Using antibiotics for an extended period of time during middle-age or later may increase the risk of cardiovascular disease in women.

The finding comes from a study published in the European Heart Journal, which revealed women aged 60 and over who used antibiotics for two months or longer had significantly increased risk of cardiovascular disease, including heart attack and stroke, compared to women who did not.1

According to a press release2 by the researchers, the results held true even after adjusting for other related factors, like obesity, other chronic diseases and diet and lifestyle. Antibiotic exposure leads to long-lasting alterations in gut microbiota, which may influence risk of cardiovascular disease.

While the use of antibiotics in younger adults between the ages of 20 and 39 was not linked to heart risks, women aged 60 and older who used antibiotics for two months or longer were 32% more likely to develop cardiovascular disease than women who did not use such drugs.

Overall, among women in late adulthood who take antibiotics for two months or more, six per 1,000 would develop cardiovascular disease, compared to three per 1,000 for women who did not. Women in middle age (40 to 59 years) who used antibiotics for longer than two months also had a 28% increased risk of cardiovascular disease.

The women used antibiotics most often for respiratory infections, urinary tract infections and dental problems, although the results held true even after the reasons behind the usage were factored in. Lead study author Lu Qi, director of the Tulane University Obesity Research Center in New Orleans, stated in a news release:3

Antibiotics’ role in wiping out beneficial gut bacteria was also highlighted as a likely reason for the increased heart risks. “Antibiotic use is the most critical factor in altering the balance of microorganisms in the gut. Previous studies have shown a link between alterations in the microbiotic environment of the gut and inflammation and narrowing of the blood vessels, stroke andheart disease,” Qi said.4

It’s becoming increasingly common knowledge that antibiotics are an enemy to the health of your gut — so much so that even mainstream pharmacies may suggest you take probiotics, or good bacteria, along with a prescription for antibiotics in order to help protect your gut.

One of the risks of taking antibiotics is that it can allow unhealthy bacteria, viruses or other microorganisms to flourish in your gut, which can take a toll on your heart.

For starters, when the bacteria in your gut break down lecithin, a fat found in meat, eggs, dairy and other animal foods along with baked goods and dietary supplements, and its metabolite choline, it leads to the creation of a by-product called trimethylamine N-oxide or TMAO.5

TMAO encourages fatty plaque deposits to form within arteries (atherosclerosis), and the more TMAO you have in your blood the greater your risk of heart disease becomes. It's not clear which types of gut bacteria lead to the formation of TMAO, but it's suggested that probiotics may help to buffer the effect and thereby help prevent heart disease.

Another study published in the journal Atherosclerosis found that patients with inexplicably high amounts of arterial plaque, based on their age and risk factors for atherosclerosis, had higher levels of TMAO, p-cresyl sulfate, p-cresyl glucuronide and phenylacetylglutamine — metabolites produced by certain gut microbes.

On the other hand, people with unexpectedly low amounts of plaque, despite having traditional risk factors, had lower levels of these metabolic products. The differences could not be explained by renal function or poor diet.

Rather, there was a difference in gut microbiome between the groups. The researchers noted, “The intestinal microbiome appears to play an important role in atherosclerosis. These findings raise the possibility of novel approaches to treatment of atherosclerosis such as fecal transplantation and probiotics.”6

One class of antibiotics known as fluoroquinolones may harm your heart by causing an increased risk of ruptures or tears in the aorta blood vessel. The aorta is the main artery in your body supplying oxygenated blood to your circulatory system.

In December 2018, the U.S. Food and Drug Administration (FDA) warned that fluoroquinolones taken by mouth or via injection could lead to these aortic dissections or ruptures of an aortic aneurysm that could lead to serious bleeding or death.7

The risk is so great that the FDA advised health care professionals to avoid prescribing such drugs, which include brand names Cipro and Levaquin, to people who have an aortic aneurysm or are at risk for an aortic aneurysm, including people with peripheral atherosclerotic vascular diseases, hypertension, certain genetic conditions such as Marfan syndrome and Ehlers-Danlos syndrome, and elderly patients.

The gut alterations that occur as a result of antibiotics use may also influence your risk of cancer. In 2014, researchers linked antibiotics use to a slightly increased risk (8% to 11%) of developing colorectal cancer, also known as bowel cancer, possibly because of alterations to the gut microbiome.8

Likewise, past research has also shown that people with less bacterial diversity in their gastrointestinal tracts are more likely to develop colon cancer.9 Then, in 2017, research published in the journal Gut found women who had used antibiotics for two months or more were at an increased risk of developing colon polyps.10

Specifically, those who used the drugs for a total of at least two months in their 20s and 30s had a 36% increased risk of polyps compared to those who did not. Among women who used the drugs long-term in their 40s and 50s, the risk of polyps increased by 69%.11

Even taking antibiotics for 15 days or more, at any age range, was associated with an increased risk of polyps. Those researchers noted that antibiotics “fundamentally alter the gut microbiome by curbing the diversity and number of bacteria, and reducing the resistance to hostile bugs.”12

Antibiotics save lives when used appropriately, but the benefits must be carefully weighed against the risks, which can occur in both the short- and long-term. From 2010 to 2011, the U.S. Centers for Disease Control and Prevention (CDC) found that, of 262 million antibiotic prescriptions written by physicians, 30% were unnecessary.13

Antibiotics prescriptions for acute respiratory conditions were most often inappropriately prescribed, which is interesting since the featured study also found respiratory infections to be a common reason why older women took antibiotics for long periods. Viruses, against which antibiotics are useless, commonly trigger upper respiratory infections.

In the short term, 20% of adults prescribed antibiotics in the hospital experienced adverse side effects and 20% of those side effects occurred in patients who didn't need the antibiotics in the first place.14 Further, every additional 10 days of antibiotic therapy led to a 3% increased risk of a related adverse event, so the longer antibiotics were taken, the higher the risk of adverse events became.

Further, just one course of antibiotics negatively alters your microbiome for up to a year,15 which is precisely why it’s crucial to only use antibiotics when absolutely necessary. In fact, previous research by Qi and colleagues found that one course of antibiotics leads to long-lasting adverse effects on gut health and increases the risk of antibiotic resistance.

Taking antibiotics for at least two months also increases the risk of death from all causes by 27% among women in late adulthood, compared to women who did not take the drugs.16 The women taking long-term antibiotics also had a 58% higher risk of death due to heart problems.

According to Qi, speaking of the featured study, "Our study suggests that antibiotics should be used only when they are absolutely needed. Considering the potentially cumulative adverse effects, the shorter time of antibiotic use the better."17

Arguably, the greatest risk of antibiotics use is the spread of antibiotic-resistant disease. Every year at least 2 million Americans acquire drug-resistant infections and 23,000 die as a result. Many others die from conditions that were complicated by antibiotic-resistant infections.18

Worldwide, 700,000 people die every year due to antibiotic-resistant disease, and it’s estimated that more people will be affected by it than cancer by 2050.19 Already, tens of thousands of Americans may be vulnerable to life-threatening infections following surgery or chemotherapy due to antibiotic resistance.

One study estimated that up to 50.9% of pathogens that cause surgical site infections, and 26.8% of those that cause infections following chemotherapy, are already resistant to common antibiotics.20 If antibiotic effectiveness drops by even another 10%, it could result in 40,000 more infections and 2,100 additional deaths following surgery and chemotherapy each year.

A 30% drop in effectiveness could mean another 120,000 infections and 6,300 deaths annually, the researchers concluded.21 Worse still, if antibiotic effectiveness declines by 70%, the US could see 280,000 more infections and 15,000 more deaths as a result.

For the protection of your heart, your gut and your overall health, it’s important to carefully weigh whether every course of antibiotics you take is truly necessary. Meanwhile, agriculture remains a driving force behind the surge in antibiotic-resistant disease, both in regard to livestock living on concentrated animal feeding operations (CAFOs) as well as thespraying of antibiotics as pesticides on crops such as citrus.

To protect yourself, choose antibiotic-free, organic food and use antibiotics for medical purposes only when necessary. If you do have to take antibiotics, add more traditionally fermented and cultured foods to your diet to optimize your gut flora, and consider the use of spore-based probiotics, or sporebiotics, which are part of a group of derivatives of the microbe called Bacillus, have been shown to dramatically increase your immune tolerance.

I also recommend taking the beneficial yeast Saccharomyces boulardii after you’ve finished your antibiotics, to prevent secondary complications of antibiotic treatment, such as diarrhea.

Sources and References

1 European Heart Journal April 24, 2019

2, 3, 4 Tulane University April 26, 2019

5 Nature April 7, 2011; 472(7341):57-63

6 Atherosclerosis June 2018; 273: 91-97

7 U.S. FDA December 20, 2018

8 Live Science June 3, 2014

9 J Natl Cancer Inst. 2013 Dec 18;105(24):1907-11.

10 Gut April 4, 2017

11 CBS News, April 5, 2017

12 BBC News April 5, 2017

13 JAMA May 3, 2016

14 JAMA Intern Med. 2017;177(9):1308-1315.

15 MBio November 10, 2015

16 Medical News Today March 26, 2018

17 Science Daily April 19, 2019

18 U.S. CDC, Antibiotic Resistance Threats in the United States, 2013

19 PBS March 28, 2018

20 Lancet Infectious Diseases October 15, 2015

21 Reuters November 5, 2015