Yes, nutrition affects human longevity, because good nutrition is essential to a healthy body and a long life. There are stories of children who eat nothing but chicken nuggets, and then need to be hospitalized by the time they are 18 for injections of vitamins. Good nutrition is vital to energy, bodily functions, and ultimately to a long life.
Studies have shown that a proper diet, with a managed amount of carbohydrates, proteins, and fats, will reduce the risk of many diseases that can cause an early death. Diseases such as heart disease and diabetes can be controlled and prevented through eating correctly. It does not depend on what you eat, so much as how regulated the amounts you eat are.
I believe nutrition does affect human longevity. In fact, this has been proved through studies. History also shows that depending on one food source too heavily can be bad, like the potato famines. On the other hand, we also know that not having access to proper food supplies can cause probelms as well, such as scurvy.
Nutrition does affect human longevity because your body needs nutrients to live. If you are missing certain nutrients it can make you sick. You raise your risks of getting certain diseases and can die much sooner than someone who is getting proper nutrition. It is very important to get the right nutrients.
The better nutrition you have, the healthier you will be in the long run. If you don't have to worry about things like heart disease, diabetes, and other issues that you can get by having a poor diet, then you can live a lot longer. We should all eat better.