Earlier this month, a major new study brought hopeful news about type 2 diabetes.

Nationwide, nearly 30 million people have diabetes, according to the American Diabetes Association. The vast majority of them have type 2 diabetes, a chronic condition in which blood glucose - sugar - builds up because the body doesn't properly use the regulatory hormone insulin.

Once known as "adult-onset" diabetes, the diagnosis is rising swiftly and now affects all ages. It is related to lifestyle - poor diet and lack of exercise.

The recent research, funded by the National Institutes of Health, found that people who intensively controlled their blood-sugar levels halved their risk of developing diabetic retinopathy, the most common cause of vision loss and potential blindness among people with diabetes.

Stella Volpe, a nutritionist and exercise physiologist who studies obesity and diabetes prevention, said the findings are a positive sign. Volpe, who was not involved with the study, chairs the Department of Nutrition Sciences in Drexel University's College of Nursing and Health Professions. She spoke to us recently about what the findings mean and why diet is so crucial to controlling diabetes.

Why is this study important?

It shows that if we can help people control their blood-glucose concentrations, it's really going to help their eye health. So many things can happen with diabetes, and retinopathy is one of the main conditions that can result with uncontrolled diabetes. Having diabetes also increases a person's risk of heart disease and kidney disease.

What are blood-sugar fluctuations, and why is it important to control them?

If a person is not controlling their diabetes well by diet, exercise, and perhaps medication, blood-glucose concentrations can fluctuate greatly. That fluctuation, whether really low or really high, places a lot of stress on the body.

With high concentrations, the body has to get rid of it, so it puts stress on the kidneys. This excess blood glucose also places stress on the eyes. It will affect the retina, and that can lead to diabetic retinopathy.

If blood-glucose levels go below normal, a person can pass out.

Clearly, many people have trouble controlling their blood sugar. What's the best dietary advice?

What is really important is to have a good, scheduled regimen of eating. Have meals and snacks that are planned, which I know can be difficult with a busy lifestyle. Don't skip meals. Meals don't have to be boring or tasteless. They can - and should - be varied and delicious.

These meals, however, have to be timed equally throughout the day to help maintain blood-glucose concentrations. It is important to consume breakfast regularly, with possibly a morning snack, followed by lunch, then a midafternoon snack, followed by dinner, and an after-dinner snack.

What are some other important dietary steps?

Watch portion sizes. In addition, they should know the foods that might increase their blood-glucose concentrations. An example would be a white potato, which is very well known to spike a person's blood-sugar concentrations. If a person is going to consume a white potato, then including a protein and vegetable with the potato, as well as adding a little bit of butter or cheese, will decrease the spike. An even better choice would be to eat a yam or sweet potato.

As for sweets, sticking to a good diet does not mean a person with diabetes cannot eat any. Portion size is the key here. If a person with diabetes has a piece of cake, be aware of the portion size. In addition, having it after a meal is better for blood-glucose concentrations than as a snack, which could greatly increase blood-glucose concentrations.

In short, people with diabetes do not need to stay away from sweets. They need to be aware of them, not have too many of them, and make sure they have them with or after a meal.

It is also important to note that exercise is a key and integral component to maintaining blood-glucose concentrations and decreasing the fluctuations. This can be in the form of a daily walk. Just like eating regularly, regular planned physical activity is important. With proper diet and exercise, a person with type 2 diabetes might even be able to reduce the amount of medication that needs to be taken.

For people who don't have type 2 diabetes, what are the best dietary steps to prevent the disease?

They should watch their overall calorie intake. Having a good, varied diet that has good amounts of fruits and vegetables is important. Maintaining a healthy body weight is also important.

Obesity is a big risk factor for acquiring type 2 diabetes. Being physically active is important. All this can help to prevent type 2 diabetes and stave off other chronic diseases, as well.