Sweet Potatoes
Unique Proteins with Potent Antioxidant Effects
Sweet potato contain unique root storage proteins that have been observed to have significant antioxidant capacities. In one study, these proteins had about one-third the antioxidant activity of glutathione-one of the body's most impressive internally produced antioxidants.
Nutrition
This root vegetable qualified as an excellent source of vitamin A (in the form of beta-carotene), a very good source of vitamin C, which are very powerful antioxidants that work in the body to eliminate free radicals. Free radicals are chemicals that damage cells and cell membranes and are associated with the development of conditions like atherosclerosis, diabetic heart disease, and colon cancer. This may explain why beta-carotene and vitamin C have both been shown to be helpful for preventing these conditions.and manganese, and a good source of copper, dietary fiber, vitamin B6, potassium and iron. Since these nutrients are also anti-inflammatory, they can be helpful in reducing the severity of conditions where inflammation plays a role, such as asthma, osteoarthritis, and rheumatoid arthritis.
In addition, sweet potatoes are a good source of vitamin B6, which is needed to convert homocysteine, an interim product created during an important chemical process in cells called methylation, into other benign molecules. Since high homocysteine levels are associated with an increased risk of heart attack and stroke, having a little extra vitamin B6 on hand is a good idea. If you or someone you love is a smoker (STOP IT), or if you are frequently exposed to secondhand smoke, then making vitamin A-rich foods, such as sweet potatoes, part of your healthy way of eating, may save your life, suggests research conducted at Kansas State University.
While studying the relationship between vitamin A, lung inflammation, and emphysema, Richard Baybutt, associate professor of nutrition at Kansas State, made a surprising discovery: a common carcinogen in cigarette smoke, benzo(a)pyrene, induces vitamin A deficiency.
Baybutt's earlier research had shown that laboratory animals fed a vitamin A-deficient diet developed emphysema. His latest animal studies indicate that not only does the benzo(a)pyrene in cigarette smoke cause vitamin A deficiency, but that a diet rich in vitamin A can help counter this effect, thus greatly reducing emphysema.
Baybutt believes vitamin A's protective effects may help explain why some smokers do not develop emphysema. "There are a lot of people who live to be 90 years old and are smokers," he said. "Why? Probably because of their diet…The implications are that those who start smoking at an early age are more likely to become vitamin A deficient and develop complications associated with cancer and emphysema. And if they have a poor diet, forget it." If you or someone you love smokes, or if your work necessitates exposure to second hand smoke, protect yourself by making sure at least one of the World's Healthiest Foods that are rich in vitamin A, such as sweet potatoes, is a daily part of your healthy way of eating.
So, the next time you have the urge for something sweet, how about a thick slice of sweet potato pie? It's one dessert guaranteed to satisfy your whole body, not just your sweet tooth.
Description
Depending upon the variety, of which there are about 400, the skin and flesh of the sweet potato may range from almost white through cream, yellow, orange, and pink to a very deep purple, although white and yellow-orange flesh are most common. Sometimes this root vegetable will be shaped like a potato, being short and blocky with rounded ends, while other times it will be longer with tapered ends.
The intensity of the sweet potato's yellow or orange flesh color is directly correlated to its beta-carotene content. The beta-carotene in orange-fleshed sweet potato, which our bodies can use to produce vitamin A and is therefore called "Pro vitamin A," has been reported to be more bioavailable than that from dark green leafy vegetables. Purple-fleshed sweet potatoes, on the other hand, are a good source of anthocyanins and have the highest antioxidant activity among sweet potato varieties. In one study, the antioxidant activity in purple sweet potato was 3.2 times higher than that of a blueberry variety! Interestingly, the antioxidant activity in sweet potato skin, regardless of its color, is almost three times higher than in the rest of the tissue.
Sweet potatoes are grouped into two different categories depending upon the texture they have when cooked: some are firm, dry, and mealy, while others are soft and moist. In both types, the taste is starchy and sweet with different varieties having different unique tastes.
The moist-fleshed, orange-colored root vegetable that is often thought of as a "yam" is actually a sweet potato. It was given this name after this variety of sweet potato was introduced into the United States in the mid-20th century in order to distinguish it from the white-fleshed sweet potato to which most people were accustomed. The name "yam" was adopted from "nyami," the African word for the root of the Dioscoreae genus of plants that are considered true yams. While there are attempts to distinguish between the two, such as the mandatory labeling by the U.S. Department of Agriculture that the moist-fleshed, orange-colored sweet potatoes that are labeled as "yams" also be accompanied by the label "sweet potato," when most people hear the term "yam," they think of the orange-colored sweet potato as opposed to the true yam, a root vegetable belonging to the Dioscoreae family, which are monocotyledons (have one embryonic seed leaf). Sweet potatoes belong to the Convolvulaceae or morning glory plant family, are dicotyledons (having two embryonic seed leaves) and are known by the scientific name of Ipomoea batatas.
Following are some common names by which sweet potatoes are known in different languages and countries around the world: batata, boniato, camote (Spain); kumar (Peru); kumara (Polynesian); and cilera abana,''protector of the children'' (eastern Africa); kara-imo, ''Chinese potato''(southern Kyushu, Japan); Ubhatata (South Africa); and satsuma-imo,''Japanese potato'' (most of the other parts of Japan). In the United States, "Jewel," "Garnet," and "Beauregard" are among the most popular varieties.
Concerns
Oxalates
Sweet potatoes are among a small number of foods that contain measurable amounts of oxalates, naturally-occurring substances found in plants, animals, and human beings. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems. For this reason, individuals with already existing and untreated kidney or gallbladder problems may want to avoid eating sweet potatoes. Laboratory studies have shown that oxalates may also interfere with absorption of calcium from the body. Yet, in every peer-reviewed research study we've seen, the ability of oxalates to lower calcium absorption is relatively small and definitely does not outweigh the ability of oxalate-containing foods to contribute calcium to the meal plan. If your digestive tract is healthy, and you do a good job of chewing and relaxing while you enjoy your meals, you will get significant benefits - including absorption of calcium - from calcium-rich foods plant foods that also contain oxalic acid. Ordinarily, a health care practitioner would not discourage a person focused on ensuring that they are meeting their calcium requirements from eating these nutrient-rich foods because of their oxalate content.
Yams
Protection Against Cardiovascular Disease
Yams are a good source of vitamin B6. Vitamin B6 is needed by the body to break down a substance called homocysteine, which can directly damage blood vessel walls. Individuals who suffer a heart attack despite having normal or even low cholesterol levels are often found to have high levels of homocysteine. Since high homocysteine levels are significantly associated with increased risk of heart attack and stroke, having a good supply of vitamin B6 on hand makes a great deal of sense. High intakes of vitamin B6 have also been shown to reduce the risk of heart disease.
Yams are a good source of potassium, a mineral that helps to control blood pressure. Since many people not only do not eat enough fruits and vegetables, but also consume high amounts of sodium as salt is frequently added to processed foods, they may be deficient in potassium. Low intake of potassium-rich foods, especially when coupled with a high intake of sodium, can lead to hypertension. In the Dietary Approaches to Stop Hypertension (DASH) study, one group ate servings of fruits and vegetables in place of snacks and sweets, and also ate low-fat dairy food. This diet delivered more potassium, magnesium and calcium. Another group ate a "usual" diet low in fruits and vegetables with a fat content like that found in the average American Diet. After eight weeks, the group that ate the enhanced diet lowered their blood pressure by an average of 5.5 points (systolic) over 3.0 points (diastolic). Dioscorin, a storage protein contained in yam, may also be of benefit to certain individuals with hypertension. Preliminary research suggests that dioscorin can inhibit angiotensin converting enzyme, which would therefore lead to increased kidney blood flow and reduced blood pressure.
A Look at Yam, Diosgenin, and Menopausal Symptoms
Many consumers have found products in the marketplace that promote wild yam or wild yam extracts as substances that can help provide a natural alternative to hormonal replacement in women who have reached the age of menopause. Many of these products are provided in the form of creams that can be topically applied. Even though the food itself is not usually promoted by natural products companies, these yam-containing products have sparked interest in the relationship between yam and menopause. Yams do contain some unique substances called steroidal saponins, and among these substances are chemicals called diosgenins. Because of similiarities between diosgenin and progesterone, questions were initially raised about the ability of our body to convert diosgenin into progesterone, but research has shown that the answer here is clearly no. Diosgenin does, however, have an impact on hormonal patterns in studies involving animals, and may be helpful in lowering risk of osteoporosis, although we don't as yet have any human studies in this area.
Wild yam also has some history of traditional use in herbal medicine, especially Chinese herbal medicine, as a botanical that can affect organ system function. While the focus here has been on kidney function, wild yam (or Chinese yam) has also been used to support the female endocrine system. For example, there has been traditional use of this root in conjunction with lactation. We've only seen one high-quality, peer-reviewed research study in which women were actually given wild yam (in the form of a topical cream) to determine the impact of this plant on menopausal symptoms. Although this research showed some very limited benefits from the wild yam cream-and no side effects-none of the symptom changes were statistically significant. In summary, we'd say that there's no research evidence to support the claim that yam has special benefits when it comes to menopause, but that more research is needed in this area because there is a clear connection between yam, diosgenin, and endocrine function that is not yet understood.
We'd also like to add some information about yam and vitamin B6. Vitamin B6 has been an especially popular supplement with respect to premenstrual syndrome (PMS) in women, especially in conjunction with the depression that can be triggered by PMS. Some companies have also advocated the use of this vitamin for menopausal symptoms. One cup of baked cubed yam contains 15.5% of the Daily Value for B6, and we rank yam as a "good" source of vitamin B6 for this reason. In research studies, however, the dose of vitamin B6 required for help with PMS depression is about 50-100 milligrams-many, many times the Daily Value level of 2.0 milligrams. So if you're a woman, even though yam might be a food well-worth including in your meal plan in conjunction with PMS, the amount of vitamin B6 that you'd be getting from this food would be insufficient (by itself) to reach the therapeutic level shown to be helpful in research studies.
Blood Sugar and Weight Control
Yams' complex carbohydrates and fiber deliver the goods gradually, slowing the rate at which their sugars are released and absorbed into the bloodstream. In addition, because they're rich in fiber, yams fill you up without filling out your hips and waistline. And one more benefit, yams are a good source of manganese, a trace mineral that helps with carbohydrate metabolism and is a cofactor in a number of enzymes important in energy production and antioxidant defenses. You've just got to hand it to Mother Nature; when She brings forth a food, She makes sure it integrates everything needed to contribute to your health and vitality.
Description
Yams are members of the Dioscoreae family. Depending upon the yam variety, of which there are about 200, its flesh may be of varying colors including white, ivory, yellow or purple while its thick skin may either be white, pink or brownish-black. Their shape is long and cylindrical (oftentimes having offshoots referred to as "toes") while their exterior texture is rough and scaly. Yams have a very starchy and slippery texture and when cooked, will either be creamy or firm, depending upon the variety. Their taste is earthy and hardy, with most varieties having minimal, if any, sweetness. Specific types of yams include Dioscorea alata (Hawaiian yam), Dioscorea batatas (korean yam) and Dioscorea esculenta (sweet yam).
Chances are this does not sound like the description of the "yams" that you had for Thanksgiving dinner. That is because most of the vegetables that are labeled "yams" in the United States are really orange-colored sweet potatoes. When the moist-fleshed orange-colored sweet potato was introduced into the United States in the mid-20th century, producers wanted to distinguish it from the white-fleshed sweet potato that most people were used to. They adopted the word "yam" from "nyami", the African word for the root of the Dioscoreae genus of plants. While there are attempts to distinguish between the two, such as the U.S. Department of Agriculture's labeling requirement that the moist-fleshed, orange-colored sweet potatoes that are labeled as "yams" also be accompanied by the label "sweet potato", for many people this does not help to clarify the distinction between the two very different root vegetables. Yet, once you experience the distinct taste and texture of the real yam you will definitely know the difference, appreciating each of these root vegetables for their unique qualities.
Individual Concerns
Yam is not a commonly allergenic food, is not known to contain measurable amounts of goitrogens, oxalates, or purines, and is also not included in the Environmental Working Group's 2009 report "Shopper's Guide to Pesticides" as one of the 12 foods most frequently containing pesticide residues.
So, if you are still reading I will put in my two-cents. It is my opinion that in the end the benefits of yams and their slow release of sugar out way the benefits of sweet potatoes and their immediate effect on insulin. When you spike your insulin levels with foods that immediately release its sugar you promote fat retention. And what is the point of eating something that may have one benefit but can potentially cause a series of other issues. As always I believe that you need to way the pros and cons of anything, sorry Thomas Gray, but ignorance is not bliss, and then make an informed decision I also follow the idea that if you can't eat it raw, you probably shouldn't be eating it all. I hope this helps answer some questions.
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