Calcium - the main component of our bones and teeth - also facilitates the healthy functioning of our nervous, muscular, cardiovascular and hormonal systems. However, most women and some men do not get enough calcium from food sources alone. Making sure you are getting enough calcium during preconception, pregnancy and nursing phases can help the baby develop strong foundations for its entire life, keep the mom healthy, maintain a healthy pregnancy and more.
What Do Calcium Do for Our Health?
Calcium is the most abundant mineral in human body. Its significance in bone and teeth health is well known, but calcium also drives multiple essential processes for the entire body:
- Nervous transmission and cellular signaling: Calcium supports the development of nerve cells. It also helps our brain remain flexible and adapt to changes from cellular to systemic levels. (This is called neuroplasticity.)
- Regulation of muscle functions: Calcium facilitates the contraction and relaxing of the muscles. This includes the regulations of muscle cells that form blood vessels, which are involved in blood pressure control and blood supply to various tissues throughout the body.
- Activation of blood-clotting factors: Calcium is necessary to activate some of the blood-clotting factors that help stop the bleeding when an injury occurs.
- Secretion of hormones: Some important hormones like insulin and leptin require calcium to be released. Insulin controls blood sugar levels, which have been suggested as influencing female reproductive health.
Only about 1% of the calcium in our body circulates in the blood and facilitates these functions. The rest of the calcium is stored in the bone. Parathyroid hormone and calcitriol (an active form of Vitamin D3) tightly regulate the amount of calcium in blood circulation. When the calcium intake form diet isn’t enough to sustain the proper calcium levels in the blood and tissue, the body takes the calcium from the bone to keep fueling these crucial metabolic functions - not a good news, as this process can weaken the bones.
Why Is Calcium Necessary during Preconception Period and Pregnancy?
There are two reasons why getting a sufficient amount of calcium is so important during pregnancy: Keeping the mom healthy, and helping the baby develop normally.
1. Calcium for the Mom: Maintenance of a Healthy Pregnancy
Pregnancy is a high-stress period for the body. Otherwise healthy moms often develop unexpected complications during pregnancy, such as preeclampsia and eclampsia. Preeclampsia is one of the most common and serious complications during pregnancy, in which expecting moms develop high blood pressure and kidney/liver problems. Because calcium facilitates blood pressure regulation through its effect on vascular muscle functions, some scientists think calcium may play a role in maintaining the mom's health during pregnancy, which also benefits the baby's growth and health in utero.
Getting enough calcium during pregnancy also protects the mom’s bones and teeth. During pregnancy, the mom’s intestines double its absorption rate of calcium to support the baby’s bone growth, but even then, there may not be enough calcium to support the bone development of the baby.
When this happens, calcium stored in the mom’s bone and teeth is diverted to the baby. It can result in weakening of the mom's bone and teeth. Getting sufficient calcium during pregnancy can also help the mom’s body recover from the loss of 5-10% of the mineral content in the bone that can happen during lactation – another period of heightened calcium need for the mom.
2. Calcium for the Baby: Healthy Bone Development
Calcium is necessary for the bone and teeth development of the baby – who is, after all, building an entire skeletal system just from the nutrients received in the uterus. The baby’s need for calcium is the most intense in the third trimester: about 80% of the newborn’s mineral mass develops in the third trimester – and in the last 6 weeks of pregnancy, a whopping 300-350mg/day of calcium is transferred from the mom to the baby.
In addition, just as calcium is necessary to drive many processes in the adult body, it’s also necessary for the healthy development and functioning of the baby’s cardiovascular system, muscles, nerves and hormones.
Does Calcium Support Fertility?
So far, researchers haven’t found a clear, clinical association between the level of calcium intake and female fertility. However, on a more molecular level, we know that calcium is necessary for the biochemical reactions in the very early stages of embryo development.
For example, one study in Molecular Reproductive Biology found that calcium signals drive the important events during fertilization and activation of embryo development in all mammals studied. On the male side, calcium deficiency has been linked to problems with sperm motility and steroidgenesis, suggesting that a healthy calcium level may be key to normal male reproduction.
Bottom line: Calcium is important for women when trying to conceive. Getting sufficient calcium before getting pregnant can prepare your body for the heavy lifting it’ll do to nurture the baby once you conceive, while protecting your own body from the stress of that work.
How Much Calcium Do I Need?
The US Institute of Medicine has gender- and age-based calcium intake recommendations.
- Adult men between 19 and 70 need 1,000 mg/day of calcium.
- Adult women between 19 and 50 need the same 1,000 mg/day, but as women hit menopause, an additional 200 mg is recommended to counter the effect of lower estrogen levels after menopause.
For pregnant and lactating women, there are two recommendations:
- Teen women should get 1,300 mg per day.
- Pregnant or lactating women over 19 should aim for 1,000 mg/day, the same as non-pregnant women in the same age group.
What Are Good Sources of Calcium?
Humans cannot synthesize calcium, so we need to get it from external sources. Some of the best sources of calcium are dairy products (data from USDA):
- Fortified milk has about 300 mg of calcium per 1-cup serving (8 oz). Non-fat or low-fat milk has the same amount of calcium as whole milk.
- Fortified orange juice has the same amount per serving.
- Cheese (2 slices or 1.5 oz): 300 mg
- Plain yogurt (8 oz): 415 mg
Non-dairy foods also have a good amount of calcium:
- Kale (1 cup, cooked): 177 mg (Kale is also a good choice among dark, leafy greens because it’s low in oxalic acid, which can interfere with calcium absorption.)
- Bok choy (1 cup, cooked): 158 mg
- Soy beans (1 cup, cooked): 184 mg
- Almonds (1 cup): 370 mg
Wheat-based products like bread, waffles and cereal are often fortified with calcium.
Do I Need to Take Calcium Supplement for Pregnancy?
You might. A recent Dutch study of over 2,000 pregnant women found a whopping 42% being deficient in calcium. In the United States, adult women get somewhere between 750 to 970 mg of calcium per day. This shows that even women who are on the high end of the range are still below the daily recommended amount. Adding prenatal vitamins with calcium to your routine can help close that gap.
Men are less likely to be deficient in calcium than women, although, like in women, it depends on age, diet and other lifestyle factors.
How Do I Know I May Be Low on Calcium?
Low calcium may not cause any noticeable symptoms. Outright calcium deficiency is rare in the United States, but there are some groups who are at a higher risk:
1. Women who don’t menstruate.
Women with amenorrhea (lack of menstruation) and postmenopausal women usually have low estrogen levels, which negatively impacts calcium balance and bone health. Female athletes who have irregular menstrual patterns or outright amenorrhea are also at risk of getting not enough calcium.
2. People who don’t drink milk or eat dairy products.
Milk and dairy are some of the most abundant sources of dietary calcium, and they contain the form of calcium that’s easier for the intestines to absorb. Those of us who don’t drink milk or eat dairy products due to lactose intolerance, allergies or dietary restrictions are more likely to not get enough calcium from diet.
3. Vegetarians and vegans.
Vegans and vegetarians who don’t eat dairy products have a smaller range of food sources for calcium from. Furthermore, diets high in plants can hinder calcium absorption due to the higher amounts of oxalic acid and phytic acid, which bind to calcium and other minerals, interfering with their absorption.
Of note, spinach contains a high amount of oxalate at over 700mg per half cup, cooked. Unfortunately, some of the vegan sources of calcium like almonds and soybeans are also high in oxalic acid content, making it even more challenging for vegans.
If you are in one of these higher-risk groups, taking a calcium supplement may be a good idea.
Calcium and Vitamin D
One additional note: Calcium works in conjunction with Vitamin D, which helps the body absorb calcium from external sources. OBGYN doctors recommend getting at least 600 IU of Vitamin D during pregnancy (some recommendations, including those from the Endocrine Society, are much higher at around 1,000 IU/day for pregnant women), along with 1,000 mg/day of calcium.
The Takeaway on Calcium and Pregnancy
- Calcium during pregnancy helps build strong bones and teeth in the baby, while protecting the mom’s.
- Because calcium facilitates the healthy functioning of the entire body, including the and endocrine systems, a healthy level of calcium supports a healthy, full-term pregnancy.
- While trying to conceive, aim for 1,000 mg per day of calcium if you are a woman over 19. If you are younger than 19 and trying to conceive, aim for 1,300 mg/day. Aim for the same amount during pregnancy. Calcium is particularly important in the third trimester.
- Most women do not get enough calcium from food sources alone. Calcium supplements may be a good idea.
If you are unsure about your calcium status, your doctor can order a blood test to measure the amount of calcium circulating in the blood. Based on the result, they can advise you whether you should make any dietary changes or take a calcium supplement. If you have any questions, please reach out. We are with you.
