According to the National Health and Nutrition Examination Survey (NHANES), about 39% of Americans don’t consume enough calcium. To be clear, the NHANES is imperfect—relying on infrequent food questionnaires—so take this stat with a grain of salt.
And this stat doesn’t necessarily reflect the calcium status in health-conscious people. For instance, I have reviewed thousands of clients eating nutrient-dense diets in my coaching career, and most of them were calcium sufficient.
The point is that, like all deficiencies, the presence or absence of calcium deficiency depends on one’s diet. It doesn’t affect everyone equally, and there are things we can do to prevent it.
Of course, some factors may be out of our control. Dairy intolerance, for instance, leads to higher risk of calcium deficiency. But it’s not impossible to eat a calcium-rich diet without dairy, it’s just a bit more difficult.
Couldn’t a calcium supplement fill in the gaps? It could—and it would likely improve calcium status—but I have concerns.
My main concern is that supplemental calcium can cause soft tissue calcification in blood vessels. Supplemental calcium, but not dietary calcium, is linked to increased heart disease risk. And there also exists evidence that calcium supplementation is associated, albeit loosely, with a higher incidence of certain breast cancers.
So why are people still so focused on supplementing calcium? For many, I think it comes down to bone health. To these people, I’d caution that it’s not actually clear that calcium inadequacy is the sole driver in most cases of osteoporosis, though it gets the most attention. Many other nutrients and lifestyle habits—vitamin D, phosphorus, vitamin K2, strength training habits, and more—factor into bone health.
But of course, calcium certainly is one of the nutrients that matter for your bones. Later, I’ll share practical tips to get enough calcium. First, though, let me establish why calcium matters.
The Need for Calcium
If you go searching for calcium (Ca) in the human body, you’ll find about 99% of it in the skeleton. Calcium is a key component of bones and teeth.
It’s not the only nutrient needed for strong bones. (We also need vitamin D, vitamin K2, phosphorus, magnesium, sodium, and potassium.) But it’s certainly the most celebrated.
Calcium’s importance in structuring the skeleton becomes obvious when we don’t get enough of it. When someone is deficient in calcium, bone density disorders like osteopenia and osteoporosis soon follow.
Yet while most calcium is found in bones and teeth, the calcium in your blood is just as crucial (probably more-so) for keeping your body humming. This significance is reflected in that skeletal calcium is used as a backup system for when maintaining serum calcium becomes difficult.
Consider that calcium in the blood, extracellular fluid, and muscles regulates:
- Vascular contraction and relaxation
- Muscle contraction and relaxation
- Hormonal secretion
- Nerve transmission
- Cellular communication
Many of these functions are tied to calcium’s role as an electrolyte. Electrolytes are charged minerals that conduct electricity in a liquid—and this electricity conduction is how your nervous system sends messages throughout your body.
Do you like having a functional nervous system? Do you enjoy thinking, moving, and breathing? If not, don’t worry about electrolytes.
What Is Calcium Deficiency?
A deficiency occurs when a person doesn’t consume enough of a given nutrient to support optimal health. Deficiencies can also result from various medical conditions, illnesses, or injuries.
In the case of calcium deficiency, a large part of “optimal health” really refers to optimal bone health. The Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine developed the adult calcium RDAs to optimize for bone maintenance. Adults generally want to maintain bone, not grow it or lessen it.
The RDAs for children, on the other hand, were set to optimize for bone accumulation. That’s why children aged 9-18 have a higher RDA (1.3 grams) than adults aged 19-50 (1 gram).
According to the FNB, most adults should aim for between 1 and 1.3 grams of dietary calcium to prevent deficiency. Check out Table 1 here for the full RDA chart.
Calcium Deficiency vs. Calcium Imbalance
A calcium deficiency is NOT the same as a calcium imbalance. This is a common point of confusion.
A calcium imbalance is when serum calcium levels get too low (hypocalcemia) or too high (hypercalcemia). These conditions cause disturbing symptoms like muscle weakness, tremors, spasms, fatigue, lethargy, and nausea. They often require medical attention.
But hypocalcemia is rarely caused by low calcium intakes alone. Why? Because if you don’t consume enough calcium, your body raids bone to restore serum levels.
Your body will use bones as calcium reservoirs. If calcium levels dip, it will happily tap these reservoirs to bring the levels up. From our bodies’ perspectives, low serum calcium is an emergency. Low skeletal calcium… not so much.
Hypocalcemia is caused by poor vitamin D status, poor magnesium status, impaired parathyroid hormone (PTH) production, critical illness, or certain medications. Calcium deficiency, however, is generally driven by poor nutritional status.
And that low calcium intake won’t show up on your serum calcium test. Just read what the National Institutes of Health (NIH) says about it: “Serum [calcium] levels do not reflect nutritional status because of their tight homeostatic control.” By the way, this is also true of sodium, potassium, and magnesium. Serum levels don’t reflect nutritional status because our bodies have systems in place to prevent their drop.
For calcium deficiency, you want to be looking at markers of bone density (like osteocalcin), markers of bone turnover (like urinary calcium excretion), and calcium intakes. Don’t look at serum calcium as a marker of deficiency.
Signs and Symptoms of Calcium Deficiency
The main sign of calcium deficiency is osteoporosis—a disorder marked by brittle bones and increased fracture risk. In someone with osteoporosis, even a low-impact fall can mean a life-changing hip fracture.
Over 50% of postmenopausal women (and 20% of men) will suffer a fracture related to osteoporosis. In senior women that fracture their hip, only 33% continue to live independently.
Why are postmenopausal women so vulnerable to osteoporosis? In part, because the perimenopausal decline in estrogen reduces calcium absorption and increases calcium losses through urine.
Dairy-intolerant people are also at higher risk for calcium inadequacy. This risk can be mitigated, however, by consuming milk-free sources of calcium.
Other bone-related disorders linked to calcium deficiency include:
- Osteopenia: A less severe form of osteoporosis.
- Rickets: A childhood disorder of fragile bones, bone pain, muscle weakness, and skeletal deformities.
- Osteomalacia: The adult version of rickets.
In combination with other factors like vitamin D deficiency and phosphorus overload, a severe calcium deficiency also increases the risk of a neuromuscular disorder called tetany. The symptoms of this condition include tremors, muscle spasms, twitching, coma, seizures, and death.
What Causes Calcium Deficiency?
The main cause of calcium deficiency is an insufficient intake of calcium-rich foods. If you aren’t eating dairy, bones, or dark leafy vegetables—you’re probably calcium deficient.
That’s calcium deficiency, but a range of other factors influence calcium’s role in bone health. Let’s talk about those.
First, an excess of phosphorus (which binds to calcium) is bad news for calcium status and bone density. Unfortunately, a modern diet high in consumption of grains, processed junk, and other phosphorus-rich foods puts most Americans into the “phosphorus overload” category.
Then there’s vitamin D, a hormone-like vitamin that 42% of Americans are deficient in. If you’re low on vitamin D, you won’t properly absorb calcium and your bones will be sad.
I can’t talk about phosphorus and vitamin D without mentioning parathyroid hormone (PTH). Both phosphorus overload and vitamin D deficiency stimulate an overproduction of PTH, which in turn makes your bones shed calcium.
Finally, there’s vitamin K2. Found in pastured dairy and fermented soy, this underappreciated vitamin activates a protein (matrix GLA protein) that brings calcium into bones while keeping it away from blood vessels.
Should You Take Calcium Supplements?
Well-meaning people often recommend calcium supplements for strong bones. The presumption is that higher calcium intakes translate to better bone health.
But the evidence for this hypothesis is mixed. In one 6 year study, 1 gram of supplemental calcium plus 400 IU of vitamin D per day did not affect height loss in postmenopausal women. Other research, however, has shown that calcium can boost bone mineral density.
You see a similar story with fracture risk. Some data shows a beneficial effect from calcium supplements while other data does not.
What’s going on here? Well, bone health is complex. As you’ll recall, it also depends on vitamin D, vitamin K2, and phosphorus status. And I didn’t even cover how sodium, potassium, magnesium, and exercise factor in!
And so getting more calcium doesn’t guarantee stronger bones. That’s the first point.
The second point is that calcium supplementation is not without risks.
When you consume a supraphysiological dose of calcium (a gram, say) it creates a temporary state of hypercalcemia. And some of this excess calcium ends up in undesirable places.
One such place is the coronary arteries. Increased arterial calcification (a well-established heart disease risk factor) likely explains why several studies have linked calcium supplementation to higher risks of heart attack and stroke.
Excess calcium also ends up in urine, increasing the rate of calcium oxalate crystals (aka, kidney stones) forming. When the stones pass, it ain’t pleasant.
So here’s my opinion: for most people, the risk-reward analysis for calcium supplementation doesn’t add up. But I do recommend getting enough calcium through diet.
How To Prevent Calcium Deficiency
To prevent calcium deficiency, eat calcium-rich foods. Here are a few good options:
- Yogurt (296 mg per cup)
- Kale (94 mg per cup)
- Sardines with bones (347 mg per 3.2 ounces)
- Salmon with bones (181 mg per 3 ounces)
- Spinach (246 mg per cup)
- Turnip greens (198 mg per cup)
- Broccoli (62 mg per cup)
- Cheese (204 mg per 1 ounce)
- Cow’s milk (138 mg per 4 ounces)
- Tofu (775 mg per 4 ounces)
Shoot for around a gram of calcium per day. (1.3 grams if you’re older). To confirm you’re hitting the target, you may want to download the app called Cronometer, log your meals, and calibrate accordingly.
Getting enough calcium means you’ll have one less osteoporosis-risk factor. That’s a good enough reason to dial in your calcium intake with a dietary analysis.