To Your Health -- CHRC Newsletter

Summer 2003

Continued from: Dietary Fats and Their Effects on Blood Cholesterol Levels, Part I

Authors: Karen Astrachan, M.S., R.D., CDE; Linda Cloney, M.S., R.D.; Darcie Ellyne, M.S., R.D., CDE, BC-ADM; Melissa Gibson, M.S., R.D., CDE; and Susan Zipin, R.D., CDE

Contributor: Diane Lesnick, MPH, R.D., CDE

Q: What are carbohydrates, and how do they affect the body?

Linda: Carbohydrates, also referred to as "energy foods," are one of three calorie-containing nutrients found in foods. The other two nutrients are proteins and fats. Carbohydrates contain 4 calories per gram, as does protein. Fat is more calorie-dense, containing 9 calories per gram.

Carbohydrates are eventually metabolized by the body into blood glucose. All cells of the body utilize glucose as the primary energy source, particularly in the brain, for which glucose provides the only source of fuel. If carbohydrates are eaten in excessive amounts, just as if any nutrient is eaten to excess, the body converts the extra blood glucose into triglycerides for storage in adipose or fat cells, leading to weight gain.

Three specific types of carbohydrate are present in the foods we eat: starch, sugar and fiber.

Starch, also known as complex carbohydrate or polysaccharide, is present in foods such as cereals, whole grains, rice, pasta, potatoes, peas, corn and legumes.

Sugar has a more simple chemical structure than starch and is found naturally in many foods. Food sources of natural sugar include fruit, vegetables, milk and yogurt. Sugar is also commonly added to many foods in the form of white table sugar (sucrose), honey, corn syrup or fructose. Foods containing natural sugars are generally very nutritious, providing many vitamins, minerals, phytochemicals (natural plant chemicals) and antioxidants. These foods also tend to be good sources of fiber, such as that found in fruits, vegetables and whole grains. However, foods high in added sugars are often referred to as sources of "empty calories," meaning they add calories to the diet but provide little benefit in terms of vitamins, minerals or fiber.

Fiber, also a carbohydrate, is found in foods of plant origin. Fiber benefits the body in numerous ways, as discussed in a subsequent question.

Q: How much carbohydrate should the average person consume per day?

Linda: Individuals vary and therefore can differ in terms of how much carbohydrate each optimally needs on a daily basis. For most people, an ideal amount of carbohydrate is at least one-half of the day's total calorie intake, or between 50% and 60% of our daily energy needs. Individuals with special needs or a chronic condition such as type 2 diabetes or insulin resistance might benefit from a more individualized plan with a lower carbohydrate recommendation. The National Academy of Sciences recommends keeping carbohydrate intake above 130 grams per day, the minimum amount of glucose utilized by the brain.

In choosing carbohydrate-rich foods, it's best to include a wide variety of foods containing starch and natural sugar, such as whole grains, cereals, legumes, fruits, vegetables and dairy products. Special attention should be given to choosing foods high in fiber and reducing intake of foods with added sugars.

Q: Are carbohydrates from fruits and vegetables created equal?

Darcie: Yes. In this business, we say "a carb is a carb is a carb." Carbohydrates from whole fruits and vegetables are similar in that they are coupled with fiber and loads of vitamins and minerals, making those foods very healthy choices. Fruits are significantly more carbohydrate-dense than vegetables, so a piece of fruit packs more carbohydrates per serving than does a portion of vegetables. However, this distinction typically is not a problem unless fruits and vegetables are juiced. It's best to steer clear of juices, because they concentrate the natural sugars in fruits and vegetables and leave behind many vital nutrients, as well as all of the fiber. Eating whole fresh fruits and smaller portions of concentrated juices and dried fruits is best. Three or more servings of raw or lightly cooked/steamed vegetables are also recommended each day.

Q: Some health experts blame the rising obesity rate in the United States on the "low-fat, high-carbohydrate" recommendation of recent years. Fact or fiction?

Darcie: Fiction. The prime factor behind America's soaring obesity rate is the significant increase in calories consumed without a corresponding increase in physical activity. According to United States Department of Agriculture (USDA) data, the average daily calorie intake in the year 2000 was 300 calories more than the 1985 level. Of that, refined grains accounted for 46%; added fats, 24%; added sugar, 23%; and fruits and vegetables, 8%. Meat and dairy intake declined by 1%. The low-fat, high-carbohydrate diets typically espoused more fruits and vegetables and whole grains. Based on the data, Americans didn't listen.

The table below captures the USDA estimate of servings per capita per day in 2000 compared to the recommendation in the food pyramid. Note the excess in added fat and added sugar.

Food Group	2000 Food Supply Data	USDA Food Pyramid Recommendation
Grains	10.6 servings	9 servings
Vegetables	3.8 servings	4.0 servings
Fruits	1.4 servings	3.0 servings
Dairy	1.6 servings	2.2 servings
Meat	6.2 ounces	6.0 ounces
Added fat	65 grams	41 grams
Added sugar	31 teaspoons	12 teaspoons

Q: What about high-protein, low-carbohydrate diets?

Darcie: They are not nutritionally sound. High-protein, low-carbohydrate diets have experienced a wave of popularity because they are successful for weight loss, albeit only in the short term. The long-term effect on one's health is not documented. Based on what we know, high-protein diets such as Atkins do not embody sound nutritional advice because they eliminate entire food groups. When fruit, whole grains, milk and yogurt are removed, the diet falls short of essential vitamins, minerals and fiber. Most notable are deficiencies of vitamin C, beta-carotene, vitamin E, B complex, calcium and potassium. These diets also encourage excessive intake of protein, fat, saturated fat and cholesterol, which have been linked to heart disease, cancers and osteoporosis.

Q: How do carbohydrates affect your lipid profile (blood cholesterol and triglycerides)?

Karen: Just as the amount and type of dietary fat affects blood lipid levels (see Part I of this series in the Winter 2003 issue of To Your Health), so does the amount and type of dietary carbohydrate. Excessive dietary carbohydrate, in all forms, can raise triglyceride levels and exacerbate insulin resistance or diabetes control. Additionally, fructose and sucrose, two specific types of carbohydrate found primarily in desserts, juices and soft drinks, modestly raise LDL (bad) cholesterol levels and therefore can increase the risk of heart disease. Unfortunately, intakes of both dietary fructose and high-fructose corn syrup have increased in the American diet over the past 30 years.

Whole grains, legumes, fruits and vegetables, foods naturally rich in fiber and plant phytochemicals are better choices than processed or refined foods.

Q: What is insulin resistance?

Karen: Insulin resistance, also known as metabolic syndrome or Syndrome X, is defined by the National Cholesterol Education Program's (NCEP) Adult Treatment Panel III as meeting at least three of the following criteria:

a. Waist circumference greater than 40 inches in men or 35 inches in women

b. Triglycerides greater than or equal to 150 milligrams per deciliter (mg/dl)

c. Fasting blood glucose levels greater than or equal to 110 mg/dl

d. HDL (good) cholesterol lower than 40 mg/dl in men or 50 mg/dl in women

e. Blood pressure equal to or higher than 130/85

Insulin resistance increases your risk of developing both heart disease and diabetes.

Achieving a healthy weight, participating in aerobic exercise and following a healthy diet can decrease insulin resistance.

Q: Discuss dietary fiber and its health benefits

Susan and Melissa: We can think of fiber simply as the parts of plant-based foods that go right through us without being digested. Even though we don't absorb fiber like other foods, it plays a vital role in keeping our bodies healthy. There are two main types of fiber with different effects: insoluble fiber and soluble fiber. Insoluble fiber doesn't dissolve in water, but soluble fiber does.

Both forms of fiber have numerous health benefits. Insoluble fiber improves elimination by increasing stool bulk, thereby preventing constipation, and is associated with decreased risk of developing colon cancer. Foods high in insoluble fiber include legumes, whole grains, vegetables, fruits, nuts and seeds.

Soluble fiber delays gastric emptying, slows the absorption of glucose into the bloodstream and inhibits cholesterol absorption, therefore lowering cholesterol levels. Fruits, vegetables, oat bran, legumes, barley, nuts and seeds are all good sources of soluble fiber.

Most foods contain a mixture of both types of fiber. Thus, by increasing your total dietary fiber intake, you reap the benefits of both. Try to consume a variety of fiber-rich foods. An added plus is that fiber-rich foods are processed by the body more slowly than lower-fiber foods, thereby promoting early satiety. This may aid in overall calorie reduction and help promote weight loss. Ill effects of chronic inadequate fiber intake have been documented and can include constipation, diverticula, hemorrhoids and possibly increased risk of colon cancer, especially if consuming inadequate amounts of fluids.

Another way to group fibers is as "dietary fiber" and "added fiber." Dietary fiber is from whole, intact plant foods. Added fibers are isolated fibers separated from their original food sources. The Food and Drug Administration uses these two groupings, adding them for the "Total Fiber" measurement seen on food nutrition facts labels.

Q: What are the guidelines for fiber intake?

Susan: The American Dietetic Association and NCEP recommend that most adults consume 20 to 35 grams of total fiber each day. On the nutrition facts label, the percent value listed for fiber is based on 25 grams per day for a 2,000 calorie diet and 30 grams for a 2,500 calorie diet.

For children older than 3 years, the American Dietetic Association recommends a minimum intake of dietary fiber that is equal to the child's age plus five. For example, an 8-year-old child would aim for 13 grams of fiber each day (8+5=13).

Most Americans average about 15 grams of total fiber per day, which is less than ideal. Although rare, it is possible to get too much fiber as well; if someone has more than 50 or 60 grams a day, nutrient absorption may be impaired.

When increasing fiber intake, do so slowly over days or weeks in order for the body to adapt. Adding fiber too quickly in the diet may result in gas and discomfort, as soluble fiber can be metabolized by gas-forming bacteria in the colon. However, this effect is usually transitory and improves with time as one consistently includes adequate fiber in the diet. It is also important to increase fluids during this process. Getting at least 6-8 cups of liquid each day is a healthy guideline for everyone, especially when increasing fiber intake.

Q: Would you discuss over-the-counter fiber supplements?

Melissa: If you are unable to achieve a desired level of fiber intake via natural food sources or to tolerate fibrous foods, a fiber supplement may be a good option. Food sources of fiber are always the best option for meeting fiber goals. However, fiber supplements have stool-softening and bulking agents designed to have an effect similar to that of natural food fiber. Many supplements contain psyllium mucilloid (e.g., Metamucil®, Konsyl® and Per Diem Fiber®). Psyllium absorbs water in the colon, resulting in bulkier stools. Hemicellulose (Citrucel®) and polycarboxisal (FiberCon®) are other bulking agents. Again, attention to adequate water intake is important when using over-the-counter fiber supplements.

One of the best ways to increase fiber content and natural sources of carbohydrate in the diet is to ensure that your daily eating plan includes two servings of fruit and at least three servings of vegetables. A serving of fruit is a medium-sized fruit, and a serving of vegetables is one cup raw or one-half cup cooked. Experimenting with a wide variety of whole-grain breads and breakfast cereals and regularly eating legumes are other healthy options.

The Education Division at the Palo Alto Medical Foundation (650-853-2960) offers a number of healthy lifestyle classes on cholesterol, diabetes, blood pressure, and weight and stress management. You may also consider seeing a Registered Dietitian for an individual consultation. Call 650-853-2961 for information and an appointment.
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