Mathematics & Milk

(The following is reprinted with permission from John M. Friedman, Jr., who sent it to me a few weeks after attending one of my classes on Label Reading.)

How do we think about eating? Most of us who think about such things do so on the basis of calories. If we take in more calories than we use up, we get fatter, and if we take in fewer than we use up, we get thinner. That is why we plan diets around how many calories we eat per day rather than how many cups or ounces of food we eat. Of course, we could think about food consumption in ounces and pounds rather than calories. The trouble with that is Freddie, eating 3 pounds of McDonald’s burgers and fries each day, will gain weight, while Frieda, eating 3 pounds a day of fruits and vegetables, will lose weight. Calories do count.

Nutritionists, too, think in terms of foods’ caloric value. When they think of “high-fat” foods, they refer to foods that supply a high amount of fat for each calorie consumed, while low-fat foods supply small amounts of fat per calorie. Just about all foods supply some of their calories as fat. Oils, of course, are 100% fat — that is, all their calories come from fat. Leafy green lettuce, by contrast, supplies only 12% of its calories from fat.

What about those low-fat dairy products? I went to the supermarket to find out. I first came to Philadelphia Low-Fat Cream Cheese.  “One-third less fat” it said, comparing itself to its older brother, regular Philadelphia Cream Cheese. One “serving” (an ounce) of regular Philly had 100 calories, 90 of which were from fat. Thus, nutritionists would say, Philly cream cheese is 90% fat. Now back to the low-fat Philly. Sure enough, a serving (also one ounce) had only 60 calories of fat in it, a reduction of 30 calories, or one-third of the original 90. However, the ounce of low-fat Philly also had only 70 calories. The result was a cheese that was 60/70 = 86 percent fat, a reduction from the original 90 percent fat of only 4 percentage points, or 4/90 = 3 percent. The Philly people thus were offering a choice between cheese that is 90 percent fat and “low-fat” cheese that is 86 percent fat. For a dieter, the spread between those spreads is minimal.

Various forms of milk, which we consume in greater quantities than cream cheese, have more troubling labeling. Whole milk supplies about 47 percent of its calories from fat: an 8-ounce serving has 150 calories of which 70 are fat calories. Meanwhile, so-called 2 percent milk actually supplies 35 percent of its calories from fat and even 1 percent milk supplies 18 percent of its calories from fat.

How can 2 percent milk be 35 percent? The government allows labels to be calculated based on the weight of the ingredients, rather than on the caloric values, though it does require calorie-based information on those nutrition labels on the side of the package.

Let me give you an example of weight-based labeling. Suppose I take nine ounces of water and one ounce of oil and mix them in a blender to form a smoothie. I am allowed to say that the beverage is just 10 percent fat, but a nutritionist would point out that my smoothie is 100 percent fat, since all its calories come from fat. Milk works the same way. The 2 percent milk is 2 percent fat by weight, but, like my smoothie, a far greater percentage of the calories come from fats — namely, 35 percent.

The dairy industry is also no slouch in promoting the calcium content of its foods. Calcium is important in bone growth and replenishment, and it is necessary for good blood clotting, nerve transmissions and many other bodily functions.

Which foods supply the most calcium? We can view this any number of ways. Let’s first compare volumes...

1 Cup Skim Milk      300 mg. Calcium

1 Cup Bok Choy       158 mg. Calcium

1 Cup Broccoli            95 mg. Calcium

Milk seems to be the winner. However, the body absorbs calcium in different ways from different foods. For example, only about 32 percent of the calcium in milk gets absorbed, while 54 percent of the calcium in bok choy does.

So, let’s modify the chart...

- Skim Milk, 300 mg. calcium, 32% absorbed, 96 net mg. Calcium

- Kale, 180 mg. calcium, 59% absorbed, 106 net mg. Calcium

- Bok Choy, 158 mg. calcium, 54% absorbed, 85 net mg. Calcium

- Broccoli, 95 mg. calcium, 53% absorbed, 50 net mg. Calcium

Now we make our final adjustment based on the calories in each...

- Skim Milk, 96 net mg. Calcium, 90 calories per cup, 107 mg. calcium per 100

- Kale, 106 net mg. Calcium, 40 calories per cup, 265 mg. calcium per 100

- Bok Choy, 85 net mg. Calcium, 20 calories per cup, 425 mg. calcium per 100

- Broccoli, 50 net mg. Calcium, 50 calories per cup, 100 mg. calcium per 100

From this information we see that if you are interested in the calories you consume, a variety of vegetables are far better sources of calcium than skim milk, and the same can be shown for other dairy products. A plate of stir-fry can get you more calcium than that “healthful” glass of skim milk, often with fewer calories and a better feeling of fullness.

You probably know that osteoporosis is reaching epidemic levels in North America and Europe, where vegetables are far from the main feature of meals, but you may not know that osteoporosis is virtually unknown among rural populations in Asia and Africa, who subsist almost exclusively on vegetables. Remember, too, that all it takes to build a healthy elephant, with a lot of bones and no osteoporosis, is grass and leaves.