Understanding the Glycemic Index
The glycemic index (GI) is a system that ranks carbohydrate-containing foods based on their effect on blood sugar levels. Foods are ranked on a scale from 0 to 100:
- Low GI: 55 or less
- Medium GI: 56–69
- High GI: 70 or higher
Foods with a low GI are digested and absorbed more slowly, causing a gradual rise in blood glucose. In contrast, high GI foods cause rapid spikes in blood sugar. For individuals managing diabetes or seeking better blood sugar control, choosing low GI foods is a recommended strategy.
Glycemic Index of Specific Nigerian Beans
Nigerian cuisine features several varieties of beans, with cowpeas (Vigna unguiculata) being among the most common. Studies conducted on healthy Nigerians have investigated the GI of different types of beans and traditional preparations. These studies highlight that processing methods can significantly influence the final GI value of the dish.
Common Cowpea Varieties
Research from the University of Lagos on healthy participants found that common cowpea varieties have very low GI values when boiled. This is primarily due to their high fiber content and the nature of their starches, which are slowly digested.
- 'Oloyin' (Honey Beans): A specific variety of cowpea, 'oloyin' had a median GI of 12.10% in one study. These are considered highly diabetic-friendly.
- 'Sokoto White' Beans: Another cowpea variety, 'Sokoto white', recorded a median GI of 12.04% in the same study, ranking it among the lowest tested.
- 'Drum' Beans (Brown Cowpea): The 'drum' variety had a median GI of 17.64%. Although slightly higher than 'oloyin' and 'Sokoto white', it is still very low on the GI scale.
Other Nigerian Legumes
Another study examined the GI of six commonly consumed legumes in Nigeria, confirming their low postprandial blood glucose impact.
- African Yam Bean: This legume recorded the lowest GI value at 17 ± 6.
- Cowpea (White Variety): Tested in this study, it gave a GI of 41 ± 10.
- Pigeon Pea: Cream and brown varieties showed similar GI values around 24 ± 10.
Glycemic Index of Popular Nigerian Bean Dishes
How beans are prepared is a crucial factor that affects their GI. Processed dishes like Moin-Moin and Akara generally maintain a low GI, but other additions can alter the final value.
Moin-Moin (Steamed Bean Pudding)
Moin-Moin, prepared from blended dehulled beans, has been shown to have a low GI. A study found the GI of Moin-Moin to be 41, which falls into the low GI category. Its low GI is attributed to the high fiber content of beans and the processing method.
Akara (Bean Cake)
Similar to Moin-Moin, Akara (bean cakes) also exhibits a low GI. The same study recorded its GI at 44. Frying the bean cakes does not appear to significantly raise the GI into the medium or high range.
Boiled Beans with Stew
This is a common meal in Nigeria, and research has investigated its GI. A specific study found that boiled beans served with stew had an intermediate GI of 56. This indicates that additions like stew ingredients can moderately impact the overall GI of the meal, although it is still on the lower end of the medium GI scale.
Factors Affecting the Glycemic Index of Beans
Several intrinsic and external factors determine the GI of Nigerian beans:
- Fiber Content: Beans are naturally rich in dietary fiber, including soluble and insoluble types. This fiber is known to slow down digestion and carbohydrate absorption, preventing sharp spikes in blood sugar.
- Starch Composition: Beans contain significant amounts of slowly digested starch (SDS) and resistant starch (RS). These starches are less readily broken down by digestive enzymes, leading to a prolonged release of glucose into the bloodstream.
- Processing Method: The way beans are cooked and prepared influences their GI. Dehulling (removing the outer skin) and blending, as seen in Moin-Moin and Akara, affects the structure of the bean starch, but the high fiber generally keeps the GI low. Boiling beans and serving them with a stew, as shown, can result in a higher GI than the base bean product alone.
- Addition of Other Ingredients: Mixing beans with other foods, especially those high in GI, can raise the overall GI of the meal. Pairing beans with low GI vegetables and healthy fats, however, can help maintain a low glycemic response.
Comparison of Glycemic Indices (GI) in Nigerian Beans
This table summarizes the GI values for different Nigerian bean varieties and preparations, based on local studies.
| Food Item | GI Value | GI Category | Source (Approximate) |
|---|---|---|---|
| 'Sokoto White' Bean Meal | 12 | Low | |
| 'Oloyin' Bean Meal | 12 | Low | |
| 'Drum' Bean Meal | 18 | Low | |
| African Yam Bean (Boiled) | 17 | Low | |
| Cowpea (Brown Variety, Boiled) | 29 | Low | |
| Cowpea (White and Black Variety, Boiled) | 30 | Low | |
| Cowpea (White Variety, Boiled) | 41 | Low | |
| Moin-Moin | 41 | Low | |
| Akara | 44 | Low | |
| Boiled Beans with Stew | 56 | Medium |
Conclusion: The Benefits of Nigerian Beans
Nigerian beans are a nutritious staple, and numerous studies confirm their low to medium glycemic index. This characteristic, combined with their high fiber and protein content, makes them an excellent food choice for managing blood sugar levels and promoting overall health. The versatility of Nigerian beans, from simple boiled preparations to complex dishes like Moin-Moin, allows for their regular inclusion in a balanced diet. However, it is essential to consider the portion sizes and overall meal composition, especially for those with diabetes, to maintain stable blood glucose levels. By understanding the glycemic impact of different preparations, individuals can make informed dietary choices while enjoying a rich and healthy part of Nigerian cuisine. For further reading, consult the research on the Glycaemic indices of some local beans (Vigna unguiculata (Linn) Walp) varieties in Nigerians.
