Your height is based in large part on genetics -- tall parents tend to have tall children. However, environmental factors, such as diet, have an influence, too. The long bones in your legs determine your height. As you grow, plates of cartilage on the ends of the long bones create new bone, which makes the bones longer. At the end of puberty, the bones seal and growth stops. For girls, this is generally two years after the first menstruation. For boys, the end of puberty may occur as late as their early 20s.
Consult your physician to determine if you have finished growing. If you are male, at age 18 you may still be in puberty and have a few years of growth left. Through an x-ray your doctor can determine if the epiphyseal growth plates have sealed.
Eat a healthy diet of complex carbohydrates, fresh produce and plenty of protein. Protein builds muscle and other tissue. The complex carbohydrates, fruits and vegetables provide the vitamins and minerals your bones need to grow.
Eat enough calories to support bone growth. An 18-year-old should consume between 1,800 and 3,200 calories per day, depending on gender, size and activity levels.
Consult your physician about growth supplements, if your epiphyseal plates have not sealed. Your doctor can determine if your growth and height are normal, and may be able to prescribe human growth hormone or other medications to stimulate growth.
Wear height-enhancing clothing if your epiphyseal plates have sealed. Wear heels or lifts in your shoes to make yourself physically taller, and wear vertical stripes or monochromatic clothing to trick the eye.
Do exercises that improve your posture. Pilates and yoga strengthen the muscles that support the spine. Proper posture makes you appear taller.
Consider limb-lengthening surgery if your epiphyseal plates have sealed. The surgery is generally used on individuals with certain forms of dwarfism to help them live more normal lives. The operation involves breaking the thigh and shin bones and installing spacers to continually pull the bones apart, which causes the body to make new bone to fill the space. Limb-lengthening surgery is painful, and it takes several months to complete the process.