Diet and functional dyspepsia: Clinical correlates and therapeutic perspectives

Table 1 Role of specific foods and their contribution to functional dyspepsia symptoms

Food	Active molecules	Study characteristics	Outcomes measurement	Proposed mechanisms of action	Effects	Ref.
Fatty foods	Lipids	Cross-sectional study (4 health subjects); Loxiglumide vs Loxiglumide plus fat	Gastrointestinal contractile activity (manometry)	Increased CCK release	(1) Hypersensitivity to gastrointestinal hormones; (2) Delayed gastric emptying; and (3) Symptoms exacerbation	[27]
		Randomized crossover study (20 FD patients); Duodenal infusion of saline vs lipid solutions	Gastric volume measurement (gastric barostat)			[28]
Almond	Tryptophan	Cross-sectional study (384 FD patients); Symptoms correlation with the intake of 114 different foods	Gastrointestinal symptoms measurement (VAS)	Indirect stimulation of serotoninergic 5-HT1 and 5-HT4 receptors	(1) Improved gastric emptying; and (2) Symptoms improvement	[29]
		Double-blind RCT over placebo; Tandospirone vs placebo				[33]
Pepper and Chili	Capsaicin	Cross-sectional study (121 FD patients); Symptom generation according to TRPV1 genotypes and the intake of spicy food	TRPV1 polymorphisms (on blood samples)	Regulation of TRPV1 receptors	(1) Hyperalgesia (acute administration); and (2) Reduced visceral hypersensitivity (chronic administration)	[35]
		Randomized crossover study (20 IBS-D patients); Standard meal vs spicy meal vs chili	Gastrointestinal symptoms measurement (VAS)			[36]
		Double-blind trial over placebo (30 FD patients); Pepper vs placebo	Gastrointestinal symptoms measurement (VAS)			[37]
Peppermint and Caraway oil		Cross-over study (6 health subjects); Peppermint caraway oil combination (enteric vs non enteric coated capsules)	Gastroduodenal motility (manometric study)	Allosteric effect on 5-HT3 receptors	(1) Antiemetic, Choleretic and spasmolytic action; and (2) Symptoms improvement	[41]
		Randomized, double-blind trial over placebo (96 FD patients); Peppermints caraway oil vs placebo	Gastrointestinal symptoms measurement (VAS)			[44]
Ginger	Gingerols and Shogaols	Double-blind trial over placebo (24 health subjects); Ginger vs placebo	Gastric emptying (US)	Inhibition of cholinergic M3 and serotoninergic 5-HT3 receptors	(1) Enhanced gastric emptying; (2) Improved gastric motility; (3) Reduced nausea and vomiting; and (4) educed inflammation	[47]
		Randomized, double-blind trial over placebo 126 FD patients); inger vs placebo	Gastrointestinal symptoms score (VAS)			[48]
		RCT over placebo (11 FD patients); inger vs placebo	Gastrointestinal symptoms (VAS) Gastric emptying (US), circulating hormones (GLP-1, motilin and ghrelin)			[50]
FODMAPs	FOS, GOS, Lactose, Fructose (excess), Polyols	Randomized crossover study (30 IBS patients and 8 health subjects); LFD vs Australian diet	Gastrointestinal symptoms score (VAS)	Increased intestinal fermentation Increased osmotic load	(1) Abnormal gas production; (2) Luminal water retention and abdominal distension; (3) Symptoms exacerbation; and (4) Enhanced duodenal inflammation	[25]

5-HT1: 5-hydroxytryptamine subtype 1; 5-HT4: 5-hydroxytryptamine subtype 4; CCK: Cholecystokinin; FD: Functional dyspepsia; FODMAPs: Fermentable oligosaccharides, disaccharides, monosaccharides and polyols; FOS: Fructo-oligosaccharides; GOS: Galacto-oligosaccharides; LFD: Low fodmaps diet; M3: Muscarinic receptor subtype 3; TRPV1: Transient receptor potential vanilloid subtype 1; GLP1: Glucagon-like peptide 1, US: Ultrasound, GI: Gastrointestinal; VAS: Visual analogue scale.