Fermented foods such as kefir, kombucha and kimchi all contain beneficial microbes that can increase the population and diversity of microbes in your large intestine, Beck says.jchizhe/Getty Images
On Sept. 11, registered dietitian Leslie Beck answered reader questions about how to make changes for better gut health. Beck, one of Canada’s leading nutritionists, is the Clinical Director of Food and Nutrition at Medcan and author of The Globe’s Food for Thought column.
Readers asked about which foods are best to eat to improve your gut health, taking probiotics and managing cholesterol levels, among other topics. Here are some highlights from the Q&A.
Fibres, fermentation and more
How do we evaluate gut health? What are the symptoms that it needs improving?
Beck: The term “gut health” is used widely but poorly defined, especially with respect to diet, the gut microbiome and supplements. Many experts define gut health by the absence of gastrointestinal symptoms (e.g., bloating, gas, abdominal pain, diarrhea, constipation) and disease (e.g., inflammatory bowel disease, diverticulitis, colon cancer). There is also no single test that defines gut health.
Earlier this year, the International Scientific Association for Probiotics and Prebiotics published a consensus statement on the definition and scope of gut health. Gut health was defined as “a state of normal gastrointestinal function without active gastrointestinal disease and gut-related symptoms that affect quality of life.”
Diet is a major determinant of gut health. For example, fibre benefits gut health by promoting regular bowel habits, improving the composition of the gut microbiome and helping build a strong gut barrier. Fermented foods with live cultures also help to build a diverse and rich gut microbiome. And the Mediterranean diet has also been associated with lower inflammation in the gut. Remember, though, that responses to diet are highly individualized. We all have a unique gut microbiome.
Lentils and beans are a great source of fibre that fuel the growth of beneficial gut bacteria.PIYASET VIA GETTY IMAGES
What are your top three recommendations for simple shifts to improve gut health?
Beck: In general, eat a diet that’s high in nutrient- and fibre-rich fruits and vegetables, whole grains, beans and lentils and nuts and seeds. Fibre benefits the gut microbiome (and also helps prevent constipation and diverticulitis). Here are four recommendations:
Include fermented foods in your daily diet, such as kefir, yogurt, kombucha, kimchi, unpasteurized sauerkraut and vegetable brine. These foods contain beneficial microbes that can increase the population and diversity of microbes in your large intestine.
Fermented foods have other nutritional benefits. For example, during fermentation, microbes release vitamins and minerals from carbohydrates, making them more available for the body to absorb. Fermented foods are also easier to digest. Fermenting milk, for instance, breaks down lactose, making kefir, yogurt and buttermilk more digestible for people with mild-to-moderate lactose intolerance.
Focus on getting prebiotic fibres in your daily diet. Prebiotics feed beneficial gut bacteria, which, in turn, produce short chain fatty acids. These compounds play a role in strengthening the intestinal barrier and decreasing inflammation. Oats, barley, whole grain rye bread, white beans, lentils, apples, artichokes, asparagus, garlic, onion and bananas contain fermentable prebiotic fibres that fuel the growth of beneficial gut bacteria.
Include polyphenol-rich foods, such as berries, red grapes, pomegranate seeds, green tea, cocoa powder, onions, kale, broccoli, citrus fruit, celery, parsley and soybeans. These also support your microbiome. Polyphenols are poorly absorbed in the small intestine – once in the large intestine, gut microbes use polyphenols as nourishment.
Finally, limit your intake of ultra-processed foods which often contain ingredients that can reduce the diversity of gut microbes and promote inflammation (e.g., added sugars, unhealthy fats and additives, such as certain artificial sweeteners and emulsifiers).
Five fibre-packed foods to add to your diet
What kind of fermented foods could I eat if I don’t usually like the taste?
Beck: Yogurt comes to mind! You can also try kombucha, a fermented tea beverage. Kombucha is made by fermenting sweetened black or green tea with a SCOBY, an acronym for symbiotic colony of bacteria and yeast. Kombucha is a little fizzy and tastes slightly sweet and slightly sour. You can buy it flavoured with fruit, ginger, rosemary, turmeric, rose petals, elderberries, lemongrass, maple, and so on. Another option is kefir. It has a tart and tangy taste, similar to buttermilk. If you find it too tart on its own, add it to a smoothie with frozen berries or other fruit. You can also use kefir to make overnight oats.
What is the best way to restore your microbiome after a round of antibiotics?
Beck: First, I don’t recommend taking a probiotic supplement. Research suggests that taking a probiotic supplement after antibiotic treatment delays the return of the gut’s normal bacteria.
The best way to restore your gut microbiome is through diet. Eat a fibre-rich diet that includes plenty of whole plant foods such as vegetables, fruit, whole grains and pulses (beans, chickpeas and lentils), and add good sources of prebiotic fibres in your diet, which feed beneficial gut bacteria promoting their growth and activity.
Add fermented foods to your diet too. A diet high in fermented foods has been shown to increase the diversity of the gut microbiome, as well as reduce levels of anti-inflammatory markers in the bloodstream.
A diet high in fermented foods has been shown to increase the diversity of the gut microbiome, Beck says.Mary Conlon/The Associated Press
Is wheat bran hard on your digestion?
Beck: Wheat bran may cause bloating in some people. Wheat contains fermentable carbohydrates called fructans, which can be poorly absorbed in the small intestine. Once they arrive in the large intestine, gut microbes ferment them, which can lead to gas and bloating in the GI tract. Some people with irritable bowel syndrome are sensitive to fructans.
I recommend adding bran to your diet gradually over a few weeks to let your gut adjust. Drink plenty of water to help the fibre work properly in your digestive tract. If you find wheat bran causes bloating, even in smaller doses, try oat bran or psyllium husk powder, which are typically better tolerated.
Healthy eating habits
What are some gut healthy foods to eat before bed that can help ensure sound sleep?
Beck: Tart cherry juice. Made from sour cherries, tart cherry juice is one the best natural food sources of sleep-promoting melatonin. It’s also an excellent source of phytochemicals called polyphenols which provide nourishment for friendly gut bacteria.
Research conducted in healthy volunteers found that, compared to a placebo beverage, drinking two tablespoons of tart cherry juice concentrate diluted in water twice daily for one-week increased melatonin in the body and improved sleep duration and quality. Tart cherry juice has also been shown to improve sleep among older adults with insomnia.
Sleep’s silent work: How a good night’s rest helps restore your body and mind
Do you have thoughts on diet choices that help people with elevated levels of cholesterol reduce them?
Beck: One diet that has been specifically studied for its ability to lower LDL (bad) cholesterol is the Portfolio diet. It’s been clinically proven to significantly reduce cholesterol – even if it’s followed only modestly.
The Portfolio diet includes four pillars, each with a daily recommended intake. Each pillar has been shown to reduce LDL cholesterol on its own. When the diet pillars are combined, however, they have additive effects on lowering cholesterol. The diet plan includes 50 g of plant protein (beans, lentils, tofu, edamame, tempeh, soy milk, soy and pea burgers), 45 g (about one third-cup) of nuts and seeds, 20 g of viscous, sticky fibre (oats, oat bran, psyllium, barley, okra, eggplant, berries, apples, oranges) and 2 g of plant sterols (typically taken as a supplement). But you don’t need to follow the Portfolio diet perfectly to get a meaningful reduction in LDL cholesterol. I wrote about this diet in my Globe and Mail column early this year.
Foods to limit to help lower LDL cholesterol include those that are high in saturated fat, such as fatty cuts of meat (e.g., ribs, ribeye steak, prime rib), processed meats and high fat dairy products (e.g., cheese, butter, ice cream). There is clear cut evidence that high intakes of saturated fat can raise LDL cholesterol.
Have high cholesterol? Follow the Portfolio Diet, even partially, to lower your level
Is there a way I can improve my “good cholesterol” level?
Beck: There isn’t a specific food that reliably raises HDL (“good”) cholesterol. Lifestyle factors have a greater impact on HDL levels, in particular regular aerobic exercise and weight loss (when appropriate). Certain dietary patterns and replacing saturated with unsaturated fats may modestly increase HDL, but no individual food has been shown to substantially raise HDL cholesterol on its own.