Low calcium in the blood (which is rare) can be dangerous as it affects nerve, muscle, and heart function.
Low calcium symptoms include numbness, tingling, palpitations, memory loss, muscle weakness, and dry skin.
Low calcium uptake into the bones is more common, and over a prolonged time can cause weak or brittle bones.
People most at risk of low calcium include postmenopausal women, those with vitamin D deficiency, people who take steroid medications, or those who have inflammatory bowel disease.
Calcium supplements have been linked with heart problems so should be used carefully and only if you struggle to meet the daily recommendation.
Getting a balanced range of other bone health nutrients including vitamin D and K2 may mean you need less calcium than the official RDA.
A healthy gut and a daily intake of probiotics may help you absorb calcium better.
Calcium is an important mineral that we all need for strong bones as well as for nerve, heart and muscle function, and correct blood clotting.
Though low calcium symptoms often aren’t obvious at first, a calcium deficiency can lead to weakened bones over time. In this article, we’ll discuss common causes of low calcium symptoms, the importance of calcium, and how to keep your levels optimized. But we’ll also take a look at bone health more holistically, as there’s a lot more to it than just calcium.
Recognizing Low Calcium Symptoms
First, it’s important to distinguish between low calcium in the bones and low calcium in the blood as the two are quite different, with different causes and different sets of symptoms.
Low Calcium in the Bone
When you have a low level of calcium in your bone, it will often be because of diet and lifestyle factors. Bones affected by low calcium and/or vitamin D over many years can become less dense (osteopenia) or brittle (a more advanced condition known as osteoporosis).
Fractures from minor falls that would not normally cause a break in a healthy bone
Fractures from bending, lifting, or even coughing
Being postmenopausal is a risk factor for osteoporosis due to the additional effect of hormonal changes (chiefly the drop in estrogen) that occurs when periods cease.
Low Calcium in the Blood (Hypocalcemia)
Low blood calcium levels are not as common as low calcium reserves in the bone, and they don’t tend to be caused by low dietary calcium. Instead, the main causes of hypocalcemia are medical conditions such as kidney failure or hypoparathyroidism 
Hypoparathyroidism occurs when the four small, pea-sized parathyroid glands behind your thyroid gland can’t make enough parathyroid hormone (PTH), usually because of damage to the glands during thyroid surgery, or (rarely) due to an autoimmune disease. Estimates suggest fewer than 200,000 people in the USA (less than 6 in 10,000) have hypoparathyroidism, so it’s not particularly common.
When blood calcium levels are chronically low, it’s possible to experience increasingly severe symptoms that can sometimes become life-threatening. These include :
Dry skin (and scaly skin)
Brittle nails and coarse hair growth
Painful muscle cramps and muscle spasms, especially in the back and legs
Tingling and muscle weakness
Confusion, memory loss, depression, and hallucinations
Irregular heart rhythm (arrhythmias) and congestive heart failure
Low blood calcium levels are rare because the body will do all it can to maintain calcium levels within a normal range for the nerves, muscles, blood, and heart to function properly. Low dietary calcium can cause the body to steal calcium from the bones to make sure there is enough in the blood to conduct life-saving functions .
How to Get Enough Calcium to Protect Your Bones
Recommended calcium intakes vary around the world but below are the US recommendations :
Recommended Intake of Calcium (RDA)
Women 19–50 years
1000mg per day
Women 51 years and over
1200mg per day
Men 19–70 years
1000mg per day
Men 71 years and over
1200mg per day
The richest sources of calcium are:
Dairy products such as milk, yogurt, and cheese (especially hard cheeses)
Other calcium rich foods include:
Fortified foods, e.g. calcium-enriched plant milk alternatives, orange juice, and breakfast cereals
Green veggies including kale, cabbage, and broccoli
Soybeans, garbanzo beans, white, and pinto beans
Fish canned with bones, such as sardines and salmon
Whole grain and rye
Almonds, Brazil nuts, and sesame seeds
Some natural mineral waters
Below are three suggestions of daily food intakes that will net you 1000mg calcium a day, per the Insitute for Equality and Efficiency in Health Care (IQWiG) :
2 slices of rye bread or whole grain bread
2 slices of gouda, gruyere or Swiss cheese
1 serving of broccoli
2 glasses of mineral water, and
1 cup of yogurt* (200g)
2 glasses of milk* (200 ml each)
2 slices of rye bread or whole grain bread,
1 slice of parmesean cheese
1 cup of raw spinach or ½ cup steamed
1 serving of muesli (50g), with milk* (100 ml)
1 cup of yogurt *(200 g)
1 slice of rye bread or whole grain bread
1 slice of gouda, gruyere or Swiss cheese
1 serving of green cabbage1 glass of mineral water
*Or calcium-fortified plant milk alternative
Calcium Supplements Aren’t Always the Best Option
You may conclude from looking at the above that it’s quite difficult to get enough calcium in your diet, especially if you are dairy-free, and that perhaps it might be easier to take supplements instead. But though that’s an option, it’s not always the best one — as my podcast with Chess Kresser pointed out, there may be downsides to taking calcium in supplement form.
Looking at meta-analyses (in which the results of many studies are combined for higher statistical power), calcium supplements have been linked with higher cardiovascular risk:
One meta-analysis in the BMJ found calcium supplements containing more than 500 mg calcium were associated with a 30% increased risk of heart attack 
A later meta-analysis found that calcium supplements increased risk of cardiovascular disease by about 15% in healthy postmenopausal women 
If you are currently taking calcium supplements there’s no need to be overly concerned, as the stats are less worrying when you consider absolute risk rather than relative risk. For example, in the BMJ meta-analysis above, 5.8% of those taking calcium had a cardiovascular event, compared with 5.5% of those taking placebo .
Nevertheless, the general rule still applies: with calcium supplements, more is NOT better.
A good idea is to work out how much calcium you are routinely getting from food and only top up your levels with supplements if needed (to a maximum of 1000-1200mg per day).
Too Much Focus on Calcium?
It’s worth noting that not all countries have such high calcium recommendations — for example, in the UK, the recommendation is 700mg for adults , and in the EU it is 800mg . The World Health Organization says osteoporosis can even be prevented at intakes of around 500mg of calcium a day.
Higher calcium intakes also don’t seem to correlate very strongly with bone strength.
One analysis showed that increasing calcium intake only affects bone density in the over-50 age group .
Another concluded that taking 1000mg a day doesn’t reduce fractures in older age groups .
It’s also fascinating that people in Asia average less than 400g of calcium a day but don’t appear to have high rates of osteoporosis (this needs to be said cautiously as detection rates for osteoporosis are probably lower in this region. People of Chinese heritage also seem to absorb calcium better).
Either way, it seems clear that people can maintain good levels of bone health at more modest calcium intakes (perhaps 700–900mg a day), and this is certainly consistent with what I have experienced clinically with my patients.
In a nutshell, there is more to healthy bones than just cramming in as much calcium as possible. And just focusing on this one nutrient may mean you neglect other important aspects of bone health.
By ensuring you target bone health from all angles, hitting the full US recommended intake of calcium may not be necessary.
Let’s now consider the other diet and lifestyle factors that are just as vital for bone health as getting adequate calcium, starting with the most important, which is vitamin D.
This vitamin (technically a hormone) can be made by sunlight acting on our skin and is particularly crucial for bone health as it is vital for the uptake of calcium from the intestine . Anyone who is deficient in vitamin D will have a limited capacity to absorb calcium, even if they consume the right amount .
A simple blood test as part of your yearly wellness check will determine your vitamin D level and whether you need to top up your levels. However, those who should definitely consider supplementing include:
People with darker skin
Those with inflammatory bowel conditions or other malabsorptive conditions who may have problems absorbing fat-soluble vitamins like vitamin D
Anybody who rarely gets sun exposure, either because they don’t go outside much or dress to stay covered at all times. Sunscreen also reduces the vitamin D your skin can produce.
You can get vitamin D from food as well as sunlight, but the only two really good sources are seafood and organ meats. Unless you eat a lot of these regularly, vitamin D supplements are recommended, but make sure to have your levels monitored.
Does Vitamin D Make Calcium Supplements Safer?
Some research suggests that vitamin D alongside calcium supplements might help to reduce any potential cardiovascular side effects of the mineral. In one meta-analysis, coronary heart disease risk went up 20% in those taking high-dose calcium-only supplements (1,000–1,400 mg/day) but not at all in those taking calcium and vitamin D together . However, not all research has shown this protective effect.
As with most nutrients, you can have too much of a good thing and should not exceed the Tolerable Upper Intake (the highest allowed amount before side effects occur). For vitamin D, this is 4,000 IU (100 mcg) a day when taking it long-term .
Recently, I’ve also been asked a lot about vitamin K2’s role in bone health — specifically whether it too can make calcium supplements safer and more effective.
The answer is that we don’t have enough information to say for sure. But, preliminary (mainly animal) research does suggest that vitamin K2 might help to prevent cardiovascular disease [16, 17, 18].
Big observational studies like the Nurses’ Health Study and Framingham Heart Study also show a link between higher dietary intake of vitamin K (particularly K2) and lower hip fracture rates / higher bone density in women [19, 20]
Putting this all together I would encourage anyone concerned about bone strength to eat K2 rich foods, which include chicken, beef liver, cheeses such as Camembert, egg yolk, and particularly fermented foods like natto and sauerkraut.
If you do take a calcium and vitamin D supplement or other bone care supplement, it makes sense (and can do no harm) to have some vitamin K2 in there too. However, those with kidney disease or who are on blood thinners should steer clear.
Other Bone Minerals
Magnesium, manganese, boron, and zinc are other important minerals that work alongside calcium to improve the strength, structure, and health of bone. Here’s a quick guide on where to find these in your diet and how they help.
How it Helps Bone
Brazil nuts, almonds, green leafy veggies, whole grains, legumes, dairy
Helps maintain the body in a mildly alkaline state, which prevents excess bone breakdown. Magnesium is also directly structural within the bone [21, 22]
Shellfish, nuts, brown rice, legumes, oatmeal, spinach
Manganese is a cofactor (helper) for several enzymes involved in bone formation 
Plays an important role in bone generation (osteogenesis), via the production and activity of steroid hormones 
Lean red meat, fish, seafood, nuts, seeds, and whole grains
Boosts the function of collagen and bone producing cells (chondrocytes and osteoblasts), while inhibiting cells that break down bones 
Protein and Plants
Protein is another vital constituent of bone, and low protein intakes correlate with reduced bone density . A high protein intake is recommended if you already have osteoporosis or are guarding against it.
The phytochemicals and antioxidants found in vegetables and other plant foods can also boost bone. In one study, extracts from pinto bean hulls with high antioxidant activity decreased bone loss and improved overall bone health, while in another, green tea polyphenols reduced oxidation and inflammation, improving bone strength in animal experiments .
Green vegetables also contain alkaline precursors that help to neutralize an acidic environment resulting from the digestion of processed foods and red meats. An acid environment in the body can leach calcium from bones, which is why veggies are so vital to help bones hold on to their calcium and stay strong .
Bones need stress to keep them strong, and any exercise that is weight-bearing, such as walking and particularly running (but not so much swimming or cycling), can help to keep your bones from deteriorating.
Jump roping ticks all the boxes of a high-impact exercise that is highly effective at preventing bone loss and averting low calcium symptoms — in one study increased ankle bone strength was noted in those who did weekly rope skipping activities . If you want to boost your bones while releasing the inner child in you, give it a go!
Resistance exercises with dumbbells, bands, or kettlebells also provide the pushing and pulling stresses needed to simulate bone-forming cells.
Gut Health Impacts Calcium Levels
Calcium intake is not the only factor in determining your blood and bone levels. Your gut has a strong impact on how much calcium we absorb and, therefore, any low calcium symptoms you might experience.
Some aspects of this are outside of your control. For example:
Your age: Babies and childrens’ guts are able to absorb more than twice the amount of calcium that adults do [30, 31]
Your genetics: More specifically, Chinese populations may have adaptations that allow their bodies to extract and absorb more calcium from their diets than Westerner :
Whether you are supplementing with calcium or getting it from your food, it will have no impact if your gut is unhealthy and your absorption is poor. However, whatever your age and background, you can optimize calcium absorption by keeping your gut microbiome healthy with a good diet and a daily probiotic supplement.
One systematic review concluded that probiotic supplements can help improve micronutrient status in children, adults, and the elderly. Overall, taking probiotics was associated with a positive impact on the absorption of calcium, B12, folate, iron, and zinc in healthy people .
Another found that fructooligosaccharides (prebiotic fibers that increase the numbers of some good gut bacteria including Bifidobacteria) improved the absorption of calcium, magnesium, and iron, especially in postmenopausal women .
Low Calcium Symptoms Can Be Avoided
In summary, ensuring you have a good intake of vitamin D, vitamin K2, and other bone minerals such as magnesium, zinc, boron, and manganese is equally, if not more important, than taking calcium supplements.
A protein and plant-rich anti-inflammatory diet like a Paleo diet will help to provide most of the good nutrition you need to tackle low calcium symptoms. But vitamin D supplements are a good idea when sunlight is in short supply.
Weight-bearing and resistance exercise is also important for preventing low calcium symptoms.
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