Best diet for runners
Training for an endurance race is stressful to more than just your legs and your lungs. It’s hard on your gut, your immune system, your mood, your sleep, and your overall sense of well-being. Race training can be grueling, and the wrong diet amplifies the damage you take during your run and reduces your recovery afterwards. I’ve previously gone over how to fuel your event training workouts, so this week I’m going to go over how to fortify your body against the stress of intensive training. With the right nutrition, you can drastically enhance your natural protective systems and prevent common ailments associated with endurance training such as:
- Gastrointestinal problems
- Increased intestinal permeability (also known as “leaky gut” syndrome)
- Mood disturbances and irritability
- Troubled sleep and insomnia
- Decreased immune function
- Upper respiratory tract infections
- Increased overall pain and inflammation
- Joint pain
- Weight gain
A simple mix of the right foods will help minimize stress, prevent the side effects listed above, maximize fitness improvements, and just make the entire experience feel better. For this particular article I’m going to refer to running, but the same advice works for any endurance training regiment.
“What should I eat during my race training program?”
You’ll find lots of variations on specific foods, but the basic dietary advice by many running blogs, books, and magazines boils down to this: eat mostly carbs to replace lost glycogen along with some protein to heal damaged running muscles. The more informed sources will also suggest various fruits, nuts, and whole grains to provide other nutrients like vitamin C (to reduce muscle soreness), potassium and magnesium (to replace lost electrolytes), and some fiber (to provide slow-release sugar and because it seems to reduce the risks of developing heart disease and cancer). It’s not bad advice, but it’s ignoring many of the side effects of endurance training that plague beginners and veteran athletes alike. Like all exercise, running is a stress that breaks down your body so it can be rebuilt stronger and more fit. Unfortunately, if you stress your body too much or eat foods that don’t help in the rebuilding process, you may end up only breaking yourself down.
How endurance training breaks you down
Training for a race is taxing, and the stresses on your body and mood only increase as you get into the longer distances. Prolonged running requires a lot of energy, so your body releases catecholamines like norepinephrine and epinephrine and stress hormones like cortisol to mobilize as much stored fuel as possible. In the short-term this isn’t a big deal, but as you get deeper into your endurance program, the levels of these stress-signals remain elevated which suppresses your immune system and causes muscle breakdown, anxiety, and sleep disturbances.
Those are just the side effect of releasing energy from storage. Burning that fuel through aerobic respiration then produces a great deal of reactive oxidant species and inflammatory cytokines. Inflammation is an important component of healing, but prolonged inflammation damages and degrades tissue. Most researchers now view inflammation and the build up of reactive oxidative species as the cause of aging and age-related diseases like cancer and heart disease.
Plus it’s a sad reality, but unless you’re training in a field in Montana, you probably also inhale a great deal of air pollution while running along the street. This further inflames the airways and increases the release of inflammatory cytokines throughout your body. Fortunately, you have all kinds of adaptive systems to limit and repair damage, and many of them start in your gut.
Running and your gut
One of the biggest mistakes runners make is they not only ignore the importance of the gut-brain axis, but they structure their diets in a way that actively harms it, which causes major side effects like gastrointestinal issues, mood disturbances, irritability, depression, anxiety, insomnia, increased overall pain and inflammation, and decreased immune function that leads to upper respiratory tract infections.
What most people don’t realize is that important hormones and neurotransmitters like gamma aminobutyric acid (GABA), neuropeptide Y, dopamine, and serotonin are manufactured by your microbiome. The beneficial bacteria in your intestines also regulate immune function, control inflammation and oxidative stress, manage hydration, and supply additional energy and nutrition for optimal functioning. The point of your microbiome is to serve as a highly adaptable digestive and endocrine organ that changes to match what’s available in your environment. In other words, what you eat can significantly change the composition of your microbiome within a few days. Unfortunately, the diet choices most runners make like sports drinks, gel packs, and processed foods quickly degrade their microbiomes.
Most race training diets harm the gut
As I mentioned above, common endurance training advice pushes simple carbohydrates for easy energy and recommends that you limit fat and fiber as much as possible because they delay gastric emptying (the speed at which food leaves your stomach for absorption) which can cause discomfort and bloating.
Ironically, avoiding fiber and focusing on simple sugars is the reason why so many endurance athletes experience gastrointestinal distress. As you run, your body directs blood flow away from the digestive system towards working muscles. This not only provides energy where it’s needed, but it also helps cool your system by moving blood away from your core and closer to your skin.
Unfortunately, this redirection of blood away from both the small and large intestines is rough on your digestion and the home of your microbiome. The combination of ischemia (decreased blood flow to an organ), hypo-perfusion (decreased blood flow through an organ), and hyperthermia (over-heating) weakens the endothelial layer of your intestines. This is referred to as leaky gut syndrome in running circles but it’s more commonly known as increased intestinal permeability. I’ve written about this before concerning how fiber keeps your your microbiome healthy, and it’s even more vital as you turn up the stress with an endurance program.
The beneficial bacteria in your microbiome digest fiber and release short chain fatty acids that the cells of your intestine use to create a protective layer of mucin. This is considered the first line of defense for your immune system. In addition, when your intestinal cells receive this steady supply of energy, they reduce the flow of oxygen from your bloodstream to your microbiome. This is important because your beneficial bacteria are anaerobic. This means they thrive in an oxygen-free environment and actually suffer in the presence of oxygen. Worse yet, harmful species like E Coli and Salmonella thrive in a higher oxygen environment which allows them to outcompete the beneficial species, takeover your microbiome and start to induce disease and dysfunction.
When you starve your microbiome of fiber and instead provide a flood of simple sugars, it sets off a chain of events that leads to leaky gut syndrome, systematic inflammation, and the whole range of side effects I mentioned above. Remember, fiber feeds the bacteria that strengthen the barrier. In the absence of fiber, those same beneficial species devour the mucin layer instead. As fiber continues to decline and oxygen levels increase, pathogenic bacteria thrive and entire strains of beneficial bacteria die off. This happens to sedentary people when they cut out fiber, but the damage is accelerated when combined with the stresses of endurance training.
We’re still learning a great deal about how the microbiome influences your health, but the one thing we do know is that the more diverse strains of bacteria you have in your gut, the healthier you are. The loss of diversity is known as dysbiosis and it has been shown to cause all kinds of dysfunction such as autoimmune diseases like type 1 diabetes, muscular dystrophy, rheumatoid arthritis, multiple sclerosis, irritable bowel syndrome, Crohn’s disease, food allergies, and celiac disease. Dysbiosis also contributes heavily to other illnesses of the mind and body like obesity, autism, depression, anxiety, bipolar disorder, eating disorders, as well as certain types of cancer.
As you lose diversity, you lose the ability to make all the metabolites, hormones, and neurotransmitters that you need to function optimally. You also lose the protective barrier that keeps all the bacteria (both good and bad) safely compartmentalized away from your bloodstream. As the intestinal wall becomes more permeable, your immune system detects these invaders and increases your inflammatory response. This not only kills bacteria from your own microbiome, but it damages tissues throughout your entire body. Worse yet, these bacteria don’t go down without a fight. The outer membranes of many types of bacteria, even the “good” ones contain molecules called lipopolysaccharides (LPS) or endotoxins. They can selectively release these molecules to harm other organisms, but they also release them when killed. These tiny endotoxins are what cross through your weakened intestinal wall and increase damage and inflammation. Measuring the levels of lipopolysaccharides in the bloodstream is how many studies examine the effectiveness of certain nutrients at reversing intestinal permeability.
Just a little context on why this matters. One study showed how this particular type of inflammation drastically increased osteoarthritis in the joints and that simply adding one type of prebiotic fiber strengthened the microbiome, reduced inflammation, and reversed damage to the cartilage, tendons, and ligaments. This inflammation also increases LDL cholesterol, hardens arteries, and increases the risk of heart disease and death. I’ve previously written about how increased intestinal permeability triggers a sustained immune response leading to increased heart disease risk. You can read more about it here if you wish, but in general, just know that increased intestinal permeability means an increased level of damaging and painful inflammation throughout your entire body.
Endurance training does so much to improve your cardiovascular health and longevity. Don’t undo all your hard work by cutting fiber out of your diet.
Running and stress eating
Another topic you’ll see in many running blogs and magazines is “why am I gaining weight during my endurance training program?”
You would figure all that cardio would trim excess body fat, but you need carbohydrates for event training and sugar is still a major contributor to fat storage. It only takes a few mistakes with your sugar intake to turn it from glycogen-restoring to fat-storing.
One important step is to try and limit the release of insulin. Carbohydrates are needed to power your run training, but insulin is not. Normally when you eat sugar, your body releases insulin to shuttle it into muscle cells. Insulin also tells your fat cells to store any ingested fat and to not release any stored body fat. The advantage of consuming carbs during your workout is that running activates GLUT4 instead of insulin to move sugar into muscles. This same pathway stays activated for a while after your workout which is why people recommend a recovery shake right after so you can restore glycogen without increasing fat storage.
Another way to limit insulin is to eat carbs early. Your insulin sensitivity is much higher in the morning than at night so it takes far less insulin to process carbohydrates in the morning than it does at night. As tempting as it will feel to eat sugar all day long because you worked it off running, you need to realize this is actually a stress response. There’s a reason we turn to sugar for stress-eating. Sugar reduces cortisol levels which does make you feel better, but it’s only temporary. We also tend to enjoy foods high in sugar and fat to relieve stress. This combo will jack up your insulin levels and store all the consumed fat in your fat cells. In addition, the closer you eat your comfort food to bedtime, the more likely it is to disrupt your sleep, causing increased stress the next day.
Endurance training depletes your willpower, saps the neurotransmitters that make you feel normal, increases your desire for comfort eating, and creates an inflamed environment that encourages fat storage. It doesn’t have to be this way. If you feed your gut properly, you can reduce pain and inflammation, avert mood disorders, and improve your overall results by preventing the training-quality declines that occur as your body and mind start to wear down.
Basic macro breakdown
Before I get into some specific food recommendations, I want to quickly review my previous advice on the amount of carbohydrates, fats, and proteins you should consume each day with a slight update in terms of how it effects the microbiome.
Carbohydrates: 65 percent of total calories on most days, but specifically aim for 7 to 12 g / kg of body weight per when training for more than 2 hours. Limit simple sugars and focus on high fiber carbohydrates. Aim for 25 g of fiber for women and 38 g for men.
Carbohydrates are still king when it comes to race training, but the more you limit simple sugars, the less side effects you’ll create. I previously recommended simple carbs before and during your run, but the more I’ve researched the microbiome, the more I have to conclude it’s a bad practice. Sugar during your workout has been shown to suppress cortisol levels and limit the immune suppressing effects of endurance training. That’s a good thing, so you should consume sugar during a longer run to reduce side effects, but not the simple sugars I previously recommended. Like others, I too thought simple carbs would cause less indigestion and gastrointestinal discomfort when your blood flow was directed away from your digestive system, but new research shows that fiber-rich carbohydrates are processed more efficiently by the body and reduce damaging inflammation.
Your body just handles fruit and fruit juice (or sports drinks) very differently. One study followed the path of isotope-tagged fructose from fruit versus a fruit drink. When you eat fruit, 90 percent of the fructose is actually absorbed by the small intestines and converted to glucose, lactate (an excellent glucose-sparing fuel source), and glycerate and released into the bloodstream. When you drink a high-fructose beverage, the small intestines becomes overwhelmed about halfway through the drink and the spill over travels on to your liver and microbiome. Conversion in the liver is known to contribute to fatty liver disease and actually triggers metabolic dysfunction by causing an excessive release of stored glycogen from the liver. Your microbiome suffers as well. It was never designed to deal with a powerful nutrient like sugar. This particular study didn’t examine how it changes your microbiome but the researchers warned that your beneficial bacteria need fiber, not sugar. It’s the pathogenic strains that prefer sugar for fuel.
Another study found an interesting benefit when they compared fueling an endurance workout with a fiber-rich energy source like a banana versus a typical energy drink. The study involved 20 competitive cyclists, both male and female. They were asked to complete a 47-mile bike ride multiple times. On one ride they only had water, on another they had water and about 8 ounces of a sports drink every 30 minutes and on the third ride, they swapped out the sports drink for half a banana every 30 minutes.
They checked their blood for markers of inflammation and hundreds of other metabolites. They also examined blood cells for signs of stress-induced gene activation. The water-only ride produced the most markers of inflammation. Both the banana and sports drink reduced inflammation, but the banana also seemed to reduce activation of the COX-2 enzyme. NSAIDS like ibuprofen reduce inflammation by inhibiting COX-2 as well, which is why they are a common component of many training regiments. As I mentioned in another article, frequent ibuprofen use is dangerous. It increases the risk of heart attack and stroke (even after a few weeks of use), it’s incredibly harmful to your digestive tract (which is already weakened from endurance training), and it actually inhibits muscle building (which means it’s also inhibiting muscle repair).
The study participants complained that the banana led to bloating but that was simply because they weren’t used to it. Your microbiome is an incredibly complex environment. Some bacteria digest the foods you eat, but entire strains live off the metabolites released by other microbes. Anaerobic digestion of fiber does create excess gasses. While this can be unpleasant at first, it tends to diminish in a week or so as other bacterial colonies sprout up to devour the released gasses. Your microbiome will adjust quickly to limit side effects like bloating, but you need to be consistent to allow new strains to thrive. In the beginning, you want to up your fiber intake after your workout to improve your microbiome without worrying about discomfort until you’ve adjusted. It will not only save you issues during your workout, but in general the benefits from a fiber-rich meal tend to come the next day.
On shorter or less intense training days, you don’t need to fuel up beforehand at all. I like to refer to the Jeff Galloway Training Method as a template for how to fuel your workouts because it is one of the safest and most effective ways to train for an endurance event. His method involves one long run a week to build up your mileage and endurance, and two short runs to maintain your gains. On the short days, try your best to do a fasted run to help improve your fat utilization. It isn’t stressful enough to induce significant inflammation and fasted training will trigger the activation of fat-burning genes. However, fasted training is not ideal for speed work. If you plan to push your intensity to improve your speed, you will want to fuel your run with carbohydrates beforehand. You also want to fuel up before and during your longer training sessions. The long run day is the best time to practice your race day eating strategy. The worst thing you can do is introduce something new on race day. Your microbiome is incredibly adaptable, but it won’t change overnight. Figure out how to eat and how to hydrate so you’re feeling strong but not needing to hit every port-o-potty along the route.
If you haven’t been eating much fiber before, you should focus on adding fiber throughout the day after you train to give your microbiome time to adjust. It’s what you should do to replenish your glycogen stores anyway. Whether it’s simple carbs or complex, fiber-rich sources, your body will replenish lost glycogen at the same rate. The difference is that simple sugar will harm your microbiome, increase your desire to comfort eat, increase fat storage, and lessen the quality of your sleep, while high fiber fruits, vegetables, nuts, and grains will do the opposite.
Look for high fiber carbohydrates as much as possible. The old running favorite oatmeal is an excellent source of beta glucans which have been shown to decrease intestinal permeability. Other whole grain sources like barley, wheat, brown rice, bulgur, and quinoa are also excellent ways to up your fiber as you restore your glycogen. Lentils, beans, nuts and seeds are an excellent mixture of healthy fats, carbs, and protein. I recommend walnuts above all other types of nuts and seeds. They contain a great mix of prebiotic fibers that will improve your microbiome, they’re one of the few nuts that have omega-3 fatty acids that reduce inflammation and strengthen your brain, and they posses polyphenols that activate the right insula area of the brain and increase your desire to make healthier food choices. Like I said before, your willpower will be tested during your endurance program so add in walnuts to power it back up.
Bananas of course are an excellent fiber source as mentioned above. You should also include a mixture of berries to provide a vital mix of antioxidants, polyphenols, and anthocyanins. These compounds have been shown to fortify your body against heart disease and cancer, but in the context of endurance training, they strengthen your immune system against respiratory infections.
Protein: 10 to 20 percent of total calories or about 1.2 to 1.6 g / kg.
Athletes need about twice as much protein as sedentary people, but more is not necessarily better. As I mentioned above, the majority of your calories should come from complex carbohydrates. If you don’t get enough carbs, your body can break down protein for fuel. This is not ideal since it not only reduces the amount of amino acids available for muscle repair and immune function, but fermentation of amino acids for energy in the microbiome can produce harmful metabolites like phenols, amines, and hydrogen sulfide which have been shown to contribute to irritable bowel syndrome, colon cancer, increased intestinal permeability, inflammation, and DNA damage. Fermentation of read meat in particular creates additional harmful metabolites like trimethylamine-N-oxide (TMAO) which contributes to atherosclerosis. Keeping protein to the amounts recommended above and including additional sources of fiber and resistant starch keeps these harmful metabolites from forming.
In general, try to limit your proteins to post-workout recovery meals and try to include a mixture of animal and plant sources. Consume protein within 2 hours of your workout to aid in recovery and try to limit meat sources high in saturated fat at night. It’s been shown that saturated fat jet-lags your circadian rhythms and diminishes the quality of your sleep. Sleep issues are already enough of a concern, so adjust your fat intake at night for best results.
While protein should mainly be consumed post-workout, there is a particular amino acid that has been shown to protect against stress-induced intestinal permeability. Taking approximately 20 to 30 g of glutamine 2 hours before an intense endurance workout as been shown to prevent increased permeability, reduce blood endotoxin levels, reduce inflammation, and reduce stress-induced infections. L-glutamine supplements are pretty cheap but it’s also abundant in animal sources like chicken, beef, fish, eggs, and dairy or in plant sources like almonds, beans, beets, cabbage, spinach, Brussels sprouts, kale and fermented foods like miso.
An important amino acid to include in your post-run meals is L-tryptophan. As I mentioned in another article, it helps reduce inflammation in your central nervous system and helps protect against diseases like multiple sclerosis, Alzheimer’s disease, glioblastoma, and ALS (Lou Gehrig’s disease). It is also a precursor for the neurotransmitter serotonin and the sleep-hormone melatonin. Both are depleted during prolonged endurance training so eat foods high in tryptophan and vitamin B6 to help your body restore them. Excellent sources include turkey breast (of course), grass-fed beef, full-fat dairy, chicken breast, tuna, eggs, almonds, pumpkin seeds, sunflower seeds, peanuts, oats, chickpeas, bananas, and chocolate.
Fats: The remaining 20 to 25 percent of your calories should come from fat.
This is probably where most runners get it wrong. They either eat too little fat or they focus on the wrong kinds of fat (“I’m running so I can eat anything I want”). Your body needs dietary fats to repair cell membranes and manufacture hormones, but you don’t want to include fats in your pre-workout or during-workout meals. While you can quickly utilize ingested carbs for fuel, that’s not true of fats. They really will slow down digestion and cause discomfort before they ever get turned into useable energy.
I’m not against saturated fat in general, but for event training, you should try to limit it as much as possible. Studies have found that your body can mobilize 50 percent more stored fat during exercise when your diet is composed primarily of unsaturated fats. This is a big deal for runners. Focusing on saturated fats means a great deal of your stored fat will actually be locked away from you during your workouts instead of being released into your bloodstream as fuel.
A high fat diet is also associated with changes to the microbiome that increases intestinal permeability. As I mentioned above, increases in fiber will prevent the loss of important bacterial strains and limit this effect. It’s another reason why fats from plant sources tend to have better overall health outcomes than those from animal sources. It’s not the fat itself that’s harmful, it’s the lack of fiber.
Focus on healthy fats from plant sources like nuts (especially walnuts), seeds, olive oil, flaxseed oil, and avocados, and also include healthy animal sources like fish (high in omega-3), grass-fed beef and dairy (high in CLA), and omega-3 enriched eggs. Omega-3 fatty acids have been shown to help reduce post-exercise inflammation and soreness. The optimal dosage of omega-3 fatty acids needed to reduce reactive oxygen species and inflammation is approximately 1 – 2 g per day.
Protective and restorative foods
I’ve already hinted at some of the protective effects of certain nutrients like fiber, but now I want to get into specific recommendations that will strengthen your microbiome and activate other protective systems that will reduce inflammation and oxidative stress before it can harm you. I won’t have as many daily values on this as I did in the macronutrient section. For one, there often aren’t agreed upon values because the science is relatively new, but in general I hate getting too obsessed about numbers. Just try to mix and match these foods in your daily meals for best results and don’t drive yourself crazy measuring every little thing.
Too little dietary fiber combined with too many antibiotics (in us and in our foods) and too much time indoors has depleted the diversity of the microbiome of most people. You need fiber to feed the beneficial bacteria in your system, but you may need probiotics to restore beneficial strains that have died off. While most probiotic sources come from foods, there’s more to restoring your microbiome than just yogurt.
First off, congratulations. Just by starting an endurance training program, you will improve the health of your microbiome. Studies have shown that exercise alone improves your microbiome independent of diet. The microbiome of exercisers shifts more towards bacteria that produce the short-chained fatty acid butyrate. While any short-chain fatty acid feeds your intestinal cells, many studies focus on the benefits of butyrate because it’s also been shown to reduce inflammation, regulate the immune system to prevent auto-immune diseases, prevent colon cancer, and control appetite and weight. This microbiome shift is just one of the many reasons why exercise improves your health and longevity.
If you run outdoors, the improvements to your microbiome will be even more pronounced. One study examined the diversity of bacteria present indoors and outdoors. Not only did they observe much less diversity in indoor environments, but the genetics of the strains they found inside were more closely related to bacteria that are known human pathogens. These same pathogenic bacteria species didn’t even exist outside. It’s why we keep seeing more and more studies showing how people living on farms have a more diverse microbiome than city dwellers which protects them from many of the “Western diseases” that I mentioned above. It’s also why kids that live around farm animals or those with outdoor pets have less incidences of food allergies and asthma. Training indoors is fine sporadically, but running outside is a healthy probiotic.
If you only train indoors, you’ll also miss out on significant fitness improvements that come from heat adaptation. Since your event is likely outside anyway, you’ll need to get used to being out in the heat. Your body quickly adapts to higher temperatures and becomes more fit with proper heat conditioning (you can read more about how to do that here, but a surprise study found that probiotic treatments can also improve your heat tolerance and increase the time it takes to reach fatigue while exercising in hot temperatures.
The study was a double-blind, cross-over trial that followed 10 male runners. They were treated for 4 weeks with either the placebo or a daily probiotic capsule containing Lactobacillus, Bifidobacterium and Streptococcus strains and then swapped again after the 4 weeks. The runners exercised to fatigue at 80 percent of their ventilatory threshold at 95°F (35°C) and 40 percent humidity. While treated with placebo, the runners averaged 33 minutes until exhaustion, but that time increased to 38 minutes with the probiotic supplement. The runners also experienced less gastrointestinal symptoms during the study while on probiotics and they showed decreased blood levels of lipopolysaccharides, meaning that their intestinal permeability was improved.
Another study showed that supplementing with Lactobacillus rhamnosus and Lactobacillus paracasei increased concentrations of antioxidants in the blood following intense activity which meant they were neutralizing higher amounts of dangerous reactive oxygen species.
Probiotics can also help reduce respiratory infections. Another double-blind, placebo-controlled, crossover trial followed 20 elite runners over a 4 month winter training session. While supplementing with Lactobacillus fermentum, the runners experienced less than half as many respiratory infections (72 days with placebo compared to 30 days with probiotics), plus they reported the severity of symptoms were significantly reduced. A study of 46 female endurance swimmers also saw similar reductions in upper respiratory infections from supplementing with a probiotic yogurt.
Another study examined the effects of probiotic supplementation on anxiety and depression. Endurance training can lead to elevated cortisol levels and increased markers for inflammation like C-reactive protein. 8 weeks of probiotic supplementation in patients with major depressive disorder improved their depression scores, reduced levels of cortisol and C-reactive protein and increased blood concentrations of the antioxidant glutathione.
One of the major benefits of probiotic foods is that they also contain important prebiotics that keep those same beneficial species alive and flourishing (that’s how they live in there in the first place). I’ll get into beneficial prebiotics in the next section, but focus on probiotic food sources instead of supplements for best results. You also want a good mixture of foods to increase the diversity of your microbiome as much as possible. For all these recommendations, make sure it says live and active cultures on the label.
Kefir and yogurt: While yogurt is the definitive food people think of when they hear probiotics, kefir is another dairy-based option you should include in your diet. Yogurt contains about 2 to 7 beneficial strains while kefir can range from 10 to 34.
Fermented cabbage: Foods like sauerkraut and kimchi are made by partially fermenting cabbage with active cultures. It’s also an excellent high-fiber prebiotic.
Sour pickles: Most any kind of pickled fruit or vegetable will do, but only if they’re pickled in brine instead of vinegar. Vinegar will kill off any active cultures and sterilize the batch.
Miso: This fermented soy bean paste is typically made into a healthy, low-calorie soup.
Tempeh: This is another probiotic food made from fermented soy. Many people actually like to use it as a meat substitute since it is a complete protein containing the full array of essential amino acids.
Kombucha: This fermented tea has soared in popularity lately to the point of becoming a health fad. It’s not the magic cure-all that many claim it to be, but it is a decent probiotic source with the added benefit of also containing a number of antioxidant polyphenols. The downside is it tends to be a bit higher in sugar and does actually contain about 0.5 percent alcohol. If you do drink kombucha, have it early in the morning or with food to improve intestinal absorption of the sugar. This will prevent the harmful effects of sugar on the microbiome that I mentioned earlier.
Prebiotics are basically the primary food source for probiotics. They are specifically defined as compounds that can’t be digested by the human gastrointestinal tract, but can be fermented by specific beneficial bacteria, which then helps those strains multiply and flourish. The primary focus of most research is on fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS), but there is evidence of other helpful fermentable fibers.
The biggest point of confusion concerning which plants are prebiotic seems to boil down to soluble versus insoluble fiber. Soluble fiber dissolves in water into a thick gel like substance and insoluble does not. While only the soluble fibers are fermentable prebiotics, there really isn’t any plant that’s 100 percent soluble or insoluble fiber. That’s why seemingly insoluble sources like walnuts still demonstrate prebiotic benefits in studies. Walnuts have been shown to alter the microbiome by increasing populations of bacteria that make butyrate as well as ones that reduce inflammation and improve insulin sensitivity. Vegetables and berries are also much higher in insoluble fiber but they still contain enough beneficial prebiotics to positively influence the composition of your microbiome. I’ll make specific recommendations on prebiotic foods, but really any type of plant will help. We’ve known for centuries that eating your vegetables reduces weight, reduces disease risk and improves longevity. The difference is that we now understand that a big reason it positively effects health is because the fiber helps maintain a strong and diverse microbiome.
Inulin: Inulin is one of the most important prebiotics and fortunately, it’s also one of the easiest to consume. It is a natural storage carbohydrate found in over 36,000 species of plants. The biggest benefit for runners concerns it’s protective effects against respiratory infections. You have two types of immune function, the innate immune system and the adaptive immune system. The adaptive system creates fine-tuned instruments to deal with specific invaders, but it moves too slow. The innate immune system quickly responds to any damage or pathogen but it’s a blunt hammer that quickly smashes the invader and all surrounding tissue before any pathogens can take root. You need both to survive, but the innate system causes a great deal of incidental damage and inflammation. Worse yet, as you grow older, your innate immune system gets stronger and more active and your adaptive system gets weaker. Inulin strengthens bacteria in your microbiome that control and lessen your innate immune response while simultaneously strengthening your adaptive response. The end result is less damaging inflammation coupled with improved protection again infection, an important win-win during endurance training.
Some great sources for inulin are asparagus, onion, garlic, Jerusalem artichoke, chicory, dandelion root, leeks and even many whole grains like wheat and oats. Food companies have found that it is easily extracted from various plants which is why they are increasingly using inulin in a lot of supplements and processed foods.
Fructo-oligosaccharides (FOS): This prebiotic is found in many of the same foods as inulin because it’s actually produced through the degradation of inulin. This is the prebiotic in particular that I mentioned above which protects against osteoarthritic joint pain and actually heals inflammation damage to cartilage, tendons, and ligaments.
Focus on getting your prebiotics from fiber-rich sources like berries, bananas (when they’re slightly green), onions, chicory root, garlic, asparagus, jícama, and leeks. You can also find them in some grains and cereals like wheat and barley. A recent study found that the improvements to the gut microbiome from barley in particular improved people’s metabolism for up to 14 hours after consumption, decreased their blood sugar and insulin levels, increased insulin sensitivity, and improved appetite control.
Galacto-oligosaccharides (GOS): Something that surprised me a few years ago during my research was finding out the saturated fat in dairy tended not to lead to weight gain. Of course, you could ruin it’s naturally protective effects by eating a lot of crappy processed foods with it, but in general, something in dairy prevented fat storage. One of the reasons is the fat-clearing effects of calcium and the other is the fact that our bodies can process lactose into a prebiotic known as galacto-oligosaccharides. One study found that galacto-oligosaccharides helped produce bacteria that reduced the release of cortisol in humans, which reduces feelings of stress and anxiety. The calming effects of this prebiotic will help reduce stress eating and improve your mood, immune function, and sleep quality. You’ll find it in the same dairy sources as your probiotic yogurt and kefir, but if you are lactose intolerant, you find it in plant sources like lentils, chickpeas/hummus, green peas, lima beans, kidney beans, Jerusalem artichoke, broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, kale, radishes and rutabaga.
Sulfoquinovose: This prebiotic was found in what was generally thought of as foods rich in insoluble fibers. Researchers recently discovered that leafy greens contain a unique sulfur-containing sugar called sulfoquinovose that fuels the good bacteria in our microbiomes. Sulfur is important for building proteins, so the bi-products from breaking down this sugar likely also serve as important nutrients for other bacteria species in your microbiome. This one hasn’t been studied yet in the context of athletic performance benefits, but leafy greens also contain a vital nutrient for endurance training, magnesium. I’ll get into that later, but leafy greens like spinach, kale, and collard greens should be an important port of your daily diet.
Resistant starch: This is another prebiotic that tends to result in the production of more butyrate so it’s another excellent anti-inflammatory fiber source. Once again, slightly green bananas are an excellent source, as are oats, beans and lentils. What’s interesting is that the resistant starches in foods like rice, pasta, and potatoes is actually increased if you cook them and then serve them cold. They have a decent amount of resistant starch before cooking, cooking breaks it down into an easily digestible starch, and then cooling it again returns it to a prebiotic resistant starch.
Other Important Nutrients
As I mentioned above, eat your leafy greens for important prebiotics, but when it comes to endurance training, you mainly want them for the vital micronutrient magnesium. Magnesium is at the center of the chlorophyll molecule so the greener the better. Your body uses magnesium as a cofactor to activate over 300 different enzymes in your body. When you get enough magnesium, all these enzymes can be activated as needed, but when magnesium levels are lacking, your body has to prioritize its use. Inadequate magnesium intake will shut off vital functions like DNA repair, it will negatively impact your mood, and as a more immediate consequence, you will have less energy during your race and you’re fitness will be slower to improve.
When you run, your body uses oxygen to make ATP (the molecule your cells use for energy), but this process also causes harmful oxidative stress that damages your cells. To reduce this damage, your body creates more mitochondria (the power plants of your cells) and improves their oxidative capacity. Your mitochondria use oxygen to create ATP but they also incur oxidative damage in the process which slows the creation of ATP during exercise. When you get enough magnesium, enzymes are activated that not only repair damaged mitochondria so they can keep cranking out ATP, but they also encourage the formation of new mitochondria. This is how you get more fit. Your body adapts to the damage by becoming more efficient at producing fuel.
Adequate magnesium intake also enhances athletic performance by improving insulin sensitivity and increasing available glucose during exercise. One mouse study found that supplementing with magnesium 30 minutes before a treadmill workout caused glucose and lactate levels to immediately rise in the muscles, blood, and brain during exercise. Remember, lactate is actually a fast-acting fuel source that powers intense exercise. It also acts as a signaling molecule that triggers mitochondrial biogenesis (the growing of new mitochondria). The study found that magnesium increased lactate clearance in the muscles during exercise which means the cells not only had more fuel available during exercise, but they were also able to use it more efficiently.
A double-blind randomized study of triathletes found that the group supplementing with magnesium for 4 weeks before their race decreased their running, swimming, and cycling times compared to the control group, had increased blood glucose levels and decreased blood insulin levels during their race, and decreased serum levels of the stress hormone cortisol before and after the race. Once again, this study found that magnesium increased the amount of fuel available to the racers and improved their efficiency in shuttling it into the muscles. As an added bonus, they also found that it reduced the stress on the body.
Other studies have shown that magnesium supplementation alone significantly reduced symptoms of depression and anxiety and that a magnesium deficiency actually contributes to depression. The typical daily recommended amount of magnesium is about 400 mg for men and 310 mg for women, but the energy demands of athletes could call for an extra 10 to 20 percent per day. Leafy greens like spinach, kale, and arugula are great sources. I would also recommend avocados and almonds because they’re great sources of healthy unsaturated fats as well, and the continually recommended banana is another great magnesium option.
Air pollution is a real concern when training for your event. Training earlier in the day helps reduce exposure, but few places are truly pollution-free. Fortunately, your body possesses the incredible NRF2 pathway which actually transforms dangerous airborne toxins into water-soluble (and less dangerous) conjugates that can then be excreted from the body in urine or bile. But you need to activate this pathway in order to receive it’s powerful detoxifying, anti-inflammatory, and anti-carcinogen benefits.
Cruciferous vegetables like broccoli sprouts, broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, and arugula contain sulforaphane, one of the most potent activators of the NRF2 pathway. This interesting compound is actually a natural insecticide formed by the action of chopping or chewing it. It’s not the compound itself, but the enzymes it triggers in your body that reduce inflammation and more importantly neutralize harmful airborne toxins like benzene, acrolein, HCAs, and PAHs. If you’re going to run outside, sulforaphane must be a component of your diet to protect your lungs against air pollution.
Studies have found that sulforaphane increases the production of detoxifying enzymes in your upper airway, so dangerous pollutants are more likely to be neutralized before they can cause harm. Benzene in particular is a known carcinogen released from the burning of fossil fuels, so anyone running along the road needs to worry about it. Fortunately, a study in the Yangtze River delta region of China showed just how quickly and effectively it neutralizes this particular toxin. The Yangtze River delta region is characterized by exposures to substantial levels of airborne pollutants. The researchers found that when participants consumed a drink containing broccoli sprouts (a rich source of sulforaphane), they showed a 61 percent increase in excretion of the neutralized form of benzene. Not only was this increase in detoxification sustained the entire time they took the drink, but the detoxifying effects started the first day.
While any cruciferous vegetable contains sulforaphane, I recommend adding broccoli sprouts to a salad or blended up in a drink. Any study of sulforaphane uses broccoli sprouts because they contain 100 times as much sulforaphane as mature broccoli. Since the action of chopping or chewing it is what creates the sulforaphane, pulverizing it in a blender is a great way to activate as much as possible.