Keto Diet, Gut Microbiota and Inflammation: new link identified

A new study has identified how low-carb, high-fat ketogenic diets (known as keto diets) can influence the composition of your gut microbiota and reduce levels of inflammation.

As we all come out of lockdown, we hope to return to our daily routines, including eating our favourite foods. But, for a lot of us, we are not alone in our return to the outside world. We are joined by the few extra kilos we gained during months of couch-style living, and we are eager to start a new diet to get back in shape.

Among the countless diets out there, one of the most popular is the so-called keto diet, which promises weight loss while allowing you to eat some of your favourite high-fat foods¹. Now, a new study found evidence for how keto diets may influence your gut microbiota and your overall health.

What is the Keto Diet?

Ketogenic diets, commonly known as keto diets, have been around for over 100 years, originally developed as an effective treatment for epilepsy². Since then, various forms of keto diets have been created, with different percentages of carbohydrates, proteins, and fats. Some common examples include:

Classic ketogenic diet

About 90% of your food intake are high-fat foods, with the remaining 10% split between carbohydrates and proteins. This diet must be medically monitored and carefully controlled³.

Standard ketogenic diet

About 75% of your allowed food is high in fat, 20% protein and only 5% carbohydrates⁴.

Cyclical ketogenic diet

This version of the keto diet alternates between periods of lower or higher carbohydrate intake and should be designed with the help of a registered nutritionist⁵.

Targeted ketogenic diet

This diet allows you to add carbohydrates around times of physical activity.

High-protein ketogenic diet

This version of the keto diet allows for more protein, usually in a ratio of 60% fat, 35% protein and 5% carbohydrates⁶.

Since their development, keto diets have remained consistent in allowing only low amounts of carbohydrates, moderate amounts of proteins and high amounts of high-fat foods¹.

The underlying principle of any keto diet is to mimic a state of fasting, forcing our body into a metabolic pathway called ketosis. This is a normal response of the body where fats are used as the primary source of fuel, instead of glucose (commonly obtained from carbohydrates). This metabolic pathway results in increased processing of fatty acids in the liver, producing ketone bodies, molecules used as an energy source.

In recent years, keto diets have become very popular due to their purported beneficial effects on health, particularly for losing weight. But keto diets have also been linked to many other health benefits.

Benefits Ketogenic Diets

A recent research review showed that following a keto diet could benefit cancer patients in multiple ways⁷. For example, following a ketogenic diet:

• May create an unfavourable environment for cancer cells, inhibiting their growth.
• Can enhance the antitumor effects of classic chemo- and radiotherapies
• Had the strongest beneficial effect on brain tumours, based on both pre-clinical and clinical studies.

Studies suggest that following a ketogenic diet can also have beneficial effects on metabolic syndrome pathologies, like obesity and type 2 diabetes. For example,

• One study found that mice fed with a ketogenic diet (90.5% fats, 9.2% proteins, 0.3% carbohydrates) had reduced body weight and fat tissue, compared to mice fed a high-fat diet with moderate levels of carbohydrates (54% fats, 21% proteins, 24% carbohydrates) ⁸.
• The same study found that mice fed a Ketogenic diet never developed mechanical allodynia and showed neuronal benefits, compared mice fed the high-fat diet. Allodynia is a condition where pain is caused by a stimulus that does not normally cause pain.
• A review study that analysed 13 clinical trials showed that people following ketogenic diets tend to lose more weight (and keep it off), compared to people following low-fat diets⁹.
• Ketogenic diets seem to have an appetite-suppressing effect, with an underlying mechanism that is not fully understood yet¹⁰.

Following a ketogenic diet may also be beneficial for the brain, as studies have established links with conditions like Alzheimer’s and Parkinson’s disease. Studies have shown that ketogenic diets¹¹:

• Can reduce levels of amyloid-β in mice. Amyloid-β is a common marker of Alzheimer’s risk.
• May help improve motor and nonmotor symptoms in people suffering from Parkinson’s diseases¹².
• May have protective effects on neuronal communication, through the protective effect ketones have on synapses, the connection site between neurons¹³.

Following a keto diet has also been implicated with benefits in immune function, which thus far, remain poorly understood. Now, a new study has identified a new role for the keto diet, affecting the composition of gut microbiota and influencing the production of specific immune cells.

Keto diet and the gut microbiota

In this new study¹⁴, researchers worked with overweight/obese participants, who had to follow either a normal diet with 50% carbs, 15% protein and 35% fat or a ketogenic diet, with 5% carbs, 15% protein and 80% fat. After four weeks, participants who followed the normal diet were switched to the ketogenic diet and those following a ketogenic diet were switched to a normal diet.

Analyses of stool samples from all participants showed that switching from a normal to a ketogenic diet significantly changed the proportions of common gut microbial groups, like Actinobacteria, Bacteroidetes, and Firmicutes. Among these bacteria, researchers studied the genus Bifidobacteria, which showed the most dramatic decrease following a ketogenic diet.

In further experiments, researchers transplanted gut bacteria from the study participants into the gut of mice. Their results showed that, following this treatment, mice produced reduced levels of Th17 immune cells, a type of immune cell that is known to promote inflammation in autoimmune diseases.

Researchers also showed that switching mice to a ketogenic diet resulted in rising levels of ketone bodies (typical of ketogenic diets) and that this increase was directly correlated to changes in their gut microbial composition. To further support this link, researchers fed ketone bodies to mice that followed a normal diet and still found changes in gut microbial composition. This finding showed that ketone bodies alone were responsible for causing changes in gut microbiota.

Overall, the results of this study show how ketogenic diets can influence the composition of gut microbiota and reduce levels of inflammation.

Is the Keto Diet safe for you?

Research so far has identified multiple benefits to following a keto diet, however, more research is needed to better understand the long-term health consequences of this diet.

While ketogenic diets seem beneficial and safe there are potential side effects that can occur, including:

• Development of “keto-flu” – this occurs when someone develops temporary flu-like symptoms like headaches, dizziness, fatigue, nausea, and constipation. These symptoms occur due to the drastic change in energy source, which causes an initial stage of dehydration and electrolyte imbalances¹⁵.

• Stress to the kidneys – changing to a ketogenic diet may increase your chances of developing kidney stones and may adversely affect people with chronic kidney disease¹⁶.

• May lead to micronutrient deficiencies, particularly for calcium, vitamin D, magnesium, and phosphorus¹⁷.

• May affect bone health, due to losses of bone mineral density, according to some studies^18-19.

If you are thinking about switching to a ketogenic diet, you should first consult with an appropriate healthcare team that is well-equipped with the knowledge and experience of how ketogenic diets affect the body.

At the Australian Centre for Functional Medicine, we have a team of health professionals that include registered nutritionists and experts in the management of ketogenic diets. An initial consultation with our team can help us determine if ketogenic diets are right for you.

References

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19. Heikura IA, Burke LM, Hawley JA, Ross ML, Garvican-Lewis L, Sharma AP, McKay AK, Leckey JJ, Welvaert M, McCall L, Ackerman KE. A Short-term ketogenic diet impairs markers of bone health in response to exercise. Frontiers in endocrinology. 2020 Jan 21;10:880. Read it!