3.5

Health Effects of Starches and Dietary Fibers

• Carbohydrate-rich foods include whole grains, vegetables, legumes, and fruit.

• Diets emphasizing whole grains, vegetables, legumes, and fruit are naturally low in harmful fats and high in dietary fiber, vitamins, minerals, and beneficial phytochemicals.

• Diets rich in starches and dietary fibers provide protective health benefits and assist in reducing the risks of several chronic conditions:

  • Obesity

  • Cancer (including certain specific types)

  • Cardiovascular disease and coronary heart disease

  • Diabetes

  • Dental caries

  • Gastrointestinal disorders

  • Malnutrition

• Diets abundant in dietary fiber support weight management efforts.

Recommended Intakes for Carbohydrates and Dietary Fiber

• Dietary Reference Intakes (DRI) Recommendations:

  • Carbohydrates should contribute between $45\%$ and $65\%$ of daily energy requirements.

  • For a person consuming a $2000\,kcal$ daily diet, carbohydrates should provide $900\text{ to } 1300\,kcal$, equivalent to $225\text{ to } 325\,g$ of carbohydrate per day.

  • Recommended Dietary Allowance (RDA) for carbohydrate is set at $130\,g/day$, based on the average minimum amount of glucose needed by the human brain.

• Food and Drug Administration (FDA) Daily Values (DV):

  • Total carbohydrate Daily Value on food labels is set at $275\,g/day$ for a $2000\,kcal$ intake, based on a guideline of $55\%$ of daily energy intake.

  • Dietary fiber Daily Value is set at $28\,g$ for a $2000\,kcal$ daily intake.

  • This fiber Daily Value is derived from the DRI recommendation of $14\,g$ per $1000\,kcal$ intake, which equals roughly $25\text{ to } 35\,g$ of dietary fiber daily.

  • The usual daily intake of dietary fiber in the United States is nearly two times lower than these recommended levels.

• World Health Organization (WHO) Guidance:

  • Sets an explicit upper limit for dietary fiber intake at $40\,g/day$.

Potential Risks and Considerations of Excessive Fiber

• Inadequate Energy and Nutrient Intake:

  • High-fiber, bulky diets can prevent individuals with marginal food intakes from consuming enough physical volume of food to meet overall energy or nutrient requirements.

  • Particularly vulnerable populations include malnourished individuals, older adults, and young children strictly following all-plant (vegan) diets.

• Dehydration Risk:

  • Fibers carry water out of the body, which can increase the risk of dehydration.

  • Recommendation: Individuals adding fiber to their diet should consume an extra 1 to 2 glasses of water alongside the fiber.

• Athletic Considerations:

  • Athletes should avoid consuming bulky, fiber-rich foods immediately prior to competition to prevent digestive discomfort.

Dietary Fiber Sources in Selected Foods

• Grains:

  • Whole-grain products provide $2\text{ to } 3\,g$ or more of fiber per serving.

  • $1\text{ slice}$ of whole-wheat, pumpernickel, or rye bread provides $2\,g$ of fiber.

  • $1\,oz$ of ready-to-eat cereal ($100\%$ bran cereals contain $10\,g$ or more of fiber).

  • $\frac{1}{2}\,c$ of cooked barley, bulgur, grits, or oatmeal provides $2\text{ to } 3\,g$ of fiber.

  • Tips to increase fiber: Choose whole-grain breads containing $\ge 3\,g$ of fiber per serving and whole-grain cereals containing $\ge 5\,g$ of fiber per serving.

• Vegetables:

  • Most vegetables contain $2\text{ to } 3\,g$ of fiber per serving.

  • $1\,c$ raw bean sprouts.

  • $\frac{1}{2}\,c$ cooked broccoli, brussels sprouts, cabbage, carrots, cauliflower, collards, corn, eggplant, green beans, green peas, kale, mushrooms, okra, parsnips, potatoes, pumpkin, spinach, sweet potatoes, swiss chard, or winter squash.

  • $\frac{1}{2}\,c$ chopped raw carrots or peppers.

  • Tips to increase fiber: Eat raw vegetables and consume vegetables such as potatoes and zucchini with their skins intact.

• Fruit:

  • Fresh, frozen, and dried fruits provide approximately $2\,g$ of fiber per serving.

  • $1\text{ medium}$ apple, banana, kiwi, nectarine, orange, or pear.

  • $\frac{1}{2}\,c$ applesauce, blackberries, blueberries, raspberries, or strawberries.

  • Fruit juices contain very little fiber.

  • Tips to increase fiber: Eat fresh and dried fruits as snacks and eat fruits such as apples and pears with their skins intact.

• Legumes and Nuts:

  • Many legumes provide approximately $8\,g$ of fiber per serving ($\frac{1}{2}\,c$ cooked baked beans, black beans, black-eyed peas, kidney beans, navy beans, or pinto beans).

  • Some legumes provide approximately $5\,g$ of fiber per serving ($\frac{1}{2}\,c$ cooked garbanzo beans, great northern beans, lentils, lima beans, or split peas).

  • Most nuts and seeds provide $1\text{ to } 3\,g$ of fiber per serving ($1\,oz$ almonds, cashews, hazelnuts, peanuts, pecans, pumpkin seeds, or sunflower seeds).

  • Tips to increase fiber: Add legumes to soups, salads, and casseroles; substitute plant sources of protein (legumes) for animal protein sources (meats and cheeses) to boost fiber while reducing fat.

Carbohydrate Contributions across Food Groups

• Grains:

  • Provide approximately $15\,g$ of carbohydrate per ounce equivalent, primarily as starch.

  • Portions equal to $1\,oz\text{ equivalent}$: $1\text{ slice}$ whole-wheat bread, $\frac{1}{2}$ English muffin or bagel, $1$ 6-inch tortilla, or $\frac{1}{2}\,c$ of rice, pasta, or cooked cereal.

  • Note: Snack crackers and baked goods (biscuits, croissants, muffins) often contain added sugars, solid fats, and sodium. At least half of all grains chosen should be whole-grain products.

• Vegetables:

  • Starchy vegetables: $1\text{ small}$ white or sweet potato, or $\frac{1}{2}\,c$ cooked dry beans, corn, peas, plantain, or winter squash provides $15\,g$ of carbohydrate (a mixture of starch and sugars).

  • Nonstarchy vegetables: $\frac{1}{2}\,c$ carrots, okra, onions, tomatoes, cooked greens, or most other nonstarchy vegetables, or $1\,c$ salad greens provides about $5\,g$ of carbohydrate (a mixture of starch and sugars), alongside a little protein, fiber, and no fat.

• Fruit:

  • A $\frac{1}{2}\,c\text{ equivalent}$ delivers an average of $15\,g$ of carbohydrate, mainly as natural sugars (including fructose).

  • Portions equal to $\frac{1}{2}\,c\text{ equivalent}$: $\frac{1}{2}\,c$ juice; $1\text{ small}$ banana, apple, or orange; $\frac{1}{2}\,c$ canned or fresh fruit; or $\frac{1}{4}\,c$ dried fruit.

  • Limit: No more than $\frac{1}{2}$ of total daily fruit intake should come from juice. Except for avocado (which is high in fat), fruit contains negligible amounts of fat and protein.

• Dairy Products:

  • $1\,c$ of milk or yogurt (or equivalent: $1\,c$ buttermilk, $\frac{1}{3}\,c$ dry milk powder, or $\frac{1}{2}\,c$ evaporated milk) provides $12\,g$ of carbohydrate, along with high-quality protein, vitamins, and minerals.

  • Cottage cheese provides about $6\,g$ of carbohydrate per cup; most other cheeses contain little or no carbohydrate.

  • Calcium-fortified soy beverages provide comparable carbohydrate amounts to milk.

  • Cream and butter contain little to no carbohydrate and are classified as solid fats.

• Protein Foods:

  • Most foods in this group contain almost no carbohydrate.

  • Exceptions: Nuts (provide small amounts of starch and fiber along with fat) and dry beans ($\frac{1}{2}\,c$ of beans provides $15\,g$ of carbohydrate and up to $8\,g$ of dietary fiber).

Food Labels and Authorized FDA Health Claims

• Food Label Metrics:

  • Labels report total carbohydrate in grams per serving, which encompasses starch, dietary fibers, total sugars, and added sugars.

  • Grams of fiber, total sugars, and added sugars are listed separately.

  • Starch content can be calculated using the formula:     $\text{Starch (g)} = \text{Total Carbohydrate (g)} - \left(\text{Dietary Fiber (g)} + \text{Sugars (g)}\right)$

  • Total carbohydrate and dietary fiber are reported as percent Daily Values ($\%\text{ DV}$) based on a $2000\,kcal$ diet; no Daily Value exists for sugars.

• Authorized FDA Health Claims:

  1. "Fiber-containing grain products, fruits, and vegetables and reduced risk of cancer."

  2. "Fruits, vegetables, and grain products that contain fiber, and reduced risk of coronary heart disease."

  3. "Soluble fiber from whole oats and from psyllium seed husk and reduced risk of coronary heart disease."

  4. "Whole grains and reduced risk of heart disease and certain cancers."

Review Questions and Assessment

• Question 1: Which of the following foods is not a good source of carbohydrates?

  • Options: Plain yogurt, Steak, Brown rice, Green peas

  • Answer: Steak

• Question 2: Disaccharides include:

  • Options: Lactose, starch, and glycogen; Starch, glycogen, and fiber; Galactose, maltose, and glycogen; Sucrose, lactose, and maltose

  • Answer: Sucrose, lactose, and maltose

• Question 3: The chief energy source of the body is:

  • Options: Sucrose, Starch, Glucose, Fructose

  • Answer: Glucose

• Question 4: The primary form of stored glucose in animals is:

  • Options: Glycogen, Cellulose, Starch, Lactose

  • Answer: Glycogen

• Question 5: The polysaccharide that is stored in plants is:

  • Options: Cellulose, Starch, Glycogen, Lactose

  • Answer: Starch

• Question 6: Which of the following terms on a food label may denote sugar?

  • Options: a. Corn syrup, b. Aspartame, c. Xylitol, d. Cellulose

  • Answer: a. Corn syrup

• Question 7: The two types of alternative sweeteners are:

  • Options: a. saccharin and cyclamate, b. sugar alcohols and nonnutritive sweeteners, c. sorbitol and xylitol, d. fructose

  • Answer: b. sugar alcohols and nonnutritive sweeteners