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Why a keto diet can be bad for your gut health

Scientific and anecdotal evidence suggests that certain types of restrictive diets can harm the gut microbiome. Experts agree

Avoid cutting out any food group completely 
Avoid cutting out any food group completely 

When Nitika Gandhi, a Delhi-based communications professional, discovered that she weighed around over 72 kgs, which at 5'2 put her in the overweight category, she was horrified. “I used to be a basketball player,” she recalls, adding that she thought it was high time she did something about it. So, she decided to go on a low carbohydrate, high-fat keto diet, replacing whole grains with things like almond flour, paneer, mushrooms, chia and flax. “I did it for 2.5 to 3 months,” says Gandhi, who planned the diet herself by researching on the internet and using weight-loss apps. By June that year, she weighed 48 kilos. Then, as she transitioned to a more balanced way of eating, she noticed something. “I seem to have developed an allergy to gluten,” she says. Her stomach, she adds, now reacts badly to chapattis, something that had never been a problem earlier. “After all, that is what I grew up eating.”

The connection between gut health and nutrition has been long-established; today, nearly everyone knows that too many ultra-processed foods drastically affect the gut biome. However, much recent research indicates that there is another thing terrible for your gut-- restrictive diets, especially high-fat, low-carb ones, like keto. According to a May 2021 study published in Frontiers, a leading open-access publisher and platform, the human gut contains around 1000 bacterial species, which have a pivotal role in maintaining overall health. “This community of microbes is often referred to as a “hidden metabolic organ” because of its enormous influence on host metabolism, physiology, nutrition, and immune function,” says the study. “Any dietary changes, despite showing beneficial effects, can affect microbiota composition, especially when protracted for a long time,” it adds. Another article, published in Science Magazine in August, explicitly outlines the keto diet’s impact on the gut. “A high-fat diet impairs mitochondrial uptake of oxygen into host enterocytes and elevates nitrate in the mucus, which in turn weakens healthy anaerobic gut function,” it says.

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Dr Avnish Seth, Director, Gastroenterology & Hepatobiliary Sciences and Director, Fortis Organ Retrieval & Transplant (FORT) at Fortis Memorial Research Institute, says that this is unsurprising. “Our gut microbiome is made up of more cells than what we have in the entire human body,” he says, pointing out that these bacteria can be primarily divided into those that are good for you and those that are not so good. “Healthy individuals have a perfect balance of the good and the bad, and this maintained ratio promotes not just gut health but also increases body immunity and prevents disorders triggered by inflammatory signals from the gut.” Very low calorie or very low carbohydrate diets reduce the population of good bacteria in the body, he agrees, adding that it makes one prone to gastrointestinal disorders like irritable bowel syndrome and colitis. “Also, systemic inflammatory diseases linked to increased transmigration of bacteria from the gut like arthritis and alcoholic liver disease may worsen,” he says.

Eat a healthy balanced diet 
Eat a healthy balanced diet  (Sara Dubler, Unsplash)

Since these microbes feed on the fibre from the carbohydrates and produce metabolites like SCFA (short-chain fatty acids), which play a key role in neuro – immunoendocrine regulation, completely avoiding carbs is always a bad idea, believes nutritionist and certified diabetes educator Madhavi Karmokar Sharma, founder of Informed Health, an organisation committed to providing authentic information and services on healthy eating. Though carbohydrates have been vilified considerably in recent times, leading to the popularity of low-carbohydrate diets, it is an essential macronutrient, she says. “Being on low carb diets brings its own set of disadvantages like irritability, insomnia, and constipation,” believes the Delhi-based Sharma. “Avoiding carbs for fear of weight gain ends up with compromised quality and population of the strains of good bacteria in your gut.”

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While certainly, the best situation is not to have gone on a highly restrictive diet and messed up your gut, what can you do if you already have? Delhi-based nutritionist, Vidhi Chawla, recommends a diet rich in prebiotic and probiotic food to replenish the gut microbiome. “Also, get 7-8 hours enough good quality sleep; this also helps,” she says. Dr Seth, however, is a bit cautious about prescribing a one-size-fits-all approach to gut health. “Our gut has an identity of its own. Each person is different. What works for your friend may not work for you,” he says. However, he says certain foods are being advocated for gut immunity, though robust scientific data is still lacking. These include turmeric, papaya, carrots, garlic, ginger, wheatgrass, green tea, sprouts, mushrooms, spinach and broccoli. Also, “fermented foods like yoghurt, kefir, kombucha tea and kimchi are rich in probiotics that increase healthy gut bacteria,” he adds. And yes, it is a myth that you need to cut out dairy or wheat to have a healthy gut. “Dairy and wheat products have been an inherent part of our diet for centuries, and several of our elders have led a very healthy and long life,” he points out. “One must only avoid these foods if there is specific lactose or gluten intolerance.” Dr Seth also advocates regular exercise. “Researchers have reported improvement in gut biome after six weeks of exercise, thus boosting the body’s immunity,” he says.

In general, believes Sharma, one must evaluate a diet taking into account the following parameters: it should include food you have grown up eating; the food should be local and regionally available; it should not force you to eliminate any food group; it should fit your earth and exercise routine and should take into account your medical condition. “We all differ from each other in terms of how our body receives, absorbs, and assimilates food,” she says, pointing out that this is influenced by genetic predispositions, cultural backgrounds, food preferences, daily routines and gut microbiome expression. “Only a sustainable diet will work towards improving and maintaining permanent weight loss,” she says.

Gandhi, for instance, has managed to keep off most of the weight by continuing to exercise regularly and eat well. She had added carbohydrates back to her diet, choosing to eat jowar chapatis or chillas made of chickpea flour instead of wheat chapattis, which she still struggles to digest. “My doctor said that completely cutting out carbohydrates was a bad idea,” she says. “I do like the fact that I lost weight, but I am still dealing with the after-effects of it.”


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