Strontium is a naturally occurring trace element that belongs to the same chemical group as calcium, giving it similar properties within the body. This element is widely distributed in the environment, found in soil, water, and ultimately, in the food supply. The discussion of strontium often involves its stable, naturally occurring form, distinct from the radioactive isotope strontium-90 or pharmaceutical drugs. This article focuses on identifying the primary dietary sources of stable strontium, helping to understand how this mineral is incorporated into the daily diet.
Strontium’s Function in the Body
Strontium plays a distinct role in the body due to its close chemical resemblance to calcium, the main mineral component of bone tissue. This similarity allows strontium to be incorporated into the bone matrix, influencing the continuous process of bone remodeling. Bone remodeling requires a balance between osteoblasts, which build new bone, and osteoclasts, which resorb old bone.
The presence of strontium ions affects both cell populations in a unique dual manner. It promotes new bone tissue formation by stimulating the proliferation and differentiation of osteoblasts and enhancing the synthesis of bone matrix proteins.
Simultaneously, strontium inhibits bone resorption by reducing the activity of osteoclasts. It achieves this by suppressing the formation and differentiation of these cells and promoting their programmed cell death. This dual action—stimulating bone formation while reducing bone breakdown—is why the element is studied for its effects on skeletal health.
Primary Dietary Sources of Strontium
The concentration of strontium in foods is highly variable, depending largely on the amount of the mineral present in the local soil and water where the food was grown or produced. Even the same type of food can show significant differences in its strontium content based on its geographic origin. Despite this variability, certain food categories are consistently recognized as containing higher amounts of the trace element.
Grains and Cereals
Grains, particularly whole grains and cereals, are substantial contributors to dietary strontium intake. The mineral tends to concentrate in the bran of grains, making whole-grain products a better source than their refined flour counterparts. Whole wheat, barley, and products like pasta can provide notable amounts.
Seafood
Seafood, particularly marine fish and shellfish, often contains high levels of strontium because the mineral is readily absorbed from seawater. Shellfish, which are filter feeders, tend to show the highest concentrations among marine life. Marine smoked fish is another source that can have a strontium-to-calcium ratio significantly higher than that found in dairy products.
Vegetables
Vegetables are another important source, with certain types accumulating more strontium than others. Root vegetables like carrots, beets, and potatoes, as well as leafy greens such as spinach, are recognized as good dietary contributors. For root vegetables, the mineral is often more concentrated in the peel, so minimal peeling can retain more of the mineral.
Dairy Products
Dairy products, including milk, yogurt, and cheese, also contribute to the total daily strontium intake. The strontium in dairy comes from the plants consumed by the livestock. While dairy is a significant contributor due to high consumption rates, the concentration of strontium is often lower compared to the highest plant-based or marine sources.
Managing Strontium Intake and Absorption
The typical daily intake of strontium for an adult consuming a mixed diet ranges approximately between 1 and 4 milligrams. The element is poorly absorbed by the body, with bioavailability estimated to be only around 25 to 30% of the ingested amount. This absorption efficiency is a major factor in determining how much dietary strontium is ultimately available to the body.
The most important factor influencing strontium absorption is its competitive relationship with calcium. Since strontium and calcium are chemically similar, they compete for the same absorption pathways in the gut. High intake of calcium can significantly inhibit the absorption of strontium, and vice versa.
To maximize the absorption of dietary strontium, it is suggested to consume strontium-rich foods separately from high-calcium foods or supplements. Other components in plant-based foods, such as phytates, can also bind to strontium and other minerals, reducing their overall bioavailability. Phytates are compounds found in whole grains, legumes, and seeds.
Maintaining a balanced, varied diet naturally provides a moderate and safe level of this trace mineral.