Here's How Sex Can Affect Your Immune System

Sex can actually directly impact your immune system, both for good and for bad sense. Sex, it turns out, is really good for you. But, it does have its risks too.

Whilst exposure to things like sexually transmitted diseases (STDs) is an obvious one, as we see, there are some other more subtle changes that can take place. From priming a woman's immune system for getting pregnant, to actually increase your likelihood of getting HIV, sexual activity has been shown to directly affect the immune system.

Does sexual behavior affect the immune system?

It has long been known that sex can affect your immune system. Researchers have explained that sex can be both beneficial and detrimental to one's immune system. The immune system boosts from sex also has a positive impact on your sex drive and general mood. People who also have regular sex tend to take less sick days. Researchers were able to show that college students who had sex once or twice a week had higher levels of a certain antibody compared to students who had sex less often. Having sex also has many other benefits to you and your well-being.

It can: 

• Lower your blood pressure; Improve bladder control in women;
• Boost your libido (obviously);
• Improve your physical fitness (it is a form of exercise after all);
• Lower your risk of heart attacks (believe it or not);
• Block pain, or lessen pain;
• Has been shown to reduce the likelihood of developing prostate cancer;
• Improves your sleeping patterns; and,
• Help reduce stress. 

Can sexual behavior affect the immune system?

One study appears to show a link between sexual activity and the subject's ability to combat pathogens. Researchers in 2001 found that males who had more sexual partners showed a marked reduction in the ability to fight off a bacterial infection. Their results suggest immunosuppression is an important cost of reproduction and that immune function and levels of disease susceptibility will be influenced by sexual selection.

But, it is important to note that the study was concerned with male flies of the Drosophila melanogaster (common fruit fly) species, not human beings. But, of course, flies are not humans. This species of fly's sexual life is very different too. In D. melanogaster there is no paternal care, and male reproductive effort is composed entirely of investment in successfully mating. In nature, an evolutionary increase in mating effort will be favored by increased sexual selection.

But it's not all bad.

There are many other studies that show sex is also beneficial to you and your immune system. It may even increase a woman's chance of getting pregnant (if you're trying for a baby of course). The study, by researchers showed a clear link between sexual activity and physical changes (including the immune system) that increased the chance of conception, even outside of the window of ovulation. It's a common recommendation that partners trying to have a baby should engage in regular intercourse to increase the woman's chances of getting pregnant even during so called 'non-fertile' periods although it's unclear how this works

This research is the first to show that the sexual activity may cause the body to promote types of immunity that support conception. But, of course, this should come as no surprise. The more you have unprotected sex, the higher the chance you will become pregnant (as a woman). But what is interesting is that the human body appears to show physical changes that appear to increase the likelihood of conception. 

Can sexual behavior affect your gut microbiome?

Your sexual behavior can, it appears, alter your gut microbiome. Some recent studies have shown a connection between your sexual preference and susceptibility to infectious diseases. For clarity, the microbiome is the community of microbes that live inside our gut. A healthy microbiome is vital for many things including the efficiency and function of your immune system.

One study, in particular, found that men who have sex with men (MSM) have a distinct gut ecology compared to men who have sex with women (MSW). Results were also not dependent on the subjects HIV-status. Their method included taking 35 stool samples of healthy men. The donors were a mixture of men who have sex with men and men who have sex with women. The stool samples were then transplanted into lab mice. They found that the stool samples from MSM showed a marked increase in the activation of CD4+ T cells within the mice. This, it turns out, would put those mice at a higher risk of being susceptible to HIV (if they were human). CD4+T cells "recognize peptides presented on MHC class II molecules, which are found on antigen-presenting cells (APCs). As a whole, they play a major role in instigating and shaping adaptive immune responses.

These results provide evidence for a direct link between microbiome composition and immune activation in HIV-negative and HIV-positive MSM, and a rationale for investigating the gut microbiome as a risk factor for HIV transmission. There is a unique microbiome associated with men who have sex with men that drives immune activation in the gut that may also drive higher levels of HIV infection. But we still don’t know exactly why this is

Whilst the study is interesting, further investigation is still needed to understand why the microbiome is important. If it is responsible for weakening immune systems, especially with regards to HIV, it may yield some fertile ground for combating the disease.