Dietary sources of calcium are common, and they're not just dairy products, so calcium normally isn't a problem. However, some people have conditions that cause them to digest too much calcium from food, which can cause health issues. In these cases, it's necessary to make changes to limit calcium intake.
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Sources of Low Calcium
Calcium is so abundant in the average human diet that searching for foods entirely without calcium is nearly impossible. Though there are some obscure exceptions that contain no calcium whatsoever, the best way to tackle a low calcium diet is by eliminating foods that are particularly high in the mineral and including those that are low in it, such as the wide variety of low calcium vegetables available.
According to UCSF Health, the amount of calcium an adult between ages 19 and 50 should be receiving daily is 1,000 milligrams. These foods have less than 100 milligrams of calcium based on a 1-cup serving, so they are safe in moderation on a low calcium diet:
- Brie cheese: This cheese has only 50 milligrams of calcium.
- Parmesan cheese: Parmesan only has 70 milligrams of calcium.
- Legumes: Between 15 and 50 milligrams of calcium depending on the variety; always check the nutrition label.
- Pinto beans: 75 milligrams
- Soybeans: With 100 milligrams, soybeans are right on the cusp, but they can still contribute to a low calcium diet.
- Tempeh: 75 milligrams
- White beans: 70 milligrams
- Brown rice: 50 milligrams
- Corn tortillas: 85 milligrams, but this can vary; check the nutrition label.
- Sunflower seeds: 50 milligrams
Low calcium vegetables — with less than 100 milligrams of calcium per cup — include:
- Bok choy: 40 milligrams
- Chicory: 40 milligrams
- Collard greens: 50 milligrams
- Corn: With 10 milligrams of calcium in a cup, corn is one of the best vegetables for a low calcium diet.
- Dandelion greens: 80 milligrams
- Kale: 55 milligrams
- Kelp: 60 milligrams
- Mustard greens: 40 milligrams
- Turnip greens: 80 milligrams
These are just some of the foods with a comparatively low calcium count; there may be others you find by checking the nutrition labels on products in your supermarket.
Read more: How to Lower Calcium Naturally
Risks Associated With Calcium
While calcium certainly has its own benefits for the body, too much of it can cause an array of issues. According to the National Institutes of Health, an excess of calcium in the body has been linked to constipation and inhibition of the ability to absorb important minerals such as iron and zinc.
Excess calcium has also been linked to increased risks of heart disease and prostate cancer, among other forms of cancer, though more research needs to be conducted on this topic before conclusive results are found.
The upper limit of calcium for an adult 19 to 50 is 2,500 milligrams, which is an exceedingly high amount ordinarily only achieved through the use of calcium supplements. These supplements are often provided to help with bone strength and to ward off osteoporosis, but there are other ways to boost bone strength beside increasing your calcium intake.
According to HelpGuide, a mental health and wellness organization that collaborates with Harvard Health Publishing, 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 to absorb calcium, and also helps to 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 phosphorous include pork, poultry, lentils and whole grains.
The more calcium the body successfully absorbs, the less likely it is that calcium will bind to uric or oxalic acids in the bloodstream. When it binds to these acids, calcium oxalate stones are formed — otherwise known as kidney stones.
Read more: What Vegetables Should Help Kidney Stones?
Kidney Stones and Calcium
The most common types of kidney stones are known as calcium oxalate stones, because their formation results from oxalate binding to calcium in the bloodstream or urine.
Oxalate is a natural substance found in the majority of foods. Food is used for energy, and once the body has absorbed all it can any waste that remains is sent through the bloodstream to the kidneys, where it is then removed. If there is too much waste, then crystals begin to form; when these crystals bind to calcium they create kidney stones.
A common misconception is that by reducing the amount of calcium in your diet you can actively reduce the risk of developing kidney stones, but this is not true. Calcium oxalate stones only form if oxalate binds to calcium in the kidneys, but if they bind in the stomach then they are disposed of effectively.
To this end, consuming dietary sources of calcium in line with daily recommendations is required so that no build-up of oxalate in the stomach occurs. Calcium supplements are often to blame for increased calcium oxalates forming in the bloodstream as opposed to dietary causation.
To reduce the risk of kidney stones, Harvard Health recommends avoiding foods that are known to be stone-forming due to their high oxalate content. These include beets, chocolate, spinach, rhubarb, tea and most nuts. They may not need to be avoided entirely, but they should be consumed in small amounts.
Foods to Avoid With Hypercalcemia
According to the Mayo Clinic, hypercalcemia is a condition in which there is too much calcium in your 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.
It can be caused by a variety of severe illnesses (such as cancer), but a common cause is the overuse of calcium supplements. Many individuals start taking calcium supplements in an effort to strengthen bones without even realizing the opposite effect may be occurring. When it comes to supplementation, it's incredibly important to stay informed.
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 are all high in calcium
- Certain vegetables: Arugula, bok choy, collard greens, corn, kale and spinach all possess a high calcium content. Dark leafy green vegetables are especially high
- Certain fruits: Figs, kiwi and orange juice all contain high calcium
- Seafood: Oysters, shrimp, salmon and sardines can all contribute to excess calcium
- Nuts and seeds: Calcium is particularly high in almonds, sunflower and sesame seeds
Symptoms of hypercalcemia vary from the imperceptible to the severe, but they include issues relating to:
- The digestive system: Nausea, vomiting and constipation
- 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 may experience severe lethargy and tiredness.
- Heart function: Though rare, hypercalcemia has been known to cause palpitations and fainting.
If you suspect you have symptoms of hypercalcemia, or have concerns regarding the calcium supplements you have been taking, contact your usual health care professional for further advice.