Severe elimination diets starve beneficial gut bacteria and may harm our guts – and our health.
AFTER A RECENT LECTURE I gave, a woman approached me to share her experience with trying to heal her leaky gut syndrome on a six-month-long elimination diet, during which time she ate only four foods. Four foods. For six months.
Such anecdotes represent the increasingly popular notion that we can heal our guts of whatever ails us by whittling down our diets to a bare minimum – whether it’s bone broth fasts, juice cleanses or stark elimination-type diets. Proponents of such regimens claim that constantly processing “hard-to-digest” foods (often defined arbitrarily) cause the gut to fatigue. As a result, the gut needs time to rest and regenerate. Another common claim is that all sorts of health problems result from having too much “bad bacteria,” and by starving them of carbs, gluten or other dietary demons, the “good bacteria” can regain a foothold and restore balance.
The Gut Microbiome
While these arguments may appeal to our sense of logic, they’re in direct opposition to what science has to say. Research is only just beginning to decode the mysteries of the trillions-strong ecosystem of microbes living in our intestines – commonly referred to as the gut microbiome. But one thing that scientists seem to agree on is that the healthiest guts are those that have the most diverse and abundant bacterial communities.The data are also clear that the single, most effective method of promoting bacterial diversity is by consuming a diverse diet rich in whole plant-based foods, like whole grains, fruit, vegetables, legumes, nuts and seeds.
In fact, carbohydrate-containing foods that are difficult to digest for humans are precisely what best fuel our gut’s good bacteria. Similarly, by withholding carbs in general – and fiber in particular – we’re more likely to starve the good bacteria than the bad ones.
In October 2018, I interviewed Daniel McDonald, Scientific Director of the American Gut Project at the University of California San Diego’s School of Medicine. Based on the lab’s analysis of over 17,000 stool samples and the self-reported dietary habits of their donors, McDonald explained that the difference in the diversity of the gut microbiome between people who eat a lot of plants and people who don’t eat a lot of plants is greater than the difference between someone who hasn’t recently taken antibiotics and someone who has.
Let that sink in: People who eat the fewest plant-based foods have such diminished diversity and abundance of their gut microbiome compared to those who eat the most plant-based foods that the effect of eating a low-fiber diet is similar to taking a round of antibiotics.
It makes sense. Our gut bacteria feed on the complex carbohydrates we eat but can’t digest, and different types of fiber and resistant starch feed different species and strains of these microbes. Foods that nourish beneficial gut bacteria are called prebiotics. Far from taxing our intestines with too much digestive work, prebiotics actually make our guts healthier and more resilient by enriching the microbial community within.
The Effect of Elimination Diets
So what happens to a gut that is deprived of a diverse, plant-rich diet – say from an elimination diet that restricts whole grains, legumes, fruit, certain nuts or seeds and certain vegetables like nightshades or those high in lectins? Exactly what you’d expect.
It’s been well-documented that elimination diets affect our gut bacteria in ways that may be counterproductive to long-term health. Even the low FODMAP diet – which has been a lifesaver to people who suffer from debilitating digestive symptoms – reduces total bacterial count in the gut and the abundance of certain beneficial species. Similar shifts in gut bacteria have been observed in children with epilepsy following a strict keto diet for seizure control. Their guts also show a relative increase in the abundance of microbial species associated with disease – the so-called bad bacteria.
Animal studies suggest another troubling possible outcome of a fiber-starved gut microbiome: Deprived of the nourishment they need to survive, our gut microbes may digest and degrade the protective mucus lining of the intestinal cells – our gut barrier’s first line of defense, potentially rendering one more susceptible to bacterial infections from not-so-nice microbial inhabitants.
Forget the old “5 a Day” campaign that urged Americans to consume five servings of fruits or vegetables daily. The emerging rallying cry from the microbiome research community is that we should be aiming to eat 30 different plants per week.
That’s right. Data from the American Gut project show that people whose diets contain 30 or more different plant foods per week have far more diversity in their gut microbiome than those who consume fewer than ten different plant varieties.
Crohn’s and Gut Health
Other research similarly suggests the importance of diverse, plant-rich diets for good gut health. A 2015 study of close to 40,000 participants found that a woman’s diet in high school was strongly predictive of her later risk of developing an inflammatory bowel disease called Crohn’s disease. Adolescent girls who ate the most fish and fiber– with fiber specifically from fruits and veggies – had a 53% lower risk of developing Crohn’s compared to their peers who ate the least amount of these foods, regardless of what their diets looked like as adults. The researchers hypothesize that diverse fiber-rich diets may cultivate a specific species of gut bacteria called Prevotella that appears to be protective against Crohn’s disease. Another possible explanation is that fiber-rich diets protect the gut’s barrier function, keeping disease-causing bacterial species from infiltrating the inner layers of the gut, where they might trigger inflammatory immune reactions. Other studies in children have similarly found associations with high intake of whole grains, nuts, vegetables and fruits (plus fish) and a lower risk of developing Crohn’s disease.
Collectively, we are nowhere near the 30 different plants-per-week goalpost. A recent report found that 60% of the plant-based calories in the typical modern diet come from just three crops: wheat, corn and rice. Even those of us actively engaged on a wellness journey might stop and take stock: How many different plant species does your purportedly anti-inflammatory grain-free, soy-free, legume-free, nightshade-free diet comprise? Your keto diet? Your carnivore diet? How will a days-long bone broth regimen nourish your closest allies in gut health?
Our fear-based public dialogue on diet is increasingly centered on foods to avoid in an attempt to limit exposure to toxins – both real and imagined. The resulting efforts to cut out certain foods in their various manifestations has us defining health based on what we avoid rather than what we eat. The science, however, suggests we’d be better off doing the opposite: How many different, fiber-rich, plant based foods can we eat on a regular basis?
We’re not just eating for one. Each one of us is eating for trillions. I, for one, am thinking a lot more about what it means to be a good host.
Best Diets for Healthy Eating
Author: Tamara Duker Freuman
Source: Health. US News: Is Your ‘Gut Healing’ Diet Actually Hurting You?