What Are Yams?
Yams are tuber vegetables (the type that grows mostly underground) native to Africa and Asia. There are over 600 species of yam, but only 15-20 are edible. Sweet potatoes are often mistaken for yams and may be mislabeled as yams in U.S. grocery stores. It's often hard to find true yams in the U.S. outside of international markets.
Yams have a long history of being used in traditional medicine in their native areas.
Yams vs. Sweet Potatoes
Yams and sweet potatoes are not the same vegetable. Although both grow underground, they come from different plants.
Yams are starchier, drier, and less sweet than sweet potatoes. Some varieties of yam can grow up to 130 pounds, in stark contrast to much smaller sweet potatoes. Typically, yams have a tough, scaly skin, while sweet potatoes have smooth skin.
True yams have skin that looks something like tree bark. Their flesh can be white, yellow, reddish, or purple.
Different varieties of sweet potatoes have white, red, purple, brown, or yellow skin, with flesh that can be yellow, white, or reddish orange. Louisiana and North Carolina produce most of the U.S. supply of sweet potatoes. In grocery stores, sweet potatoes are labeled as either firm or soft. Firm sweet potatoes usually have thin skins and thick flesh and remain firm when cooked. Soft sweet potatoes soften when cooked and are often mislabeled as yams in grocery stores.
Types of Yams
There are many varieties of yam, including:
- African white yams. They are also known as Guinea or Ghana yams. They've been grown in West Africa since 5000 B.C. They're the most commonly eaten yams in Africa.
- Chinese yams. This species of yam is native to China. This species can grow in more temperate climates than other yams. Unlike other types of yams, Chinese yams are non-toxic when eaten raw.
- Cushcush yams. Native to the Caribbean, they are popular for their flavor. They're commonly eaten in South America and the West Indies.
- Purple yams (ube). Also called ube, they are native to Africa and Asia and are most commonly used in Asian cuisine. They grow best in tropical and subtropical regions and are a staple in tropical countries. They contain high levels of antioxidants, substances found in food that fight harmful molecules in your body. Their real nutritional power comes from anthocyanin, pigments that have antioxidant properties.
Yams are rich in vitamins and minerals and are a nutritious food staple in many places outside the U.S.
They have many other reported health benefits, though most of the research on this has been on compounds extracted from the yam root. Research is in its early stages. But it has looked at these possible benefits:
May prevent and ease arthritis symptoms
Wild yam root contains diosgenin, which has been shown to limit the progression of both osteoporosis arthritis and rheumatoid arthritis.
In one study, mice who were given wild yam extract daily for 90 days showed a drop in inflammation and, at higher doses, pain levels. We need much more research to determine whether it might have these same effects in humans.
May reduce cholesterol
When diosgenin taken from wild yam root was given to mice for 4 weeks, it lowered both their overall cholesterol levels and their LDL (bad) cholesterol levels. Researchers say their results suggest that diosgenin could lower body weight and cholesterol levels. But human studies are still needed.
May improve hormone balance
Scientists can use the diosgenin in yams to produce estrogen, progesterone, cortisone, and other hormones for medical use.
In alternative medicine, yam cream is often used in place of estrogen cream to relieve symptoms of menopause. Women are sometimes advised to eat yams to help balance their hormones, and people with hormone-related conditions are discouraged from using yams medicinally.
But studies seem to disprove this usage. The human body doesn't seem to be capable of converting diosgenin into hormones. We need more research, but there's no evidence that using yams to treat menopause, PMS, infertility, and low libido is effective.
Nutrients per serving
Yam nutrition per a 5-inch yam:
- Calories: 112
- Fat: 0 grams
- Cholesterol: 0 grams
- Sodium: 4 grams
- Carbohydrates: 26 grams
- Fiber: 4 grams
- Protein: 2 grams
A single yam packs a whopping 369% of your daily vitamin A requirement. Yam vitamins and minerals also include vitamin C, calcium, and iron.
Things to watch out for
Yams must be peeled and cooked before eating. Many types contain natural toxins that could make you ill.
People with hormone-related health issues like endometriosis and uterine fibroids or anyone using estradiol-based birth control or hormone therapy should avoid yam-based medicines or large quantities of yams.
How to Prepare Yams
When shopping, you may see sweet potatoes marketed as yams. To be sure you're buying the right thing, look for a long, tapered shape and a skin that looks more like bark than potato skin.
True yams have a very neutral flavor and tough flesh. Like potatoes, they can be baked, boiled, or fried. They also make a nice addition to soups and stews. You can prepare purple yam like you do other yams. Try including cooked purple yams include them in smoothies for color. Ube can also be turned into a powder or paste, which is commonly used to color sweet pastries, cakes, and other baked goods.