Sunlight is an excellent source of vitamin D, and it’s free. Researchers recommend spending some of your days soaking up the sun’s rays -- 20 minutes should do it. Other sources include salmon; vitamin D-fortified milk, rockfish, tuna and fortified orange juice. A bonus is that fish abundant in Omega-3 fatty acids help protect the heart and with age-related memory problems.

2.    Vitamin A is important for healthy eyesight, especially in low light conditions. It is also involved in maintaining a robust immune system and tissue growth.

Low intake levels of vitamin A can cause the following signs: dry eye, corneal disorders, night blindness, loss of taste, macular degeneration, photophobia, dry or bumpy skin, poor wound healing, dry and brittle hair, and a weakened immune system.

Good sources of vitamin A include dark green and brightly colored vegetables such as sweet potatoes, spinach, pumpkins, squash and carrots. Calf’s liver is another excellent source of vitamin A. A bonus is that these foods are also high in fiber and vitamin C.   

3.    Potassium plays a very important role in nerve impulse transmission. As an electrolyte, it supplies charged ions to maintain correct nerve impulses that travel between the brain, body and back. So potassium maintains heart activity, builds and sustains muscles, and assists in protein synthesis.

Symptoms of potassium deficiency include muscle cramps; pins and needles; excessive thirst, urination or sweating; low blood pressure; and heart arrhythmias and palpitations. Not getting enough potassium increases the risk of kidney stones and osteoporosis, too.

Sources of potassium are carrots, yogurt, tomatoes, spinach, lentils, orange juice, fish, peas, bananas and apples.