Why Boxer dog's die young
To get back to the original topic of "why boxers die young", the boxer breed has the highest rate of cancer of any breed. I lost my first boxer, Plato, to lymphoma. Boxers are also prone to intestinal issues which lead to colitis. If you've ever had a boxer with severe colitis, which is an inflammation of the large intestine, you'd know how terrible it can be to try to clean up after a dog with constant projectile diarrhea. Colitis can be caused by bacteria, stress, allergies, parasites and colon cancer. I lost my fourth boxer to heart failure triggered by severe colitis.
While only 3% of allergies in dogs are food related (most are topical from pollen or flea bites), a boxer's sensitive stomach is a good reason to avoid foods with corn, soy or wheat, or prepackaged dog food with too many ingredients. Garlic is small doses can actually work as a natural flea repellant. Since it would require intake of over 5 cloves of garlic daily to cause negative reactions in a 60 lb. dog, 1/2 teaspoon a couple of times a week can actually be beneficial.
My fifth and current boxer, Hemi, is 10 years old and still going strong...