Good fats for better fertility

Once upon a time, and not that long ago, fat was a four-letter word. Diet and nutrition gurus told us (and some still tell us) to cut back on fat whenever and wherever possible. Millions of Americans have dutifully followed that advice. Guided by the low-fat mantra, we tossed out salad dressings and mayonnaise made with olive oil or canola oil in favor of fat-free versions made with extra sugar. We replaced other fats in the diet with carbohydrates, usually the rapidly digested ones in white flour, potatoes, white rice, and sugar. This purge didn’t make us any healthier. It had no effect on heart disease, its intended target. And it may have contributed to the epidemic of obesity sweeping the country.

The big problem with the low-fat approach is that not all fats are bad. Let me say that again, because it runs against what we’ve been hearing for years: Not. All. Fats. Are. Bad. In fact, some fats are downright good for you. This good fat–bad fat dichotomy applies to fertility, too. Some types of fat can help you get pregnant, others get in the way:

• Artery-clogging trans fats contribute to infertility.
• Saturated fat has little effect on fertility, but isn’t so hot for your heart.
• Unsaturated fats are good for fertility, and they’re important for pregnancy, a baby’s healthy development, and long-term heart health.

Out with the bad

Trans fat, the “stealth” fat found in many foods, harms the body in a variety of ways. It boosts the amount of artery-clogging low-density lipoprotein (LDL, or bad cholesterol) in circulation, depresses the amount of protective high-density lipoprotein (HDL, or good cholesterol), promotes low-grade inflammation, and increases the tendency of blood to form clots inside blood vessels. Trans fats are so bad for the heart that eliminating them from the food supply could prevent tens of thousands of heart attacks, strokes, and other cardiovascular events each year in the United States alone. Trans fats are just as harmful to reproduction. In the Nurses’ Health Study, the participants who ate the most trans fats were the most likely to have developed ovulatory infertility. An effect was seen at the fairly low level of about four grams a day, an amount you can easily exceed with a small order of fast-food fries.

The Institute of Medicine says there’s no safe level of trans fats, and recommends getting less than two grams a day. Foods that contain trans fats include solid margarines, vegetable shortening, some commercial baked goods, and some fast foods. Until 2006, it was tough to tell if a food contained trans fat because it wasn’t listed on food labels along with saturated fat and cholesterol. Today, food labels must carry information about trans fats (see figure). This change has food makers scrambling to find trans-free fats for their products.

A loophole in the law lets food companies say “no trans fat” on the package and list zero trans fat on the label as long as the food contains less than 0.5 grams of per serving. So if you’re serious about clearing trans fats from your diet, you need to squint at food labels’ fine print, where the ingredients are listed. If “partially hydrogenated vegetable oil” or “vegetable shortening” appears in the list, the food contains some trans fat.

Detecting trans fats in a restaurants isn’t as easy, since they don’t have to provide nutrition information about the food they serve. You’re in luck if you live in New York City or Boston, which have banned restaurants from using oils containing trans fats. California is set to phase out trans fats by 2011. Other cities and states are certain to follow suit. One good strategy is avoiding deep-fried foods when eating out, since many restaurants still use partially hydrogenated vegetable oils in their fryers. A KFC Chicken Pot Pie, for example, has 14 grams of trans fat. A Sausage, Egg, and Cheese Biscuit with a large order of hash browns at Burger King gives you 18 grams, nearly 10 times the daily healthy limit. Other examples are here.

Moderation in the middle

Saturated fats aren’t across-the-board bad for you like trans fats are. A healthy diet can include some saturated fat. Just don’t overdo it.

In the Nurses’ Health Study, women whose diets included a lot of saturated fat were no more likely to have had ovulatory infertility as women whose diets were low in saturated fat. That isn’t a green light to chow down on foods rich in saturated fat. It strongly influences cholesterol levels, and thus heart health. To stay strong for the baby you hope to be carrying—and the grandchildren you may someday have—go easy on saturated fats. For someone who takes in 2,000 calories a day, that means keeping saturated fat intake under 17 grams. That’s the amount in a fast-food cheeseburger, a three-ounce sirloin steak, or a half slice of a Cheesecake Factory Chocolate Mousse cheesecake.

In with the good

Two fat families—the monounsaturated and polyunsaturated fats—are essential for good health. They’re to be embraced, not avoided. That’s doubly true for the group of unsaturated fats known as omega-3 fats. They are especially important for fertility, pregnancy, a baby’s healthy development, and long-term heart health.

Monounsaturated and polyunsaturated fats benefit the body in many ways. They lower levels of harmful LDL and increase protective HDL. Monounsaturated fats improve the body’s sensitivity to insulin and ease inflammation. Omega-3 polyunsaturated fats are an important part of cell membranes, and so help regulate what goes in and out of cells. They provide the body with the raw material for hormones that regulate blood clotting, the contraction and relaxation of artery walls, and inflammation. Babies need omega-3 fats to make connections between nerves, both in the womb and after birth. Later in life, omega-3 fats help the heart beat steadily and not lapse into erratic and potentially deadly rhythms.

Good sources of monounsaturated fats are olive oil, peanut oil, canola oil, avocados, nuts such as cashews and almonds, and seeds such as sesame and pumpkin seeds. Good sources of polyunsaturated fats include vegetable oils, especially corn, soybean, and safflower oils; soybeans and other beans; and walnuts. Make it a point to get some omega-3 fats every day. Good sources of these include fatty fish such as tuna, salmon, herring, and anchovies. (In a separate column I’ll try to clear up the confusion about eating fish.) Plants that are good sources of omega-3s include chia seeds (sold as Salvia), flax seeds and flaxseed oil, walnuts and walnut oil.

More detailed information on the health effects of fats in food are available from the Harvard School of Public Health’s NutritionSource.

Next up: Slow carbs for fertility, not no carbsÂ

How Diet Affects Fertility

You’ve probably been hearing for years that what you eat and how you live affect the health of your heart and blood vessels, your chances of developing certain kinds of cancer, the strength of your bones, and more. What about fertility—can what you eat help you get pregnant? It certainly makes sense. After all, the reproductive system is subject to the same influences as the circulatory system, nervous system, and others.

Farmers, ranchers, and animal scientists know a fair amount about how nutrition affects fertility in cows, pigs, sheep, chickens, and other commercially important animals. But until recently, fertility experts knew next to nothing about whether food and fertility are linked in humans. That hasn’t stopped folks from offering advice on what to eat to get pregnant. There are a few infertility diet books in circulation, and the Internet is rife with dietary advice for couples trying to get pregnant. But their recommendations—eat oysters, yams, kelp, and garlic; go organic; stop drinking coffee and alcohol—are scatter-shot approaches based on limited information.

The first systematic study of diet, lifestyle, and fertility has revealed several common-sense strategies, and at least one surprising approach, that can help women avoid ovulatory infertility. This type of infertility stems from trouble making mature eggs or releasing eggs at the right time. It is the single most common cause of infertility in America today.

This work is part of the landmark Nurses’ Health Study, the grandmother of research into women’s health. It is based on information supplied by nearly 19,000 women who were trying to get pregnant at one time or another over an eight-year period. The results were initially published in respected, peer-reviewed medical journals such as the American Journal of Obstetrics and Gynecology, Human Reproduction, and Fertility & Sterility. Rather than have this information languish in medical journals, we decided to get it to the people who need it the most—women and couples having trouble getting pregnant. So I helped researchers Jorge Chavarro and Walter Willett, both of the Harvard School of Public Health, compile the findings, translate them from science speak, and add some recipes. The end result was The Fertility Diet (McGraw-Hill, 2007), which offers a natural way to boost ovulation and improve the odds of getting pregnant.

The plan described in The Fertility Diet doesn’t guarantee a pregnancy any more than in vitro fertilization or other forms of assisted reproduction. But it helps restore the balance of hormones essential for reproduction provides a nutritionally receptive environment for conception and the survival of a fertilized egg. The Fertility Diet focuses on:

• avoiding harmful fats and choosing healthful ones
• switching to whole grains and other slowly digested carbohydrates
• eating more vegetable protein, like beans and nuts, and less animal protein
• taking a multi-vitamin that contains folic acid and other B vitamins, and getting plenty of iron from fruits, vegetables, beans and supplements (not from red meat)
• picking the right beverages
• getting into the “fertility zone” for weight and exercise
• and for women who drink milk or eat dairy foods, choosing the best ones

In the Nurses’ Health Study, women who said their diets or lifestyles included five or more of the ten steps described in The Fertility Diet were 84% less likely to have had ovulatory infertility as women who didn’t practice any of them.

The steps we describe are virtually free, available to everyone, and have no negative side effects. They work for women who have neverf had a child as well as for those experiencing secondary infertility. Best of all, they set the stage for a healthy pregnancy and form the foundation of a healthy eating strategy for motherhood and beyond. That’s a winning combination no matter how you look at it.

I’ll outline the plan in installments that focus on different parts of a fertility boosting plan, from fats and carbs to beverages and exercise. First up: Fats and fertility.