A low glutamate diet is an eating plan centered on reducing the intake of foods containing high levels of free glutamate. This dietary approach aims to lessen potential symptoms for individuals who may be sensitive to this particular amino acid. The focus is specifically on free glutamate, as opposed to glutamate bound within proteins, which the body processes differently.
The Role of Glutamate in the Body
Glutamate is the most abundant amino acid in the human body, found in nearly every food, particularly those rich in protein like meat, eggs, and cheese. Beyond its role as a building block for proteins, glutamate functions as the primary excitatory neurotransmitter in the brain and central nervous system, important for processes like learning and memory.
While bound glutamate is naturally present in proteins and generally not a concern, “free” glutamate is unbound and can directly impact nerve cells. Monosodium glutamate (MSG) is a well-known, purified form of free glutamate added to foods to enhance savory flavors. The body processes free glutamate from natural sources and MSG identically, as its chemical structure remains the same regardless of origin.
Foods to Limit on a Low Glutamate Diet
Adopting a low glutamate diet involves identifying and limiting foods that naturally contain high levels of free glutamate or those where it is added or formed during processing. The ripeness and age of food can influence its free glutamate content; for example, a riper tomato will have more free glutamate than a pale one. Curing or fermenting foods also increases free glutamate as proteins break down.
Certain food categories are high in free glutamate:
Aged Cheeses: Parmesan, Roquefort, Camembert, Brie, and Gruyere are examples of cheeses with elevated free glutamate levels due to their aging process.
Cured and Processed Meats: Cured ham has significantly more free glutamate than fresh pork, and processed meats like salami and pepperoni also contain high amounts.
Fermented Products: Soy sauce, miso, fish sauce, yeast extracts, chocolate, raw cacao, coffee, and tea are notable for their high free glutamate content resulting from fermentation.
Specific Vegetables and Legumes: Ripe tomatoes and tomato products (like tomato sauce and paste), mushrooms (especially shiitake and enokitake), peas, corn, potatoes, and spinach are examples of vegetables that can be high in free glutamate. Beans and lentils, including soy, navy, pinto, black, and lima beans, also contain high levels.
Nuts and Seeds: Walnuts, peanuts, cashews, and pistachios generally have high glutamate levels.
Processed food additives are a source of hidden free glutamate. Manufacturers often use various names for added MSG or other forms of free glutamic acid. Common ingredients that always contain processed free glutamate include monosodium glutamate, glutamic acid, gelatin, calcium caseinate, sodium caseinate, textured protein, yeast nutrient, yeast extract, autolyzed yeast, and any hydrolyzed protein (e.g., hydrolyzed vegetable protein, hydrolyzed corn gluten). Ingredients that often contain or create free glutamate during processing include carrageenan, maltodextrin, malt extract, natural flavorings (like natural chicken or beef flavoring), bouillon, broth, stock, and seasonings. Disodium guanylate and disodium inosinate are also indicators, as they synergistically work with MSG and are typically not used without its presence.
Foods to Include on a Low Glutamate Diet
A low glutamate diet emphasizes fresh, unprocessed foods, which are generally low in free glutamate. Including a variety of these foods helps ensure adequate nutrition while managing glutamate intake. The guiding principle is to choose foods in their natural, whole state.
Examples of foods to include are:
Fresh Meats and Poultry: Plain cooked fresh meat, poultry, and fish like wild-caught salmon and cod are good protein sources with lower free glutamate.
Most Fresh Vegetables: Many fresh vegetables are low in glutamate, such as cucumbers, carrots, most leafy greens (excluding spinach), bell peppers, and broccoli. Aim for a variety of colorful vegetables.
Fruits: Most fresh fruits, including cherries, blueberries, apples, and oranges, are suitable choices.
Unprocessed Grains: Brown rice, quinoa, and other whole, unprocessed gluten-free carbohydrates are typically low in glutamate.
Healthy Fats: Healthy oils like olive oil are suitable for cooking and consumption.
Potential Health Connections
The connection between dietary glutamate intake and certain health conditions is an area of ongoing research, with individual sensitivities playing a significant role. High glutamate intake may contribute to symptoms in specific conditions. For example, a study found that individuals with fibromyalgia (FM) and irritable bowel syndrome (IBS) who had improved on an excitotoxin elimination diet experienced a significant return of symptoms, including worsening fibromyalgia severity and decreased quality of life related to IBS, when challenged with MSG. This suggests dietary glutamate may play a role in FM symptoms for some patients.
Fibromyalgia and IBS frequently coexist, and both conditions involve complex interactions, including potential alterations in gut microbiota and the gut-brain axis. Headaches, including migraines, are also commonly associated with fibromyalgia and irritable bowel syndrome. While research continues to explore the mechanisms, individuals sensitive to glutamate often report improvements in symptoms related to these conditions when following a low glutamate diet. This dietary approach is considered an area of interest for personal symptom management, rather than a definitive medical cure, reflecting the highly individual nature of glutamate sensitivity.