Surgical penis enlargement usually takes the form of implants for increasing girth or severing of the ligament that attaches the base of the penis to the pelvis for added length. This is major surgery done on an in-patient basis with general anesthesia. As any surgery, this is risky. The results are not always what people expect. A common side effect of the ligament severing is inability to control direction of the penis. Sometimes during surgery nerves can be severed and all sensation in the penis can be lost completely.
Generally, doctors will only do this in cases of severe deformity or trauma.
Non-surgical enlargement methods are various forms of stretching by hand, mechanical device or attachment of weights and the use of vacuum pumps. All of these carry the risk of severe trauma and potential loss of sexual function if done improperly or excessively. The inner tissues of penis, the corpora cavernosa, are fairly delicate and can be damaged. The gains are seldom dramatic.
Hand stretching, also called jelquing, is probably the most harmless, as a person will likely stop before hurting himself. However, there is no medical evidence that it is effective for anything beyond pleasuring oneself.
Traction by use of weights or mechanical devices can add some length, but it is not a permanent effect and will reverse if the practice is discontinued. Excessive traction can tear penile tissue which may negatively affect the ability to achieve erections and deform the penis. Also, if the attachment is too tight it can impair blood circulation. This can lead to scarring, loss of sensation, and, in extreme cases, necrosis of tissue, which requires surgery to treat. Untreated, it can be life-threatening.
Vacuum pumps do not produce a permanent enlargement effect either. They are really just sex toys. They can, however, cause permanent deformation of the penis due to scarring if the suction is strong enough to break blood vessels.
There are no pills, creams, powders, or drops that will make a penis grow larger or longer. The emails offering these are scams and the advertisements are lies. These "medicines" are usually not tested for safety, either. At best, there will be no effect whatsoever. At worst, you can develop an allergic reaction or get poisoned with substandard ingredients.
There are no "miracle foods" that affect penis size. Vegetables are good for you, but for completely unrelated reasons.
It should be noted that one thing that affects perceived penis size is excess body weight. Having "extra padding" will conceal some of the length of a penis. Getting some exercise and improving your general physical fitness is the best way to improve your sexual performance and length. A healthy diet would definitely be helpful in this.
Masturbation is very harmful for overall health.