How traditional leafy vegetables combat micronutrient deficiencies through their remarkable phytonutrient content
In the bustling local markets and rich farmlands of Southeast Nigeria, a silent crisis known as "hidden hunger" persists.
While many have enough food to feel full, their diets lack the essential micronutrients necessary for proper health and development. This narrowing food base—over-reliant on a handful of starchy staples like yam, maize, and rice—has contributed to the high incidence of non-communicable diseases such as stunted growth, goiter, and blindness2 .
Recent research has turned its attention to five Neglected and Underutilized Traditional Leafy Vegetables (TLVs) of southeast Nigeria. These plants, often overlooked by modern agriculture, represent a powerful, locally-available solution to the region's nutritional challenges2 .
The five key vegetables identified are: Abelmoschus esculentus (Okra), Ageratum conyzoides (Goat weed), Acanthus montanus (Leopard's tongue), Bombax buonopozense (Kapok Tree), and Mucuna flagellipes (Devil bean)2 .
Phytonutrients, or phytochemicals, are natural bioactive compounds produced by plants. These compounds are responsible for the vibrant colors, distinctive aromas, and protective qualities of plant foods. When consumed by humans, they provide various biological functions that extend beyond basic nutrition, leading to the promotion of health as well as reduced risk of chronic diseases1 7 .
Among the most studied phytonutrients are carotenoids—the fat-soluble pigments that give plants their bright yellow, orange, and red hues. Beta-carotene, a particularly important carotenoid, serves dual roles in human health: it acts as a potent antioxidant that protects cells from damage, and it functions as provitamin A, which the body converts into retinol to support vision, immune function, and skin health1 3 .
The health benefits of these plant compounds are extensive. Carotenoids like lutein and zeaxanthin concentrate in the retina, where studies show they can decrease the risk of developing macular degeneration by 43%7 . Other phytonutrients, including various flavonoids and glucosinolates, demonstrate cancer-protective properties and support cardiovascular health1 7 .
When researchers analyzed the nutritional composition of the five underutilized vegetables, the results were striking. These traditionally consumed plants contained appreciable amounts of protein, fat, fibre, carbohydrate, and mineral elements, with generally low levels of toxicants2 .
| Vegetable Name | Protein (g) | Fat (g) | Fibre (g) | Carbohydrate (g) | Ash (g) |
|---|---|---|---|---|---|
| Abelmoschus esculentus (Okra) | 1.57 ± 0.02 | 0.57 ± 0.02 | 0.92 ± 0.02 | 7.25 ± 0.02 | 2.50 ± 0.20 |
| Ageratum conyzoides (Goat weed) | 1.13 ± 0.02 | 0.43 ± 0.02 | 1.03 ± 0.02 | 7.88 ± 0.02 | 3.50 ± 0.20 |
| Acanthus montanus (Leopard's tongue) | 0.99 ± 0.02 | 0.37 ± 0.02 | 0.78 ± 0.02 | 8.97 ± 0.02 | 1.75 ± 0.02 |
| Bombax buonopozense (Kapok Tree) | 2.21 ± 0.02 | 0.93 ± 0.02 | 1.12 ± 0.02 | 6.51 ± 0.02 | 2.75 ± 0.02 |
| Mucuna flagellipes (Devil bean) | 2.59 ± 0.02 | 0.67 ± 0.02 | 1.24 ± 0.02 | 7.15 ± 0.02 | 2.25 ± 0.02 |
Source: Research on traditional leafy vegetables in Southeast Nigeria2
| Vegetable Name | Vitamin A (IU) | Vitamin C (%) | Vitamin E (mg/100g) |
|---|---|---|---|
| Abelmoschus esculentus (Okra) | 191.50 ± 0.02 | 10.23 ± 0.02 | 12.40 ± 0.20 |
| Ageratum conyzoides (Goat weed) | 189.64 ± 0.02 | 12.65 ± 0.02 | 8.60 ± 0.20 |
| Acanthus montanus (Leopard's tongue) | 340.43 ± 0.02 | 11.34 ± 0.02 | 4.40 ± 0.20 |
| Bombax buonopozense (Kapok Tree) | 230.14 ± 0.02 | 9.45 ± 0.02 | 19.60 ± 0.20 |
| Mucuna flagellipes (Devil bean) | 695.40 ± 0.02 | 8.56 ± 0.02 | 14.80 ± 0.20 |
Mucuna flagellipes (Devil bean) demonstrated exceptionally high levels of vitamin A—approximately 695 IU per 100g—far surpassing the other vegetables analyzed2 . This provitamin A activity, primarily from beta-carotene, is essential for addressing vitamin A deficiency, a serious public health concern in Southeast Nigeria that contributes to vision impairment and compromised immune function.
Discovering that these traditional vegetables contain high levels of beta-carotene is only the first step in understanding their nutritional potential. The critical question for researchers became: How much of this beta-carotene can the human body actually use?
The proportion of a nutrient that is absorbed, becomes available for physiological functions, and is utilized by the body.
The amount of an ingested nutrient that is released from the food matrix during digestion and becomes potentially available for absorption5 .
For beta-carotene and other fat-soluble compounds, bioavailability depends on a complex sequence of events:
From food matrix during chewing and digestion
Into mixed micelles with bile salts
By intestinal epithelial cells
To determine how much beta-carotene from these traditional vegetables actually becomes available for absorption, researchers employ sophisticated in vitro (test tube) methods that simulate human digestion. These approaches provide valuable insights without the complexity and expense of human trials5 .
| Reagent/Equipment | Function in Bioaccessibility Research |
|---|---|
| Pepsin | Simulates gastric digestion in the stomach phase |
| Pancreatin | Provides pancreatic enzymes for intestinal digestion |
| Bile Salts | Critical for forming micelles to solubilize beta-carotene |
| Dialysis Membranes | Separates micellar fraction from undigested material |
| Caco-2 Cell Lines | Human intestinal cell model for absorption studies |
| High-Performance Liquid Chromatography (HPLC) | Precisely quantifies beta-carotene content |
Spins samples at high speed to isolate micelles
Uses filters with specific pore sizes to separate micellar fraction
Relies on diffusion across a membrane
Research Insight: Membrane filtration provides similar results to ultracentrifugation, while equilibrium dialysis proves less suitable for carotenoid bioaccessibility studies.
Studies show that how we prepare these vegetables significantly impacts beta-carotene bioaccessibility. Heat treatment through pressure cooking increases bioaccessibility by 19-100%, while stir-frying with a small amount of oil leads to even more dramatic improvements—53-263% increases across different vegetables. This highlights the importance of traditional cooking practices in maximizing nutritional benefits.
The health benefits of plant foods likely come from the combined effects of multiple phytonutrients working together rather than from single compounds alone1 9 . This "entourage effect" means that consuming the whole vegetable, with its complex mixture of bioactive compounds, may be more beneficial than taking isolated supplements.
These underutilized vegetables represent more than just nutritional value—they offer a sustainable, climate-resilient, and culturally appropriate approach to addressing malnutrition in Southeast Nigeria2 . As locally adapted species, they're accessible to low-income communities and can play a crucial role in improving food security while preserving agricultural biodiversity.
The story of Southeast Nigeria's traditional leafy vegetables is one of rediscovery—of looking back to move forward. As research continues to unveil the remarkable phytonutrient profile and bioavailability of these neglected foods, we're reminded that solutions to complex problems like hidden hunger often lie in preserving and valuing traditional knowledge and biodiversity.
By incorporating these nutrient-dense plants into our daily diets, prepared using methods that maximize their nutritional potential, we take a significant step toward addressing the silent crisis of micronutrient deficiencies. The path to better health for Southeast Nigeria's population may well be found in these humble, overlooked vegetables that have been growing in local fields all along—waiting for science to confirm what traditional wisdom has long known.