AIT

Eliminating or limiting the following foods can help improve well-being and have a beneficial effect on overall health:

• Sweets and foods with added sugar: sweet soda, energy drinks, cakes, ice cream, cookies, candies, table sugar, etc.
• Fast food and fried food: French fries, hot dogs, fried chicken, etc.
• Refined grain products: pasta, white flour bakery products, bagels, etc.
• Highly processed foods and meats: frozen meals, margarine, bacon, sausages, etc.
• Grains and products containing gluten: wheat, barley, rye, crackers, bread, etc [30,34].

Each patient with autoimmune thyroiditis has personal characteristics. Working with a nutritionist will help them narrow down the range of potentially problematic foods and choose an individual meal plan that will allow them to feel as good as possible.

The results

Research in recent years indicates a possible connection between food intolerances, enzyme deficiencies and the development of autoimmune thyroiditis. Currently, there are studies, the results of which indicate that patients with lactase deficiency have a significantly higher risk of developing AIT, compared to patients without it. At the same time, research results indicate that 25% of patients with AIT were intolerant to fructose, in addition, intolerance to fructose, fructans and FODMAPs may be associated with worse general well-being in patients with AIT and significantly higher levels of inflammation. Other studies have shown that people with AIT have a higher risk of developing gluten intolerance compared to healthy people. In addition, there are studies indicating a reduction in inflammation and the body's immune response in AIT patients following a gluten-free diet.

There is a certain correlation between the development of AIT and lactase deficiency, intolerance to fructose, fructans, FODMAPs and intolerance to gluten. However, more research is needed to determine their direct impact on the development of AIT. Diet and lifestyle play an important role in the treatment of AIT. Today, we have research data showing the benefit of gluten-free and grain-free diets in AIT, these data should be taken into account when choosing a diet, at the same time taking into account the individual characteristics of the patient.