Question is about scientific aspects and not islamic of Anal Sex.. While as we are muslims we will never debate to make anal intercourse legal but there are always non-muslim readerz ..... If you talk just about Medically proven disadvantages i am just giving few points here actually its a real lengthy topic ....
1) PHYSICAL TRAUMA TO ANUS :
A)as nature has not made anus for intercourse so it is not elastic like vagina tearing , lacerations and cuts are v.common even with best lubrication and not just the first two three times but even after many trials.
B)incidence of hemorrhides(piles) , anal fissure and anal fistula , Rectal mucosa prolapse is way high in such people
C)ANAL INCONTINENCE: the worst of all problems to have leaky , incontinent,no cöntrol anal passage due to tearing of muscle fibre due to inelastic nature... And its a medical fact once a person gets teared anal sphincter its there for whole life.. As what ever operatiön u do, make it more worse .
2) INECTION TRANSMISSION :
A) sexually transmitted diseases, if by vaginal intercourse to transmit STD rate is 40percent its 100percent by anal Because vagina is rich in a particular cell type of WBC to resist infection of STD's .. I am nt saying its risk free the ratio is HIV be transmitted in 40percent cases with each coitus vaginally but its 100percent with anal .
B) Other than STD's:
Our gut or git is having a whole army of organisms and Worst of these are Coliforms .. Even modren science is amazed by the organism we have in gut and how they are not supposed to enter blood if they do .. Create severe infection and death
so the point is penis is exposed to all these in intercourse and worst of all infection can occur to the penis and male partner(even in normal condition and healthy personnel, like in normal vaginal sex you dnt get this)..
the issue of condom usage and lubrication has far more debated and condom tear rate is way up in anal sex due to inelastic and difficult penetration
so not only STD rate is way high But Also Other Lethal Gram negative , aerobic and coliform bacteria infection chance is there in sex in "normal healthy anus"which are Not in healthy vagina
here i want to mention anal sex never originated as to AVOID pregnancy but as HOMOSEXUALITY .. Medicine does say that there is a chance of pregnancy with anal sex as
a)the semen may leak on ejaculation and enter mouth of vagina and even a single drop is enough for preg
b) anus and vagina internally are seperated by just membranes so if there is a minute minute tear or fistula it may leak...
4) LACK OF FEMALE ORGASM:
its a fact that anal sex was for male male sex or gay why? Because in gay sex the part stimulated is PROSTATE when penis rubs in and PROSTATE has been considered male G-spot ..
But there is no female G-spot in anal canal and if you ask couples with anal sex for females its Painful and Lack Orgasm .. Its done
a) as a new experience gaining act ..
b) mostly combined with vaginal sex .. To givè female orgasm .. And when has to be done this way then why go against nature?
c) and if if anal sex done and immediately after penis inserted in vagina it creats Havoc .. The worst of all bacteremia
i have just told the few main medical disadvantages .. Not touched religiön at all and there are more hazards even medically.
its good to find Reasoning to make Nön-BELIVERS know how pure ,true and Scientific our religion is
one thing more.. Our body anatomy and functioning ,its science and medicine is made by Almighty(NATURE FOR NON-BELIVERS) so how it could be that nature prohibits a certain act with body and it be just a religious myth or fact and nothing scienific?
it has scientific aspects and hazards..definately.