Wednesday, September 8, 2010

Health, weight and the energy/nutrient density of foods

Have you ever thought of food as medicine?  Well, if you have you're in esteemed company, because Hippocrates had the same thought when he said, "Let your food be your medicine and your medicine be your food." In our so-called modern age, how have we managed to stray so far from this ancient wisdom?  It's a well-established fact that what we eat impacts our health. Yet, for many of us who have access to an abundant variety of foods, often times what we select are foods like a fast food burger and soft drink, that have a higher energy density, but are more nutrient poor (USDA).

World Cancer Research Fund
When it comes to making decisions about what to eat, it's helpful to understand the energy and nutrient densities of foods. You're probably familiar with calories. A calorie is a unit of measuring energy. When referring to food the term kilocalorie is used. A kilocalorie (or kcal) "approximates the energy needed to increase the temperature of 1 kilogram of water by 1 °C" (Wikipedia).  This is important to understand because the nutrient and energy density of foods relates to calories. In general:
  • Nutrient dense foods provide more nutrients with fewer calories per unit volume than other foods in the same food group (USDA). Another way to look at it is the ratio of nutrients to calories (energy) a food contains.  
  • Energy dense foods  provide more energy with more calories for their volume than nutrient dense foods. At first impression, more energy dense foods may sound healthier, but typically the reverse is the case. Energy dense foods often contain "empty calories" that come from fat and refined sugars making them a less healthy choice ( Foods that are lower in energy density provide fewer calories per gram than foods with a higher energy density (CDC)
For example, foods such as candies, desserts and processed foods, are high in energy density and calories, but they are not very nutrient dense. Whereas, foods like fruits and vegetables contain fewer calories for their volume, so they are lower in energy density, but are higher in nutrient density. This is important to note, especially when it comes to weight loss, because for the same amount of calories a person can consume a larger portion of a lower energy dense food (like an apple) and feel fuller for longer than they would if they ate a higher energy dense food (like a doughnut) (CDC). Plus, they would be getting much greater nutritional value from the apple than the doughnut. It's a win/win situation.

When grocery shopping the nutrition label found on prepackaged foods can be helpful in determining its energy content per 100 grams. The World Cancer Research Fund has a useful food energy density calculator here, but as a general rule:
  • high energy density (fast food, chips, cakes, cookies, butter and margarine) fall in the 225-275 kcal/100g range
  • medium energy density (bread, lean meat, poultry, fish) fall in the 100-225 kcal/100g range
  • low energy density foods (cooked grains like brown rice, whole meal pasta, beans and lentils) fall in the 60-150 kcal/100g range
  • lower energy density foods (most fruits and vegetables) fall in the 10-100 kcal/100g range

How does the composition of food affect energy density? Three factors play an important role in the energy density of food:
  • Water - Adds volume/weight to food, but not calories because water contains 0 kcal/gram. Fruits and vegetables contain a lot of water. For example, grapefruit "is about 90 percent water and has just 38 calories in a half-fruit serving. Carrots are about 88 percent water and have only 52 calories in 1 cup" (Mayo Clinic).
  • Fiber - Adds volume and 1.5-2.5 kcal/gram to food, but fiber also increases the time it takes to digest foods and this contributes to our feeling fuller for a longer period of time after eating fiber rich foods.
  • Fat - On the other side of the energy density spectrum is fat, which contains 9 kcal/gram.  Fat increases the energy (calorie) density of foods. For example, "one teaspoon of butter contains almost the same number of calories as 2 cups of raw broccoli." (CDC).
Keeping these factors in mind, it's not too difficult to spot a high energy density food.  They are usually high in sugar and fat, low in fiber and water and processed.

    Weight loss/maintenance and energy density of foods - Research has shown that eating a diet that is "rich in low energy dense foods like fruits, vegetables, whole grains, lean meats and low fat dairy products helps people lower their caloric intake" (CDC).  However, even though calories consumed are usually lower with this type of eating, typically eating a diet that contains low energy foods doesn't mean skimping on nutrients. On the contrary, veggies and fruits are the superstars on our plates and will provide us with a good heaping of the required daily allowance of nutrients (CDC).

    Not only can there be a weight loss/maintenance benefit from eating lower energy dense foods, but there is also strong evidence to suggest a reduction in the risk of certain cancers. In 2007, the UK's World Cancer Research Fund (WCRF) published findings from a panel of 21 of the world's top health experts who reviewed the current scientific research. After 6 years of work they produced the Expert Report. It is the most comprehensive statement "on the links between lifestyle and cancer risk. Because of the thoroughness of the Report and the expertise of the panel, people can be confident that it is the best advice on how to reduce cancer risk that is available anywhere in the world." (WCRF). Although it's been suggested for some time, the science is proving that taking steps toward improving nutrition, increasing physical activity and just generally making a healthy lifestyle a priority will actually help reduce risk for a recurrence of cancer, among other things.

    In an effort to increase awareness of the health benefits of eating more fruits and vegetables, the CDC has designated September as National Fruits and Veggies More Matters Month. (Their site provides some useful information, along with a fruits and veggie consumption calculator.) So, it seems appropriate that step one of creating a diet that is low in energy density has to do with, you guessed it, fruits and veggies! 

    First step to take to create a diet low in energy density:

    Incorporate a larger portion of fruits and veggies into meals.  For many people, purchasing fruits and vegetables can be limited by their cost. The CDC has a helpful resource entitled 30 Ways in 30 Days to Stretch Your Fruits and Veggies Budget. You can find it here. Eating more fruits and veggies is the first step in reducing our diet's energy density because they contain more water and fiber and less fat than other foods.

    However, not all fruits and veggies are created equal. The CDC suggests incorporating more cruciferous vegetables.  These include "broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, kale, kohlrabi, mustard, rutabaga, turnips, bok choy, and Chinese cabbage. Arugula, horse radish, radish, wasabi, and watercress are also cruciferous vegetables" (Linus Pauling Institute). Then rounding out meals "by adding starchy fruits and vegetables, legumes, lean meats and low-fat dairy food.  These foods are important for creating a healthy, balanced diet" (CDC).

    The next post will discuss the other steps as well as a few helpful strategies that will aid in creating a diet that is low in energy density and high in nutrient density.  Even though the term "diet" is used, this way of eating is a lifestyle.  The TLC way to weight loss discusses in more detail here the importance of adopting healthy habits, rather than attempting various diets.  Also, dieting is usually associated with calorie counting and hunger.  This isn't the case with eating more low energy/high nutrient density foods. With all the mounting scientific evidence that underscores the importance of healthy nutrition, it seems more critical than ever to get back to thinking about our food as medicine.

    National Institutes of Health

    No comments:

    Post a Comment