What happens to my gut microbiota when I eat a ketogenic diet ?
This is one of great controversies in the online health community. I asked nutrition researcher Dr. William Lagakos for some insight about this one. He notes that the composition of the gut microbiome is primarily regulated by diet, especially the types and quality of dietary fibers, but there is currently a lack of research studies on ketosis’s impact on gut microbiota.
However, a study published in the January 23, 2014, issue of the scientific journal Nature found that ketogenic dieting increased microbes of the genus Bacteroides and decreased Firmicutes. This may be of clinical relevance for many reasons.
For example, the opposite pattern—an increase in Firmicutes and decrease in Bacteroides—has been associated with obesity and an increased ability to harvest energy from food in animal and human studies. Furthermore, the microbial alterations induced by the ketogenic diet were associated with reduced levels of inflammation in a human study.
Cardiologist and New York Times bestselling author of Wheat Belly Dr. William Davis notes the critical importance of adding indigestible fibers to the diet for optimal gut health. He said that “they cause proliferation of healthy bacterial bowel flora species, such as Lactobacillus and Bifidobacteria . . .
while also allowing [the] conversion of such fibers to fatty acids, such as butyrate, that nourish intestinal cells, thereby reducing colon cancer risk and even triggering a cascade of metabolic events that result in reduced blood sugars, reduced triglycerides, higher HDL, reduced blood pressure, and reduced visceral fat.” Enriching the gut flora with more Lactobacillus is critical for preventing bile acid from being reabsorbed, causing it to instead be discarded into the stool.
Here’s what Dr. Davis says is the key to obtaining all the benefits of ketosis while consuming the indigestible fibers that provide a prebiotic function: limit carbohydrate-rich legumes and tubers to no more than 15 grams net carbohydrates (total carbohydrates minus grams of fiber) per six-hour digestive window, while increasing your consumption of indigestible fibers that do not convert to blood sugar.
This translates to half of a raw sweet potato daily, an unripe banana or plantain, or even a product like a Quest bar, all of which provide the fructooligosaccharides that feed your gut flora.
Unfortunately, this is far from settled science, and so much about it remains unknown. It is possible that eating certain foods on a ketogenic diet may feed gut flora. One study has also shown that body type and genetic predisposition seem to exert a bigger influence than diet. Regulation of the gut microbiome is complex and involves both dietary and nondietary components. There is no reason why gut health should not flourish on a ketogenic diet, and preliminary data suggest the gut microbiome may actually be improved by this way of eating.
Will drinking caffeine prevent me from getting into ketosis ?
This is a question I have heard for many years from people who are struggling to get into ketosis. Dr. Atkins mentioned in his book Dr. Atkins’ New Diet Revolution that “excessive caffeine has been shown to cause a hypoglycemic reaction” in some people—in other words, that it can cause blood sugar to drop.
That may lead in turn to food cravings (usually for carbohydrates) and then to the consumption of excess carbs or protein, which would kick you out of ketosis. He recommended that people who experience hypoglycemia from consuming caffeine give it up or “consume caffeine only in moderation.”
Jackie Eberstein, a registered nurse who worked with Dr. Atkins in his medical clinic in New York City for nearly three decades, says that there have been no scientific studies looking at caffeine and ketosis, but that the negative effects of caffeine on blood sugar could impact ketone levels.
“Some people are more sensitive than others, and of course the amount of exposure matters,” Eberstein explained. “Other factors [also] matter, such as having caffeine when the blood sugar is more stable after eating a low-carb meal, [when caffeine] may have no or only limited negative effects. For some of us, [consuming] caffeine when we are stressed for other reasons can provoke [carb cravings].”
That’s why she encourages people to “determine their tolerance,” and if their blood sugar is unstable, to avoid caffeine altogether. For everyone else, limiting consumption to, at most, three servings daily is probably a good idea. I have personally never had any problems from consuming caffeine, and neither has my wife, Christine, who drinks a latte made with heavy whipping cream almost every day. It’s something you’ll need to tinker around with to see how it affects your body. Self-experiment and see what happens.
Can I eat dairy on a ketogenic diet ?
This is another one of those “your mileage may vary” issues. Everyone is different, but personally, my ketogenic diet includes lots of dairy products, including heavy cream, sour cream, cream cheese, and hard cheeses. These are a big part of my personal low-carb, high-fat diet, and they have never given me any issues with producing adequate ketones.
However, others are very sensitive to dairy and need to cut it out of their diet because of digestive and metabolic side effects. If you are concerned that full-fat dairy might be an issue for you, try cutting it out for thirty days and see how you feel. (By the way, never consume low-fat milk or yogurt; not only does the absence of fat reduce satiety and lower ketone production, the fat that’s removed is replaced with a lot of sugar.)
DOCTOR’S NOTE FROM DR. ERIC WESTMAN: Many proponents of a Paleo lifestyle think dairy should be avoided. Dr. Loren Cordain, author of The Paleo Diet, once showed a slide of an intimidating moose with huge antlers and asked, “Are you going to milk that?” But while milk products should be avoided because they contain lactose (sugar), most people can remain ketogenic very well while consuming full-fat dairy like cream and cheese.
How long will it take for me to see improvements in my weight and health after getting into ketosis ?
Many people on a ketogenic diet have tried many different diets in the past. They may begin to doubt what they are doing is correct if they don’t see the desired results quickly. This often turns into an obsession, and they spend a lot of time reading about what they’re doing wrong in their diet and looking for loopholes.
They seek out anecdotes for permission to stop pursuing ketosis. This anxiety and doubt manifests itself in many physical symptoms until the person finally gives up, eats more carbs, and feels better psychologically that they’ve done something good for themselves. But they never got to truly experience the full benefits that a ketogenic diet could offer them.
– Dr. Zeeshan Arain
This is a tricky question because the answer depends on individual factors: how long it takes you to become keto-adapted, what your state of health was like prior to beginning the ketogenic diet, and how well you adhere to your personalized strategy for getting into ketosis (sticking with your carbohydrate tolerance and protein threshold levels is key).
But most people begin to lose both weight on the scale and inches around the waist within a few days. Once you reach nutritional ketosis, you should have more energy, complete appetite control, more even moods, and much clearer thinking.
Certain health issues—elevated blood sugar, high blood pressure, problematic cholesterol markers (namely higher triglycerides and lower HDL)—should begin to normalize within a matter of weeks. But even if you don’t see results that quickly, be patient. Persistence pays off, and if you’re showing good ketone levels in your testing, then you should see these effects soon. Don’t doubt yourself just when you’re on the verge of experiencing what keto can do for you.