The Long-Term Effects of Antibiotics on Health and Immunity

Garlic is the famous natural antibiotic. (Photo by stijn)

This is the third and last installment in a series of posts on immune function and gastrointestinal health. Given that the swine flu is still making rounds around the world, learning more about how beneficial bacteria can ward off viral infections has been very useful at least for me.

So far, we've seen that foods and supplements containing probiotics can reduce the occurrence and severity of the common cold. Probiotics also have other benefits, such as protection from cancer and increased resistance to cancer. We've also seen that another way to increase beneficial bacteria in the gut are prebiotics, which are a form of fiber found in foods such as Jerusalem artichoke and chicory root. The combinations of prebiotics and probiotics are known as synbiotics and may be superior to either one alone.

Antibiotics and resistant bacterial strains

The one group of biotics that's left to tackle is antibiotics. Most people have probably gotten a prescription of antibiotics at least once in their life. Most people are probably also aware that antibiotics are prescribed way too frequently these days by many doctors, even for health issues that antibiotics can't relieve. As antibiotics only work against bacterial infections, not viruses, taking them for flu symptoms is useless.

The commonly known problem is that as the use of antibiotics becomes more and more widespread, the bacteria become more and more resistant. This is especially common when people quit their antibiotics prescription halfway through because they "feel fine"; some of the surviving bacteria then mutate into more resistant strains and spread into other people.

In a way, there is an evolutionary war going on between medicine and bacteria, and while antibiotics are a fantastic discovery and have many applications, their overuse is a serious problem. That's why taking antibiotics "just in case" is not a great idea long-term.

Other health problems from antibiotics

If the well-being of the rest of humanity doesn't bother you all that much, there are also other, less known reasons to stay away from antibiotics unless you actually need them. Let's look at some of the evidence showing the harmful effects of antibiotics.

Most of the negatives stem from the positive fact that antibiotics are so effective. The problem is that antibiotics are not as specific as we'd like: while they do destroy harmful bacteria, they also destroy beneficial bacteria. That's why it's never recommended to take probiotics at the same time with antibiotics, because the probiotics are just rendered useless.

Since one of the functions of intestinal bacteria is to aid in food digestion, it's no surprise that antibiotics can cause digestive problems. Diarrhea occurs in about 25% of patients receiving antibiotics (link). Probiotics, on the other hand, can counter some of this effect. At least Lactobacillus GG and Saccharomyces boulardii appear to be effective. As mentioned before, leave about 3 hours between taking antibiotics and probiotics to avoid killing the beneficial bacteria right away.

The effect of antibiotics may be especially pronounced in babies, whose bacterial colonies have not yet matured. In one study, rats who were given an antibiotic for 10-17 days saw a near complete eradication of Lactobacillus in the intestine along with a drastic reduction in other bacteria (link). This would obviously have a negative effect on immunity in general.

Another group to whom antibiotics may pose a real danger are the critically ill. One study showed that not only did the microflorarl biodiversity of patients in the intensive care unit significantly decrease with antibiotics, but there were also more organ failures and deaths in patients given antibiotics (link).

Antibiotics also seem to have a negative effect on phytoestrogens. The levels of the lignan enterolactone, a type of phytoestrogen, were significantly lower in men and women who had taken oral antibiotics up to 16 months before measurement (link). The reduction was associated with the number of treatments and time from last treatment. Although not life-threatening, this reduction should be of some concern to those who are taking for example flax lignans for hair growth or other health benefits.

Long-term impairment of immunity from antibiotics

If the above reasons didn't put you off antibiotics for good, here comes the worst part: the previously unknown long-term effects of antibiotics.

Until recently, the effect of antibiotics was thought to be temporary. As long as you took your prebiotics at least 3 hours after your antibiotics, you'd be fine. Any long-term changes in intestinal microflora were considered to last only a few months, after which everything would return to normal.

Unfortunately, some new studies have begun to show that this is not necessarily the case. A study funded by the Finnish Academy found that the earlier estimates were too conservative, and that the effects of antibiotics on intestinal bacteria were visible even after a year (link). Surprisingly, they also discovered that using one type of antibiotic (such as penicillin or tetracycline) increases the resistance of bacteria to other types of antibiotics as well. The old idea of switching to a different antibiotic to avoid resistance doesn't seem so good after all.

A study from last year confirms these findings. Using a novel method of observing the human gut microbiota, the authors found that antibiotic treatment "influenced the abundance of about a third of the bacterial taxa in the gut, decreasing the taxonomic richness, diversity, and evenness of the community" (link). While the conditions partly returned to normal after four weeks, several bacterial taxa failed to recover even after six months.

Conclusion

While antibiotics certainly have their uses, taking them when unnecessary can be harmful in many ways. Here's a summary of the negatives:

• Increased resistance to antibiotics
• Diarrhea and digestive problems
• Reduction in beneficial phytoestrogens
• Impaired immunity, especially in children and the critically ill
• Long-term changes in gut microflora

Since antibiotics, by definition, are substances or compounds that kill or inhibit the growth of bacteria, it's good to keep two things in mind. First, antibiotics destroy not only bad bacteria but also good ones. Second, antibiotics are only effective against bacteria, not viruses. So before getting antibiotics for an infection, make sure it really is a bacterial and not a viral infection (the common cold, for example, is a viral infection).

For more information on health and immunity, see these posts:

Prebiotics, Synbiotics and the Immune System
The 7 Types of Aging Damage That End up Killing You
Intermittent Fasting Reduces Mitochondrial Damage and Lymphoma Incidence in Aged Mice
Swine Flu and Avoiding the Cytokine Storm: What to Eat and What Not to Eat?