Including more milk in our diet is common advice we hear from health professionals. But what they really mean is including more calcium in our diet. Milk (through clever marketing) has become the “poster child” for calcium and while it does contain a goodly amount of calcium, it is not the only source – and perhaps not the best.
The National Institutes of Health recommends a minimum of 1,000 mg of calcium per day for ages four years old and up. When our ages reach 50 and older, this requirement gets even bigger due to the risk of osteoporosis.  In order to meet this calcium requirement, we would need to drink at least 3 glasses of milk a day – however according to recent research, milk is controversial. The human body has a hard time digesting some of its components, and a significant number of people are allergic to it. Furthermore, milk sold in many markets may have been heavily processed, affecting the way our bodies absorb its nutrients.
It’s not so simple to just consume calcium. Simple calcium compounds (such as those found in chalk or limestone) are typically insoluble, meaning that they cannot be assimilated by the body. It’s essential to absorb bioavailable calcium from food and one of the best forms of this is from vegetables, that have already absorbed a chelated form of calcium from the soil. In other words – you can’t just eat calcium carbonate (not that you would want to) in order to get your RDA of calcium. It has to be in bioavailable form and this is taken care of you by tiny soil microorganisms such as lichens which chelate minerals in soil into bioavailable form. Unless they were all killed by the use of pesticides (but that’s another story…)
Calcium is one of the essential minerals the human body needs to function. Our bones and our teeth are made of calcium and without adequate calcium supplementation in our diet, our bones and teeth can become brittle and prone to breakage. Beyond this, calcium ferries electric signals from our organs and muscles to the brain and back. Without enough (or too much!) calcium, our heart begins to beat irregularly and our muscles become difficult to control. 
Here are 7 foods that are naturally rich in calcium. (Compare with whole milk which contains 113mg calcium per 100g).
7 Foods That Contain More Calcium Than Milk
#1: Kale (150mg calcium per 100g)
Kale is a popular choice because it can be eaten in a variety of ways. You can turn it into a smoothie or pop a few leaves in the oven with some flour and seasoning for kale chips. Kale is not only high in calcium, it is a potent antioxidant that has been proven to have protective properties against prostate and colon cancers because of its vitamin K content .
#2: Spinach (cooked – 136mg calcium per 100g; raw – 99mg per 100g)
A cup of spinach in your salad for lunch will give you some calcium, but steamed spinach will give you more. A study on spinach yielded great results for the cardiovascular system as well – being able to reduce blood pressure by improving arterial stiffness because of its nitrate content. 
#3: Collard greens (raw 232mg calcium per 100g, cooked 141mg calcium per 100g)
Collard greens are best served steam or stir-fried, with a little bit of garlic and seasoning. This is a delicious way to add more calcium to your diet, but also to improve your intake of phenols. Collard greens (as well as broccoli and kale) are rich in phenolic compounds  that help fight cancer and heart disease. 
#4: Sesame seeds (975mg calcium per 100g)
We find sesame seeds in many Chinese dishes, on top of burger buns and in some snacks – but did you know just how much calcium they contain? According to the USDA, 100 grams of sesame seeds is equal to an astonishing 975 mg of Calcium – that almost meets the 1000 mg daily calcium requirement! Now you probably aren’t going to want to eat 100g of sesame seeds as this is almost a quarter of a pound. But they are a valuable addition to your diet – being high in “good fats” and dietary fiber. 
#5: Organic yogurt (100-150mg calcium per 100g)
Yogurt, which is a dairy product, has high calcium content. However, compared to ultraprocessed milk, organic yogurt brings us the best source of calcium from a dairy product because the natural fermentation process preserves the nutritional content of the milk – with added benefits of probiotics.
#6: Cheese (cheddar = 721mg calcium per 100g)
Cheeses contain variable amounts of calcium depending on the variety. Cheddar is fairly typical. Other varieties of cheese typically around 500mg-1000mg calcium per 100g.
#7: Tofu (350mg calcium per 100g)
Tofu has a low calorie count and relatively large amounts of protein. It is high in iron, and depending on how it is manufactured can have higher calcium or magnesium content.
 National Institutes of Health (2010). New Recommended Daily Amounts of Calcium and Vitamin D. http://www.nlm.nih.gov/medlineplus/magazine/issues/winter11/articles/winter11pg12.html
 Ministry of Health. Calcium. https://www.nrv.gov.au/nutrients/calcium
 Nimptsch, K., et. al. (2008). Dietary intake of vitamin K and risk of prostate cancer in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition. http://www.ncbi.nlm.nih.gov/pubmed/18400723
 Jovanovski, E., et. al. (2015). Effect of Spinach, a High Dietary Nitrate Source, on Arterial Stiffness and Related Hemodynamic Measures: A Randomized, Controlled Trial in Healthy Adults. http://www.ncbi.nlm.nih.gov/pubmed/26251834
 Lin, L. & Harnly, J. (2009). Identification of the phenolic components of collard greens, kale, and Chinese broccoli. http://www.ncbi.nlm.nih.gov/pubmed/19627150
 Martinez-Valverde, I., Periago, M. & Ros G. (2000). Nutritional importance of phenolic compounds in the diet. http://www.ncbi.nlm.nih.gov/pubmed/11048566
 Kamchan, A., et. al. (2004). In vitro calcium bioavailability of vegetables, legumes and seeds. http://www.sciencedirect.com/science/article/pii/S0889157504000377
Source : www.herbs-info.com