context: No one likes to think -- let alone talk -- about constipation, but most everyone has it at one time or another. More than 40 million people in the U. S. have it pretty often. So if you're dealing with tummy troubles, you're not alone. Most of the time it doesn't last long, and simple changes can help your digestive system run smoothly again. To understand how to prevent constipation, it helps to know what causes it. As food passes through your colon, your body absorbs the water from it, and what's left forms into stool. Your muscles move it through the colon to the rectum, where you pass it. When this movement slows down, your colon draws too much water. Stools get dry and hard to pass, causing constipation. The problem often happens because of a low-fiber or high-fat diet, lack of exercise, and not drinking enough fluids. Certain medications, not going when you feel the urge, laxative abuse, and pregnancy can also lead to constipation. If your bowel habits get sluggish, you don't have to rush out to buy a laxative. Most people don't need them for mild constipation. Instead, look at your diet. Are you getting enough fiber? Fiber is the part of plant foods that the body can't break down. When you eat foods that have a lot of it, the extra bulk helps keep stools soft and speeds digestion. All plant foods, including fruits, vegetables, whole grains, and beans, have fiber. The Academy of Nutrition and Dietetics recommends 25 grams per day for women and up to 38 grams for men. After age 50, we need less fiber -- about 21 grams for women and 30 grams for men. Unfortunately, most of us only get about 15 grams per day, which may help explain why so many people get constipated. Examples of high-fiber foods include: 1/2 cup navy beans: 9.5 grams 1 small pear: 4.4 grams 1/4 cup dates: 3.6 grams 1 medium apple: 3.3 grams 1 medium sweet potato: 4.8 grams Simple changes can improve your diet and help relieve constipation: Add veggies. You don't have to count grams of fiber to get the amount you need. Instead, aim to eat 2 cups of fruit and 2 1/2 cups of vegetables every day. Make sandwiches with roasted veggies, add a salad instead of fries to your meal, buy pre-cut vegetables to snack on with low-fat dip, keep the fruit bowl full for a handy and healthy snack, and add chopped, dried fruit to oatmeal and cereal. Go for grains. Replace white bread, white rice, and regular pasta with whole-grain bread, whole wheat pasta, and brown rice. Eat more whole oats, multigrain cereals, and whole wheat crackers -- but be sure to choose low-fat and low-sugar options. Snack on air-popped popcorn instead of chips. When you buy cereal, choose brands that have at least 5 grams of fiber per serving. Bulk up on beans. Replace meat with a bean or legume dish at least once or twice a week. Add cooked beans to salads, and try bean soups and stews as main courses. Add fiber gradually. Make changes slowly over the course of a week or so -- if you up fiber too quickly, you could end up feeling bloated and gassy. Be patient -- it may take time for your body to adjust. Consider a fiber supplement. If you have trouble getting enough fiber in your diet, a supplement might help. Also called bulk-forming laxatives, they're generally safe. Just be sure to talk with your doctor before you use them as they can make some medications not work as well. Stay hydrated. If you add more fiber to your diet either with food or supplements, be sure to drink more fluids, too. Choose low or no-calorie beverages -- sugary soda and fruit drinks will add extra calories you don't need. Exercise not only keeps you fit, it may help you stay regular. It can help food move more quickly through your colon. It's not always easy to find time to be active, but try these tips: Start exercising about 20 minutes, 3 days a week, and build up to at least 30 minutes on five or more days of the week. Always check with your doctor before you start any type of fitness plan. Short on time? Break up activity throughout the day -- three 10-minute walks count as much as one 30-minute workout. Most of the time, healthy changes to your diet and exercise habits will smooth out any digestive woes. But if you've tried these tips for 3 weeks and haven't noticed a change, talk with your doctor. She may suggest that you take a laxative for a few days to help retrain your system. You should also call your doctor right away if you notice blood in your stool, have belly pain, or lose weight without trying.