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CHICAGO – , according to a lecture delivered at Freston Conference 2019, sponsored by the American Gastroenterological Association.
Although the literature is highly consistent, it contains discordant findings, and many questions remain unanswered. “We need more rigorous studies, and particularly more interventions, to truly understand the role diet may play in patients with IBD,” said Ashwin N. Ananthakrishnan, MD, MPH, associate professor of medicine at Massachusetts General Hospital in Boston.
Food can cause symptoms in IBD
Many patients with IBD are convinced that their diet caused their disease. A relevant point for physicians to consider is that these patients are at least as likely as is the general population to have intolerance or sensitivity to food components such as lactose and gluten. In a prospective questionnaire of 400 consecutive patients with IBD in the United Kingdom, 48% expressed the belief that diet could initiate IBD, and 57% said that diet could trigger a flare-up. In addition, 60% of respondents reported worsening of symptoms after eating certain foods, and about two-thirds deprived themselves of their favorite foods to prevent relapses (Inflamm Bowel Dis. 2016;22[1]:164-70). A French study found similar results. “Clearly there’s something there,” said Dr. Ananthakrishnan. Patients’ beliefs about the relationship between food and their symptoms are not simply misconceptions, he added.
A Canadian study published in 2016 found that almost one-third of patients with IBD avoid many food groups. “But there is significant heterogeneity in the foods that are avoided, and sometimes we mistake this heterogeneity for a lack of association between diet and symptoms in IBD,” said Dr. Ananthakrishnan. A larger number of patients avoid certain foods during periods of active disease, which suggests that food exacerbates their symptoms, he added. The same study showed that patients with IBD have more restrictive diets than do community controls. Patients eat fewer fruits and vegetables and generally consume less iron-rich food and less protein-rich food than healthy controls. GI intolerance, rather than professional advice, is the most common reason that patients with IBD restrict their diets (JPEN J Parenter Enteral Nutr. 2016;40[3]:405-11.).
A cross-sectional survey of 130 patients with IBD and 70 controls yielded similar results. Among patients, GI symptoms that resulted from consuming foods were not related to disease activity, disease location, or prior surgery. Patients with IBD tended to have greater frequency of GI intolerance to foods than did controls (Scand J Gastroenterol. 1997;32[6]:569-71.).
Diet may cause intestinal inflammation
International research has recorded increases in the consumption of sugar and fat (particularly saturated fat) and concomitant decreases in fiber consumption during the past several decades. The incidence of IBD has increased in parallel with these dietary changes with a remarkably similar trajectory, said Dr. Ananthakrishnan. The correlation between dietary changes and IBD incidence “holds true even more strikingly in countries that are now experiencing Westernization,” he added. These countries have undergone more rapid dietary changes, and their IBD incidence has doubled or tripled. The transition to “less traditional diets” appears to promote intestinal inflammation, said Dr. Ananthakrishnan.
An analysis of data from the European Prospective Investigation into Cancer (EPIC) study found an association between high consumption of sugar and soft drinks, together with low consumption of vegetables, and risk of ulcerative colitis (Inflamm Bowel Dis. 2016;22[2]:345-54.). A subsequent analysis of data from two prospective Swedish cohorts, however, found no association between consumption of sugary beverages and risk of Crohn’s disease or ulcerative colitis (Clin Gastroenterol Hepatol. 2019;17[1]:123-9.).
Although the data on sugar are mixed, data on the association between other macronutrient groups and risk of IBD are more consistent. When Dr. Ananthakrishnan and colleagues examined data from the Nurses’ Health Study, they found that the highest quintile of dietary fiber intake was associated with a 40% reduction in risk of Crohn’s disease, compared with the lowest quintile. The observed reduction of risk seemed to be greatest for fiber derived from fruits. Fiber from cereals, whole grains, or legumes, however, did not affect risk of Crohn’s disease (Gastroenterology. 2013;145[5]:970-7.).
A separate analysis of the Nurses’ Health Study suggested that high intake of n-3 polyunsaturated fatty acids (PUFAs) and low intake of n-6 PUFAs was associated with a 31% reduction in risk of ulcerative colitis and a 15% reduction in the risk of Crohn’s disease. These data were consistent with a previous analysis of EPIC data that found that high intake of n-6 PUFAs was associated with increased risk of ulcerative colitis (Gut. 2009;58[12]:1606-11.). Other analyses indicate that genetic polymorphisms likely modify the association between PUFAs and risk of ulcerative colitis, said Dr. Ananthakrishnan. “There may be an additional layer of complexity beyond just measuring your dietary intake.”
In addition to macronutrients, micronutrients can modify a patient’s risk of ulcerative colitis or Crohn’s disease. When Dr. Ananthakrishnan and colleagues examined the Nurses’ Health Study, they found an inverse association between vitamin D intake and risk of Crohn’s disease (Gastroenterology. 2012;142[3]:482-9.). In a separate study, they found that a zinc intake greater than 16 mg/day was associated with reduced risk of Crohn’s disease (Int J Epidemiol. 2015;44[6]:1995-2005.).
Patients aged older than 40 years and patients of European ancestry tend to be overrepresented in cohort studies, which reduces the generalizability of their conclusions, said Dr. Ananthakrishnan. Furthermore, cohort studies have not produced consistent findings regarding the relationship between various dietary components and risk of IBD. Nevertheless, the data suggest that dietary patterns may be associated with incident Crohn’s disease or ulcerative colitis.
An influence of diet on IBD risk is plausible
One mechanism through which diet may exercise a causal influence on the risk of IBD is by affecting the microbiome. In 2011, investigators studied 98 healthy volunteers who answered questionnaires about their diet. The researchers also used 16s rDNA sequencing to characterize the population’s stool samples. A diet high in animal protein, amino acids, and saturated fats was associated with large populations of Bacteroides. A diet low in fat and in animal protein, but high in carbohydrates and simple sugars was associated with large populations of Prevotella. When the investigators conducted a controlled-feeding study of 10 patients, microbiome composition changed within 1 day of initiating a high-fat-and-low-fiber or a low-fat-and-high-fiber diet (Science. 2011;334[6052]:105-8.). A more recent study showed that the diversity of the microbiome increased with the adoption of an animal-based diet (Nature. 2014;505[7484]:559-63.).
Diet also may exert a causal influence on IBD risk by altering the intestinal barrier. In an experimental model, 5-mg/mL concentrations of fiber from plantain and broccoli significantly reduced the translocation of Escherichia coli through a human intestinal epithelial barrier (Gut. 2010;59[10]:1331-9.). Increased fiber intake may thus result in reduced intestinal inflammation, said Dr. Ananthakrishnan.
Observational and experimental evidence thus support an effect of diet on the risk of IBD, and experimental evidence indicates that this effect is biologically plausible. Nevertheless, “there are many missing links,” and further study will clarify the role of diet in IBD incidence, said Dr. Ananthakrishnan.
CHICAGO – , according to a lecture delivered at Freston Conference 2019, sponsored by the American Gastroenterological Association.
Although the literature is highly consistent, it contains discordant findings, and many questions remain unanswered. “We need more rigorous studies, and particularly more interventions, to truly understand the role diet may play in patients with IBD,” said Ashwin N. Ananthakrishnan, MD, MPH, associate professor of medicine at Massachusetts General Hospital in Boston.
Food can cause symptoms in IBD
Many patients with IBD are convinced that their diet caused their disease. A relevant point for physicians to consider is that these patients are at least as likely as is the general population to have intolerance or sensitivity to food components such as lactose and gluten. In a prospective questionnaire of 400 consecutive patients with IBD in the United Kingdom, 48% expressed the belief that diet could initiate IBD, and 57% said that diet could trigger a flare-up. In addition, 60% of respondents reported worsening of symptoms after eating certain foods, and about two-thirds deprived themselves of their favorite foods to prevent relapses (Inflamm Bowel Dis. 2016;22[1]:164-70). A French study found similar results. “Clearly there’s something there,” said Dr. Ananthakrishnan. Patients’ beliefs about the relationship between food and their symptoms are not simply misconceptions, he added.
A Canadian study published in 2016 found that almost one-third of patients with IBD avoid many food groups. “But there is significant heterogeneity in the foods that are avoided, and sometimes we mistake this heterogeneity for a lack of association between diet and symptoms in IBD,” said Dr. Ananthakrishnan. A larger number of patients avoid certain foods during periods of active disease, which suggests that food exacerbates their symptoms, he added. The same study showed that patients with IBD have more restrictive diets than do community controls. Patients eat fewer fruits and vegetables and generally consume less iron-rich food and less protein-rich food than healthy controls. GI intolerance, rather than professional advice, is the most common reason that patients with IBD restrict their diets (JPEN J Parenter Enteral Nutr. 2016;40[3]:405-11.).
A cross-sectional survey of 130 patients with IBD and 70 controls yielded similar results. Among patients, GI symptoms that resulted from consuming foods were not related to disease activity, disease location, or prior surgery. Patients with IBD tended to have greater frequency of GI intolerance to foods than did controls (Scand J Gastroenterol. 1997;32[6]:569-71.).
Diet may cause intestinal inflammation
International research has recorded increases in the consumption of sugar and fat (particularly saturated fat) and concomitant decreases in fiber consumption during the past several decades. The incidence of IBD has increased in parallel with these dietary changes with a remarkably similar trajectory, said Dr. Ananthakrishnan. The correlation between dietary changes and IBD incidence “holds true even more strikingly in countries that are now experiencing Westernization,” he added. These countries have undergone more rapid dietary changes, and their IBD incidence has doubled or tripled. The transition to “less traditional diets” appears to promote intestinal inflammation, said Dr. Ananthakrishnan.
An analysis of data from the European Prospective Investigation into Cancer (EPIC) study found an association between high consumption of sugar and soft drinks, together with low consumption of vegetables, and risk of ulcerative colitis (Inflamm Bowel Dis. 2016;22[2]:345-54.). A subsequent analysis of data from two prospective Swedish cohorts, however, found no association between consumption of sugary beverages and risk of Crohn’s disease or ulcerative colitis (Clin Gastroenterol Hepatol. 2019;17[1]:123-9.).
Although the data on sugar are mixed, data on the association between other macronutrient groups and risk of IBD are more consistent. When Dr. Ananthakrishnan and colleagues examined data from the Nurses’ Health Study, they found that the highest quintile of dietary fiber intake was associated with a 40% reduction in risk of Crohn’s disease, compared with the lowest quintile. The observed reduction of risk seemed to be greatest for fiber derived from fruits. Fiber from cereals, whole grains, or legumes, however, did not affect risk of Crohn’s disease (Gastroenterology. 2013;145[5]:970-7.).
A separate analysis of the Nurses’ Health Study suggested that high intake of n-3 polyunsaturated fatty acids (PUFAs) and low intake of n-6 PUFAs was associated with a 31% reduction in risk of ulcerative colitis and a 15% reduction in the risk of Crohn’s disease. These data were consistent with a previous analysis of EPIC data that found that high intake of n-6 PUFAs was associated with increased risk of ulcerative colitis (Gut. 2009;58[12]:1606-11.). Other analyses indicate that genetic polymorphisms likely modify the association between PUFAs and risk of ulcerative colitis, said Dr. Ananthakrishnan. “There may be an additional layer of complexity beyond just measuring your dietary intake.”
In addition to macronutrients, micronutrients can modify a patient’s risk of ulcerative colitis or Crohn’s disease. When Dr. Ananthakrishnan and colleagues examined the Nurses’ Health Study, they found an inverse association between vitamin D intake and risk of Crohn’s disease (Gastroenterology. 2012;142[3]:482-9.). In a separate study, they found that a zinc intake greater than 16 mg/day was associated with reduced risk of Crohn’s disease (Int J Epidemiol. 2015;44[6]:1995-2005.).
Patients aged older than 40 years and patients of European ancestry tend to be overrepresented in cohort studies, which reduces the generalizability of their conclusions, said Dr. Ananthakrishnan. Furthermore, cohort studies have not produced consistent findings regarding the relationship between various dietary components and risk of IBD. Nevertheless, the data suggest that dietary patterns may be associated with incident Crohn’s disease or ulcerative colitis.
An influence of diet on IBD risk is plausible
One mechanism through which diet may exercise a causal influence on the risk of IBD is by affecting the microbiome. In 2011, investigators studied 98 healthy volunteers who answered questionnaires about their diet. The researchers also used 16s rDNA sequencing to characterize the population’s stool samples. A diet high in animal protein, amino acids, and saturated fats was associated with large populations of Bacteroides. A diet low in fat and in animal protein, but high in carbohydrates and simple sugars was associated with large populations of Prevotella. When the investigators conducted a controlled-feeding study of 10 patients, microbiome composition changed within 1 day of initiating a high-fat-and-low-fiber or a low-fat-and-high-fiber diet (Science. 2011;334[6052]:105-8.). A more recent study showed that the diversity of the microbiome increased with the adoption of an animal-based diet (Nature. 2014;505[7484]:559-63.).
Diet also may exert a causal influence on IBD risk by altering the intestinal barrier. In an experimental model, 5-mg/mL concentrations of fiber from plantain and broccoli significantly reduced the translocation of Escherichia coli through a human intestinal epithelial barrier (Gut. 2010;59[10]:1331-9.). Increased fiber intake may thus result in reduced intestinal inflammation, said Dr. Ananthakrishnan.
Observational and experimental evidence thus support an effect of diet on the risk of IBD, and experimental evidence indicates that this effect is biologically plausible. Nevertheless, “there are many missing links,” and further study will clarify the role of diet in IBD incidence, said Dr. Ananthakrishnan.
CHICAGO – , according to a lecture delivered at Freston Conference 2019, sponsored by the American Gastroenterological Association.
Although the literature is highly consistent, it contains discordant findings, and many questions remain unanswered. “We need more rigorous studies, and particularly more interventions, to truly understand the role diet may play in patients with IBD,” said Ashwin N. Ananthakrishnan, MD, MPH, associate professor of medicine at Massachusetts General Hospital in Boston.
Food can cause symptoms in IBD
Many patients with IBD are convinced that their diet caused their disease. A relevant point for physicians to consider is that these patients are at least as likely as is the general population to have intolerance or sensitivity to food components such as lactose and gluten. In a prospective questionnaire of 400 consecutive patients with IBD in the United Kingdom, 48% expressed the belief that diet could initiate IBD, and 57% said that diet could trigger a flare-up. In addition, 60% of respondents reported worsening of symptoms after eating certain foods, and about two-thirds deprived themselves of their favorite foods to prevent relapses (Inflamm Bowel Dis. 2016;22[1]:164-70). A French study found similar results. “Clearly there’s something there,” said Dr. Ananthakrishnan. Patients’ beliefs about the relationship between food and their symptoms are not simply misconceptions, he added.
A Canadian study published in 2016 found that almost one-third of patients with IBD avoid many food groups. “But there is significant heterogeneity in the foods that are avoided, and sometimes we mistake this heterogeneity for a lack of association between diet and symptoms in IBD,” said Dr. Ananthakrishnan. A larger number of patients avoid certain foods during periods of active disease, which suggests that food exacerbates their symptoms, he added. The same study showed that patients with IBD have more restrictive diets than do community controls. Patients eat fewer fruits and vegetables and generally consume less iron-rich food and less protein-rich food than healthy controls. GI intolerance, rather than professional advice, is the most common reason that patients with IBD restrict their diets (JPEN J Parenter Enteral Nutr. 2016;40[3]:405-11.).
A cross-sectional survey of 130 patients with IBD and 70 controls yielded similar results. Among patients, GI symptoms that resulted from consuming foods were not related to disease activity, disease location, or prior surgery. Patients with IBD tended to have greater frequency of GI intolerance to foods than did controls (Scand J Gastroenterol. 1997;32[6]:569-71.).
Diet may cause intestinal inflammation
International research has recorded increases in the consumption of sugar and fat (particularly saturated fat) and concomitant decreases in fiber consumption during the past several decades. The incidence of IBD has increased in parallel with these dietary changes with a remarkably similar trajectory, said Dr. Ananthakrishnan. The correlation between dietary changes and IBD incidence “holds true even more strikingly in countries that are now experiencing Westernization,” he added. These countries have undergone more rapid dietary changes, and their IBD incidence has doubled or tripled. The transition to “less traditional diets” appears to promote intestinal inflammation, said Dr. Ananthakrishnan.
An analysis of data from the European Prospective Investigation into Cancer (EPIC) study found an association between high consumption of sugar and soft drinks, together with low consumption of vegetables, and risk of ulcerative colitis (Inflamm Bowel Dis. 2016;22[2]:345-54.). A subsequent analysis of data from two prospective Swedish cohorts, however, found no association between consumption of sugary beverages and risk of Crohn’s disease or ulcerative colitis (Clin Gastroenterol Hepatol. 2019;17[1]:123-9.).
Although the data on sugar are mixed, data on the association between other macronutrient groups and risk of IBD are more consistent. When Dr. Ananthakrishnan and colleagues examined data from the Nurses’ Health Study, they found that the highest quintile of dietary fiber intake was associated with a 40% reduction in risk of Crohn’s disease, compared with the lowest quintile. The observed reduction of risk seemed to be greatest for fiber derived from fruits. Fiber from cereals, whole grains, or legumes, however, did not affect risk of Crohn’s disease (Gastroenterology. 2013;145[5]:970-7.).
A separate analysis of the Nurses’ Health Study suggested that high intake of n-3 polyunsaturated fatty acids (PUFAs) and low intake of n-6 PUFAs was associated with a 31% reduction in risk of ulcerative colitis and a 15% reduction in the risk of Crohn’s disease. These data were consistent with a previous analysis of EPIC data that found that high intake of n-6 PUFAs was associated with increased risk of ulcerative colitis (Gut. 2009;58[12]:1606-11.). Other analyses indicate that genetic polymorphisms likely modify the association between PUFAs and risk of ulcerative colitis, said Dr. Ananthakrishnan. “There may be an additional layer of complexity beyond just measuring your dietary intake.”
In addition to macronutrients, micronutrients can modify a patient’s risk of ulcerative colitis or Crohn’s disease. When Dr. Ananthakrishnan and colleagues examined the Nurses’ Health Study, they found an inverse association between vitamin D intake and risk of Crohn’s disease (Gastroenterology. 2012;142[3]:482-9.). In a separate study, they found that a zinc intake greater than 16 mg/day was associated with reduced risk of Crohn’s disease (Int J Epidemiol. 2015;44[6]:1995-2005.).
Patients aged older than 40 years and patients of European ancestry tend to be overrepresented in cohort studies, which reduces the generalizability of their conclusions, said Dr. Ananthakrishnan. Furthermore, cohort studies have not produced consistent findings regarding the relationship between various dietary components and risk of IBD. Nevertheless, the data suggest that dietary patterns may be associated with incident Crohn’s disease or ulcerative colitis.
An influence of diet on IBD risk is plausible
One mechanism through which diet may exercise a causal influence on the risk of IBD is by affecting the microbiome. In 2011, investigators studied 98 healthy volunteers who answered questionnaires about their diet. The researchers also used 16s rDNA sequencing to characterize the population’s stool samples. A diet high in animal protein, amino acids, and saturated fats was associated with large populations of Bacteroides. A diet low in fat and in animal protein, but high in carbohydrates and simple sugars was associated with large populations of Prevotella. When the investigators conducted a controlled-feeding study of 10 patients, microbiome composition changed within 1 day of initiating a high-fat-and-low-fiber or a low-fat-and-high-fiber diet (Science. 2011;334[6052]:105-8.). A more recent study showed that the diversity of the microbiome increased with the adoption of an animal-based diet (Nature. 2014;505[7484]:559-63.).
Diet also may exert a causal influence on IBD risk by altering the intestinal barrier. In an experimental model, 5-mg/mL concentrations of fiber from plantain and broccoli significantly reduced the translocation of Escherichia coli through a human intestinal epithelial barrier (Gut. 2010;59[10]:1331-9.). Increased fiber intake may thus result in reduced intestinal inflammation, said Dr. Ananthakrishnan.
Observational and experimental evidence thus support an effect of diet on the risk of IBD, and experimental evidence indicates that this effect is biologically plausible. Nevertheless, “there are many missing links,” and further study will clarify the role of diet in IBD incidence, said Dr. Ananthakrishnan.
REPORTING FROM FRESTON CONFERENCE 2019