Friday, August 27, 2010

Food Calorimetry

I've always wondered how scientists determine how many calories are in what foods, and the derivation of the source of calories.  From an article on Slate, laboratories freeze samples in liquid nitrogen then blend it into a fine monochromatic powder from which to test.  Removal of the nitrogen via the Kjeldahl process allows scientists to calculate the amount of protein.  Fats are determined through a hexane extraction, and carbohydates are what remains after fats and proteins are isolated.

Of course, one could always burn the sample and measure all the heat released as calories (in the chemical sense) and convert that to kilocalories, which is what we all call "calories."  All that is given off during the burn process, however, doesn't accurately describe the amounts that is taken up by the body.

While the FDA requires that companies publish nutritional facts on foods, it doesn't specify how they are to obtain those figures.  Companies may even guesstimate values based on the USDA's published tome of nutritional data, which is available online.

Wikipedia also shows an energy density table which standardizes food energy into values actually absorbed by the body.
Food component Energy Density
kJ/g kcal/g
Fat 37 9
Ethanol (alcohol) 29 7
Proteins 17 4
Carbohydrates 17 4
Organic acids 13 3
Polyols (sugar alcohols, sweeteners) 10 2.4
Salatrims (reduced energy fat) [1][2][3][4] 25 6
Fibre 8 2
Erythritol 0 0

Pretty neat, huh?


USDA Nutrient Data Laboratory

Wednesday, August 25, 2010

Ten Anti-Wrinkle Foods

Here are some anti-wrinkle foods to eat that contain the necessary nutrients to nourish the body and fight against the effects of aging.

  1. Red peppers - As much as I dislike peppers, I force myself to eat them because they contain 95 mg of vitamin C which is needed to make collagen.  As we all know, collagen keeps skin supple, firm, resilient, and moist.
  2. Sweet potatoes - contain vitamins C and A, specifically carotenoids.  Carotenoids prevent the breakdown of collagen.
  3. Sunflower seeds - contain vitamin E and linoleic acid.  Vitamin E acts as an antioxidant, protecting against sun damage when combined with vitamin C.
  4. Wild salmon - Eat in moderation, of course, but this is a good source of protein which contain EPA and DHA (types of amino acids).  These protect from sun damage and prevent the onset of wrinkles.
  5. Safflower oil - contains vitamin E and linoleic acid.  Assists with skin moisture and firmness.
  6. Watermelon - contains vitamins A and C.  As an antioxidant, vitamin C can reverse UV damage to skin (according to the Academy of Dermatology).
  7. Spinach - contains vitamins A, C, and E.
  8. Oranges - contains heaps of vitamin C.  Prevents the sailor's blight, scurvy, and aids in maintaining moisture in skin with fewer wrinkles.
  9. Tuna - source of EPA, DHA, and niacin.  Niacin increases collagen production.
  10. Peanuts - great source of protein, vitamin E and niacin.
This information was pulled from, a great site with a wealth of information on health, fitness, diet and nutrition articles.  Sophie and I started monitoring our consumption and exercise using their MyPlate tool.  Mildly tedious because you need to be on the computer frequently or write it down and transfer later, the extensive database of foods and their caloric content make it worth it and I think are a pretty accurate measure of daily net calories.  MyPlate is available as an iPhone application, but not on the Android (yet) *sad face*.

Web MD provides a great wallet-sized printout for serving sizes as well as a healthy shopping guide and list.  I also really like Web MD's BMI Plus Calculator.

Let's get healthy and stay happy!    ^.^


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