Calcium is a vital mineral for various bodily functions, including building strong bones and teeth, muscle contraction, blood clotting, cell membrane maintenance, and nerve transmission. While adequate calcium intake is essential for maximizing bone density and preventing osteoporosis, certain conditions may necessitate a low-calcium diet. This article provides a detailed overview of low-calcium diets, including foods to include and avoid, the importance of other nutrients for bone health, and potential health concerns associated with excessive calcium intake.
The Importance of Calcium
Calcium plays a crucial role in maintaining overall health. It is a mineral used for numerous functions, including building bones and teeth, muscle contraction, blood clotting, maintenance of cell membranes, and nerve transmission. Calcium in the blood is tightly regulated; Vitamin D plays an important role in maintaining calcium homeostasis. In response to a drop in blood calcium, vitamin D acts in three ways to maintain calcium levels in the blood: increasing absorption of calcium from the gut; increasing reabsorption of calcium by the kidney to limit urinary excretion; and mobilizing calcium from bone.
Adequate intake of calcium is essential for maximizing bone density. Therefore, an inadequate intake of calcium can adversely influence bone formation and may contribute to osteoporosis. Osteoporosis is a decrease in bone density and strength that results in increased susceptibility to bone fractures. It is a debilitating disease most commonly found in postmenopausal women; however, men are also at risk for this disease. In the United States, 8 million women and 2 million men are estimated to have osteoporosis. Osteoporosis cannot be cured; it can only be prevented or its progression delayed.
When a Low-Calcium Diet is Necessary
While calcium is crucial for bone health, certain conditions may require limiting calcium intake. These include:
- Kidney Stones: The most common types of kidney stones are calcium oxalate stones, which form when oxalate binds to calcium in the bloodstream or urine.
- Hypercalcemia: This condition occurs when there is too much calcium in the blood. Despite calcium's role in strengthening bones, too much of it can actually weaken them. On top of this, hypercalcemia can create kidney stones, cause heart problems, and have a negative impact on brain function.
Foods to Include on a Low-Calcium Diet
It is almost impossible to find foods entirely without calcium. The best way to follow a low-calcium diet is by eliminating foods particularly high in the mineral and including the wide variety of low-calcium vegetables available.
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These foods have fewer than 100 mg of calcium based on a 1-cup serving, so they are safe in moderation on a low-calcium diet:
- Pinto beans: 78mg
- Black beans: 46mg
- Lentils: 37mg
- Brown rice: 19mg
Low-calcium vegetables, with fewer than 100 mg of calcium per cup, include:
- Collard greens: 84mg
- Mustard greens: 64mg
- Carrots: 42mg
- Celery: 40mg
- Chicory greens: 29mg
- Corn: 11mg
Foods to Avoid or Limit on a Low-Calcium Diet
According to UCSF Health, the following foods are all high in calcium and thus should be avoided if you are concerned about hypercalcemia:
- Dairy products: Cheese, milk, cream, and yogurt
- Certain vegetables: Arugula, bok choy, kale, and spinach; dark leafy green vegetables are especially high
- Certain fruits: Figs, kiwi, and orange juice
- Seafood: Oysters, shrimp, salmon, and sardines
- Nuts and seeds: Almonds, sunflower, and sesame seeds
Other Nutrients Important for Bone Health
Calcium does not work alone to keep us strong. As children grow, their bodies also needs other minerals, such as phosphorus and magnesium, and other nutrients such as vitamin D and vitamin K. The following nutrients are all beneficial for calcium and bones:
- Magnesium: Aids the body in absorbing and retaining calcium. Magnesium can be found in nuts, seeds, tofu, seafood, spinach, and broccoli.
- Vitamin D: As with magnesium, vitamin D helps absorb calcium and helps regulate calcium levels in the blood. Vitamin D is found in certain fortified cereals, fish, shrimp, oysters, and eggs.
- Phosphorous: Works in tandem with calcium to build bones, provided both are taken in moderation. Good sources of phosphorus include pork, poultry, lentils, and whole grains.
Calcium Supplements: A Word of Caution
Calcium supplements are available without a prescription in a wide range of preparations (including chewable tablets, gummy preparations, powders and liquid) and in varying amounts and sizes. The best supplement is the one that meets your needs for tolerability, convenience, cost, and availability. Choose brand-name supplements with proven reliability. Look for labels that state “purified” or have the USP (United States Pharmacopeia) symbol. Read the product label carefully to determine the amount of elemental calcium, which is the actual amount of calcium in the supplement, as well as how many doses or pills you have to take.
Read also: Calcium D-Glucarate Precautions
Calcium is absorbed best when taken in amounts of 500 - 600 mg or less. This is the case for both foods and supplements. Try to get your calcium-rich foods and/or supplements in small amounts throughout the day, preferably with a meal. Take (most) calcium supplements with food. Eating food produces stomach acid that helps your body absorb most calcium supplements. When starting a new calcium supplement, start with a smaller amount to better tolerate it. When switching supplements, try starting with 200-300 mg every day for a week, and drink an extra 6-8 ounces of water with it.
However, it is best to obtain calcium through dietary sources and to limit supplements so that the DRIs are not exceeded. At calcium intakes above the UL, serious side effects may occur, including severe renal damage and abnormal calcium deposition in the body’s soft tissue. Some individuals may also develop hypercalcemia (excessive amounts of calcium in the blood) or hypercalciuria (excessive amounts of calcium in the urine).
Potential Health Concerns with Excessive Calcium Intake
At elevated calcium intakes above the UL, serious side effects may occur, including severe renal damage and abnormal calcium deposition in the body’s soft tissue. Some individuals may also develop hypercalcemia (excessive amounts of calcium in the blood) or hypercalciuria (excessive amounts of calcium in the urine).
Symptoms of hypercalcemia vary from very subtle to severe and can include issues relating to:
- The digestive system: Nausea, vomiting, and constipation may occur.
- Bones and muscles: You may feel weaker, or your muscles ache. This is due to the calcium moving from your bones into your blood, weakening them.
- Brain function: You may feel confused or dizzy and experience severe lethargy and tiredness.
- Heart function: Though rare, hypercalcemia has been known to cause palpitations and fainting.
Kidney Stones and Calcium: Addressing Common Misconceptions
A common misconception is that you can actively reduce the risk of kidney stones by reducing the amount of calcium in your diet, but this is not true. Calcium oxalate stones only form if oxalate binds to calcium in the kidneys. If they bind in the stomach, they are disposed of effectively.
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To this end, consuming dietary sources of calcium in line with daily recommendations is required so that no buildup of oxalate in the stomach occurs. Calcium supplements are often to blame for increased calcium oxalates forming in the bloodstream as opposed to calcium from foods.
To reduce the risk of kidney stones, avoid foods that are known to be stone-forming due to their high oxalate content. These include beets, chocolate, spinach, rhubarb, tea, and most nuts. You may not need to avoid these foods entirely. Rather, you can consume them in small amounts.