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Often confused with sweet potatoes, yams rarely appear in American markets, except in cities with large ethnic populations. This thick tuber, grown on tropical vines, is a staple food in Africa, where it originated, and in Indonesia, the Caribbean, China, Korea, and India. Yams are similar in size and shape to sweet potatoes, but contain more natural sugar and have a higher moisture content.
There are more than 150 species of yam, with a wide variety of sizes and shapes. The flesh ranges in color from off-white and yellow to purple and pink.
Scrub yams just before using them, and cook them as you would a potato, either baking, steaming, frying, or boiling and mashing.
Yams, 1 cup (125g) (raw, cubes)
Total Fat: 0.25g
*Excellent source of: Potassium (1,224mg), Vitamin C (25.6mg), and Vitamin B6 (0.44mg)
*Good source of: Thiamine (0.168mg)
*Foods that are an “excellent source” of a particular nutrient provide 20% or more of the Recommended Daily Value, based upon United States Department of Agriculture (USDA) guidelines. Foods that are a “good source” of a particular nutrient provide between 10 and 20% of the USDA Recommended Daily Value. Nutritional information and daily nutritional guidelines may vary in different countries. Please consult the appropriate organization in your country for specific nutritional values and the recommended daily guidelines.
Vitamin C, present in fruits and vegetables, is a powerful antioxidant and anti-inflammatory. This anti-inflammatory activity may influence the development of asthma symptoms. A large preliminary study has shown that young children with asthma experience significantly less wheezing if they eat a diet high in fruits rich in vitamin C.
Carbohydrate food is the most efficient fuel for energy production and can also be stored as glycogen in muscle and liver, functioning as a readily available energy source for prolonged, strenuous exercise. For these reasons, carbohydrates may be the most important nutrient for sports performance. Depending on training intensity and duration, athletes require up to 4.5 grams of carbohydrates per day per pound of body weight or 60 to 70 percent of total dietary calories from carbohydrates, whichever is greater. Including starchy vegetables in the diet is one good way to obtain these carbohydrates.
Many Americans eat insufficient amounts of foods containing vitamin C; the disease caused by vitamin C deficiency, scurvy, causes easy bruising. While very few people actually have scurvy, even minor deficiencies of vitamin C can increase the incidence of bruising. People who experience easy bruising may want to try eating more fruits and vegetables—common dietary sources of vitamin C.
The strong association between increased intake of beta-carotene from food and a reduced risk of lung cancer does not necessarily mean that supplementation with natural beta-carotene supplements would reduce the risk of lung cancer. Dietary beta-carotene may be a marker for diets high in certain fruits and vegetables that contain other anticancer substances that may be responsible for the protective effects. Until more is known, some doctors advise smokers to avoid all forms of beta-carotene supplementation—even natural beta-carotene.
Eating plenty of flavonoid- and vitamin C-rich fruits and vegetables helps to support the structure of capillaries.
Some, but not all, studies have reported that eating more foods rich in beta-carotene or vitamin A was associated with a lower risk of cataracts. Synthetic beta-carotene supplementation has not been found to reduce the risk of cataract formation. It remains unclear whether natural beta-carotene from food or supplements would protect the eye or whether beta-carotene in food is merely a marker for other protective factors in fruits and vegetables high in beta-carotene.
A controlled trial showed that eating a diet high in fruits and vegetables containing folic acid, beta-carotene, and vitamin C effectively lowered homocysteine levels. Healthy people were assigned to either a diet containing a pound of fruits and vegetables per day, or to a diet containing 3 1/2 ounces (99g) of fruits and vegetables per day. After four weeks, those eating the higher amount of fruits and vegetables had an 11 percent lower homocysteine level compared to those eating the lower amount of fruits and vegetables.
Potassium reduces urinary calcium excretion, and people who eat high amounts of dietary potassium appear to be at low risk of forming kidney stones. The best way to increase potassium is to eat fruits and vegetables. The level of potassium in food is much higher than the small amounts found in supplements.
People who eat plenty of fruits and vegetables high in beta-carotene appear to be at lower risk for macular degeneration than people who do not eat these foods. However, another study found no association between age-related macular degeneration and intake of antioxidants, either from the diet, from supplements, or from both combined. More research is needed to reconcile these differences. In the meantime, beta-carotene-rich vegetables continue to be part of a healthful diet.
Multiple sclerosis (MS)
In one survey, researchers gathered information from nearly 400 people (half with MS) over three years. They found that consumption of vegetable protein, fruit juice, and foods rich in vitamin C, thiamine, riboflavin, calcium, and potassium correlated with a decreased MS risk.
Low intake of fruits and vegetables containing beta-carotene, which the body can convert into vitamin A, may contribute to a vitamin A deficiency.
Most dietary studies have found that women receiving high amounts of nutrients from fruits and vegetables have less risk of cervical dysplasia. Protective effects may be especially strong from diets high in dark yellow and orange vegetables (carrots, winter squash, etc.) and tomatoes.
Researchers have found an association between diets low in potassium and increased risk of stroke. However, the association of increasing dietary potassium intake and decreasing stroke mortality only occurred in black men and hypertensive men in one study. Others have found an association between increased risk of stroke and the combination of low dietary potassium plus high salt intake. Increasing dietary potassium has lowered blood pressure in humans, which by itself should reduce the risk of stroke; however, some of the protective effect of potassium appears to extend beyond its ability to lower blood pressure. Maintaining a high potassium intake is best achieved by eating fruits and vegetables.
Health benefits and
concerns for vegetables
Many health benefits and concerns associated with this food are applicable to other vegetables. Read about health benefits and concerns for vegetables for a full description.
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The information presented in VitaminLore is for informational purposes only and was created by a team of U.S. registered dietitians and food experts. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements, making dietary changes, or before making any changes in prescribed medications.