In entertainment, some pairings are greater than the sum of their parts. Think Batman and Robin, or Mel Gibson and Danny Glover in the Lethal Weapon movies.

So, too, in nutrition, some pairings work better together. Although you can get vitamins and minerals from dietary supplements, most experts recommend getting them from food sources because foods contain a multitude of other necessary nutrients.

Here are some examples of dietary dynamic duos:

Calcium and vitamin D: Calcium is essential for strong bones. Like most nutrients, it is absorbed in the small intestine. In large amounts, this mineral simply diffuses across the intestinal lining. In smaller amounts, however, its absorption is actively assisted by vitamin D. Two other essential minerals – phosphorus and magnesium – also are more efficiently absorbed in the presence of vitamin D.

Current guidelines for young and middle-aged adults are a daily intake of 1,000 mg of calcium and 400 IU of vitamin D. The recommendation for older adults is slightly higher: 1,200 of calcium for people ages 50-plus, and 600 IU of vitamin D for people ages 70-plus.

One 8-ounce glass of fortified milk contains 300 mg of calcium and 100 IU of vitamin D.

Iron and vitamin C: We need iron because it’s an essential component of the red blood cells that transport oxygen to all of our bodily tissues. Iron accounts for up to 75 percent of hemoglobin, a protein in red blood cells.

Dietary iron comes in two forms: heme iron, the type found in animal sources such as meats, poultry, and seafood; and non-heme iron, the type found in plant sources such as dark leafy vegetables, legumes, and fruits.

Of the two types, non-heme iron is more difficult to absorb. But vitamin C rides to the rescue by binding to non-heme iron and escorting it to the intestines, which enhances absorption.

To optimize the absorption of iron from plant sources, experts recommend eating it with vitamin C-rich foods such as citrus fruits, strawberries, and bell peppers. As a rule of thumb, you should consume about 1 gram of vitamin C for every 3 mg of non-heme iron.

Note: Caffeine and calcium inhibit the absorption of non-heme iron. So the next time you have a spinach salad (preferably with a lemon vinaigrette dressing) don’t chase it down with a double latte.

Niacin and tryptophan: Niacin deficiency can lead to pellagra, the symptoms of which include rash, diarrhea, and dementia. To avoid this disease, experts recommend a daily niacin intake of 16 mg for men and 14 mg for women. One of the best dietary sources of niacin is tryptophan, an amino acid found in chicken and turkey.

Vitamin B12 and folate: In combination, these two nutrients support cell division and replication, and metabolize the inflammatory amino acid homocysteine, high levels of which are a risk factor for heart disease. In addition, vitamin B12 cannot be optimally absorbed without folate.

As dynamic duos go, these are the oddest couple. Vitamin B12 is primarily found in animal sources such as meat, eggs, and milk while folate is primarily found in plant sources such as leafy green vegetables and legumes.

The recommended daily intakes are 2.4 micrograms of B12 and 200 micrograms of folate.

Zinc and copper: In some respects, zinc and copper are partners that work together to enhance immunity and support the nervous and digestive systems. But they’re also antagonists that compete for the same absorption sites in the small intestine. If you get too much of one, you’ll get too little of the other, and the resulting imbalance can cause of multitude of symptoms ranging from diarrhea to depression.

Research suggests that the ideal ratio of zinc to copper should range from 8:1 to 12:1. Many foods provide an optimal balance of these two essential trace minerals. These include animal sources such as beef, liver, and oysters, and plant sources such as sprouted pumpkin seeds.

The recommended daily intake for zinc is 11 mg for men and 8 mg for women while the recommendation for copper is 900 micrograms for all adults.