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I’m writing from the annual meeting of the American College of Nutrition, and I happen to be the co-Chair for this year’s meeting here in Orlando. I’m speaking on how medical providers can assess nutrient intake and cognitive function, and which nutrients improve brain performance.

The Gut/Brain Axis symposium of the meeting has captured my attention with compelling, new information. There is growing evidence that our gut bacteria (our microbiome) impact many aspects of our health, from weight control, to inflammation, to your risk for neurological diseases, like memory loss, depression, autism, and attention deficit disorder (ADD).

How can gut bacteria impact your weight? Well, antibiotics generally kill off many healthy gut bacteria and allow an overgrowth of bacteria that cause us to gain weight. Bad gut bacteria produce chemical compounds (like propionic acid) that induce cravings, hunger, and inflammation. Additionally, inflammation will decrease your calorie burn rate all day long.

This doesn’t just apply to people. This is why feedlots give animals antibiotics to fatten them up. Without any increase in food intake, feeding antibiotics increases weight gain in chickens, cows, and pigs. So don’t be surprised if you gain weight after taking an antibiotic.

As if a jump in body fat isn’t bad enough, people with bad gut bacteria are also much more likely to have neurological diseases, like memory loss, autism, depression, ADD, and Parkinson’s disease. Not only does bad gut bacteria increase brain inflammation levels, but bad bacteria release compounds that first make your gut lining leak, and can increase leaking between the brain and the blood stream.

As I am processing this microbiome information, it came to me that it is November, and we are on the verge of winter cold and flu season, and pretty soon people will start calling the office asking for antibiotic treatments for respiratory infections, and we’ll need to explain how harmful it is to use antibiotics inappropriately.

Likely the most common cause of a sudden change in gut bacteria is antibiotic therapy. Antibiotics don’t just kill bacteria causing an infection, but they also kill billions of healthy gut bacteria at the same time. I’m not suggesting that you skip treatment for a life-threatening infection like pneumonia, but the reality is that more than 90% of the time when doctors treat patients for upper respiratory infections (more than 90% are colds) they will get better whether they are treated with antibiotics or not. Give a cold 10+ days, treat your symptoms if need be, and it resolves whether you are treated with antibiotics or not. If you get sick this winter, ask your doctor if an antibiotic is absolutely necessary, or if you could safely wait and give it more time. Absolutely, don’t ask your doctor to treat you over the phone for an infection without even being seen.

What to do if you have a serious infection and you must take an antibiotic? At the clinic I founded, we offer a probiotic with Saccharomyces boulardii to help prevent bad bacteria from taking over during the week that you are taking antibiotics (S boulardii is a beneficial yeast that is not impacted by antibiotic use and will inhibit the growth of bad bacteria, such as C Difiicile. Then  post antibiotic take a probiotic with at least 20 billion and up to 60 billion organisms daily for at least 8-12 weeks to help restore your gut microbiome with mixed species of Acidophilus, Bifidobacterium, and Lactobaccilus species.

What else can kill off your healthy microbiome besides antibiotics? Well, first and foremost is food. Surprisingly, consuming diet foods and diet sodas have been shown to cause weight gain over time. Why if they don’t have calories can they make you gain weight? Part of the reason is that many sweeteners kill healthy gut bacteria. So avoid artificial diet sweeteners.

Another clear cause for an overgrowth of bad gut bacteria is eating too much sugar and not eating enough fiber. Sugar and refined grain products feed bad gut bacteria. Eating more fiber from vegetables, fruits, beans, and nuts nourishes good bacteria. To maintain your microbiome, you should be eating at least 30 grams of fiber from these specific food sources every day. And this is the amount of fiber that also helps you lose weight and keep it off, decrease your blood sugar, blood pressure, cholesterol profile, and lower inflammation.

The other good news is that the healthier you eat, the less likely you’ll get sick, making it easier to stay active, productive, and feel fantastic.

I wish you the best of health!

Steven Masley, MD, FAHA, FACN, FAAFP, CNS