When Jose Canseco’s book “Juiced” hit shelves in 2005, it rocked the baseball world with its stories of the illegal use of performance-enhancing drugs like steroids. Juicing is never good in exercise and can be just as unhealthy for your diet. For example, if you drink filtered kale juice instead of eating whole leaves, you will be deprived of glucose-controlling, good-loving fiber. And bottled “vegetable juices” may contain more water, fructose, and artificial ingredients than anything found in natural vegetables.

But smoothies and pure juices can be a healthy way to eat more vegetables – depending on how you juice things up. That is the result of a new study. Researchers used three different methods at home to liquefy organic and non-organic cauliflower, kale, beets, radishes, beetroot, and carrots of various colors, and then measured the resulting levels of phytonutrients and antioxidants.

It turns out that blenders, high-speed centrifugal juicers, and low-speed extractors produce different amounts of health-promoting nutrients because they expose the inner tissues of vegetables to oxygen, light, and heat, releasing the enzymes they contain.

Overall, the best choice for maximum nutrition came from low-speed juicing. In contrast, using the blender resulted in the lowest total nutrient content, but provided the highest fiber content and therefore the best blood sugar control. So if you’re thinking about juicing, unless blood sugar control is your primary concern, consider one of the “low speed juicers”. For this we say stick to whole veggies most of the time and only use the blender when needed.

Mehmet Oz, MD, is the host of the “Dr. Oz Show, ”and Mike Roizen, MD, is the chief wellness officer emeritus at the Cleveland Clinic.