Interview by Sofia Campos Caminos
Grisel Aranzabe is a digestive health specialist and nutritionist who focuses on the intestinal microbiota and the low FODMAP approach, designed for individuals with irritable bowel syndrome (IBS) and SIBO. Her interest in this field began with her own struggles with digestive issues and low energy. Through study and practice, she discovered that many ailments share a common origin: the gut.
In this insightful conversation with Simple People, Grisel explains why the gut microbiota is essential for immunity, mood, and overall well-being—and how to support it through diet. She highlights the mindful use of supplements, clarifies the difference between prebiotics, probiotics, and synbiotics, and shares practical advice for improving gut health even with limited time for cooking. She also reflects on the importance of flexibility and sustainable habits for long-term change.
SIMPLE PEOPLE: How did your work as a nutritionist begin, and what led you to specialize in the intestinal microbiota and the low FODMAP approach?
GRISEL ARANZABE: When I started working, I initially focused on people with overweight and obesity. I wasn’t so drawn to these topics. Whenever someone came to me with digestive issues—bloating, constipation, or diarrhea—I was very interested and could relate to them, because I had experienced similar intestinal problems as a child (…).
Different professionals would often tell them, over and over again: “there’s nothing wrong”, but their symptoms continued, and I also didn’t have the tools to help. Seeking to support these patients and myself, I began researching and discovered the fascinating world of the microbiota (…). I specialized in microbiota and the low FODMAP approach, created by Monash University, especially for individuals with IBS. It is a valuable tool for those with SIBO and works well alongside antibiotics prescribed by a physician when needed.
This personal exploration was transformative; not only did it reduce my intestinal symptoms, but I also regained energy and understood what was happening better. Many patients are frustrated when told, “there’s nothing wrong,” and it’s difficult to comprehend how unwell they feel. This work is compelling because it does not focus solely on diet but also considers lifestyle factors and incorporates strategies to improve the overall quality of life (…).
SP: How important is the microbiota for mood, immunity, inflammation, and overall health?
GA: The microbiota is a collection of viruses, bacteria, and fungi in our gut with multiple functions. To support immunity, mood, body composition, energy levels, or digestive health, it is essential to maintain these organisms in balance. You can think of it as a forest with different tree species. The more diverse and nourished it is, the healthier the system. If some species disappear, balance is lost, leading to immune and digestive problems. Diet plays a central role in keeping this “forest” balanced.
SP: What dietary changes are most effective for nourishing this intestinal “forest”?
GA: A simple approach is to visualize the colors of foods. When shopping, choose one violet, one orange, and one green item. This ensures a variety of fruits and vegetables that provide fiber, which feeds the gut bacteria. Keep it simple and avoid relying on supplements.
SP: You mentioned fermentable fiber and resistant starch in a Simple People article. Could you explain them simply and how to incorporate them?
GA: Fiber and resistant starch feed gut bacteria and are considered prebiotics—essentially, a “fertilizer” for the forest. Including fruits, vegetables, seeds, and legumes provides fermentable fiber. Resistant starch—found in foods such as rice, potatoes, or sweet potatoes—is effective and affordable. Cooking them and letting them cool for 24 hours allows the starch to reach the bacteria intact. It also helps regulate blood sugar and insulin, which can support body fat reduction. For convenience, a tray of potatoes and sweet potatoes prepared for several days is an easy way to provide excellent nutrition for the microbiota (…).
SP: Many people use supplements like vitamin C, zinc, selenium, magnesium, or B-complex. What is your view on this?
GA: Firstly, diet must be optimized and the gut repaired to absorb nutrients properly. An inflamed gut does not absorb supplements well. Adequate sleep is also critical, as no supplement can compensate for poor rest. I frequently use supplements such as magnesium, with types chosen based on specific needs, and omega-3 for its anti-inflammatory properties. I always recommend prior testing and mindful supplementation with professional guidance.
SP: What is the difference between a prebiotic and a synbiotic?
GA: Probiotics are beneficial bacteria consumed, usually via supplements. Prebiotics are their food, supporting their colonization. Synbiotics combine both. Synbiotics are not recommended for those with excessive fermentation or abdominal bloating, as they may worsen symptoms. However, a woman receiving antibiotics for recurrent urinary infections without digestive symptoms could benefit from a synbiotic.
SP: How do antioxidants interact with the microbiota, and why are they important?
GA: Polyphenols, a type of antioxidant, feed gut bacteria. They are present in colorful foods such as blueberries, red berries, green tea, and 80% dark chocolate. Including polyphenols stimulates bacteria to produce anti-inflammatory compounds that benefit health. They are accessible and easy to incorporate daily.
SP: Beyond ultra-processed foods, sugar, and alcohol, are there other silent threats to the microbiota?
GA: Ultra-processed foods are highly damaging (…). They feed the bacteria we do not want to overgrow, which communicate with the brain. Excessive consumption promotes cravings for more processed foods, making them the main group to avoid. Another silent threat are sweeteners (…). Switching from sugar to sweeteners in many foods can harm the microbiota. Using high-quality stevia, solely stevia, in limited instances is preferable, avoiding continuous sweetening, as research shows these sweeteners can be harmful (…).
SP: For those with limited time or cooking skills, what small changes can support gut health?
GA: Start with simple, low-cost strategies, such as digestive rest (…). Aim for at least 12 hours between dinner and breakfast to allow the gut to undergo natural cleansing processes. Organization helps: choose a day to shop for vegetables, select a variety of colors, and have them ready (…). Simple options include a breakfast or snack of plain natural yogurt with frozen berries and some nuts—just combine and consume. These small, practical strategies can support gut health even with limited cooking time (…).
SP: Finally, any closing advice or practices you have incorporated into your life as a nutritionist?
GA: Before making dietary changes, listen to your body and apply strategies to reduce anxiety, such as breathing exercises and meditation. Adding color to meals and maintaining flexibility is important. If an event changes your eating, resume your usual habits the next day. Flexibility is key for sustaining changes long-term and maintaining energy.
