Kale calcium
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Calcium Absorption and Nutritional Value of Kale
High Calcium Absorption from Kale
Kale is recognized for its high calcium content and excellent calcium absorption rates. Research comparing calcium absorption from kale to milk found that kale has a significantly higher fractional calcium absorption rate, averaging 0.409 compared to 0.321 for milk1. This makes kale an excellent source of calcium, especially for those who are lactose intolerant or prefer plant-based diets.
Impact of Saline Stress and Calcium Nitrate on Kale Production
The mineral nutrition of kale, particularly under saline stress, is crucial for maintaining its calcium content. Studies have shown that using calcium nitrate in nutrient solutions can mitigate the negative effects of salinity on kale production. The highest leaf production and agronomic efficiency were observed with standard nutrient solutions, but adding extra calcium nitrate helped reduce the impact of salinity on magnesium absorption and overall kale production2.
Nutritional Profile of Kale
Kale is not only rich in calcium but also contains a variety of other essential minerals. One cup of cooked kale provides significant amounts of calcium, potassium, copper, iron, magnesium, and phosphorus3. This makes kale a highly nutritious vegetable that supports overall health, including bone health due to its high calcium and vitamin K content.
Seasonal Variation in Mineral Content
The mineral composition of kale can vary depending on the season. Research indicates that kale harvested in winter has higher concentrations of calcium and other minerals compared to summer-harvested kale. The average calcium content in winter was found to be 551 mg per 100 g, slightly higher than the 535 mg per 100 g in summer4. This seasonal variation should be considered when sourcing kale for its nutritional benefits.
Effect of Processing on Mineral Content
Processing methods such as blanching, cooking, freezing, and canning can significantly affect the mineral content of kale. Blanching and cooking can reduce the mineral content by 26-75%, but freezing helps retain a higher percentage of minerals over long-term storage. After 12 months, frozen kale retained 24-74% of its macroelements, including calcium5. Therefore, for maximum nutritional benefit, consuming fresh or properly frozen kale is recommended.
Influence of Harvesting Stage
The stage of leaf development also influences the mineral content of kale. Early-stage kale, such as microgreens, tends to have higher levels of minerals compared to mature leaves. This includes higher concentrations of calcium, making young kale leaves particularly nutrient-dense9.
Conclusion
Kale is an exceptional source of calcium with high absorption rates, making it a valuable addition to diets aimed at improving bone health. Its nutritional profile is rich in various essential minerals, and its mineral content can be influenced by factors such as saline stress, seasonal variations, processing methods, and the stage of leaf development. For optimal calcium intake, consuming fresh or properly frozen kale, particularly during the winter season or at early leaf stages, is highly beneficial.
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Most relevant research papers on this topic
Calcium absorption from kale.
Kale, a low-oxalate vegetable, exhibits excellent calcium absorption compared to milk, offering a potential alternative to spinach for calcium supplementation.
Non-RCT
Highly CitedMineral nutrition and hydroponic kale production under saline stress and calcium nitrate
Adding 50% calcium nitrate to saline nutrient solutions reduces the negative effects of salinity on Mg absorption and NaCl addition on kale production under saline stress.
RCTNUTRITIONAL VALUE
Kale is a nutritious, low-calorie food that provides essential vitamins and minerals for bone health, eye health, and anti-inflammatory regulation.
Highly Cited