Rhubarb is one of the least calorie vegetables. 100 g fresh petioles provide just 21 calories. Nonetheless, it holds some vital phyto-nutrients such as dietary fiber, poly-phenolic anti-oxidants, minerals, and vitamins. Further, its petioles contain no saturated fats or cholesterol.
The stalks are rich in several B-complex vitamins such as folates, riboflavin, niacin, vitamin B-6 (pyridoxine), thiamin, and pantothenic acid.
Red color stalks carry more vitamin-A than in the green varieties. Further, the stalks also contain small amounts of poly-phenolic flavonoid compounds like β-carotene, zea xanthin, and lutein. These compounds convert into vitamin A inside the human body and deliver same protective effects of vitamin A. Vitamin A is a powerful natural anti-oxidant which is required by the body for maintaining integrity of skin and mucus membranes. It is also an essential vitamin for healthy eye-sight. Research studies suggest that natural foods rich in vitamin A help the body protects against lung and oral cavity cancers.
As in other greens like kale, spinach, etc., rhubarb stalks too provide good amounts of vitamin-K. 100 g of fresh stalks provide 29.3 µg or about 24% of daily recommended intake of this vitamin. Vitamin K has a potential role in bone health by promoting osteotrophic (bone formation and strengthening) activity. Adequate vitamin-K levels in the diet help limiting neuronal damage in the brain; thus, has established role in the treatment of Alzheimer’s disease.
Its stalks also contain healthy levels of minerals like iron, copper, calcium, potassium, and phosphorus. However, most of these minerals do not absorb into the body as they undergo chelate into insoluble complexes by oxalic acid, which then excreted out.
[ source: nutrition-and-you.com ]