Children with Functional Abdominal Pain Disorders Successfully Decrease FODMAP Food Intake on a Low FODMAP diet with Modest Improvements in Nutritional Intake and Diet Quality

Abstract

Background:

We sought to determine how a low fermentable oligosaccharide, disaccharide, monosaccharide, and polyol (FODMAP) diet (LFD) affected high FODMAP food intake, nutrient intake, and diet quality in children with functional abdominal pain disorders (FAPD).

Methods:

Children (ages 7-13 years) with Rome IV FAPD began a dietitian-guided LFD. Three-day food records were captured at baseline and 2-3 weeks into the LFD. Intake of high FODMAP foods, energy, macronutrients, micronutrients, food groups, and ultra-processed foods were determined.

Key Results:

Median age of participants was 11 yrs. and 19/31 (61%) were female. Twenty-eight (90%) decreased high FODMAP food intake on the LFD: overall median (25-75%) high FODMAP foods/day decreased from 5.7 (3.6-7.3) to 2 (0.3-3.7) (P<0.001). A more adherent subset (n=22/71%) of participants consumed on average ≤ 3 high FODMAP foods per day during the LFD. Baseline nutritional intake and quality were generally poor with several micronutrient deficiencies identified. Diet quality improved on the LFD with increased servings of vegetables and protein and decreased consumption of ultra-processed foods, trans-fatty acids, and added sugars. On the LFD there were significant decreases in total carbohydrates and thiamin (remained within recommended intake) and significant increases in vitamin B6 (P=0.029), vitamin C (P=0.019), and vitamin E (P=0.009). Children more adherent to the LFD further increased vitamin D, magnesium, potassium, and fat servings.

Conclusions & Inferences:

The majority of children with FAPD on a dietitian-led LFD successfully decreased high FODMAP food intake. Children with FAPD on the LFD (vs. baseline) modestly improved micronutrient intake and diet quality.

Graphical Abstract

INTRODUCTION

Functional abdominal pain disorders (FAPD) are disorders of gut-brain interaction characterized by symptoms of chronic abdominal pain.¹ The low fermentable oligosaccharide, disaccharide, monosaccharide, and polyol (low FODMAP) diet (LFD) is used as a treatment for FAPD (such as irritable bowel syndrome) and improves symptoms in 50-80% of patients.² FODMAPs are carbohydrates that are poorly absorbed in the small intestine.³ When FODMAPs enter the large intestine they are fermented by bacteria, leading to gas production, which along with osmotically-driven water secretion into the lumen can contribute to feelings of discomfort and pain, flatulence, bloating, and diarrhea.^3–5 Examples of FODMAP sugars include fructans, galacto-oligosaccharides, lactose, fructose in excess of glucose, and polyols. The LFD is traditionally composed of three phases: comprehensive restriction of FODMAPs, reintroduction challenges of select FODMAPs, and personalization based on the reintroduction results.⁶ This study focuses on the restriction phase, which aims to eliminate all foods from the diet that are concentrated sources of FODMAP sugars.⁶

Dietary adherence, defined as following the advice of, and actively participating in, any dietary interventions can be challenging.⁷ Recognizing that the current literature lacks a consensus method to define adherence to a LFD,^8–16 adherence rates in adults have been reported to be as low as one-third¹⁶ to as high as 100%.¹² While the LFD is a treatment option for children with FAPD, how well they can follow a LFD based on dietitian-provided education has not been studied previously.

Furthermore, given the dietary restriction demanded by the LFD, there are concerns it may negatively impact nutritional adequacy and diet quality. In adults with irritable bowel syndrome, studies on the impact of a LFD on nutrient intake and diet quality have not identified uniform results, with studies suggesting little nutritional change,¹⁷ decreased general diet quality scores,¹⁷ decreases in energy,^8,18 carbohydrate,^8,18,19 fat,⁸ total sugars,¹⁹ starches,^17,19 and/or dietary fiber^8,18,20 and changes in micronutrients (vitamin B12 and calcium)^17,19. One study in adults identified inadvertent weight loss with use of a LFD.²¹

We sought to assess how well children with FAPD follow a LFD and the impact of the diet on nutrient intake and diet quality. We hypothesized that the majority of children with FAPD would significantly decrease their high FODMAP food intake on a LFD. We also hypothesized that the LFD would lead to changes in some nutrients, such as vitamin B12 and calcium, as reported in adults. In contrast to the findings in adults, we expected the LFD to improve diet quality due to an increased number of meals, increased consumption of fruits, and decreased consumption of ultra-processed foods. Consumption of dairy and grains also was expected to decrease on the LFD.

MATERIALS AND METHODS

Study Design

The data used in this study were derived from an ongoing study of children with FAPD enrolled in a randomized parallel group intervention trial; one arm is a LFD, the focus of this study, and the other a cognitive behavioral therapy intervention. We analyzed data from children enrolled in the LFD arm of the study between March 2019 to February 2021. Parents of participants completed a 3-day food record of their child’s habitual diet (baseline). Parents then received education on the LFD through three 1-hour telephone visits given one week apart with one of the study’s registered dietitians, all of whom have extensive experience with the LFD. Supplemental educational materials (e.g., low FODMAP food charts and menus, and access to a low FODMAP smartphone app) were provided with weekly homework (e.g., menu selection) which involved the children. Study participants were instructed to follow the LFD for three weeks. A second 3-day food record of the children’s diet was completed by the parents between two and three weeks into the LFD. Dietitians were encouraged to practice basic adherence-enhancement strategies when presenting dietary recommendations, as outlined by Levy and Feld.²²

Study Population

Participants were 31 children ages 7-13 years who met pediatric Rome IV criteria for FAPD: chronic abdominal pain for ≥3 months occurring ≥ 4 days per month without an organic etiology to identify the etiology of the pain.²³ Children with any recent weight loss, specialized dietary needs such as iron supplementation, eating disorders, or major gastrointestinal diseases such as ulcerative colitis, cancer, Crohn’s disease, or celiac disease were excluded. Demographic information collected included age, sex, race, and ethnicity.

The study was approved by the Institutional Review Board for Human Subjects Research for Baylor College of Medicine & Affiliated Hospitals. Written informed consent was obtained from study participants’ parents and/or guardians and assent was obtained from study participants.

Data Collection

Food records contained information on the foods and beverages consumed each day. Details included type of food, amount, and components of the food if the food had multiple elements (e.g., a sandwich had all components listed). A registered dietitian entered and analyzed the information from the 3-day food records using the University of Minnesota Nutrition Data System for Research (NDSR) software version 2019 (January 2020).²⁴ In cases where a day was not recorded in the food record, the daily intake was averaged over the available days.

Determining High FODMAP Food Intake

High FODMAP foods were identified using guidelines derived from the Monash University Low FODMAP dietary food guide and smartphone app.²⁵ The average number of high FODMAP foods eaten over each 3-day period was calculated for both baseline and LFD periods for each participant. Total FODMAP content was not able to be determined as fructo-oligosaccharide and galactan content of many American foods has not yet been determined.

Since there is no agreed-upon gold standard of overall adherence to a LFD, for purposes of our study we used the following steps: First, the average number of high FODMAP foods/day consumed by each participant at baseline was determined. Next, a cutoff value for the number of high FODMAP foods/day that was below baseline intake for >95% of participants was determined. Those participants who consumed less than this number while on the LFD were considered more adherent to the LFD (see Results).

Assessment of Nutrient Intake and Diet Quality

The impact of the LFD on nutrient intake and diet quality was assessed for the entire cohort and for the subset considered to be more adherent to the LFD. Mean daily intake of energy (kcal), macronutrients, and micronutrients was calculated for each 3-day baseline and LFD period for each participant. The mean intake of each nutrient for each group (entire cohort and more adherent subset) was compared against the recommended dietary allowance (RDA) and adequate intake (AI) standards.²⁶

Diet quality was assessed based on the intake of the food groups in servings, number of ultra-processed foods, consumption of trans-fatty acids, added sugars, and dietary fiber. Ultra-processed foods were identified from the diet records using the NOVA classification system.²⁷

Statistical Analysis

Data are presented as mean ± standard deviation unless otherwise specified. The Kolmogorov-Smirnov test was used to determine the normality of the data. Either paired t-tests or Wilcoxon signed ranks tests were used as appropriate to determine if there was a difference in intake between the baseline and LFD for each nutrient and diet quality measure studied. P-values < 0.05 were considered statistically significant. IBM SPSS version 27 (Armonk, NY) was used to carry out statistical analyses and calculations.

RESULTS

Thirty-one children with FAPD had their diet records analyzed. The median (25%-75%) age of the study participants was 11 (9-12) years and 19 (61%) were female. Eight participants were White/non-Hispanic, 13 were Black/non-Hispanic, 4 were White/Hispanic, 3 were Black/Hispanic, and 3 did not identify a race but identified as Hispanic ethnicity. The median [25%-75%] BMI percentile was 83.5% [59.5% – 95.2%] with 1 child excluded due to lack of height data. Of the 30 with BMI data, 8 (27%) were obese (BMI ≥ 95%). Socio-economic features related to parental caregivers included 18 (58%) being employed full-time, 9 (29%) part-time, and 4 (13%) unemployed. Health insurance types for the participants included: 23 (74%) with private health insurance, eight (26%) public health insurance, and 1 participant who did not identify a health insurance plan. All participants returned complete 3-day food records for the baseline diet. On the LFD, 27 participants completed 3-day food records, three completed 2-day food records, and one completed a 1-day food record.

The cutoff value defining the number of high FODMAP foods/day that was below baseline intake for >95% of participants was ≤ 3 high FODMAP foods/day (Figure 1). Based on this cut-off, 22 (71%) children were considered more adherent to the LFD (i.e., consumed an average of ≤ 3 high FODMAP foods/day; Figure 1).

Figure 1: Distribution of Mean Number of High FODMAP Foods Consumed per Day.

(A) during the baseline habitual diet and (B) during a low FODMAP diet.

Red bars denote participants defined as not adherent to the LFD. Study participants who consumed on average ≤ 23 high FODMAP foods per day were considered more adherent to the low FODMAP diet (green bars) compared to the rest of the cohort.

Twenty-eight out of 31 (90%) participants consumed fewer high FODMAP foods on the LFD compared to baseline. For the entire cohort (n=31), the median (25%-75%) daily number of high FODMAP foods decreased from 5.7 (3.6-7.3) to 2 (0.3-3.7) (P<0.001). For the more adherent subset, the decrease was greater: 5.7 (3.7-7.8) to 0.7 (0.3-2.8) (P<0.001). On a preliminary analysis of those included in this nutritional evaluation of a LFD, there was an overall trend toward decreased abdominal pain frequency on the LFD regardless of adherence status.

Table 1 shows the average macronutrient intake values for the entire cohort (n=31) and the more adherent subset (n=22) for both the baseline habitual diet and LFD. For the entire cohort during the LFD, there were significant decreases in the consumption of total carbohydrates (P=0.019), 5 mono- and disaccharides, total sugars (P<0.001), and available carbohydrate (P=0.014). Gluten consumption also decreased (P<0.001). The adherent subset experienced many of the same differences (though not all reaching statistical significance) noted for the entire cohort while also increasing consumption of galactose on the LFD (P=0.022).

Table 1.

Macronutrient intake in children with functional abdominal pain at baseline and during a low FODMAP^* diet. Mean intake values are provided for the entire cohort that completed the baseline and low FODMAP diets (n=31) and for a subset of the cohort considered more adherent to the low FODMAP diet (n=22). Daily values are presented as mean ± SD.

	Entire Cohort (n=31)			More Adherent Subset (n=22)
Nutrient	Baseline Intake	Low FODMAP Diet Intake	P value	Baseline Intake	Low FODMAP Diet Intake	P value
Energy (kcal)	1,603 ± 496	1,432 ± 566	0.186	1,526 ± 443	1,418 ± 555	0.168
Water (g)	1,218 ± 424	1,260 ± 439	0.634	1,206 ± 460	1,214 ± 353	0.910
Total Protein (g)	58.9 ± 18.0	60.3 ± 21.9	0.716	58.5 ± 14.6	61.0 ± 20.2	0.515
Total Carbohydrate (g)	191 ± 62	158 ± 87	0.019	176 ± 58	151 ± 87	0.082
Glucose (g)	17.8 ± 11.9	13.5 ± 10.9	0.024	14.3 ± 8.5	11.4 ± 8.1	0.062
Fructose (g)	16.6 ± 11.6	10.8 ± 10.8	0.006	14.1 ± 9.3	8.1 ± 8.7	0.004
Galactose (g)	0.9 ± 2.1	1.8 ± 3.3	0.071	0.8 ± 2.0	2.5 ± 3.7	0.022
Lactose (g)	9.3 ± 8.6	3.8 ± 5.4	0.001	7.9 ± 5.6	2.7 ± 4.6	0.006
Maltose (g)	2.6 ± 1.7	0.9 ± 0.9	<0.001	2.4 ± 1.7	0.7 ± 0.7	0.001
Sucrose (g)	31.1 ± 17.6	21.4 ± 19.5	0.002	28.4 ± 18.4	20.6 ± 22.2	0.009
Starch (g)	89.2 ± 34.1	84.4 ± 56.0	0.272	86.5 ± 34.4	84.7 ± 59.7	0.390
Total Polyols (g)	0.7 ± 0.8	0.6 ± 0.7	0.422	0.7 ± 1.0	0.6 ± 0.7	0.408
Total Sugars (g)	77.7 ± 34.1	52.4 ± 31.4	<0.001	67.0 ± 30.3	46.1 ± 28.6	0.002
Available Carbohydrate (g)	180 ± 59	147 ± 83	0.014	166 ± 55	140 ± 84	0.050
Tagatose (mg)	1.1 ± 1.8	0.2 ± 0.7	<0.001	0.8 ± 1.4	0.2 ± 0.7	0.007
Total Fat (g)	68.4 ± 27.7	63.5 ± 28.7	0.462	66.2 ± 24.0	64.6 ± 28.6	0.827
Total Saturated Fatty Acids (g)	23.5 ± 10.9	20.5 ± 10.0	0.190	23.3 ± 9.8	21.0 ± 9.7	0.350
Total Monounsaturated Fatty Acids (g)	23.2 ± 10.5	21.8 ± 10.1	0.610	22.3 ± 8.3	21.9 ± 9.8	0.758
Total Polyunsaturated Fatty Acids (g)	15.8 ± 5.8	15.8 ± 10.2	0.456	14.6 ± 5.4	16.1 ± 10.9	0.733
Omega-3 Fatty Acids (g)	1.6 ± 0.7	1.5 ± 0.8	0.444	1.5 ± 0.7	1.4 ± 0.7	0.803
Alpha-linoleic Acid (PUFA 18:3 n-3) (g)	1.5 ± 0.7	1.3 ± 0.7	0.208	1.4 ± 0.7	1.3 ± 0.7	0.427
Gluten (g)	6.9 ± 3.3	2.2 ± 2.8	<0.001	7.1 ± 3.8	1.0 ± 1.2	<0.001

^*FODMAP= Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols

Table 2 shows the average micronutrient intake values for the entire cohort and the more adherent subset during the baseline habitual diet and LFD. At baseline, the average intakes of vitamin A, pantothenic acid, vitamin C, vitamin D, vitamin E, calcium, phosphorus, magnesium, potassium, manganese, and choline were below recommended daily allowance or adequate intake thresholds. This parallels data related to inadequate micronutrient intake identified in healthy children within the United States.^28,29 While on the LFD, the entire cohort increased their intakes of vitamin B6 (P=0.029), vitamin C (P=0.019), and vitamin E (P=0.009), and decreased thiamin intake (P=0.032). The average intake of thiamin remained above the recommended dietary allowance value for age. The more adherent subset experienced many of the same micronutrient changes (except for thiamin) noted for the entire cohort but also had significantly increased intake of vitamin D (P=0.008), magnesium (P=0.042), and potassium (P=0.028).

Table 2.

Micronutrient intake in children with functional abdominal pain at baseline and during a low FODMAP^* diet. Mean intake values are provided for the entire cohort that completed the baseline and low FODMAP diets (n=31) and for a subset of the cohort considered more adherent to the low FODMAP diet (n=22). Daily values are presented as mean ± SD. Recommended dietary allowance (RDA) or adequate intake (AI) values for the 9-13 year old age group are provided to aid with interpretation.

	Entire Cohort (n=31)			More Adherent Subset (n=22)
Nutrient	Baseline Intake	Low FODMAP Diet Intake	P value	Baseline Intake	Low FODMAP Diet Intake	P value	RDA/AI#
Vitamin A (Retinol Activity Equivalents) (mcg)	456 ± 251	551 ± 309	0.213	407 ± 194	567 ± 282	0.062	600
Thiamin (mg)	1.4 ± 0.5	1.1 ± 0.5	0.032	1.3 ± 0.5	1.1 ± 0.5	0.087	0.9
Riboflavin (vitamin B2) (mg)	1.6 ± 0.6	1.4 ± 0.6	0.155	1.5 ± 0.6	1.4 ± 0.6	0.576	0.9
Niacin (vitamin B3) (mg)	17.8 ± 5.9	18.6 ± 6.7	0.565	17.4 ± 5.4	19.3 ± 6.3	0.217	12
Pantothenic Acid (mg)	3.4 ± 1.0	4.0 ± 1.4	0.058	3.2 ± 0.9	3.9 ± 1.3	0.059	4
Vitamin B6 (mg)	1.3 ± 0.6	1.7 ± 0.6	0.029	1.3 ± 0.5	1.8 ± 0.6	0.003	1
Total Folate (mcg)	313 ± 240	270 ± 167	0.108	315 ± 280	265 ± 183	0.158	300
Vitamin B12 (cobalamin) (mcg)	3.7 ± 1.7	4.0 ± 2.1	0.597	3.5 ± 1.7	4.1 ± 2.0	0.108	1.8
Vitamin C (ascorbic acid) (mg)	42.1 ± 39.0	69.6 ± 59.3	0.019	37.5 ± 31.0	65.6 ± 61.6	0.031	45
Vitamin D (calciferol) (mcg)	4.2 ± 2.5	5.1 ± 3.3	0.207	3.6 ± 1.7	5.8 ± 3.4	0.008	15
Vitamin E (Total Alpha-Tocopherol) (mg)	5.6 ± 1.9	9.1 ± 6.1	0.009	5.2 ± 1.6	9.5 ± 6.4	0.008	11
Vitamin K (phylloquinone) (mcg)	60.0 ± 55.0	86.0 ± 76.0	0.085	58.7 ± 62.9	82.0 ± 60.6	0.077	60
Calcium (mg)	694 ± 371	589 ± 275	0.163	650 ± 323	594 ± 270	0.531	1,300
Phosphorus (mg)	926 ± 315	869 ± 299	0.331	890 ± 267	871 ± 261	0.743	1,250
Magnesium (mg)	169 ± 47	198 ± 94	0.240	162 ± 46.0	205 ± 95	0.042	240
Iron (mg)	11.2 ± 4.9	9.9 ± 4.7	0.176	10.9 ± 5.2	10.1 ± 4.6	0.355	8
Zinc (mg)	8.4 ± 3.6	8.0 ± 3.5	0.607	8.2 ± 3.7	8.2 ± 3.2	0.808	8
Copper (mg)	0.7 ± 0.2	0.8 ± 0.5	0.754	0.7 ± 0.2	0.7 ± 0.3	0.309	0.7
Selenium (mcg)	89.1 ± 28.8	80.3 ± 36.1	0.178	89.6 ± 27.1	76.4 ± 32.0	0.082	40
Sodium (mg)	2,581 ± 928	2,229 ± 904	0.093	2,461 ± 909	2,049 ± 657	0.094	1,200
Potassium (mg)	1,523 ± 481	1,845 ± 832	0.077	1,393 ± 391	1,836 ± 787	0.028	2,500
Manganese (mg)	1.8 ± 0.7	1.9 ± 0.8	0.499	1.7 ± 0.8	2.0 ± 0.7	0.305	1.9
Choline (mg)	236 ± 101	286 ± 155	0.114	232 ± 95	278 ± 135	0.213	375

^*FODMAP= Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols

^#Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine, National Academies²⁶

Table 3 shows the consumption of the different food groups expressed as servings between the baseline diet and LFD. At baseline, participants on average consumed fewer than the recommended servings/day of fruits, vegetables, total grains, and dairy. While on the LFD, the entire cohort increased servings of vegetables (P=0.046) and protein (P=0.041). Servings of sweets decreased on the LFD (P=0.008). Total grain consumption decreased (P=0.007) and appeared to be driven by a marked decrease in the average intake of refined grains (P=0.001). An additional change seen within the more adherent subset was increased servings of fat on the LFD (P=0.046).

Table 3.

Food group servings consumed in children with functional abdominal pain at baseline and during a low FODMAP^* diet. Mean intake values are provided for the entire cohort that completed the baseline and low FODMAP diets (n=31) and for a subset of the cohort considered more adherent to the low FODMAP diet (n=22). Daily values are presented as mean ± SD. Recommended servings for the 9-13 year-old age group are provided to aid with interpretation.

	Entire Cohort (n=31)			Adherent Subset (n=22)
Food Group	Baseline Intake	Low FODMAP Diet Intake	P value	Baseline Intake	Low FODMAP Diet Intake	P value	Recommended Servings/Day#
Fruits	0.8 ± 1.0	1.2 ± 1.2	0.096	0.7 ± 1.1	1.0 ± 1.1	0.104	3
Vegetables	1.3 ± 0.8	1.9 ± 1.2	0.046	1.1 ± 0.9	1.7 ± 1.1	0.082	4
Total Grains	5.9 ± 3.0	4.2 ± 2.6	0.007	5.7 ± 2.9	3.9 ± 2.5	0.015	9
Refined Grains	4.3 ± 2.2	2.2 ± 2.0	0.001	4.1 ± 2.2	1.7 ± 1.6	0.002
Some Whole Grains	0.4 ± 0.7	0.6 ± 0.7	0.248	0.4 ± 0.8	0.7 ± 0.8	0.170
Whole Grains	1.2 ± 1.2	1.4 ± 1.6	0.222	1.2 ± 1.1	1.6 ± 1.8	0.126
Protein	4.4 ± 1.9	5.7 ± 3.1	0.041	4.6 ± 1.7	5.8 ± 2.8	0.106	2
Dairy	1.5 ± 1.1	1.1 ± 0.8	0.126	1.3 ± 0.9	1.2 ± 0.8	0.594	3
Fats	3.4 ± 3.1	4.4 ± 3.8	0.183	3.0 ± 2.5	4.8 ± 4.0	0.046
Sweets	0.7 ± 1.0	0.3 ± 0.6	0.008	0.8 ± 1.2	0.4 ± 0.7	0.013

^*FODMAP= Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols

^#2000 Dietary Guidelines for Americans³⁰

Table 4 shows the evaluation of diet quality measures such as ultra-processed foods, trans-fatty acids, added sugars, and dietary fiber. While on the LFD (vs. baseline), the entire cohort had significant decreases in the intake of ultra-processed foods (P<0.001), trans-fatty acids (P=0.002), and added sugars (P<0.001). There were no significant changes in total dietary fiber, soluble dietary fiber, and insoluble dietary fiber intake. Pectin consumption increased on the LFD (P=0.002). The more adherent subset had the same findings as in the entire cohort.

Table 4.

Comparison of diet quality in children with functional abdominal pain between baseline and low FODMAP^* diets using ultra-processed foods, trans-fatty acids, added sugars, and fiber intake. Daily mean intake values are provided for the entire cohort that completed the baseline and low FODMAP diets (n=31) and for a subset of the cohort considered more adherent to the low FODMAP diet (n=22). Values are presented as mean ± SD.

	Entire Cohort (n=31)			Adherent Subset (n=22)
Diet Quality Measure	Baseline Intake	Low FODMAP Diet Intake	P value	Baseline Intake	Low FODMAP Diet Intake	P value
Ultra-Processed Foods	6.1 ± 2.5	3.9 ± 2.1	<0.001	5.8 ± 2.6	3.5 ± 2.1	<0.001
Trans-Fatty Acids (g)	1.8 ± 0.9	1.2 ± 0.7	0.002	1.8 ± 0.9	1.2 ± 0.6	0.001
Added Sugars (g)	57.8 ± 33.2	29.7 ± 25.3	<0.001	49.2 ± 31.8	25.1 ± 24.7	0.001
Total Dietary Fiber (g)	10.7 ± 3.8	11.4 ± 4.7	0.566	10.0 ± 3.9	11.2 ± 4.4	0.412
Soluble Dietary Fiber	3.5 ± 1.4	3.1 ± 1.4	0.399	3.3 ± 1.5	3.0 ± 1.4	0.570
Insoluble Dietary Fiber (g)	7.0 ± 2.6	8.1 ± 3.6	0.168	6.6 ± 2.7	8.1 ± 3.3	0.114
Pectins (g)	1.0 ± 0.5	1.7 ± 1.3	0.002	0.9 ± 0.5	1.7 ± 1.4	0.010

^*FODMAP= Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols

Table 5 shows the number of meals, snacks, breakfasts, lunches, and dinners eaten per day. Only the average number of dinners eaten per day over the 3-day recording periods increased significantly between baseline and LFDs for both the entire cohort and the more adherent subset.

Table 5.

Comparison of meals consumed per day in children with functional abdominal pain between baseline and low FODMAP^* diets. As all data is not normally distributed, median (25-75%) values are presented. Median intake values are provided for the entire cohort that completed the baseline and low FODMAP diets (n=31) and for a subset of the cohort considered more adherent to the low FODMAP diet (n=22).

	Entire Cohort (n=31)			Adherent Subset (n=22)
Per Day	Baseline Intake	Low FODMAP Diet Intake	P value	Baseline Intake	Low FODMAP Diet Intake	P value
Total Number of Meals	2.7 (2.0-2.7)	2.7 (2.3-3.0)	0.208	2.7 (2.25-2.7)	2.7 (2.3-3.0)	0.112
Number of Snacks	0.7 (0.3-1.0)	0.7 (0.3-1.0)	0.249	0.7 (0.3-1.0)	0.7 (0.3-1.0)	0.599
Number of Breakfasts	0.7 (0.3-1.0)	1 (0.7-1.0)	0.326	0.7 (0.6-1.0)	1 (0.7-1.0)	0.192
Number of Lunches	1 (1-1)	1 (0.7-1)	0.746	1 (0.9-1.0)	1 (0.9-1)	0.791
Number of Dinners	1 (0.7-1)	1 (1-1)	0.016	1 (0.7-1.0)	1 (1-1)	0.046

^*FODMAP= Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols

DISCUSSION

Our study aimed to address several areas of uncertainty regarding the use of a LFD in children with FAPD. We found that following a dietitian-directed education program, parents reported that the vast majority of children with FAPD ate fewer high FODMAP foods. Baseline nutritional intake and diet quality were, on average, inadequate in several micronutrients and in servings per day of items such as fruits and vegetables prior to starting a LFD.³⁰ We identified that changes in nutrient consumption on the LFD included decreases in several carbohydrates and thiamin but increases in vitamin B6, vitamin C, and vitamin E. Overall diet quality while on the LFD (vs. baseline) modestly improved over baseline as supported by decreased consumption of ultra-processed foods and increased consumption of vegetables.

As we had hypothesized, implementing a LFD with dietitian-directed education resulted in a large majority of participants decreasing the number of high FODMAP foods eaten. This suggests that following a LFD is feasible for children with FAPD receiving dietitian-directed education. It should be noted that the education involved three sessions and dietitians had been given materials on adherence and adherence strategies. One limitation of this study may be in its generalizability: this level of training and involvement may be greater than that available in standard clinical practice. Nonetheless, these data are helpful in that they may inform future LFD dietary education-based interventions and the results may be compared to other forms of education such as only providing LFD food lists, which has been found to result in significant adherence discrepancies among institutions.³¹ Additional randomized controlled trials are needed to determine the most effective means by which adequate adherence to a LFD may be achieved.

As would be expected, on the LFD, children consumed less total carbohydrate as has been reported in adults with FAPD.^8,18,19 However, in contrast to what has been identified in some adult studies, we did not identify decreases in energy or fat intake.^8,18 We also did not identify a decrease in protein intake on the LFD (vs. baseline); rather participants had an increase in the number of protein food servings. These results suggest unexpected weight loss, which has been identified in adults with FAPD on a LFD,²¹ may be less likely to occur in children with appropriate LFD education and guidance. We speculate that our dataset and that of Staudacher et al.(which evaluated adults) differ for multiple reasons, including US vs UK national consumption differences and pediatric vs adult dietary consumption differences. As an example of overarching national differences, a comparison of vegetable and fruit consumption in France vs. United States identified that the French eat more vegetables and fruits than Americans.³² Regionally within the United States, rural (vs. non-rural) Americans are less likely to consume vegetables and fruits.³³ In the context of this pediatric study, it is well known that United States children have different dietary consumption than adults in several areas including dietary quality.³⁴ This information provides context to our study results of non-rural children within the United States with FAPD who are undergoing a LFD intervention. Additional studies of children with FAPD on a LFD diet in different contexts are needed.

As we had hypothesized, there were changes in consumption of micronutrients while on the LFD, though not all changes paralleled those reported in adults. There were several generally positive changes in micronutrient intake on the LFD including increases in vitamin B6, vitamin C, and vitamin E. The more adherent subset had even greater increases in these vitamins as well as in vitamin D, magnesium, and potassium. An increase in vegetable and meat intake during the LFD may have been responsible for the identified modest increases in several micronutrients.^26,35–39 For example, vegetable oils, nuts, and some seafood contribute significant amounts of vitamin E.³⁸

In contrast, thiamin intake decreased on the LFD. A reduction in thiamin-containing foods (e.g., fortified wheat products (cereals and bread) and beans) on the LFD may have been responsible.³⁵ That said, the average thiamin intake on the LFD remained above the RDA. Of note, we did not identify decreases in calcium or increases in vitamin B12 as has been observed in adults.^17,19 Given the incongruent results between adult studies as they relate to micronutrient intake changes on the LFD, we speculate that cultural foods restricted and/or consumed on the LFD may have a strong influence on resultant micronutrient changes.

Intake of certain micronutrients, such as calcium and magnesium, were low at baseline. While magnesium intake did increase while on the LFD, the intake of both micronutrients remained lower than recommended during the LFD. On average, the subjects in our study had lower calcium and magnesium intake than in the overall United States youth population.⁴⁰ Therefore, we speculate that intake of these two micronutrients is affected by the overall poor quality diets of children with FAPD as compared to the general population. This data may increase awareness that augmenting intake of food sources rich in calcium and magnesium or supplementation may be needed for children with FAPD on a LFD in order to meet recommended dietary intake goals.

Diet quality while on the LFD improved as indicated by several measures such as decreased intake of ultra-processed foods, increased intake of pectin, and increased servings of vegetables. Grain consumption decreased on the LFD as hypothesized; a possible reason is decreased consumption of wheat, which is a major grain in the American diet and also high FODMAP. Dairy intake did not decrease significantly on the LFD compared to baseline. Some children consumed regular milk on the LFD, while others consumed milk fortified with the enzyme lactase. Cheese and yogurt (regular and low lactose versions) also were consumed on the LFD. Though using different measures of quality, our findings are in contrast to Staudacher et al. who identified lower diet quality on the LFD compared to a habitual control diet in adults with FAPD.¹⁷ We did identify a larger number of fat servings in the more adherent subset. Upon further review of the food records, the increase in fat servings appeared to be due to the fats added in home cooked meals as cooking oils, butter, and margarine being more readily identified by Nutrition Data System for Research 2019. Given this, and the lack of change in overall fat consumption, it is unlikely that a dietitian directed LFD will result in excessive fat intake. Ultra-processed foods are increasingly being recognized as a component of an unhealthy diet.⁴¹ We found consumption of ultra-processed foods significantly decreased on the LFD; to our knowledge, this has not been reported previously. Many ultra-processed foods contain artificial sweeteners, and/or high fructose corn syrup, and other high FODMAP foods as major ingredients. Given that vegetable intake, though increased from baseline, was still low on a LFD, the largest improvements in diet quality related to decreasing ultra-processed foods and added sugars.

It should be noted that total dietary fiber intake within our sample of pediatric FAPD patients was well below the recommended adequate intake values both at baseline and following LFD implementation. Inadequate fiber intake in United States youth has been well documented and continues to be a persistent problem.⁴² Although decreased dietary fiber intake resulting from the elimination of dietary fibers containing fructans and galactans is a point of concern regarding the LFD for adults,^8,18,20 overall dietary fiber intake did not change within our sample of children with FAPD. Rather, we identified an increase in pectin consumption which is likely due to increased vegetable and fruit intake. However, supplementation with other fiber sources compatible with a LFD is likely to be needed to reach recommended dietary intake goals; not only from an overall health perspective but also because low fiber intake has been associated with recurrent abdominal pain in children.⁴³ One such fiber supplementation strategy recently was reported in adults with FAPD.⁴⁴ Concomitant supplementation of fiber (sugarcane bagasse and resistant starch) to a LFD did not alter the symptoms response in comparison to a LFD alone and had the additional benefits of improving stool bulk and normalizing slow transit.⁴⁴

Contrary to our hypothesis, we did not identify significant changes in meal numbers when participants were on a LFD. The number of total meals, snacks, breakfasts, and lunches did not differ significantly from baseline. We did identify a small increase, likely not clinically significant, in the number of dinners consumed while on the LFD. These data provide reassurance that the LFD does not cause significant disruption of established meal patterns in children with FAPD.

In addition to the generalizability of this education format mentioned above, there are some other limitations to this study. Though the majority of FODMAP carbohydrates were able to be quantitatively determined, FODMAP carbohydrates such as fructo-oligosaccharides and galacto-oligosaccharides could not be quantified. Once further FODMAP analyses of American foods are completed, evaluation of these and other sugars can be carried out. Another limitation is reliance on parent-reported food records. Parents may not have recorded food intake accurately. Nonetheless, 3-day food records are currently considered the best tool to gather dietary intake and superior to other methods such as 24 hour recall.⁴⁵

Strengths of the study include that this is the first study of the dietary impact of the LFD in children with FAPD. We used a rigorous method of food record capture and assessment. It should be noted that assessment of diet quality included evaluation of several measures, including a never-before completed evaluation of ultra-processed foods in children with FAPD. In addition, the population of children studied was racially/ethnically diverse, thus enhancing an important and often neglected aspect of the generalizability of our findings.

In summary, the majority of children with FAPD in this study were able to decrease high FODMAP food intake with dietitian guidance. The LFD resulted in modest improvements from baseline in consumption of several micronutrients, minerals, and diet quality. These results should help inform other investigators as well as dietitians and other healthcare providers implementing a LFD in children with FAPD.