Question Concerning Portion Sizes

[Judah Maccabee]

So we're all aware of the edict to eat 5 or more servings of fruits and veggies every day.

But here's my issue.

I understand a cup to be 8oz of something. So when nutrition advice advocates something like a cup of spinach, I know they're talking about volume and not weight. The same would go for something like blueberries - 8oz of blueberries is a lot; it's a half-pound. I'm not entirely sure that we're being asked to eat a minimum of 2.5lbs of fruits and veggies every day.

Some checking of nutritional labels confirms my point.

http://www.ilovespinach.com/nutrition.html

You can clearly see that 1 1/2 cups of fresh spinach weighs the same as a 1/3rd cup of frozen spinach - about 85 grams.

For something like milk or juice, the weight of the fluid (weight) measurement closely corresponds with the measurement by volume.

Does anyone know how to solve for this inconsistency between weight and volume? Why is there a dependence on a serving size by volume for solid foods when there is a clear disparity between the weight of the food for that volume and total volume (such as 1 1/2 cups [12oz liquid] being applied for the equivalent weight for 3oz spinach [3oz = 85.05g]???)

[BSDaemon]

Its just a question of density and moisture.

Mass = Volume * Density

Packed frozen spinach is compressed to be more compact, hence a higher density than fresh spinach, therefore less volume for a serving. But serving size isn't ever going to be a constant weight or volume since concentration of the food is also a factor.

[Cullion]

I think they are just giving the advice in the measurements that most people will use in the kitchen. Describing things in terms of roughly standard sized food vessels & containers most people own means they are more likely to follow the advice than if they had to weigh things carefully. It's hardly an exact science anyway.

In real life, everybody's ideal portions of each type of nutrient would have to be calculated from many variables.

[Ronin]

Keep it simple, eat till you puke.

[Judah Maccabee]

In real life, everybody's ideal portions of each type of nutrient would have to be calculated from many variables.

Very true, but I have a decent idea of how much nutrient I need, and I know the nutritional values of the foods I'd like to get them from. Properly determing portion sizes is a little tougher.

[warnerj5000]

Keep it simple, eat till you puke.

and then eat some more.

[Judah Maccabee]

My only solution seems to be to try to find nutritional info on the packaging or the web, and use the weight measurement that they do.

See my "nutritiondata.com" thread for more info.

[beka]

I imagine weight would be the more accurate measurement if you're looking for nutrients. A cup of broccoli florets is going to have a lot of negative space in it because the broccoli is oddly shaped. A cup of milk is uniform and you won't have to worry about negative space. So yeah, do they want me to have 8 weighted ounces of broccoli, or a cup with the blank space?

My answer is to just eat more vegetables than I could possibly need anyway. The calories are negligable, and the benefits are pretty good. With the fruit thing I just eat whole big fruits (apples, bananas, mangoes, etc) instead of the little ones like berries, and hope to god that the nutrient info for "one small apple" is accurate.

[Judah Maccabee]

Problem is that big fruits generally don't come frozen, and fresh produce and I don't get along well. It generally goes bad, then I have a **** load of fruitflies to deal with.