Prof. Raphael Nyarkotey Obu

One study by (Chandrasekara and Kumar, 2016) explained that yams (Dioscorea) are a type of tuber vegetable that originated in Asia, Africa, and the Caribbean. About 95% of yams today are grown in Africa. History has it that yams got their name from the Fulani (a language spoken in Guinea, West Africa) word nyami, which means “to eat.”

Yams come in white, yellow, purple, or pink flesh. In Ghana, there are many varieties of white yam, but the most important ones include Puna, Lariboko, Denteh (Punjo), Asana, and Araba.

The colour depends on the maturity of the yam. White yams are high in potassium, while yellow, orange, and purple flesh yams are full of antioxidants, complex carbohydrates, and vitamins. They have a ton of health benefits. For example, they are a source of resistant fiber, which makes them an ideal food option for digestion and weight loss. Yams help prevent spikes in blood sugar after a hearty meal. In addition, they have several other qualities that make them nutritious.

Types of yams grown:

Indian yam (D. trifida)

Winged or water yam (D. alata)

Guinea yam (D. rotundata)

Yellow Guinea yam (D. cayenensis)

Lesser yam (D. esculenta)

Chinese yam (D. polystachya), also known as cinnamon vine

Yam Nutrition Facts

Yams are rich in vitamins, minerals, and fiber.

According to the US Department of Agriculture, one cup (136 grams) of baked yams provides:

• Calories: 158
• Carbs: 37 grams
• Protein: 2 grams
• Fat: 0 grams
• Fiber: 5 grams
• Vitamin C: 18% of the Daily Value (DV)
• Vitamin B5: 9% of the DV
• Manganese: 22% of the DV
• Magnesium: 6% of the DV
• Potassium: 19% of the DV
• Thiamine: 11% of the DV
• Copper: 23% of the DV
• Folate: 6% of the DV

Two studies (Weaver, C.M, 2013; Aschner and Dorman, 2006) also found that apart from the rich fiber content in yam, it is also high in potassium and manganese, which play an important role in aiding bone health, growth, metabolism, and heart function. Yams also provide good amounts of other micronutrients, such as copper and vitamin C.

For instance, four studies (Collins and Klevay, 2011; National Academy of Sciences (US) and National Research Council (US) Division of Medical Sciences. Conference on Hemoglobin: 2–3 May 1957. Washington (DC): National Academies Press (US); 1958; Padayatty et al, 2003; Chambial et al. 2013) found that  Copper plays a significant role in red blood cell production and iron absorption, on the other hand, vitamin C acts as a strong antioxidant that can boost your immune system.

Yams, Science

Support brain function

Studies have linked the consumption of yams to brain support.  For instance, Tohda et al.(2017) 12-week study, used respondents who took a yam extract supplement and found that they recorded advanced brain function tests as compared to the placebo group. The reason why the participants experienced such a higher brain function was attributed to the specific compound in yam called diosgenin, which has been found to promote neuron growth and boost brain function.

In animal studies (Chiu et al, 2011) diosgenin has been found to enhance memory and learning abilities in mice in various maze tests.  Studies are still ongoing to examine how the consumption of yams improves brain health.

Yams, menopause                                   

Studies have also been conducted on yams and found that it aids some symptoms of menopause. For instance, (Wu et al. 2015), employed a 30-day study, where 24 postmenopausal women shifted from their normal rice consumption and focused on eating yams in 2 out of 3 meals (390 grams total) per day.  The study found that their blood levels of estrone and estradiol increased by 26% and 27%, respectively.

Two studies (Santoro et al. 2015; Peacock et al. 2022) found that during menopause, blood levels of estrone and estradiol — two estrogen hormones — naturally decrease. Hence, anything that helps in restoring estrogen levels may ease menopause symptoms and yams do exactly that.

An earlier clinical trial by Komesaroff et al. (2011) conducted over a six-month found that topically applied wild yam cream had very little effect on menopause symptoms, such as flushing and night sweats, compared with a placebo. Still, more studies are ongoing to establish the role that yams could play in aiding menopause symptoms.

Yams, cancer-fighting properties

Studies have also been conducted to establish the cancer-fighting abilities of yams. For example, two studies (Hou et al. 2002; Son et al. 2014) found that yams are loaded with many antioxidants that could have anticancer properties.

For instance, two animal studies (Son et al. 2014; Shin et al. 2012) found that eating a yam-rich diet significantly decreased colon tumor growth. How yams were found to decrease colon tumor growth was linked to antioxidants. This means, the more frequently we eat a yam diet, the more we are protected from cancer.

Apart from animal studies, two test-tube studies (Liu et al. 2016; Chiu et al. 2013) also found that extracts from Chinese yam, precisely the peel, inhibited liver tumor growth and aided antioxidant properties.  More studies are needed to establish its effects on humans.

Yams, inflammation

Studies have also confirmed that the antioxidants in yams could decrease inflammation. For instance, three studies (Kolb and Mandrup-Poulsen, 2010; Pearson et al. 2003; Gregor and Hotamisligil, 2011) found that chronic inflammation is the foundation for increased risk of many illnesses, including heart disease, diabetes, and obesity.

Hence, human studies established that the consumption of yams as an anti-inflammatory food, could help avert chronic inflammation (Casas et al. 2014; Koloverou et al. 2012).

Also, four rat studies (Son et al. 2014; Chiu et al. 2013; Park et al. 2013; Chen et al. 2017) found that yam powder decreased inflammation linked to numerous illnesses, such as colon cancer, irritable bowel syndrome (IBS), and stomach ulcers.

Yams, blood sugar control

Studies have also confirmed that yam consumption could support blood sugar levels.

For instance, in one study (Go et al. 2015), rats were given yam powder or yam water extract and they had reduced fasting blood sugar and hemoglobin A1C (HbA1c) levels, juxtaposed with the control groups. HbA1c is a measure of long-term blood sugar control.

Another study (Helen et al. 2013) found that rats given higher amounts of purple yam extract experienced decreased appetites, greater weight loss, and better blood sugar control, juxtaposed with a control group.

Additionally, another study in rats (Harijono and Endang, 2016) found that complementing with yam flour, reduced the rate of blood sugar absorption, which led to better blood sugar control. These effects have been credited to the resistant starch and fiber in yams.  Birt et al. ( 2013) explained that resistant starch passes through your gut undigested. This type of starch is linked to various health benefits, including decreased appetite, as well as improved blood sugar levels, and insulin sensitivity.

Other benefits

Yams are associated with several other health benefits, including:

Digestive health. 

Two studies ( Li et al. 2019; Chen et al. 2003) found that the resistant
starch in yams may enhance  digestive
enzymes that help break down food and increase the number of good bacteria
in your gut.

Weight loss. 

One animal study (Harijono and Endang, 2016) found that yam
the extract decreased food intake, signifying that these tubers could aid in reducing
appetite and increasing weight loss. The fiber in yams could aid weight
loss.

Antimicrobial effects.

Two studies (Kelmanson et al. 2000; Kuete et al. 2012) found thatyam extract may protect against certain drug-resistant bacteria.

Improved cholesterol levels.

In one study (Wu et al. 2005), women who ate 18 ounces (390 grams) of yams per day for 30 days had a 6% decrease in blood cholesterol levels.

Warnings

Yams contain compounds that are potentially toxic when eaten raw. Always cook yams before eating them, which also makes their starch easier to break down. If you’re following a low-glycemic diet or low-carb diet, limit the number of root veggies you consume.

Deep-frying yams or eating with them lots of added sugar is not advisable. Boiling, roasting, or baking them with a bit of avocado oil, herbs and spices are good for consumption.

Take home

Studies have confirmed the numerous benefits of eating yam specifically on brain function and menopausal health. Compared to refined grains, most root vegetables are also lower in calories and lower on the glycemic index, which means they won’t spike your blood sugar as much. The fiber in starchy veggies slows down the release of glucose (sugar), which is important for energy and insulin balance.

Additionally, plant foods that contain fiber have been shown to promote gut health and exhibit other beneficial activities, including anti-carcinogenic, anticoagulant, and immune-stimulating and antioxidant effects. A high-fiber diet not only helps prevent inflammation and disease formation, but it also works wonders for helping with digestion and preventing IBS or naturally relieving constipation.

NB:

Prof. Nyarkotey has strict sourcing guidelines and relies on peer-reviewed studies, academicresearchinstitutions,andmedicalassociationstojustify hiswrite-ups.My articlesare foreducationalpurposesanddonotserveasMedicaladviceforTreatment.Iaimtoeducatethepublicaboutevidence-based scientificNaturopathicTherapies.

The writer is a Professor of Naturopathic Healthcare, a Medical Journalist, and a science writer. President, Nyarkotey University College of Holistic Medicine & Technology (NUCHMT)/African Naturopathic Foundation, Ashaiman, Ghana. Currently BL Candidate at the Gambia Law School, Banjul. E. mail: [email protected].