Fruit Smoothie Nutrition

May 28, 2011 7:40 AM

Couple nutrition-related questions concerning fruit smoothies.

3 questions:

1) I'm wondering if blending fruits tears up the cells of the fruits and what not and hence significantly diminishes the nutritional value of a smoothie, compared to eating the fruits whole. I mean, I imagine the juice of the fruits is largely unaffected by the blending, so this probably only concerns the pulp and other solids.

2) I heard somewhere that the metal blade of the blender causes oxidation in the smoothie. But I remember also reading that the oxidation is minimized if you drink the smoothie soon after blending it. Is there any truth to this oxidation thing?

3) Raspberry and blackberry seeds remain pretty much in tact when using my blender. Can the body extract and/or digest the nutrients from the seeds when they're still whole? Or must they be ground up or pulverized to get any real value? And this question extends to all such small seeds, like flax for example.

Thanks!

posted by frankly mister to health & fitness (11 answers total)

1. Probably so, but chewing also tears them up. No nutritional value is lost.
2. Being cut in our good old oxygen-filled atmosphere will start the fruit's oxidation. Think about slicing open an apple, and how long it takes to brown. That's the kind of timespan you might think about...but still, not really an issue.
3. Maybe it depends on the seed, but it seems like most pass through intact, and would need to be ground a little, at least by chewing.
posted by mittens at 7:48 AM on May 28, 2011

Fruit seed are pretty much designed around the concept of passing through digestive tracts intact.
posted by StickyCarpet at 7:51 AM on May 28, 2011 [3 favorites]

I grind flax seeds in my coffee grinder and add the ground flax to smoothies. As mittens pointed out, they will otherwise pass through your body intact. Clean out your coffee grinder by grinding rice or another grain in it - it's unbelievably loud, but really works. That way your ground flax won't taste like stale coffee.
posted by lulu68 at 7:55 AM on May 28, 2011 [5 favorites]

Some portion of whole flax seeds will be digested and some portion will pass straight through you. Pulverizing them in a mortar and pestle would be the answer to your concerns, though putting them through a coffee grinder would be OK, too.

As for the cells of a fruit being torn by a blender--not a concern. The nutritional value does not disappear into the ether merely because they have been destroyed in your shake and not your body.
posted by dfriedman at 8:02 AM on May 28, 2011

for 1: this comment by VikingSword.
posted by ilk at 8:06 AM on May 28, 2011

1. Probably so, but chewing also tears them up. No nutritional value is lost.

Nutritional value aside, there's a difference between chewing an apple with your teeth enough that the pulp can pass into your esophagus and puréeing fruit to a fine liquid, at least in terms of health and weight loss (I don't know if that's a concern for you). When the cell walls are that essentially annihilated, your body doesn't have to work nearly as hard to get at the sugars. A finely puréed smoothie hits your blood stream much more quickly than if you simply bit down on an apple, so you're likely to get a high spike in your insulin and thus a bigger sugar rush, leading to fat storage. It's not as bad as eating a Snickers bar, but not necessarily as healthy as simply eating fruit whole.

But of course, puréeing a fruit won't ruin the integrity of vitamins and minerals.
posted by zoomorphic at 8:07 AM on May 28, 2011 [3 favorites]

Also, this answer pretty much sums up my point.
posted by zoomorphic at 8:08 AM on May 28, 2011

zoomorphic, do you have any scientific data to back up your comment? Just wondering.
posted by catseatcheese at 8:19 AM on May 28, 2011

lower down in the same thread zoomorphic and i linked to, the user provides a citation.
posted by ilk at 8:35 AM on May 28, 2011

I'm pretty sure a blender isn't changing the microstructure of your fruit (more than chewing would). For example, you don't expect a blender to kill bacteria in the fruit, but bacteria are just single cells. The articles on food microstructures deal with things like cooking, freezing, adding chemicals to, or drying foods.

The main problem with smoothies is that you can drink them very quickly and with no effort. It takes a while for your body to recognize that it is full. In that time you'll eat, say, another half an apple... or you'll drink three apples worth of smoothie.

Also, fruit is OK, but the berries you're going for are sugary and generally low nutrition/calories however you eat them. Better would be to use some green, leafy vegetables (yuck) and a source of protein like beans (yuck).
posted by anaelith at 9:03 AM on May 28, 2011

2nd what zoomorphic said. Google "fruit juice versus whole fruit" for some scientific explanations. The slower release of sugars in eating a whole fruit is easier for your body to handle in terms of the insulin surge.

The metal blade doesn't cause oxidation. Second what lulu68 said re: the coffee grinder. It's wonderful for grinding flax, and even more making almond flour in small batches.

Raspberries are a wonderful choice for a lower sugar fruit. Might I recommend adding vegetables and high protein dairy to your smoothies? :) Kale and broccoli are both undetectable in terms of taste, I've found. Wonderful lower carb, nutrient dense add-ins for you to try - couple tablespoons of almond butter, whole milk yogurt, greek yogurt, couple tablespoons of heavy cream, raw egg (becomes very creamy and doesn't taste like egg - just buy organic eggs), coconut milk, and protein powders. Whey and hemp protein powder are popular options, although I'd sample hemp first since it can be gritty. Happy smoothie making!
posted by sunnychef88 at 10:18 AM on May 28, 2011 [1 favorite]