Obesity Weekly

A weekly update about some aspect of Obesity. Published Monday mornings

Refined or Whole Grain?

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Increases in obesity rates correlate with increases in food portion sizes over time.  From 1910 to 1982 the average amount of food available for consumption remained within a range of 3000 to 3500 calories per day per person (1).  From 1982 to 2000 the calories available for consumption and the amount consumed increased in parallel by over 10%, or about 300 calories per day (1).  During the same time the rate of obesity went from 15-20% to approaching 30%.  For a dramatic visual of this effect see the map published by the CDC.  These data demonstrate the dramatic increase in obesity over time.  There are some really interesting data in the types of calories that are consumed.  The amount of carbohydrates consumed increased from just under 7 servings per day to almost 10 servings per day from 1970 to 2000.  Unfortunately, most of the carbohydrates were of the refined type, the least nutritious and satiating of the carbohydrates.  Examples of refined carbohydrates are white rice, white flour and white pasta.  If its white, its refined.  Whole grains still contain the outer bran and inner germ. The bran and germ contain fiber, B vitamins and antioxidants.  The white endosperm is the food supply for the developing seedling. Because it is supposed to support the rapid growth rate of the new seedling, it is calorie dense.  Whole grains tend to be darker in appearance and have more of a texture, or mouth feel, when eaten than the white variety.  Whole grains have a shorter shelf life than refined grains which explains why white is preferred by manufacturers.

Compare the nutritive value of white and wheat flour or white or brown rice (2).

nutrition-table2

One of the things that should be obvious from the nutritional chart is the decrease in dietary fiber, vitamins and minerals upon refining.  These nutrients are important and converting the product to a refined version is not in our interest as an informed consumer.  I think most understand that whole grains are more nutritive that refined grains, but still consumers prefer refined grains.  Why?  Is it because refined tastes better?  There have been only a couple studies actually testing this hypothesis.  It is one of the larger, untested assumptions in consumer America.  Ask any parent whether their child will prefer white bread to wheat bread, and the answer will most likely be white bread.  However, a study done by Zata Vickers at the University of Minnesota demonstrated that children either have an equal preference for white bread and wheat bread or that wheat bread was preferred (3).  In a follow-up study it was shown that participants liked Artisan bread, either white or whole grain, more than the bread made using standard production techniques (4).  Those participants who preferred white bread tended to like the white bread in the study.  Those who preferred refined bread cited familiarity and price as the significant contributing factors while those who preferred whole grain cited nutrition as a significant factor.  Reasons for preference including taste, texture, smell, freshness and convenience were not significant.  One of the novel aspects of this study was the use of 6-n-propylthiouracil (PROP) to assess the ability of the participants to taste bitter flavors.  The ability to taste PROP is genetically determined and those who are supertasters will avoid bitter food.  About 25% of the population are supertasters, 50% are medium tasters, and 25% are non-tasters. Interestingly, the supertasters were significantly averse to consuming whole grain bread, suggesting that some bitterness compounds in the unrefined flour contributed to the perceived bitter taste.

So about 1 in 4 people will have a real, biologic aversion to whole grain products.  3 out of 4 will have a small aversion or no aversion to whole grain products.  To assess which group you fall in, try a high quality whole grain bread to test if you can consume the product without an adverse taste.   If you really want to test whether your aversion to whole grain is due to the ability to taste bitterness, then you can have a friend give you samples in a blinded fashion, that way you don’t know what you are tasting and your expectations will not affect the results.  For the majority of the population, a good quality whole grain product is similar to a refined product in our perceived preference.  Since familiarity was a significant factor in the selection of a refined wheat bread, one just has to figure out which whole grain products they like.  There are a variety of options and choices and there is no nutritional reason to consume refined grain products when whole grain is better for you and when prepared in a preferred manner, a much more interesting and flavorful consumable.  And once the kids get used to it, they will continue a good nutritional habit as they mature.

1. http://ers.usda.gov/publications/FoodReview/DEC2002/frvol25i3a.pdf

2. USDA National Nutrient Database. http://www.nal.usda.gov/fnic/foodcomp/search/

3.Delk J, Vickers Z. 2007. Determining a series of whole wheat difference thresholds
for use in a gradual adjustment intervention to improve children’s liking of whole
wheat bread rolls. J Sensory Studies 22: 639-652.
4. Bakke and Vickers Journal of Food Science 2007

5.  For a complete nutritional comparison see the linked PDF file.

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Written by ecable

March 16, 2009 at 5:00 am

Posted in Health

Tagged with , ,

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