What is Strontium and How Does it Enter the Food Chain?
Strontium is a silvery-white alkaline earth metal, naturally present in the Earth's crust and oceans. Its ability to mimic calcium's physiological behavior allows it to be incorporated into the skeletal structure. Plants absorb strontium from the soil and water, with concentrations varying widely based on the geographical location and soil mineral content. This uptake forms the primary pathway for strontium to enter the food chain, where it is then consumed by animals and humans.
Unlike calcium, strontium is not considered an essential nutrient for humans, and no official dietary reference intake has been established. A typical daily intake ranges from 1.5 to 5.7 mg, with most coming from food and drinking water. However, the amount absorbed can be influenced by various factors, including age and the level of calcium and phosphorus in the diet.
The Relationship Between Strontium and Calcium
Given their chemical similarities, strontium and calcium share the same transport pathways for absorption in the gut and incorporation into bone. This creates a competitive relationship, where the body preferentially absorbs calcium. Therefore, for proper strontium absorption, it is often recommended to take supplements at a different time from calcium. Inadequate calcium intake, particularly during childhood, can lead to the higher incorporation of strontium into the developing skeleton, which can potentially cause bone abnormalities like rickets. However, at the low levels typically found in food, strontium does not pose a health risk to healthy individuals with adequate nutrition.
Excellent Food Sources of Strontium
While strontium is found in trace amounts in many foods, some sources provide a more concentrated dietary intake. The mineral content of plant-based foods can be affected by agricultural practices, with commercially-produced crops grown with synthetic fertilizers having lower levels compared to organic ones.
Primary Sources of Dietary Strontium
- Cereals and Grains: Wheat bran and whole grains are among the most significant sources of natural strontium. Bread, in particular, has been cited as a good source.
- Seafood: Filter-feeding shellfish, such as oysters and scallops, accumulate strontium from seawater and are considered a hearty source. Fatty fish like salmon also contain it.
- Leafy Green Vegetables: Vegetables such as spinach and lettuce absorb strontium from the soil and are good dietary contributors.
- Root Vegetables and Legumes: Carrots, peas, and beans contain relatively high levels of strontium. Studies have also shown that foods like lentils can absorb significant amounts of strontium from cooking water.
- Dairy Products: Milk and cheese contain strontium. Some studies indicate that lower-fat products might have higher concentrations than their full-fat counterparts.
- Nuts: Brazil nuts are another robust plant-based source.
Comparison of Strontium Levels in Various Food Categories
To illustrate the typical concentrations, here is a comparison of strontium levels across different food categories. These values can vary widely, but the table offers a general perspective based on available data.
| Food Category | Average Strontium Concentration (ppm dry weight) | Key Examples | Notes |
|---|---|---|---|
| Nuts | ~8.67 | Brazil nuts | High natural concentration. |
| Cereals and Grains | ~1.3-3.7 | Bread, wheat bran | Varies based on growing conditions. |
| Seafood | ~3.6 | Fish, shellfish | Filter-feeders may have higher levels. |
| Root Vegetables | >1 | Carrots, parsnips | Content is soil-dependent. |
| Leafy Greens | >1 | Spinach, lettuce | Also highly dependent on soil. |
| Dairy | <1 | Milk, cheese | Concentration varies with fat content. |
| Meat and Poultry | <1 | Meat, poultry | Lower levels than plant-based sources. |
The Role of Strontium in Bone Health
The mineral's similarity to calcium means that 99% of the strontium in the human body resides in the bones and teeth. In controlled studies using the pharmaceutical form strontium ranelate (which is not available in the U.S.), the mineral has shown a dual effect on bone metabolism. It works by stimulating bone-forming cells (osteoblasts) and inhibiting bone-resorbing cells (osteoclasts). This dual action can lead to increased bone mineral density and a reduced risk of fractures in postmenopausal women with osteoporosis. However, it is crucial to differentiate between the natural, trace amounts of stable strontium from food and the synthetic, concentrated pharmaceutical version, which is associated with serious side effects like blood clots.
Natural, stable strontium from food is generally not considered to be harmful at typical dietary intake levels. The risk of developing bone growth problems (rachitic-like effects) from excessive strontium intake is primarily seen in children with poor nutrition, specifically those with calcium and vitamin D deficiencies. Therefore, a balanced diet rich in calcium remains the most important factor for bone health.
Final Conclusion
Yes, it is possible to get strontium from food, as it is a naturally occurring element found in many parts of our diet. The concentration in food varies widely based on the soil and water composition where the food is grown, with some of the best sources being whole grains, seafood, leafy greens, and nuts. While dietary strontium contributes to the body's trace mineral content and offers some benefits due to its chemical similarity to calcium, the quantities are small. The substantial bone health benefits are primarily associated with a specific pharmaceutical form of strontium, which is not available in the U.S. and carries potential health risks. For the average healthy individual, a balanced diet is sufficient for normal strontium intake, with the most important mineral for bone health remaining calcium. For more information, the National Institutes of Health provides comprehensive toxicological profiles and research data on minerals like strontium.
