The world's oldest magic trick, acetabula et calculi, reportedly dates back to early Rome. Today, it's known as cups and balls. While there are endless variations, it all comes down to trying to figure out how small balls pop in and out of three upside-down cups unseen.

Making sure you get enough nutrition as you get older also requires a little sleight of hand. You need extra nutrients to protect your strength, cognition, immune function, and bone, eye and heart health — all while taking in fewer calories daily.

Here are four nutrients you should pack into every day:

1. Calcium. For bone health, aim for three servings a day of fat-free dairy and two servings daily of dark leafy greens such as kale, spinach, and collards. Also good: canned fish such as sardines.

2. Vitamin D. Get a good daily dose from fish such as salmon, as well as mushrooms and fortified foods. And get your blood level checked. Most people need to take a supplement of vitamin D, which helps with immune function and bone strength.

3. Vitamin B12. Essential for nerve and blood cell health, this vitamin is in found in fortified whole grain cereals, lean meat, and fish. A blood test will show if you need to take a supplement.

4. Protein. Whole grains and legumes, tofu, fish, nuts, and lean poultry can deliver the protein you need to gain and maintain muscle mass and function. A 150- to 160-pound senior might need 65-70 grams daily. That could come from 6 ounces of salmon (40 grams), 3 ounces of white meat turkey (24 grams), and 1 cup of brown rice (5 grams).