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The Prediabetes Nutritionist

Nigerian Yam for Type 2 Diabetes

Is Nigerian Yam Good for (Type 2) Diabetes?

Wondering if Nigerian yam is good for prediabetes or type 2 diabetes? Let’s find out.


Your blood sugars are higher than normal. Your doctor says you have prediabetes, and if you do nothing about it, you may progress to type 2 diabetes.

He has advised you to eat plenty of beans, moi moi and unripe plantain. You’re committed to controlling your blood sugars, so you follow his advice diligently. It’s been several weeks, but you’re bored and want more variety.

Yam looks appealing, but it isn’t on your doctor’s list of acceptable foods.  

Can you eat it?

You can eat Nigerian yam if you have prediabetes or type 2 diabetes, but you must watch your portion size and pair it with quality protein, fat and vegetables to avoid blood sugar spikes. You must also choose an appropriate cooking method to prevent weight gain and raise your LDL or ‘bad’ cholesterol.

This article discusses the nutritional value and medicinal benefits of Nigerian yam. It also details the best ways to cook and eat yam to avoid blood sugar spikes.

The Varieties of Yam in Nigeria

You may have seen yams referred to as sweet potatoes on the internet or social media sites, but they are entirely different foods.

Yams belong to a family of crops botanically known as Dioscoreaceae and the genus (group) Dioscorea. It is a staple crop in West Africa and is the third most important tuber after cassava (Manihot esculenta) and sweet potato (Ipomoea spp.) (Obidiegwu et al., 2020).

The three varieties available in Nigeria (and West Africa in general) are: white yam (Dioscorea rotundata), yellow yam (Dioscorea cayenesis) and water yam (Dioscorea alata) (Obidiegwu et al., 2020).  

White Yam

White yams are the most common type. They are dark brown on the outside, with a firm, white flesh inside. It is eaten all year round becasue it has a long shelf-life.

Yellow Yam

Yellow yams are not as popular as white yams; they are dark brown on the outside with a firm, yellow flesh on the inside. Yellow yams have a long shelf-life and are also eaten all year round. Rural communities in Enugu, Nigeria, use them to treat diarrhoea (Aiyeloja & Bello, 2006).

Water Yam

Water yam is perhaps the second most popular type of yam in Nigeria. It is dark brown outside and white with purple streaks on the inside. It has a longer shelf-life than white and yellow yams, possibly due to the softer texture of its flesh (Dufie et al., 2013).  

Scientists have studied its medicinal benefits more extensively than the other two types. So far, cell culture and animal studies show that water yam peel extracts have anti-fungal, anti-cancer and anti-diabetic properties (Padhan & Panda, 2020).

Other studies show that they contain many antioxidants, including phenols, tannins and flavonoids that neutralise free radicals – unstable compounds that damage cells and tissues in the body, causing disease (Padhan & Panda, 2020). Interestingly, rural communities in Enugu use water yam leaves to treat fevers (Aiyeloja & Bello).

Nigerian water, white and yellow yam and diabetes
image credit:@spoiledhounds.com

The Nutritional Value of Nigerian Yam

Yam is carbohydrate and fibre-rich but low in protein and fat. Despite its low protein content, yam is a good a source of the essential amino acids, phenylalanine and threonine. It is also a source of several minerals and vitamins that play crucial roles in the body’s functioning.

Yams are sources of potassium, calcium, phosphorus, magnesium, and manganese, but the levels of these minerals vary between species. The potassium content of yam is quite high, making it a better potassium source than other tubers (cassava, potatoes, and sweet potatoes) and cereals, including maise, rice and wheat (Obidiegwu et al., 2020).

Although yams contain beta-carotene, vitamin B1, vitamin B2, and vitamin C, they are considered poor sources of these vitamins (except vitamin C) relative to human needs.

The nutritional value of white, yellow and water yam per 100g are presented in the table below (Adepoju et al., 2016; Padhan & Panda, 2020, USDA).

It is worth noting that yams on their own are not a balanced food (Baah et al., 2009). They contain antinutrient compounds such as tannins, oxalates and phytates that block the absorption of protein, minerals and vitamins and reduce the nutritive value of the food (Padhan & Panda, 2020).

Eaten in excess, these antinutrient compounds can cause mineral deficiencies with severe health consequences. Eating yams (and other root vegetables) with fruits, vegetables, meat and fish products rich in minerals is crucial to avoid deficiencies (Baah et al., 2009).

Per 100gWhite Yam
(USDA)
Yellow Yam
(Adepoju et al., 2016)
Water Yam
(Adepoju et al., 2012)
Average
(Padhan & Panda, 2020)
Energy (kcal)116108125118
Carbohydrate (g)
Of which sugar (g)
27.5
0.5
29.7
26.5
28
Protein (g)2.52.62.41.5
Fat (g)0.10.30.10.2
Fibre (g)3.90.2g4.14.1
Minerals
Potassium (mg)
Magnesium (mg)
Calcium (mg)
Iron (mg)
Zinc (mg)

670
18
14
0.5
0.2

262.3
61.5

0.8
0.4

816
21
15
0.8
0.43

816
21

0.54
Vitamins
Beta-carotene (mcg)
Vitamin B1 (mg)  
Vitamin B2 (mg)
Vitamin C (mg)
Folate (mcg)
 

0.1
0.07
12.1
16.0

7.65
0.14
0.06
14.4

30
0.05
0.03
15

83
0.111

17.1

How do yams affect blood sugar?

Scientists use the glycaemic index (GI) to determine how carbohydrate-rich foods affect your blood sugar. Foods that raise your blood sugar levels very quickly are known as high glycaemic foods, while those that raise it moderately or slowly are known as medium-glycaemic or low-glycaemic foods, respectively.

Foods are ranked on a scale of 0-100. Low glycaemic foods have a rating of 0-55, medium glycaemic foods have a rating of 56-69, and high glycaemic foods have a rating of 70 and above.

Are yams a high glycemic food? i.e., do they raise blood sugar significantly?

According to a recent study, the impact of yam on blood sugar depends on the variety of yam and the cooking method. Boiled and roasted white yam and water yam are low glycaemic, while fried white yam and water yam are medium glycaemic. However, fried yellow yam is medium glycaemic, but boiled and roasted yellow yam are high glycaemic (Ampofo et al., 2020).

Glycaemic Index
Cooking MethodWhite YamWater YamYellow Yam
Boiled445475
Fried596965
Roasted505470
Glycaemic index of white, yellow and water yam according to the cooking method (Ampofo et al., 2020)

Yam is eaten in other forms besides boiling, frying and roasting. It can be pounded with a mortar and pestle after boiling to form a thick dough called pounded yam. Or it is boiled, soaked in water overnight and dried before grinding into a light-brown powder (elubo). The powder is cooked in boiling water to create a thick, brown dough known as amala. Both pounded yam and amala are eaten with local vegetable or seed-based stews.

While previous studies have shown that pounded yam and amala are low glycaemic, a recent study has found otherwise.

 A team of Nigerian scientists investigated the GI of amala and pounded yam made from three varieties of white yam (Eyinla et al., 2022). According to their findings, amala has a GI of 83-89, while pounded yam’s GI is 92-104, suggesting that they are both high glycaemic foods.

The Best Way to Cook and Eat Nigerian Yam if You Have Diabetes

Cooking methods significantly impact yam’s GI.

Based on current evidence, boiling and roasting are the best ways to cook yam. Choose white or water yams instead of yellow yams where possible since they have much lower glycaemic indices.

Avoid eating yams alone, even if you boil or roast them. You must always pair them with vegetables, protein (e.g., meat, fish, chicken, or eggs) and fat (e.g., avocado, nuts, oils, or seeds) as they slow down digestion and prevent blood sugar spikes.

Although amala and pounded yam are highly glycaemic when eaten alone, pairing them with proteins, vegetables, and fat significantly reduces their glycaemic effect. You can still eat them, but once again, your portion size matters!

Now you know the nutritional benefits of yams and how they affect your blood sugar. You also know you can eat yams even if you have prediabetes or type 2 diabetes.

The most important thing to remember is to always pair them with proteins, vegetables, and fats and to eat small to moderate portions to avoid blood sugar spikes.

And if you want extra blood sugar bonus points, choose boiled or roasted white or water yam instead of yellow yam. Of course, amala and pounded yam can remain on the menu. Simply follow the pairing principle, watch your portion size, and you’ll be OK!

That said, if you’re unsure what the correct portion size is for you or how to plan your meals, schedule a free assessment call to learn how I can support you in controlling your blood sugar.

REFERENCES

  1. Obidiegwu, J.E.., Lyons, J.B., & Chilaka, C.A. (2020) The Dioscorea genus (Yam) – An appraisal of nutritional and therapeutic potentials. Foods, 9: 1304.
  2. Aiyeloja A.A. & Bello, O.A. (2006) Ethnobotanical potentials of common herbs in Nigeria: a case study of Enugu state. Educational Research and Review, 1(1): 16-22.
  3. Padhan B., & Panda, D. (2020) Potential of neglected and underutilised yams (Dioscorea spp.) for improving nutritional security and health benefits. Frontiers in Pharmacology, 11:496
  4. Adepoju, O.T. (2012) Effects of processing methods on nutrient retention and contribution of white yam (Dioscorea rotundata) products to nutritional intake of Nigerians. African Journal of Food Science, 6 (6): 163-167
  5. Adepoju, O.T., Boyejo, O., Adeniji, P.O. (2016) Effects of processing methods on nutrient and antinutrient composition of yellow yam (Dioscorea cayenensis) products. Food Chemistry, https://dx.doi.org/10.1016/j.foodchem.2016.10.071
  6. Dufie, W-M, F., Oduro, I., Ellis, W.O., Asiedu, R., & Maziya-Dixon, B. (2013) Potential health benefits of water yam (Dioscorea alata). Food and Function, 4: 1496
  7. Nutrition facts label for yam, cooked, boiled, drained or baked, without salt. Available: https://nutritiondata.self.com/facts/vegetables-and-vegetable-products/2726/2.  Accessed: 05 October 2022.
  8. Ampofo, D., Agbenorhevi, J.K., Firempong, C.K., Adu-Kwarteng, E. (2020) Glycaemic index of different varieties of yam as influenced by boiling, frying and roasting. Food Science & Nutrition, 9: 1106-1111.
  9. Baah, F.D., Maziya-Dixon, B., Asiedu, R., Oduro, I., & Ellis, W.O. (2009) Nutritional and biochemical composition of D. alata (Dioscorea spp.) tubers. Journal of Food, Agriculture & Environment, 7(2): 373-378.
  10. Eyinla, T.E., Sanusi, R.A., & Maziya-Dixon, B. (2022) Evaluation of in vitro and in vivo glycaemic index of common stapes made from varieties of white yam (Dioscorea rotundata). Frontiers in Nutrition, 9: 983212.

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The Comments

  • Michael Umusu
    November 8, 2022

    This write up is very educational and beneficial. Can we have similar studies on plantains

    • Somi Igbene PhD ANutr
      > Michael Umusu
      November 8, 2022

      I’m glad to hear you found it useful! Yes, plantain is in process; it will be posted this week 🙂