The rationale for juicing vegetables comes out of a few schools of thought. First, vegetables just aren’t as fun to eat as hamburgers, so most of us don’t eat enough vegetables. We’re supposed to eat at least three servings of vegetables a day. One way to sneak veggies into our diet is to juice them.
The second reason this makes sense is that the bulk of the nutrients in vegetables end up in the juice. Whereas in fruit, the edible peels or skins house the nutrients. When juiced, some of the healthiest part of the fruit ends up in the compost pile. Apples, mangoes, and kiwis all have nutritious peels. So do bananas, but most people won’t eat them straight up.
There’s also the difference between juicing something yourself or buying pre-made juice blends. Many store purchased blends have added sugars. Another downside of juicing is that you miss out on the fibers. The fibers of fruit lower their glycemic index.
The glycemic index is a measure of how quickly the food’s glucose gets into the blood stream. The lower the number, the slower it goes in. This has a direct affect on the body’s blood sugar level. Foods with a high glycemic index (over 70)—such as sports drinks—cause both insulin and blood sugar to spike. This can lead to insulin resistance and ultimately Type II diabetes. Whereas foods with a low glycemic index (under 55), can have the same number of calories, but cause a more gradual increase in blood sugar levels. The complexity of the food (meaning a mix of fat, protein, and carbohydrate) will lower the glycemic index. Foods high in glucose or supplemented with high fructose corn syrup (like many canned fruits) have a high glycemic index.
The glycemic index of both fruits and vegetables can be altered. For instance, the riper a fruit is, the more sugars it has in it, the higher its glycemic index will be. But cooking a food can increase the index, too. Cooking tends to break down cellular structure of foods, making them easier to digest.
Many vegetables and some fruits have a low glycemic index because they have a high amount of fiber. A high-fiber diet helps control the blood sugar level, helps lower cholesterol, is good for your bowels, and makes you feel full. The resistant starches (indigestible) in bananas are proven to trigger the feeling of satiety.
The anti-juicers opine that drinking a lot of juice, particularly for cleanses, doesn’t help the rest of our body. Juices tend to digest quickly, leading to hunger. Because of their glycemic index, they can lead to blood sugar spikes and then falls. Unstable blood sugar levels can lead to headaches and lightheadedness. As a result, people tend to have a harder time working out while on a juice cleanse.
Studies have also proven that juiced fruits and vegetables quickly lose their nutritional value. Orange juice loses its vitamin C when exposed to light, heat (pasteurization) or oxygen. Some orange juice sellers supplement their juice with vitamin C to compensate for this loss. Surprisingly, it’s better to store orange juice in the freezer and drink it upon thawing, than to store it long term in your refrigerator. But watch out, once it thaws it loses its nutritional value quickly, too.
A recent study following thousands of patients tried to isolate the benefits and risks of drinking juices versus eating fruit. Researchers found that patients with high juice consumption had an associated increase risk of developing Type II diabetes by about 20 percent. The exact opposite was found in patients who consumed regular servings of intact fruit. They lowered their incidence of Type II diabetes by about 20 percent.
If you insist on drinking your fruits and vegetables, stick with a blender rather than a juicer. This way you can sneak in a little of the banana peel for extra fiber and potassium. But it turns out the best option is to get your food in its natural package, just the way Mother Nature made it. Nothing beats the fragrance of a fresh peeled orange, the satisfying crunch of a carrot, or the taste of a ripe strawberry.
Salvatore Iaquinta, M.D., is a head-and-neck surgeon at Kaiser Permanente. He is also the author of “The Year They Tried to Kill Me.”
