I've heard it's best to take calcium with vitamin D, otherwise calcium won't be absorbed. Is this true? Are there other nutrients I should pair?
It's true that certain nutrients interact with each other and, in so doing, affect how much of one is absorbed or how well one is used to perform its functions in the body. It's not true, however, that you need to consume calcium – in food or as a supplement – with vitamin D to ensure its absorption.
Vitamin D is needed for calcium absorption, but in a different way. In order for calcium to be absorbed from foods or supplements, you need to have a sufficient level of vitamin D in your body. That's because the active vitamin D hormone, called calcitriol, stimulates calcium to be transported into intestinal cells so it can then enter the bloodstream.
If you lack vitamin D, calcium absorption will be hindered which can lead to weaker bones and osteoporosis. You need to meet your daily calcium and vitamin D requirements, but you don't need to consume them together.
To get enough vitamin D you need a supplement since very few foods contain vitamin D – oily fish and fortified milk are the best sources – and the fact that Canadians don't make vitamin D in their skin during the fall and winter months.
Osteoporosis Canada recommends taking vitamin D3 year-round: adults aged 19 to 50 need 400 to 1000 IU per day; older adults should take 800 to 2000 IU daily. Children are advised to get 600 IU of vitamin D3.
When it comes to calcium, adults aged 19 to 50, need 1000 milligrams each day; daily requirements increase to 1200 mg for women after 50 and after age 70 for men. Teenagers need 1300 mg of calcium daily and children, aged four to eight, should get 800 milligrams.
One cup of milk, 3/4 cup plain yogurt and 1.5 ounces of cheese all contain roughly 300 mg of calcium. Other sources include fortified plant beverages (330 mg per 1 cup), canned salmon with bones (1/2 tin = 212 mg), firm tofu made with calcium sulfate (1/2 cup = 253 mg), cooked spinach (1 cup = 245 mg), cooked rapini (1 cup = 200 mg) and almonds (1/4 cup = 94 mg).
All nutrients – vitamins, minerals, protein, carbohydrate and fat – have the potential to interact and affect your nutritional status, some positively, others negatively. Here are four other nutrient pairings to be mindful of.
Iron + Vitamin C
Iron transports oxygen throughout the body, bolsters the immune system and makes healthy skin, hair and nails.
Animal foods such as meat, poultry, fish and eggs contain heme iron, a form that's easily absorbed. Iron-rich plant foods (e.g. beans and lentils, tofu, pumpkin seeds, cashews, almonds, quinoa, barley, bulgur, leafy greens) provide non-heme iron, which is harder to absorb.
Including a source of vitamin C with iron-rich plant foods will help you get more iron from your diet. That's because vitamin C transforms non-heme iron into a well-absorbed form.
What to eat: Add sliced strawberries or orange segments to a spinach salad; squeeze lime juice over a black bean salad; sauté sliced red peppers with kale or collard greens; mixed steamed broccoli florets into quinoa.
Vitamin C + Vitamin E
As antioxidants, both nutrients mop up harmful free radical molecules before they can damage cells. Vitamin E's major role is to protect fatty cell membranes – such as those in the brain – from free radical destruction.
Once it's performed its job, vitamin E's protective powers are lost. Vitamin C, however, recycles vitamin E and restores its antioxidant properties.
What to eat: Include good sources of both vitamins in your daily diet. Top picks for vitamin C include red and green bell peppers, citrus fruit, kiwi fruit, strawberries, cantaloupe, broccoli, Brussels spouts, cabbage, cauliflower and tomato sauce. Vitamin E-rich foods include wheat germ oil, sunflower seeds, almonds, sunflower oil, safflower oil, grapeseed oil, hazelnuts, peanuts and cooked spinach.
Vitamin B12 + Folate
One of vitamin B12's most important roles is to help activate folate (folic acid) in the body. A deficiency of B12 can lead to a shortage of folate, which is needed to make and repair DNA in cells. B12 also works closely with folate to form red blood cells and help iron work better in the body.
What to eat: B12 is found naturally only in animal foods including meat, poultry, fish, eggs and dairy products. It's added to fortified non-dairy milks, ready-to-eat breakfast cereals and some soy products. Nutritional yeast, sold in natural food stores, is also an excellent source. With age, we become less efficient at absorbing B12 from foods. Adults over 50 are recommended to get B12 from supplement (multivitamin, B complex or separate B12) or foods fortified with the vitamin.
Calcium + Iron
Minerals such as calcium and iron have a similar size and molecular charge, which causes them to compete with each other for absorption in the intestine. (Magnesium also falls into this category.)
If you take a calcium supplement, don't take it at meals that include iron-rich foods. Instead, take a calcium citrate supplement between meals. (Calcium citrate is well absorbed on an empty stomach.) Likewise, if you take iron to treat a deficiency, avoid taking it with a calcium-rich meal.