Nutrient Information: Calcium, Ca

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Nutrient Key Information 
Nutrient Name: Calcium, Ca
Nutrient Category: Minerals
Measuring Unit: mg
Nutrient Summary: Calcium plays a key role in bone and teeth health. We should take adequate calcium to help the bone and teeth formation and development.
Nutrient Function: About 99% of body calcium are in bones and teeth.
• Calcium plays key role in bone formation, growth and health. It is an integral part of bone structure together with phosphorus and other minerals.
• Similarly, calcium plays key role in teeth formation.
• Calcium in bones also serves as a calcium bank.

About 1% of the body calcium are circulated in the body fluid. They play the roles:
• Calcium in the extracellular fluids helps maintain normal blood pressure.
• Calcium in the intracellular fluids binds with protein calmodulin to activate some enzymes which help muscles to contract.
• Constriction and relaxation of blood vessels
• Help release hormones and activate some enzymes
• For nervous system function, it helps to transmit messages between the brain and body parts.

Vitamin D's role in calcium absorption:
• Vitamin D enhances calcium absorption in the intestines
• Vitamin D stimulates calcium reabsorption from the kidneys into the blood.

Bone Health
Most of people reach their peak bone mass at around 30 years old, then gradually lose bone. When bone loss reaches a certain point, osteopenia occurs. Further bone loss causes osteoporosis, in which state the risk of bone fracture increases. There is no obvious symptoms for bone loss, so it occurs silently. Usually the blood calcium level maintains at a constant level, when it is low, body automatically draws calcium from bone, when it is high, calcium is returned to bone.

While calcium is the most critical nutrient for the bone health, other nutrients also play important roles, for example:
• Other minerals: phosphorus is a major component of bones and teeth, it helps bone formation and development. Magnesium and potassium help maintain bone mineral density. Too much sodium contribute to the bone loss.
• Vitamins: Vitamin D is necessary for calcium metabolism. Vitamin K regulates bone and cartilage mineralization and decreases bone cell turnover. Vitamin A participates in the old bone cell dismantling process, but too much vitamin A may be associated with osteoporosis.
• Others: Omega-3 fatty acids may help preserve bone integrity.

Calcium, Ca Interactions With Other Nutrients 
Vitamin D (D2 + D3)
Vitamin D is necessary for calcium absorption

For calcium to be properly absorbed, the intestines need calcitriol, the hormonally active form of vitamin D. Vitamin D goes through a conversion process in the liver and then kidneys to become calcitriol. Calcitriol enhances the absorption of calcium and phosphate from the intestines, ensuring adequate levels for bone mineralization. It also regulates the secretion of parathyroid hormone (PTH), which in turn controls calcium levels in the blood.

Phosphorus, P
High phosphorus or high calcium can reduce the absorption of the other if the other intake is low

Phosphorus and calcium can bind each other in the intestines to form insoluble complexes. These complexes are not easily absorbed by the intestines, so the overall absorption of both minerals are reduced.

Both calcium and phosphorus are essential for bone health, so their balance and absorption are critical. The ideal ratio for calcium:phosphorus by weight is between 1:1 - 2:1.

In addition, high phosphorus levels can stimulate the release of Parathyroid Hormone (PTH) which increases calcium resorption from bones to maintain normal blood calcium levels. This can potentially weaken bones over time.

Iron, Fe
Calcium can inhibit the absorption of iron

Several studies have shown that calcium, whether from food or supplements, can reduce the absorption of non-heme iron (found in plant-based foods) when they are consumed simultaneously. The calcium-iron complexes that form in the intestine reduce the amount of iron that can be absorbed. However, this inhibitory effect is temporary.

To optimize iron absorption, it is better to consume calcium-rich foods or supplements at different times than iron-rich meals, especially meals containing iron-rich vegetables.

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Food Sources

• Dairy products: such as milk, yogurt, cheese
• Green vegetables: such as kale, mustard greens, collard greens, turnip greens, bok choy, and broccoli
• Tofu made with calcium sulfate
• Canned seafood with bones: such as sardines
• Nuts: such as almond
• Calcium-fortified orange juice
• Fortified plant-based beverages: such as soy, rice, and almond milk
• Fortified ready-to-eat cereals

For vegan diet (pure vegetarian), the key food sources of Calcium are:
• Dark-green leafy vegetables, such as bok choy, broccoli, collard greens, kale, mustard greens, turnip greens, watercress
• Fortified cereals
• Fortified juices, figs
• Fortified soy products
• Nuts (almonds) and seeds (sesame seeds)

1) Calcium may be poorly absorbed from foods that are rich in oxalic acid or phytic acid. Example foods:
• Rich in oxalic acid: spinach, sweet potatoes, and beans
• Rich in phytic acid: whole grains (wheat bran, rice bran), nuts (almonds, walnuts, peanuts), and sesame seeds.
2) Different foods have different calcium bioavailability. In general green vegetables (except spinach) have the best bioavailability, then dairy products and calcium-fortified foods, and then nuts and beans.
3) Calcium from foods are generally preferred over calcium supplementation because of the concern on the potential increasing risk of developing kidney stones.

Sample Foods High in: Calcium, Ca
View Additional Food Sources
Food Description Nutrient Amount1 Daily Value%2
Yogurt, plain, skim milk
Category: Dairy and Egg Products
199 mg 15.31%
Milk, reduced fat, fluid, 2% milkfat, with added vitamin A and vitamin D
Category: Dairy and Egg Products
126 mg 9.69%
Cheese, parmesan, shredded
Category: Dairy and Egg Products
1,253 mg 96.38%
Fish, sardine, Atlantic, canned in oil, drained solids with bone
Category: Finfish and Shellfish Products
382 mg 29.38%
Kale, raw
Category: Vegetables and Vegetable Products
254 mg 19.54%
Turnip greens, cooked, boiled, drained, without salt
Category: Vegetables and Vegetable Products
137 mg 10.54%
HOUSE FOODS Premium Firm Tofu
Category: Legumes and Legume Products
149 mg 11.46%
Soybeans, green, raw
Category: Vegetables and Vegetable Products
197 mg 15.15%
Nuts, almonds, oil roasted, lightly salted
Category: Nut and Seed Products
291 mg 22.38%
1 Nutrient amount is in 100 gram food
2 Use FDA 2000 calorie diet as Daily Value reference

Additional Nutrient Information
Nutrient Summary Calcium plays a key role in bone and teeth health. We should take adequate calcium to help the bone and teeth formation and development.
Deficiency Health Effects The primary effects of calcium deficiency (caused by inadequate intake or poor intestinal absorption) include:
• Osteopenia (lower than normal bone-mineral density)
• Osteoporosis (very low bone-mineral density)
• Increased risk of bone fractures
Effects if Above Upper Limit Excess intake of calcium may increase the level of calcium in the blood. The primary effects of excess intake are:
• Kidney stones
• Hypercalcemia and renal insufficiency
• Decrease absorption of certain minerals (such as magnesium, zinc)
External References
Additional Information Calcium is a major mineral (also called macromineral) which means human body requires in relatively large amounts (greater than 100 milligrams per day).

Daily Value Age Group Recommended Daily Values Daily Value Upper Limits
Toddler 1 to 3 years old: 700 mg 2,500 mg
Child 4 to 8 years old: 1,000 mg 2,500 mg
Male 9 to 13 years old: 1,300 mg 3,000 mg
Male 14 to 18 years old: 1,300 mg 3,000 mg
Male 19 to 30 years old: 1,000 mg 2,500 mg
Male 31 to 50 years old: 1,000 mg 2,500 mg
Male 51 to 70 years old: 1,000 mg 2,000 mg
Male Senior 71 or older: 1,200 mg 2,000 mg
Female 9 to 13 years old: 1,300 mg 3,000 mg
Female 14 to 18 years old: 1,300 mg 3,000 mg
Female 19 to 30 years old: 1,000 mg 2,500 mg
Female 31 to 50 years old: 1,000 mg 2,500 mg
Female 51 to 70 years old: 1,200 mg 2,000 mg
Female Senior 71 or older: 1,200 mg 2,000 mg
Female Pregnancy (>18): 1,000 mg 2,500 mg
Female Lactation (>18): 1,000 mg 2,500 mg
FDA (Based on 2000 calorie daily diet): 1,300 mg

Dietary Reference Intakes The nutrient Dietary Reference Intakes and nutrition facts is from Institute of Medicine of National Academies 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press.
US FDA Nutrition Education Nutrition facts knowledge are based on U.S. FOOD & DRUG Administration Nutrition Education Resources & Materials.
National Institutes of Health Nutrition facts knowledge are based on National Institutes of Health Dietary Supplement Fact Sheets.
Disclaimer The nutrient information provided here should not take the place of medical advice. We encourage you to talk to your healthcare providers (such as your doctor) about your dietary requirements which are best for your overall health. We also recommend you to read organization or professional reference documents or articles mentioned, but not limited to, in this page. Any mentions and reference links in this page don't represent our endorsement of their services and advice.

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