In the early days, before antiviral therapy, there was a study that suggested that beta carotene, as an antioxidant, might be helpful in combating HIV because it seemed to increase the T-cell count. Other studies looking at lung cancer prevention in smokers have shown that those taking beta carotene supplements had a higher incidence of the cancer. The bottom line is, take your multivitamin, and eat more of the brightly colored fruits and veggies that are high in beta carotene and other carotenoids. Your best bet is to eat lots of fruits and vegetables of every color every day. It helps you absorb the mineral calcium, which you need for healthy bones, from the food you eat.
Vitamin D is found in milk, liver, fish, and eggs.
Like vitamin A, vitamin D is toxic in excess because it is stored in the body. Too much vitamin D can cause calcium deposits in soft tissues, such as the kidney and lung. Except for what is contained in a standard multivitamin with mineral supplement, vitamin D supplements should be taken with caution. This vitamin is essential for blood clotting. Found primarily in green leafy vegetables, with lesser amounts in egg yolks, liver, and whole wheat, vitamin K is also synthesized by friendly bacteria in the intestine.