Calcium is an essential mineral and is needed by your body for structure and cell function. You must get adequate intake of it through your diet. Unfortunately, many individuals do not get enough because of food sensitivities, dietary choices, or poor absorption. Just like other nutrients, it needs to be balanced with other nutrients for it to work properly. Here are some things to consider.

Calcium 101

Calcium is the most abundant mineral in the body. Your bones and teeth are the major storehouse of calcium for skeletal strength and metabolic needs. Ninety-nine percent of calcium is stored in bone in the form called hydroxyapatite. The remaining one percent circulates in your blood. This amount in your bloodstream is tightly regulated primarily by two hormones, calcitonin and parathyroid hormone. If blood levels are not sufficient, it is moved from your bones to supply the needs of the rest of your body.

Calcium Benefits

Besides structural uses, calcium is needed by a large number of critical processes throughout the body. Calcium is involved with blood vessel contraction and relaxation, nerve transmission and neurotransmitters. It is used for cell signaling pumps, transporters, and buffers, cell proliferation and apoptosis (programmed cell death), gene expression, and hormone secretion and activity.

Calcium is needed for the skeletal growth and development in infants to young adults, management and comfort of the menstrual cycle, blood clotting systems, heart rhythm, cardiac muscle, and skeletal muscle function. It is vital for energy production. Calcium is involved with colon health, weight management, and electrolyte balance and much more.

Calcium Measurement

There are two types of blood tests used for general calcium measurement. Serum calcium measures total calcium levels in the blood and is most used. It is considered a good overall indicator. Reference range is 8.8-10.4 mg/dL.

The other test is ionized serum calcium which measures only the “free” or metabolically active calcium form. This is used when serum calcium tests are out of reference range.

Calcium Related Symptoms

Inadequate calcium levels may lead to muscle cramps especially in hands and feet, numbness or tingling in fingers, facial twitching, slow or irregular heartbeat, lightheadedness, anxiety, depression, anger, sleep disruption, confusion, hallucinations, or seizures. There may be brittle nails, coarse hair and dry skin. Low calcium may lead to softening of bones or a decrease in bone density.

Some nutritional causes of low calcium levels include lack of dietary calcium and poor dietary absorption. Low vitamin D levels, insufficient magnesium, and low protein intake may also affect calcium levels. Alcohol and caffeine also impact calcium absorption.

Increased intake of phosphorus, a mineral, may cause calcium levels to decline. Soda pop and processed, pre-packaged foods contain high amounts of phosphorus, which may contribute to low calcium and bone softening and loss in children and adults.

High calcium levels in the blood may provoke other symptoms like constipation, nausea, vomiting, abdominal pain, weakness, loss of appetite, fatigue, increased thirst, and urinary frequency. Excessive vitamin D intake, some types of diuretics or water pills like thiazides/hydrochlorothiazide, and other health concerns may lead to increased calcium levels in the blood.

Recommended Dietary Intake

The RDA intakes for calcium in male and female are:

0-6 months: 200 mg
7-12 months: 260 mg
1-3 years: 700 mg
4-8 years: 1000 mg
9-13 years: 1300 mg
14-18 years: 1300 mg*
19-50 years: 1000 mg*
51-70 years: 1000 mg (men), 1200 mg (women)
71 and older: 1200 mg

*The RDA for calcium intake and pregnant and breastfeeding women is the same.

Food Sources and Dietary Challenges

Calcium is found in many foods. Milk and dairy products provide significant amounts of calcium for many. The milk sugar – lactose helps increase calcium (calcium lactate) absorption, so lactose-free dairy products lead to less calcium absorption.

Plants also contain calcium and can supply dietary needs. Plant-based diets, though, are more difficult to obtain adequate calcium. Fiber and phytic acid naturally found in plants impair calcium absorption and make it less bioavailable compared to dairy products. Calcium bioavailability may be improved in plant-based foods by soaking, germinating, or using sour-dough leavening. Making good food choices and being mindful and knowledgeable about calcium-rich foods are important in maintaining good daily intake.

Food Sources

Here are some examples of calcium amounts in non-fortified whole foods.

1. Milk, low-fat 16 oz 610 mg
2. Milk, whole 16 oz 551 mg.
3. Yogurt, Non-fat, unsweetened 8 oz 487 mg
4. Collard greens, chopped, 1c 357 mg
5. Buttermilk, cultured 1 c 350 mg
6. Ricotta, lowfat ½ c 337 mg
7. Parmesan, (hard), grated 1 oz 336 mg
8. Mozzarella Cheese 1 oz 273 mg
9. Spinach, cooked 1c 245 mg
10. Kale, cooked 1c 195 mg
11. Chia Seeds 1 oz 179 mg
12. Peas, podded, cooked 1 c 94 mg
13. Squash, Acorn, cooked 1 c 90 mg
14. Sweet potatoes, cooked 1 c 88 mg
15. Almonds 1 oz 82 mg
16. Orange, Florida 1 c 80 mg
17. Mixed Nuts ½ c 70 mg
18. Green beans, canned 1c 70 mg
19. Almonds 1 oz 82 mg
20. Broccoli, cooked 1 c 62 mg

More on Plant-Based Diets and Calcium

Any time there is discussion about calcium, there are concerns about bone health. Numerous studies have debated plant-based diet calcium versus omnivore (plant-animal) diet calcium and bone health. Several studies over the years have shown that individuals who consume a plant-based diet are at higher risk of nutrient deficits including calcium.

A systematic review and meta-analysis published June 2021 evaluated 17 cross-sectional studies that involved 13,888 patients. This population analysis showed that vegetarians and vegans had lower bone mineral density due to inadequacy of calcium and other factors than those who ate an omnivore (meat and plant) diet.

Other studies show, however, that if you consume a well-planned plant-based diet with adequate calcium and vitamin D, you can still have good bone density. Individuals with underlying endocrine imbalances with blood sugar, thyroid, parathyroid, etc. may need to more mindful and diligent about calcium intake with vitamin D intake for bone health.

The goal is to be mindful and obtain a well-planned dietary calcium intake in either diet. You may be at risk for inadequate calcium intake if have an omnivore diet but are dairy-free. If you are on a plant-based diet, avoid dairy or oxalate-rich foods, follow a FODMAP or Vegan Keto-Diet, or other scenarios, you may not get enough calcium. Be mindful and diligent about your choices otherwise you rob your bones and teeth of calcium to pay for the dietary lack. To make up for the difference, supplement wisely.

Calcium Type Matters

Calcium carbonate is added to foods and beverages to fortify dietary intake as it is cheap and easy to make, but it has poor bioavailability compared to other forms. Calcium carbonate is found in chalk, marble, limestone, egg shell, and oyster shell. It requires adequate stomach acid for absorption. If you have low/no stomach acid or are on acid blocking medications, this interferes further with the poor absorption of calcium carbonate.

Calcium supplements such as microcrystalline hydroxyapatite, coral minerals, calcium amino acid chelates like taurate and citrate, and calcium AEP have high bioavailability and superior absorption compared to calcium carbonate. The form of calcium stored naturally in bones is hydroxyapatite.

Team Player with Other Nutrients

Calcium is a team player with other nutrients. Vitamin D, vitamin K2, magnesium, silica, boron and other nutrients affect how calcium works, especially for bone health.

Gut health and the beneficial flora in your intestinal tract powerfully impacts calcium absorption. If your gut flora is out of balance or in dysbiosis, this disturbs calcium absorption, which ultimately affects bone health. Gut dysbiosis with non-beneficial bacteria or yeast overgrowth happens with high stress, consumption of processed foods and sugar, alcohol, use of antibiotics, steroid or other pain medications, and antacids, etc.

If you have never taken time to complete a diet diary for a few days to check your calcium or other nutrient intake, I encourage you to do so. Write down all the foods and beverages with the amounts that you consumed in a three-day period. Add up the amount of calcium for each day as listed on the package or through any number of apps or websites available commercially or by the FDA. Do this too for the kids and seniors in your life. I have talked with many individuals over the years who believe they are getting enough by their guesstimate only to find that they repeatedly fall short of the RDA when they actually check their calcium intake by doing this. Are you meeting your calcium needs?