Thursday, November 15, 2012

Vegetable Juicing

1. Does fresh vegetable juice cause a huge insulin spike in one’s bloodstream?
2. Would this spike be higher than if you ate the vegetables themselves (because you’re not eating the fiber at the same time)?
3. Would the number of carbs in the juice of one beet or the juice of one cucumber be the same as eating one whole beet or one whole cucumber?
I would still like to lose about 15 pounds of fat, so if you think my extra intake of veggies is going to cause my carb intake to skyrocket then I will think twice about continuing with the juicing.

1. It totally depends on the vegetable you’re juicing. The main reason, after all, that I suggest you limit fruit juice is that it’s a huge bolus of sugar without the fiber and the satiation that comes from eating whole fruit. You can eat an apple and you’ll be pretty satisfied, but a glass of apple juice goes down like water, doesn’t really fill you up, and contains the sugar of four apples. That’s four times the sugar (and nearly four times the calories) with a fraction of the satisfaction. Sitting down to breakfast with a tall glass of apple juice, then, is like adding a bag full of apples to your breakfast.
Most vegetables don’t have that problem. Yeah, if you were drinking nothing but carrot and beet juice, you’d be getting a fair amount of sugar, but even a four ounce portion of carrot or beet only has about ten grams of sugar. And all the other vegetables you’re probably juicing, like lettuce, kale, chard, spinach, cucumbers, broccoli, are so low in calories and carbs that they’re not worth fretting over. Honestly, I wouldn’t worry too much about the carbs in vegetable juice.
2. Yes, the (insignificant) spike will be higher after consuming juice than after consuming the whole vegetable. In studies with whole fruit and fruit juice (very few, if any, studies are out there comparing vegetable juice to whole vegetables, so we’ll have to use the fruit juice research), whole fruit tends to elicit a lower insulin spike than fruit juice, an effect authors attribute primarily to the fiber. In fact, fiber has even been used in diabetics to help maintain their glucose control. That said, vegetable juice doesn’t have much sugar with which to spike your insulin. Again, I wouldn’t worry too much about it.
3. The number of carbs will be the same minus the fiber from the whole vegetable. If a beet has around 2 grams of fiber, that amount will be subtracted from the juice.
Although juicing vegetables won’t really affect your insulin levels one way or the other, I would caution that by discarding the fiber, you’ll be missing out on some polyphenols. Fruit and vegetable fiber isn’t “just fiber”; it also contains bioactive phytochemicals that may be of some use to you. Also, the effects of some polyphenols seem to be compounded when eaten with plant fiber, as is the case with apple pectin (a soluble fiber) and apple polyphenols. Overall, the fiber increases the bioavailability of plant antioxidants. Whole foods win again! Luckily, you state that you’re eating plenty of whole vegetables in addition to the juice, so I wouldn’t be too concerned. If you weren’t eaten the whole vegetables, I’d probably urge you to consider smoothies over juice, since smoothies retain the fiber.

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