Women's nutrition addresses the dietary requirements of females after they reach adulthood. Nutritional needs change over time due to factors such as menstruation, pregnancy, lactation, menopause, and aging.
A nutritious diet and regular physical activity are part of a healthy lifestyle that promotes health and helps prevent chronic diseases such as type 2 diabetes, heart disease, high blood pressure (hypertension), high cholesterol, osteoporosis, and certain cancers. Certain phases of a woman's life, such as preg-nancy and menopause, have different nutritional requirements.
As a woman ages, changes in the body occur that affect nutritional needs. After age 25, the basal metabolic rate (BMR) begins to decline. Metabolism is the process of the body converting food into energy. When metabolism slows, the body needs fewer calories to function. If calorie intake is not adjusted or any additional calories are not expended through physical activity, the resulting imbalance causes weight gain. Continued weight gain further slows the BMR, reducing overall calorie requirements.
The BMR is based on factors including size and particularly muscle mass. People who are larger or have more muscle mass use more calories than those who are smaller or have less muscle mass. Women have more body fat than men, so they generally require fewer calories than men of the same age and weight. Muscle mass tends to decline with age—after age 30, muscle mass decline occurs at a rate of 3% or more per decade. Failure to exercise muscles can result in a loss of up to 30%–40% of muscle strength by the time a person is 65.
Bone density also decreases with age, starting after age 40. The decline accelerates after menopause, which is when a woman's period ends. Bone loss is accompanied by a loss in bone strength and an increased risk of osteoporosis, a condition described as “brittle bones.” Bone loss leaves older women more vulnerable to bone fractures. Adequate calcium intake during a woman's younger years can help protect against bone loss later in life. Other factors contributing to osteoporosis include physical inactivity and smoking.
The U.S. Department of Agriculture's (USDA) Dietary Guidelines for Americans contains the U.S. federal guidelines for healthy eating. The guidelines are represented by MyPlate, a graphic representation of the general daily recommendations for the five food groups. The graphic is of a plate divided into four sections—on one half are fruits and vegetables and on the other half are grains and proteins. To the side is a small circle representing dairy products.
Some of the MyPlate guidelines include:
The amount of calories required each day depends upon how active a person is, according to the Dietary Guidelines. The USDA provides general calorie recommendations for women based on age and activity level.
Women between the ages of 19 and 30 should consume approximately:
Women between the ages of 31 and 50 should consume approximately:
Women 51 or older should consume:
All dietary calories come from macronutrients—carbohydrates, fats, and proteins. Macronutrients are dietary compounds that provide energy. Proteins and carbohydrates contain four calories per gram, and fat contains nine calories per gram. Alcohol is also considered a macronutrient and contains seven calories per gram. Carbohydrates serve as the primary source of fuel for the body. When food is consumed, the sugars and starches in carbohydrates are used (as glucose) for energy. Excess glucose is stored in the muscles as glycogen. If the glycogen reserves are not used, they are converted to fat, resulting in weight gain.
CARBOHYDRATES. Sources of healthy carbohydrates include vegetables, fruits, legumes, and whole grains. Other carbohydrates include sugars, starches, and fiber.
Soluble fiber is found in many vegetables and fruits. Other sources include legumes, barley, oats, and oat bran. Soluble fiber helps to slow digestion so that a person fills full for a longer period of time. This sense of fullness, known as satiety, helps with appetite control and weight loss. Soluble fiber also helps to decrease cholesterol levels, which lowers the risk for heart disease. Insoluble fiber is found in vegetables such as green beans, wheat and other grains, and the skins of vegetables and fruits. This fiber, which is known as roughage, helps to prevent constipation.
FATS. Because fats contain more calories than protein or carbohydrates, people should choose healthy fats and consume them in limited amounts. Healthier fats include monounsaturated or polyunsaturated fats. These unsaturated fats help to reduce blood cholesterol levels. Saturated fats and trans fats, on the other hand, promote heart disease if consumed in high amounts.
PROTEIN. Protein is the major functional and structural component of every cell in the body. Proteins are composed of amino acids, nine of which cannot be synthesized to meet the body's needs. These amino acids must be obtained from the diet. Food proteins, known as dietary proteins, include meat, eggs, seafood, beans and peas, nuts, seeds, and soy products. The quality of a source of dietary protein depends on its ability to provide the nitrogen and amino acid requirements needed for growth, maintenance, and repair.
Some studies have indicated that regular alcohol consumption may have health benefits, such as a reduced risk of developing heart disease. According to the Mayo Clinic, these benefits may only apply to older adults or those with existing risk factors for heart disease, such as high cholesterol. For younger and middle-aged women, the risks of regular alcohol consumption (in excess of recommendations) could outweigh any potential benefits.
The Mayo Clinic advises women who drink alcohol to talk to their doctors about taking folate (folic acid) supplements to help reduce the risk of breast cancer associated with alcohol use.
RECOMMENDED INTAKES. The recommended dietary reference intakes (DRIs) for adults are that 45%– 65% of daily calories should come from carbohydrates, 10%–35% from protein, and 20%–35% from fat. People should limit intakes of dietary cholesterol, trans fats, and saturated fats. The recommended adequate intake (AI) levels for omega-3 fats are 1.1 grams for women 19 and older (including pregnant women) and 1.3 grams for breastfeeding women. The AI for omega-6 fats is 12 grams for women aged 19–50, 11 grams for women 51 and older, and 13 grams for pregnant or breastfeeding women.
The AI for fiber is 14 grams per 1,000 calories, or 25 grams per day for women. Most people in the United States do not consume enough dietary fiber, and usual intake averages around only 15 grams per day. To meet the recommendations for fiber, women should increase their consumption of beans and peas, vegetables, fruits, and whole grains. Whole grains can vary in fiber content, so consumers should check the nutrition facts label to find out a product's fiber content.
The Dietary Guidelines identify four nutrients of concern that tend to be lacking in the typical American diet, due to low consumption of vegetables, fruits, whole grains, milk and milk products, and seafood. These nutrients are calcium, vitamin D, potassium, and dietary fiber.
CALCIUM AND VITAMIN D. Diets low in calcium and vitamin D may increase the chance of developing osteomalacia and osteoporosis, characterized by weak or brittle bones. Good nutrition and weight-bearing exercise, such as walking, hiking, or climbing stairs, help to build and maintain bones.
Good sources of calcium include low-fat dairy products such as cheese, yogurt, and milk; canned fish with bones, such as salmon and sardines; dark green leafy vegetables; and calcium-fortified foods such as orange juice, bread, and cereal. The recommended intake of calcium for women ages 19–50 is 1,000 mg per day. Pregnant and lactating women need 1,000 mg per day. Women above the age of 50 should consume 1,200 mg of calcium per day.
Women can obtain vitamin D in three ways: from sunlight on the skin, from the diet, and from supplements. Experts recommend a daily intake of 600 IU of vitamin D up to age 70. After age 70, women should increase their uptake to 800 IU daily. This can be obtained from supplements or vitamin D-rich foods such as egg yolks, saltwater fish, liver, and fortified milk. The Institute of Medicine recommends no more than 4,000 IU per day for adults. Doctors may prescribe higher doses for people who are deficient in vitamin D.
POTASSIUM AND SODIUM. Dietary potassium can help lower blood pressure by reducing the adverse effects of sodium. Other possible benefits of a diet rich in potassium include a reduced risk of developing kidney stones and decreased bone loss. The Dietary Guidelines recommend that U.S. adults should consume no more than 2,300 mg of sodium per day. This drops to 1,500 mg per day for people aged 40 or older, people with high blood pressure, and African Americans, who are at higher risk for hypertension. According to the Centers for Disease Control and Prevention, 69% of U.S. adults fall within these categories.
The AI for potassium for adults is 4,700 mg per day. Dietary sources of potassium include bananas, white beans, plain yogurt, baked potatoes, and clams.
Dietary recommendations change throughout a woman's life. Phases that have special nutritional considerations include menstruation, pregnancy, and menopause.
Because of the blood lost during menstruation, iron is an important mineral in a woman's diet. Low iron can result in iron-deficiency anemia, a condition characterized by low red blood cell count. The recommended dietary intake for iron is 15 mg per day for women aged 14–18; this increases to 18 mg for women aged 19–50 and then drops to 8 mg for women 51 and older. Pregnant women require 27 mg of iron daily.
PREGNANCY. Good nutrition is important during pregnancy and breastfeeding, as there is an increased need for calories and for many nutrients. A particularly important nutrient during pregnancy is folic acid, which is one of the B vitamins. Folic acid reduces the chance of having a baby with brain or spinal cord defects. Experts recommend that women of childbearing age consume 400 micrograms (mcg) of folic acid every day. Pregnant women should consume 800 mcg per day. Good sources of folic acid include dark green leafy vegetables, oranges and orange juice, dried beans and peas, and folate-fortified breads and cereals.
Omega-3 fatty acids may play a role in infant visual and cognitive development. The Dietary Guidelines recommend that women who are pregnant or breastfeeding consume 8–12 oz. of a variety of seafood each week. Women should be cautious, as some types of fish— especially tilefish, shark, swordfish, and king mackerel—have high levels of mercury. Women can consult with their physicians if they are unsure about which types of fish are safe to eat. The Mayo Clinic advises women to avoid raw fish and shellfish, particularly oysters and clams, as well as fish caught in polluted water.
Women who may become pregnant or are pregnant should avoid alcohol. After the baby is born, alcohol should not be consumed at all until consistent latch-on and breastfeeding patterns are established. Women should then wait at least four hours after drinking alcohol before breastfeeding.
MENOPAUSE. Perimenopause refers to the time leading up to menopause. This usually occurs when a woman is in her 40s, although it may happen earlier or later. Hormone fluctuations could cause irregular periods and symptoms like hot flashes and night sweats. Menopause occurs when menstruation ceases for 12 consecutive months. After 12 months, a woman is considered post-menopausal.
The Academy of Nutrition and Dietetics recommends that women in their mid- to late 40s reduce their daily calorie intake by 200 calories. Healthy food choices include calcium-rich foods, fruits, and vegetables, which are also sources of fiber. The risk of breast cancer rises by 20% when women gain more than 20 lb. (9.08 kg) after menopause, according to the Academy. That risk goes back down when women lose that weight.
Diets low in calcium, vitamin D, or magnesium or high in caffeine, alcohol, sodium, or protein may increase the chance of developing osteomalacia and osteoporosis. Good nutrition and weight-bearing exercise, such as walking, hiking, or climbing stairs, helps to build strong bones and prevent bone loss.
Women should consult their doctors before beginning a diet or exercise program.
Of the many diseases that may affect women, five have a scientific-based connection to nutrition: iron-deficiency anemia, osteoporosis, heart disease, type 2 diabetes, and some types of cancer.
As women age, the risk of developing chronic disease increases. Women over age 45 who are overweight, physically inactive, and have a family history of diabetes are more likely to develop type 2 diabetes. Maintaining a healthy weight, eating a varied and balanced diet, and engaging in an active lifestyle can reduce this risk.
Women are at a higher risk of developing osteomalacia and osteoporosis than men are. There are many factors that contribute to this disease, including genetics, diet, hormones, age, and lifestyle factors. The disease usually has no symptoms until a fracture occurs.
Breast cancer is the most common type of cancer among American women other than skin cancer. Obese, sedentary women are more likely to develop breast cancer, and dietary factors may possibly play a role in its development. Some studies suggest that excessive fat intake may increase breast cancer risk, either by raising estrogen levels or by altering immune function. Diets that include adequate amounts of fruits, vegetables, and fiber-rich foods may help protect against breast cancer. However, controversy exists as to whether diet is actually a contributing factor. Excessive alcohol consumption may raise the risk of breast cancer in women.
According to the American Heart Association, more than one in three women has cardiovascular disease (CVD), and deaths from CVD in women have exceeded those in males since 1984. There are many forms of heart disease. According to the CDC, risk factors for heart disease include high cholesterol, hypertension, diabetes, obesity, poor diet, alcohol use, and physical inactivity.
Obesity is defined as an abnormal accumulation of body fat. It is usually determined by the body mass index (BMI), a measurement for adults based on height and weight. A BMI of 18.5–24.9 is considered a normal weight, a BMI of 25–29.9 is considered overweight, and a BMI of 30 or higher is considered obese. Waist size is also a measure of health. Abdominal weight, also known as belly fat, places people at risk for conditions such as high blood pressure, type 2 diabetes, and heart disease. A person can have a normal BMI but a high proportion of abdominal fat. A waist measurement of 35 inches (89 cm) or more indicates an unhealthy concentration of belly fat in women.
Obesity is considered an epidemic that affects all age groups in the United States. According to the CDC, 35.7% of adults aged 20 and older were obese in 2009–2010, including almost 41 million women.
See also Dietary guidelines ; Dietary supplements .
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American Cancer Society, 250 Williams St. NW, Atlanta, GA, 30303, (800) 227-2345, http://www.cancer.org .
American Diabetes Association, 1701 North Beauregard St., Alexandria, VA, 22311, (800) DIABETES (342-2383), askADA@diabetes.org, http://www.diabetes.org .
American Heart Association, 7272 Greenville Ave., Dallas, TX, 75231, (800) 242-8721, http://www.americanheart.org .
American Pregnancy Association, 1425 Greenway Dr., Ste. 440, Irving, TX, 75038, (972) 550-0140, Fax: (972) 550-0800, Questions@AmericanPregnancy.org, http://www.americanpregnancy.org .
British Nutrition Foundation, High Holborn House, 52-54 High Holborn, London, UK, WC1V 6RQ, +44 20 7404 6504, Fax: +44 20 7404 6747, email@example.com, http://www.nutrition.org.uk .
Centers for Disease Control and Prevention, 1600 Clifton Rd. NE, Atlanta, GA, 30333, (800) CDC-INFO (232-4636), TTY: (888) 232-6348, firstname.lastname@example.org, http://www.cdc.gov .
Food and Nutrition Information Center, National Agricultural Library, 10301 Baltimore Ave., Rm. 105, Beltsville, MD, 20705, (301) 504-5414, Fax: (301) 504-6409, email@example.com, http://fnic.nal.usda.gov .
National Osteoporosis Foundation, 1150 17th St. NW, Ste. 850, Washington, DC, 20036, (202) 223-2226, (800) 231-4222, Fax: (202) 223-2237, http://www.nof.org .
Office on Women's Health, Department of Health and Human Services, 200 Independence Ave. SW, Rm. 712E, Washington, DC, 20201, (202) 690-7650, Fax: (202) 205-2631, http://www.womenshealth.gov .
U.S. Department of Agriculture, 1400 Independence Ave. SW, Washington, DC, 20250, (202) 720-2791, http://www.usda.gov .
Weight-Control Information Network (WIN), 1 WIN Way, Bethesda, MD, 20892-3665, (202) 828-1025, (877) 946-4627, Fax: (202) 828-1028, win@http://win.niddk.nih.gov, http://win.niddk.nih.gov .
WomenHeart: The National Coalition for Women with Heart Disease, 818 18th St. NW, Ste. 1000, Washington, DC, 20006, (202) 728-7199, Fax: (202) 728-7238, (877) 771-0030, firstname.lastname@example.org, http://womenheart.org .
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Revised by Liz Swain