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Adults (19 to 50 years old)

Calorie needs decrease when you’re done growing. That means adults have less leeway for satisfying nutrient needs on a balanced diet that helps achieve and maintain a healthy weight.

A woman’s iron needs increase again in adulthood, to 18 mg daily. During pregnancy, iron requirements rise to 27 mg daily, which is difficult to satisfy with food alone.

Folic acid is another important nutrient during the childbearing years. This B vitamin helps to prevent birth defects during early pregnancy, when women may not know they have conceived. The Institute of Medicine encourages women who may become pregnant to consume 400 micrograms of folic acid daily from fortified foods, dietary supplements, or a combination of the two.

With the exception of pregnancy, calcium absorption starts decreasing during adulthood. Women, and men, should satisfy their daily calcium needs during this stage, which are 1,000 mg, to reduce the risk of bone fractures later on in life. 

Calcium and vitamin D supplements make sense if you don’t consume the recommended 24 ounces of low-fat (1%) milk or fat-free milk or yogurt, or a combination of these every day -- or if you don’t get the recommended calcium and vitamin D from other foods besides dairy.

Seniors (50 years old and older)

Nutrient needs change with advancing age for several reasons: the body absorbs less, it requires more, or it needs less of certain nutrients. For example, after menopause, women need less iron -- 8 mg daily – compared to 18 mg daily during childbearing years -- but they require more calcium.

As estrogen production decreases during menopause, more bone is broken down than constructed. In addition, the body absorbs less calcium than it did earlier in life.

After age 51, women should consume 1,200 mg of calcium daily (males need 1,000 mg). Vitamin D needs go up with age, too. After age 71, you should get 800 IU daily. Unless you drink 64 ounces of milk each day, you need a vitamin D supplement. 

It’s harder to absorb naturally occurring vitamin B12 after age 50, Sheth says, because your body is less able to grab the vitamin B12 from foods and absorb it. The body easily absorbs synthetic B12, however, which is why experts recommend it as the primary B12 source for people over 50. Foods fortified with vitamin B12, such as breakfast cereals and other grains, or a multivitamin can help you meet your vitamin B12 needs.

Also keep in mind that certain nutrients interfere with over-the-counter and prescription medications. Ask your doctor or pharmacist about the dietary supplements you take and how they may affect your medications.