Gut Health Diet: The Negative Impact of Low Carb Diets

Low Carb Diets Have Got to Go!

Gut health is all over the media right now, but exactly what a gut health diet means is less clear. I’m frequently asked about my opinions on low carbohydrate diets, and whether or not a low carb diet can be good for gut health.

Anyone who has done any reading on health and wellness or who has tried to lose weight in the past ten years has a basic understanding of low carbohydrate diets, such as paleo, keto, or Atkins diet. With their increased popularity, the public has conceptualized that carbohydrates are the reason for weight gain, health problems and overall unhealthy lifestyles. 

Here’s a quick overview of some of the most popular low carb diets: 

• Carnivore diet: includes only animal products and spices.
• Atkins diet: includes four phases which gradually increase carb allowance. Restricts dairy, whole grains, starchy vegetables, and fruit. 
• Low sugar diets: restrict all sources of sugars, including fruit and dairy.
• Paleo diet: doesn’t specifically limit carbohydrates however eliminates key food grounds including whole grains, legumes and dairy.
• Ketogenic diet: to achieve ketosis most are limited to a very low level of carbohydrates (i.e. 20-50g/day) as well as restricting dairy, whole grains, starchy vegetables, fruit and legumes. 

Although they may be effective for short term weight loss, there are numerous health concerns associated with low carbohydrate diets, including negatively impacting heart health, digestive health, and mental health. Of particular concern is the adverse impact of low carbohydrate diets on the gut microbiome. Fiber (a type of carbohydrate) is the primary source of fuel for your healthy gut microbes. High fiber diets are associated with an abundant and diverse gut microbiota aka GUT HEALTH! Not only do low carbohydrate diets starve your gut microbes, but they are notoriously constipating thanks to restricting most high fiber foods. No thanks! 

As reviewed above, low carb diets tend to avoid whole grains and fruit, and replace them with meat, seafood, and (in some cases) high fat dairy products. This excessive focus on animal fats is harmful for your heart because of the high saturated fat content. High quantities of saturated fat can restrict blood flow in your arteries and are associated with increased risk of cardiovascular disease. On the other hand, certain types of fiber have been shown to restore and preserve this blood flow and help to manage blood cholesterol levels.

Carbohydrates are vitally important to our overall health. Carbohydrates are our main energy source and fuel all areas of the body, including our brains. If fact, we require around 135g (at minimum) of carbohydrates per day to promote optimal brain function. If we are depriving our brain of carbohydrates, we are more likely to have negative thoughts or be irritable and impatient. That’s one of the reasons that low carbohydrate diets are often associated with “brain fog” and feeling sluggish. The phenomenon of being “hangry” is a true physiological condition.

Are there any benefits to low carbohydrate diets? 

• There is some evidence to support lower carb diets for adults with type 2 diabetes. However, this may be a quality vs quantity issue. Choosing higher quality whole grains (e.g. quinoa, sweet potato, bulgur etc.) instead of lower quality carbs (e.g. white rice or white bread) likely has a larger impact than carb counting. 
• There is strong evidence to support ketogenic diets in epileptic children, particularly those who are medication resistant. This should only be done under the supervision of a trained dietitian. 

The takeaway: Low carbohydrate diets, and restrictive diets in general, make us irritable, constipated, and tired (and generally unhappy) as well as negatively impacting our gut health and being potentially dangerous. Beware of any diets that recommend eliminating entire food groups or promise too good to be true results! As always, focus on a primarily whole foods, plant centered diet whenever possible – but don’t be worried about including carbs in your diet – especially high fiber whole grains, fruits and beans/legumes!