Redefining Longevity Through Science
When most people think of longevity, they picture a longer life. But living longer is not the same as living better. On the latest episode of In the Mix, Dr. Rosa Keller explains her perspective. She believes the real goal should be healthspan. This means the number of years we live in good health, energy, and mobility.
Dr. Rosa Keller is a PhD, RDN, and nutrition scientist. She is a registered dietitian with expertise in exercise performance. She also specializes in cardiovascular health and the gut–metabolism connection. Her work bridges clinical nutrition and research. She explores how everyday foods influence blood flow. This includes plant-based compounds like dietary nitrates. They also affect energy metabolism and long-term health outcomes.
In this episode of In the Mix, Dr. Keller explains how gut microbiome diversity supports metabolic flexibility, how nitrates from vegetables improve oxygen efficiency during exercise, and why healthspan — the quality of your years — matters more than lifespan alone. She also discusses the surprising ways sleep, stress, and environmental factors can influence gut balance. These factors affect recovery as well. Additionally, eating more whole, diverse plant foods builds resilience from the inside out.
Whether you’re an athlete optimizing performance or someone seeking better energy, focus, and recovery, Dr. Keller’s insights reveal how science-backed nutrition can help your body adapt, perform, and thrive for the long haul.
From the Garden to the Lab: Dr. Keller’s Path to Performance Nutrition
Dr. Keller’s passion for nutrition started early. Her father was an avid gardener; her mother ran restaurants. Surrounded by food and culture, she became curious about how diet influences the body. That curiosity led her to study biochemistry. She eventually pursued nutrition science at Oregon State University. There, she completed her PhD researching how nitrates from vegetables impact cardiovascular and exercise performance.
During her doctoral work, she noticed that nitrates are often criticized for their link to processed meats. However, they could actually enhance health when they come from plants. Her first paper, Dietary Nitrate and Nitrite Concentrations in Food, revealed an interesting finding. Asian cuisines are rich in leafy greens such as bok choy and Chinese cabbage. These foods naturally contain higher nitrate levels than the Western diet. That insight became the foundation for her later research on nitric oxide, oxygen efficiency, and endurance.
Healthspan vs. Lifespan: The Years That Matter Most
Dr. Keller prefers the term healthspan because it focuses on the quality of time, not the quantity. She challenges clients to imagine what they would do if they had all the time and money in the world—then asks, can your body keep up?
It’s a simple question that reframes aging from a countdown into a performance goal. A long life is meaningful only when you have the energy, mobility, and strength to enjoy it. For Dr. Keller, the key to that endurance is metabolic flexibility—the body’s ability to adapt to change.
Metabolic Flexibility: How Your Body Learns to Adapt
Metabolic flexibility is the capacity to switch smoothly between using carbohydrates, fats, and proteins for fuel. When that flexibility is lost, the body struggles to respond to stress, exercise, or changes in diet.
Dr. Keller explains that the modern lifestyle—sedentary work, processed foods, irregular sleep, and chronic stress—makes many people metabolically inflexible. It isn’t about one bad meal or skipped workout; it’s about losing the ability to adjust.
This rigidity contributes to common lifestyle diseases such as diabetes, hypertension, and obesity. Reclaiming flexibility means retraining the body to adapt again—and that begins in the gut.
The Gut–Metabolism Connection
Our gut microbiome is a living, adaptable ecosystem. The microbes in our intestines help digest food, produce vitamins, and generate signals that affect our metabolism, mood, and recovery.
Dr. Keller calls the microbiome our body’s “metabolic playground.” A diverse gut helps us metabolize sugars, fats, and proteins efficiently. It aids in faster recovery from stress or exercise. Additionally, it helps maintain stable energy. When gut diversity declines, inflammation and metabolic rigidity often follow.
“The way you treat your gut directly impacts your metabolic flexibility long term,” she explains.
At NuLiv Science, we study these same mechanisms. AstraGin® supports gut integrity and nutrient absorption, while Senactiv® promotes healthy cellular turnover for energy and recovery. Together, they help keep the body resilient—supporting the very adaptability Dr. Keller describes.
How Gut Diversity Builds Resilience
A healthy gut thrives on variety. Dr. Keller encourages clients to eat mostly whole foods. These include fruits, vegetables, beans, grains, nuts, and lean proteins. She also promotes flexibility and cultural foods. She calls this the “80/20 rule”: nourish your microbiome most of the time, and it can handle the occasional indulgence.
Whole foods provide fiber that our bodies can’t digest but our gut bacteria can. These microbes ferment fiber to produce short-chain fatty acids like butyrate. These acids power the cells of the colon. They strengthen the gut barrier. They also lower inflammation throughout the body.
When the diet lacks fiber—as in heavily processed foods—the gut loses its energy source. Over time, microbial diversity drops, and so does the body’s ability to adapt. Eating colorful, plant-rich meals restores that flexibility, improving digestion, mood, and recovery.
Nitrates and Nitric Oxide: The Hidden Link Between Plants and Performance
Dr. Keller’s fascination with nitrates began in her PhD research. She discovered that when we eat nitrate-rich vegetables such as spinach, arugula, or beets, the body converts these compounds. They become nitric oxide. This molecule relaxes blood vessels and improves oxygen delivery to muscles.
This mechanism supports endurance, lowers blood pressure, and enhances cardiovascular function. Her later study, The Impact of Dietary Nitrate on Blood Pressure and Exercise Performance, confirmed that regular intake of these vegetables can increase nitric-oxide availability. It shows that regular consumption increases nitric-oxide availability. It also improves performance under low-oxygen conditions like intense exercise.
Unlike synthetic additives, plant-based nitrates come packaged with antioxidants. They include polyphenols that protect against the harmful nitrosamines linked to processed meats. It’s a reminder that context matters. In vegetables, nitrates are part of a larger system designed to support life. They do not harm it.
This research aligns with the International Olympic Committee’s consensus statement. The statement recognizes nitrate supplementation, along with creatine and caffeine, as one of the few performance enhancers with consistent evidence.
Gut Health and Athletic Performance
For athletes, gut health can be the difference between progress and plateau. Digestive discomfort, nutrient malabsorption, and inflammation can sabotage performance long before fatigue sets in.
Dr. Keller points out that the gut and brain communicate constantly. Stress can alter digestion, and poor digestion can feed back into stress and fatigue. When the gut environment improves, athletes often notice steadier energy, faster recovery, and better mental focus.
It’s all connected: a stronger gut supports nutrient absorption. It enhances improved oxygen delivery and ensures consistent energy metabolism. These are the same pathways supported by Senactiv® and InnoSlim® in our research.
Eating for Adaptability
Despite the complexity of microbiome science, Dr. Keller’s nutrition advice remains refreshingly simple. Build meals around whole, colorful foods. Slow down while eating to support digestion. Enjoy food as part of your lifestyle, not a list of restrictions.
She emphasizes that eating well should feel sustainable. Diversity on the plate translates to diversity in the gut. That diversity is what keeps us metabolically flexible as we age.
Food, Flexibility, and Healthspan
Everything Dr. Keller teaches ties back to adaptability. The gut adapts to what we feed it. The metabolism adapts to how we move and rest. And our healthspan—the years we live well—depends on how resilient those systems remain.
Her research shows that food is not just fuel but communication. Each bite sends signals that shape our microbiome, metabolism, and even our mindset.
At NuLiv Science, that philosophy drives our work. Through ingredients like AstraGin®, Senactiv®, and InnoSlim®, we aim to extend not just life, but the life in your years—by supporting nutrient absorption, cellular regeneration, and metabolic balance.
FAQ: Gut Health, Metabolic Flexibility, and Dietary Nitrates
What does metabolic flexibility mean?
Metabolic flexibility is your body’s ability to switch between using carbohydrates, fats, and proteins for energy. When your metabolism is flexible, you adapt easily to exercise, fasting, or different eating patterns.
A lack of flexibility can make it harder to manage energy, recover from stress, or maintain a healthy weight. Supporting your metabolism with whole foods, balanced activity, and ingredients like InnoSlim® can enhance metabolic health. It helps regulate glucose and energy metabolism, which can improve long-term metabolic efficiency.
How does gut health affect metabolism?
Your gut microbiome—the community of bacteria living in your digestive system—plays a major role in how your body digests food and produces energy. A healthy gut helps stabilize blood sugar, manage inflammation, and improve recovery after exercise.
Dr. Keller explains that when your gut microbiome is diverse, your body becomes more adaptable. But when gut balance declines, your metabolism slows down and becomes less efficient. Products like AstraGin® help maintain gut integrity and support nutrient absorption, which is essential for keeping metabolism strong.
What are dietary nitrates and why are they important?
Dietary nitrates are natural compounds found in vegetables such as spinach, arugula, celery, and beets. Once consumed, they convert into nitric oxide, a molecule that improves blood flow and oxygen delivery throughout the body.
Nitrates from vegetables are safe and beneficial—unlike those added to processed meats—because they come packaged with antioxidants that protect against harmful compounds.
Are nitrates from vegetables safe?
Yes. Nitrates from vegetables are not only safe but essential for cardiovascular health. They increase nitric oxide production, which improves circulation and supports heart function.
The confusion comes from studies on processed meats, where nitrates combined with fats and heat can form harmful nitrosamines. Vegetables naturally contain antioxidants that prevent this, making them one of the healthiest nitrate sources.
How can I improve my gut health naturally?
Improving gut health starts with whole, plant-based foods that provide fiber and polyphenols to feed beneficial bacteria. Eat a variety of fruits, vegetables, legumes, nuts, and whole grains.
Dr. Keller recommends following the “eat the rainbow” approach—adding different colors to your plate each day—to build microbial diversity. Adequate sleep, stress management, and hydration are also essential for gut balance and overall metabolic health.
Can gut health affect athletic performance?
Yes. Gut health directly influences energy levels, nutrient absorption, and recovery. When your microbiome is balanced, your body can use nutrients like amino acids and carbohydrates more efficiently, improving stamina and mental focus.
Dr. Keller’s findings highlight that a strong gut supports both physical and mental performance. It reduces inflammation and improves communication along the gut-brain axis. NuLiv Science’s Senactiv® further supports recovery by promoting muscle cell regeneration after intense training.
What’s the difference between healthspan and lifespan?
Lifespan is how long you live. Healthspan is how long you stay healthy and active.
Dr. Keller emphasizes that improving gut health, metabolic flexibility, and nitric oxide production are key to extending healthspan.
Your metabolism works efficiently. Your body adapts easily to stress. As a result, you stay strong, energized, and resilient well into older age. That’s what healthy aging is really about.
Can supplements improve metabolic flexibility?
Supplements can complement a balanced lifestyle by supporting energy metabolism and gut function.
InnoSlim® promotes healthy glucose metabolism, AstraGin® enhances nutrient uptake in the intestines, and Senactiv® assists in cellular renewal and muscle recovery.
Dr. Keller stresses that supplements should work with food, not replace it. The best results come when science-backed ingredients support an already healthy foundation of whole foods, movement, and rest.
What foods increase nitric oxide naturally?
Leafy greens, beets, celery, and bok choy are excellent natural sources of nitrates. Chewing these foods helps oral bacteria convert nitrates into nitrite, then into nitric oxide, improving oxygen delivery and endurance.
Eating these foods regularly, rather than in one large dose, maintains nitric oxide levels over time. Pairing nitrate-rich vegetables with antioxidant-rich foods like citrus or berries can further protect nitric oxide molecules from breaking down too quickly.
How do sleep and stress affect the gut?
Even a few nights of poor sleep or high stress can disrupt your gut microbiome. Lack of rest changes hormone balance, digestion, and microbial diversity, leading to bloating, cravings, and low energy.
Stress also affects gut motility and increases inflammation. Dr. Keller explains that mental wellness and gut wellness are deeply connected. Managing stress and prioritizing quality sleep are essential parts of maintaining both metabolic flexibility and a healthy gut.
Why does Dr. Rosa Keller focus on healthspan?
Dr. Keller believes that nutrition and lifestyle choices should aim to extend healthspan—not just lifespan. Her research on the gut microbiome, dietary nitrates, and metabolic flexibility shows that these systems are all connected. When you support your gut, you support your metabolism, energy, and longevity.
As she puts it, “Aging well isn’t about avoiding time—it’s about staying adaptable and capable throughout it.”
Learn More
📖 Explore related topics on our blog, including AstraGin® for nutrient absorption, Senactiv® for recovery, and InnoSlim® for metabolic health.
🧩 Read Dr. Keller’s companion article on Top 5 Supplements for Athletic Performance for practical applications of her research.
References
Keller R et al. Dietary Nitrate and Nitrite Concentrations in Food. Nutr Today. 2020.
Keller R et al. The Impact of Dietary Nitrate on Blood Pressure and Exercise Performance. Front Physiol. 2023.
IOC Consensus Statement on Dietary Supplements and the High-Performance Athlete. Br J Sports Med. 2018.