Gamma-aminobutyric acid, widely known as GABA, is a naturally occurring compound in the body that serves as a primary inhibitory neurotransmitter within the central nervous system. This means it plays a significant role in calming nerve activity in the brain and spinal cord, helping to regulate neuronal excitability. Beyond its production within the body, GABA is also present in various foods, offering a natural dietary source of this compound.
Foods Naturally Rich in GABA
GABA is found in a diverse array of foods, with varying concentrations depending on the food type and processing methods. Fermented foods are particularly recognized for their GABA content, as microorganisms like lactic acid bacteria (LAB) produce GABA during fermentation. Examples include kimchi, sauerkraut, yogurt, kefir, tempeh, and sourdough, where specific LAB strains convert glutamic acid into GABA.
Green, oolong, and black teas also contain GABA. Beyond fermented products and teas, vegetables, grains, and some fruits contribute to dietary GABA. Noted vegetable sources include spinach, broccoli, cabbage, cauliflower, Brussels sprouts, potatoes, and sweet potatoes, with raw spinach containing high levels.
Among grains, brown rice, sprouted grains, and oats are recognized for their GABA content, with brown rice germ and sprouted cereals being particularly good sources. Fruits like tomatoes, apples, grapes, and citrus also contain GABA. Concentrations typically range from 1 to 40 milligrams per 100-gram serving, varying widely by food and preparation.
Physiological Impact of Dietary GABA
In the brain, GABA acts as the main inhibitory neurotransmitter, reducing neuronal excitability. This contributes to a calming effect, helping to prevent overstimulation.
Consuming GABA through food is thought to influence physiological processes by supporting this calming effect. Dietary GABA may promote relaxation, reduce feelings of stress, and support restful sleep. Research suggests adequate GABA levels are associated with a more positive mood and less anxiety. While direct effects from dietary sources are complex and still being explored, GABA’s presence in foods aligns with its known functions.
GABA receptors are present throughout the body, including the gastrointestinal tract, indicating a broader physiological role beyond the central nervous system. This widespread distribution suggests ingested GABA could interact with these receptors, influencing various bodily functions. The calming properties linked to GABA are a primary benefit of consuming GABA-rich foods.
Understanding GABA’s Bioavailability from Food
A significant question regarding dietary GABA is its bioavailability, particularly its ability to reach the brain. Historically, GABA from food or supplements was believed to have limited ability to cross the blood-brain barrier (BBB), a protective membrane regulating substance passage into the brain. Recent research challenges this, suggesting small amounts might cross, possibly via specific transporter systems. However, human data on direct brain absorption remain limited.
Even if direct brain absorption is restricted, dietary GABA may still influence brain activity through the gut-brain axis. This complex system connects the gut to the brain via neural, hormonal, and immune pathways. GABA absorbed in the intestines can interact with the enteric nervous system, which contains GABA receptors, potentially transmitting signals to the brain via the vagus nerve. This indirect pathway offers a plausible mechanism for dietary GABA to exert systemic effects.
The amount of GABA in typical food servings is generally lower than dosages in most supplements. While supplements provide concentrated amounts, food GABA is part of a complex matrix including other nutrients. Fermentation, utilizing lactic acid bacteria, can significantly increase GABA content, making these foods richer sources. Oral GABA from both food and supplements is absorbed, leading to a temporary increase in plasma concentrations.