Saturday, March 10, 2012

Metric Problems at the Supermarket - What's the Big Deal?

It seems the average American is inhabiting the ozone when it comes to the basic metric system and say, applying it to the practical science of shopping for groceries or other essentials. According to a piece in today's WSJ ('Measuring Metric's Limits in the Grocery Aisle'. p. A2) Americans are floundering when it comes to recognition of metric units as well as converting them. Since so much information is now given in those units - see graphic - that means American shoppers are likely risking their health as well as their wallets.

As an indication of this dysfunction, the piece noted the results of a recent survey by Consumer World which tested 721 readers of their site about their knowledge of grams. The question on the survey displayed two labels for yogurt which were identical except that one gave the sugar content as "25 grams" and the other as six teaspoons. Most respondents incorrectly gave the grams answer as the "more healthy" one when in fact they are equivalent.

Had these readers known the basic conversion fact that there are roughly 4.2 grams of sugar per teaspoon, this wouldn't have been a problem. But it goes beyond mere sugar content to comparing actual costs between disparate products, as well as other content such as saturated fats, sodium etc.

In this blog, I basically give a 'quick and dirty' template for being able to compare using the metric system without getting too many headaches.

Ok, first a basic comparison cost problem: You are looking at two products, say packaged brown rice- and product X contains 350 g (labeled) and sells for $5.50 while Y displays 10 oz. and sells for $6.00. Which is the better deal? You can't make the determination until you get the units uniform. The key conversion to know here is that 1 pound (or 16 oz.) is roughly equal to 450 grams.

Therefore 10 oz. translates into:

(10/16) x 450 g = (4500 g)/ 16 = 281.2 g (approx.)

and this is almost 70g less than the quantity for product X. Hence, unless you have some emotional brand committment to Y, you purchase X and come out ahead.

Now, more and more sodium content is in the news and we hear it's a leading cause of high blood pressure. The health mavens based at the Center for Science in the Public Interest are now insisting that most people should not consume more than about 1500 grams of sodium per day. Let us go back to our rice examples, and use them as a basis where the sodium content for product X is indicated as: 240 g per serving, and the box has four servings in all. This means each such defined serving for this product will be 87.5 g each.

The other product, Y, lists 120 g sodium per serving and indicates it contains three servings. This yields 93.7 g per serving, and a lower sodium content than product X. (By a factor two, which is not insignificant).

In other words, one will look at the decision for purchase not merely in economic but also in health terms. Yes, the rice product Y costs more, but eating one of its servings still leaves you with almost 1400 g of sodium "balance" left to work with the rest of the day - and you will be amazed how fast those can go, for example when you factor in the sodium content in items like regular bread. For example, pumpernickel bread has 190 g of sodium per slice. Two slices of ham contains almost 500 g of sodium. Thus, making one sandwich will deliver (2 x 190g) + 500g = 880 g of sodium! That's more than half a person's healthy quota for the day.

So, in deciding between product X and Y which is more important, the sodium content or the cost? Of course, another option, even healthier, is just buy the ordinary bag of brown rice and cook it yourself then add the salt to that. This is likely the most economic move of all.

What about saturated fats? Most doctors say that for heart health this amount needs to be kept to 5 g or LESS per day. Thus, those turkey bologna meats on offer at Safeway, for example, yielding 1.5 g of saturated fat per slice, will only allow you about 3 slices per day. And if you eat those, you have to be aware of how your 'saturated fat' balance has declined for other foods...the rest of the day.

What about plain old regular fats? Doctors recommend they should consume no more than 10% of the calories in one's daily diet. So, say you consume 1,800 calories a day, then the fat caloric total ought to come in no higher than 180 calories.

Let's say that the liverwurst you bought has 10 g of fat per 2 oz. serving. There are 9 calories associated with each gram of fat so that is 10g x 9 cal/g = 90 calories right there, and with that one liverwurst sandwich you've eaten half your allotment. Then for your other two meals you will have to ensure you get no more than 90 calories of fat (or 10 g in all) to stay reasonably healthy. (Of course, there are many physicians who insist on zero grams, period, but I deem them as not living in the real world, or as oat-cereal and vegetarian obsessives.)

Lastly, let's return to the sodium example. A way to be able to consume more sodium is to add at least one third the sodium amount in potassium. In effect, potassium reduces the nasty, higher BP effects of the sodium , so say that product X listed above also contains 80 g of potassium- then it is just as effective healthwise to purchase that and more economical than product Y.

Hopefully this provides some basic guidelines next time you end up at the grocery wondering about product comparisons based on the metric system!

No comments: