Antibiotics During Infancy May Lead to Permanent Alterations in Metabolism

By Dr. Mercola

While antibiotics are given to combat bacteria responsible for illness, these drugs indiscriminately kill off beneficial bacteria in your gut as well, dramatically altering your gut microbiome.

Gut bacteria, we now know, have an extensive repertoire of functions in your body. They even play a role in obesity. And, while your microbiome can change rather quickly based on your diet, exposure to antibiotics early in life may have serious long-term ramifications.

According to recent research, infants given penicillin are at increased risk of obesity later on in life due to this early alteration of their gut flora. According to The Guardian:¹

“The findings emerged from a series of experiments in mice, but build on earlier work that found children who had antibiotics before six months of age were more likely to be overweight as seven-year-olds.

‘This is part of a growing body of evidence that antibiotics have a biological cost,’ said Martin Blaser, a microbiologist who led the study at New York University. ‘Our study shows that there can be permanent consequences.’

'If a kid is very ill, there is no question that they should get antibiotics, but if it's marginal perhaps the doctor should be saying 'let's wait a day or two' before taking another look. Doctors give out antibiotics thinking they won't do any harm, but this provides evidence that they might,' Blaser added.”

Early Disruption of Gut Flora May Have Long-Term Consequences

The research, published in the journal Cell,² points to there being a window of time when changes to the microbiome can have a serious and long-term impact on your body’s metabolism.

This window was the first month of life in mice. Translating that to a human time scale—provided the effect fully applies to humans—it would correlate to a time frame of the first six months, potentially up to the first three years.

Mice given antibiotics for the first four weeks of life grew up to be 25 percent heavier, and had 60 percent more body fat than the controls. Understanding the role of the microbiome in obesity—especially childhood obesity—is important for a number of reasons, an increased cancer risk being at the top of the list.

In one recent study,³ which analyzed data from more than five million people over the age of 16, every 11-pound increase in body weight was associated with an increased risk for 10 types of cancer, including leukemia, uterine, gallbladder, kidney, cervix, and thyroid cancer.

Getting back to the featured mouse study, the researchers identified four specific species of gut bacteria that appeared to be of particular importance with regards to metabolism: Lactobacillus, Allobaculum, Rikenelleceae, and Candidatus arthromitus (the last one is not found in humans).

Eradicating these four species of bacteria in the mice’s guts triggered metabolic changes that led to obesity. The problem stems from the fact that when you kill off certain bacteria, it allows other, more resilient ones to take over and thrive.

Several studies have documented differences in the composition of gut bacteria in obese versus non-obese people (see below), but what’s interesting here is that when this alteration occurred early in life, it turned out to have a permanent impact. According to the lead author, Dr. Martin Blaser:

"We found that four weeks of antibiotics was enough to perturb the microbiome, and even though it returned to normal after a few weeks, the mice still became fat."

Earlier animal research by Dr. Blaser⁴ also showed that mice fed antibiotics (in dosages similar to those given to children for throat or ear infections) had significant increases in body fat despite their diets remaining unchanged.

Antibiotics Also Affect Hunger Hormones

In 2011, Dr. Blaser co-authored a study^5,6 in which they assessed the effect antibiotics have on ghrelin and leptin—two hunger hormones. Both ghrelin and leptin are found in the mucous membranes of your stomach. Ditto for helicobacter pylori (H. pylori), a bacteria associated with stomach ulcers.

The researchers wanted to see whether ghrelin and leptin might be affected when you eradicate H. pylori with antibiotics. Interestingly, they found that 18 months after antibiotics are used to eradicate H. pylori, there was a:

• 6-fold increase in the release of ghrelin (the "hunger hormone") after a meal
• 20 percent increase in leptin levels (leptin is a hormone produced by fat tissue)
• 5 percent increase in BMI

Levels of ghrelin should ordinarily fall after a meal. This drop in ghrelin signals your brain that you're full. An increase, on the other hand, tells your brain to continue eating, which will tend to lead to weight gain due to overeating.

So, simply by altering the gut microbiome with antibiotics (to eradicate H. pylori), these two hunger hormones were dramatically affected as well... This again highlights the importance of maintaining a healthy gut if you’re struggling with your weight.

The increase in leptin levels is particularly concerning because overexposure to high levels of the hormone can lead to leptin resistance, which means your body is unable to properly hear leptin's signals.

The way your body stores fat is a highly regulated process that is controlled, primarily, by leptin. If you gain excess weight, the additional fat produces extra leptin that should alert your brain that your body is storing too much fat and needs to burn off the excess.

To do this, signals are sent to your brain to stop being hungry and to stop eating. When you become leptin-resistant, your body can no longer hear these messages, so it remains hungry and stores more fat.

It’s important to realize that while antibiotics will certainly upset your microbiome, you can also easily become leptin-resistant by eating a diet full of sugar (particularly fructose), refined grains and processed foods, as these too will upset the balance of bacteria in your gut.

Sugar feed pathogenic yeast and fungi, and processed foods tend to have a very detrimental effect on beneficial bacteria—together, they create the perfect environment for health-harming microbes to thrive.

More Evidence Showing the Tandem Dance Between Your Gut Bacteria and Your Waistline

As mentioned earlier, a number of studies have shown that obese people have different intestinal bacteria than slim people, and that altering the microbial balance in your gut can influence your weight. Here are four more such studies:

• British Journal of Nutrition, 2011:⁷ Rats given lactic acid bacteria while in utero through adulthood put on significantly less weight than other rats eating the same diet. They also had lower levels of minor inflammation, which has been associated with obesity.
• European Journal of Clinical Nutrition, 2010:⁸ Obese people were able to reduce their abdominal fat by nearly five percent, and their subcutaneous fat by over three percent, just by drinking a probiotic-rich fermented milk beverage for 12 weeks.
• American Journal of Clinical Nutrition, 2008:⁹ Babies with high numbers of Bifidobacteria and low numbers of Staphylococcus aureus -- which may cause low-grade inflammation in your body, contributing to obesity -- appeared to be protected from excess weight gain. This may be one reason why breast-fed babies have a lower risk of obesity, as Bifidobacteria flourish in the guts of breast-fed babies.
• Nature, 2006:¹⁰ Two separate but related studies found that obese individuals had about 20 percent more of a family of bacteria known as Firmicutes, and almost 90 percent less of a bacteria called Bacteroidetes than lean people. Firmicutes help your body to extract calories from complex sugars and deposit those calories in fat. When these microbes were transplanted into normal-weight mice, those mice started to gain twice as much fat.

How to Optimize Your Microbiome

The best way to optimize your gut flora is through your diet. Most people need to drastically reduce grains and sugar. Avoid genetically engineered ingredients, processed foods, pasteurized foods, and chlorinated tap water. Pasteurized foods can harm your good bacteria, and sugar promotes the growth of pathogenic yeast and other fungi. Grains containing gluten are particularly damaging to your microflora and overall health.^11,12 Chlorine in your tap water not only kills pathogenic bacteria in the water but beneficial bacteria in your gut.

A gut-healthy diet is one rich in whole, unprocessed, unsweetened foods, along with traditionally fermented or cultured foods. Examples of healthy fermented foods include sauerkraut, kimchee, and other fermented vegetables; fermented dairy products, such as yogurt and kefir made from raw (unpasteurized) organic dairy; miso; tempeh; and olives. Fermented foods are also a key component of the GAPS protocol, a diet designed to heal and seal your gut.

Your goal should be to consume one-quarter to one-half cup of fermented veggies with each meal, but you may need to work up to it. Consider starting with just a teaspoon or two a few times a day, and increase as tolerated. If that is too much (perhaps your body is severely compromised), you can even begin by drinking a teaspoon of the brine from the fermented veggies, which is rich in the same beneficial microbes. You may also want to consider a high-potency probiotic supplement, but realize that there is no substitute for the real food.

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