What is strontium?
Strontium is a trace element, found naturally in food. Dietary intake of strontium has linked to increased bone density and decreased risk of hip fracture. Food should be the only source of strontium, though. Taking it from supplements may increase the risk of heart attacks and blood clots!
Is strontium good against osteoporosis?
Strontium is an element important for strong bones and teeth. Strontium can replace calcium in the bones. Scientific data suggest that it’s beneficial for increasing bone density and stimulating bone formation! Strontium deficiency may lead to osteoporosis and increase risk of hip fracture. Dietary intake from food is the best source.
Strontium seems to help against osteoporosis in many ways. It has unique effects on the bones. Firstly, strontium promotes bone formation and inhibits bone resorption. It affects all bone cells. 
Why should you avoid taking strontium supplements?
If you want strong bones, taking strontium supplements isn’t the best option. Taking strontium supplements may have serious side effects!
The most important side effects of taking strontium supplements seem to be heart attack, blood clots, skin reactions, disturbances in thinking, seizures, and liver inflammation, and reduced numbers of red blood cells. 
Therefore, we should try to increase the dietary intake of calcium. It’s the most important element for strong bones and teeth. There are so many plant-based options. See the whole list here!
Certainly, cow’s milk and dairy aren’t necessary for healthy bones and teeth. On the contrary, dairy has linked to certain diseases in adults.
Moreover, strong bones and teeth need more than calcium or strontium. For instance, healthy teeth need adequate amounts of magnesium, phosphorus, zinc, iron, and many more. You can see all foods that promote strong teeth (and bones!) here.
Foods rich in strontium
Most people consume about 2 mg of strontium a day. 
As a rule of thumb, foods high in calcium are also good sources of strontium. Furthermore, plant-based foods are good sources of strontium.
Cereals and whole grains are particularly high in strontium. They are the best sources of strontium, among all other foods. Strontium is concentrated in the bran. Endosperm of grains has almost no strontium. So, prefer whole grains. Avoid refined products.
Most greens contain strontium, as well. Potatoes, carrots, cabbage, peas, and lettuce are particularly rich in strontium, though.  Brazil nuts are also high in strontium.
How can I increase strontium absorption?
Eating certain foods can help you increase strontium absorption. Adequate amounts of vitamin D and magnesium intake seem to increase strontium absorption.
You can find ways to boost your daily vitamin D intake here.
Moreover, excess calcium may inhibit strontium absorption.