Calcium: “Getting enough calcium is important for all ages, but it's particularly important during adolescence and early adulthood, when bones are absorbing calcium,” says Heather Schwartz, MS, RD, a medical nutrition therapist at Stanford University Hospital and Clinics. Calcium and vitamin D are often paired in fortified foods such as milk. The reason: The body needs D in order to absorb calcium.
Protein should provide about 15% of a healthy person's daily calories. As a rule of thumb, people of both sexes and any size will do fine with about 60 grams of protein a day. Athletes who have large muscles and work out hard may need 20% more. But even that's not very much; 8 ounces of chicken or 6 ounces of canned tuna, for example, will fit the bill.
If you usually head to the gym after work, take heed: Mental exhaustion can make you feel physically exhausted, even when you have plenty of energy, reports a Medicine & Science in Sports & Exercise study. When people played a brain-draining computer game before exercising, they reported a subsequent workout as being harder, yet their muscles showed the same activity as they did doing the same workout after an easy mental game. So if you think you can’t eke out those last 10 minutes on the rowing machine, remember: You can! [Tweet this motivation!]
Fluids: Fluid needs increase as women age. The reason: Kidneys become less efficient at removing toxins. “Drinking more fluids helps kidneys do their job,” Schwartz says. “Unfortunately, thirst signals often become impaired with age, so people are less likely to drink enough water and other fluids.” Rather than fret about how many glasses to drink, Frechman says, check the color of your urine. "It should be clear or very pale colored. If it becomes darker, you need more fluid.”