Tuesday, August 12, 2008

Are You Juiced?

It seems that a lot of people think that an easy way to meet their daily requirement of fruits and veggies is juicing. Although convenient, even homemade juice is nutritionally inferior to whole fruits and vegetables. Brad Schoenfeld explains why.

Juice Your Way to Better Health…?
Brad Schoenfeld, CSCS

I recently happened upon an infomercial where none other than Jack LaLanne is seen touting the benefits of his "Power Juicer." Listening to his spiel, you'd think that the juicer was the best thing since the invention of the wheel. Now I have nothing but respect for Mr. LaLanne. He is unquestionably one of the people who brought exercise into the mainstream and for that deserves a huge amount of credit. Unfortunately, his claims regarding juicing are simply off-base. Way off base…

Fact: fruit juice is generally a poor substitute for whole fruits. Why? Well, juicing removes fiber and phytonutrients from a fruit or vegetable. Not only does this deprive you of important nutritional benefits, but it also decreases transit time through the gut. Since liquids require very little digestion, they quickly pass through your gastrointestinal tract and are rapidly assimilated into the bloodstream. This is detrimental on a couple of different levels.

First, rapid assimilation of a carbohydrate source increases blood sugar levels, causing a corresponding spike in insulin secretions. Insulin is a storage hormone that turns on various fat storage mechanisms and blocks certain enzymes that are responsible for lipolysis (i.e. fat breakdown). When insulin levels are high, excess
nutrients are more readily shuttled into adipose cells, facilitating increases in body fat deposition.

Worse, the rush of insulin clears sugars from your circulatory system in such an expeditious fashion that it creates a rebound effect, producing a sudden and dramatic drop in blood sugar levels. A hypoglycemic state is induced, causing hunger pangs and food cravings. This creates a vicious cycle that encourages binge eating.
As a result, more calories are consumed (especially in the form of high-glycemic foods) and fat storage is heightened even further.

Second, juices don't satisfy hunger in the same way as whole fruits and vegetables. When whole foods are consumed, they activate satiety-inducing stretch receptors in the gut. The stretch receptors, in turn, send signals back to the brain indicating a sense of fullness. The end result is that you eat less than you otherwise would. Juices, though, don't stay in the gut long enough to activate these stretch receptors. The net effect is that you tend to be hungrier and thus inclined to consume excess calories.

The one time it is beneficial to consume juice is immediately after a workout. The reason: during the post-exercise period, it is actually advantageous to spike insulin. You see, insulin has both anabolic and anti-catabolic functions, helping to increase protein synthesis, decrease protein breakdown, and shuttle glycogen into cells. Just as importantly, the elevated insulin levels won't promote increases in
body fat. Because your muscles are in a depleted state, nutrients will tend to be used for lean tissue purposes rather than fat storage. It's a win/win proposition.

Take home message: stick to whole fruits and veggies except for after a hard workout. It will keep you leaner and healthier in the long run.

Brad Schoenfeld, CSCS, is an internationally renowned expert on fitness and sports nutrition. As the owner/operator of the exclusive Personal Training Center for Women in Scarsdale, NY, he is regarded as one of the leading authorities on women's fitness. He is a lifetime drug-free bodybuilder, and has won numerous natural bodybuilding titles including the ANPPC Tri-State Naturals and USA Mixed Pairs crowns.

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