Vitamins - Dietary Health Benefits

Evidence of Protection against Other Diseases with Vitamins, Carotenoids, and Phytochemicals

Disease or Condition

Vitamins

Carotenoids, Phytochemicals, and Healthy Foods

Alzheimer's Disease

Vitamin E. There is some evidence that foods providing good amounts of vitamin E might reduce the risks of dementia and Alzheimer's disease.

B Vitamins. Some studies suggest that deficiencies of vitamins B6, B12, and folate (folic acid) may be a risk factor for Alzheimer's disease. However, there is no evidence from randomized, controlled trials that these supplements prevent Alzheimer's disease.

Vitamin D. There is some evidence that older adults with low vitamin D levels are more likely to experience cognitive decline, including problems with thinking, learning, and memory. Whether supplementing with vitamin D can help reverse these cognitive changes is unclear.

Infectious Disease

Studies are mixed as to whether vitamin supplements protect against upper respiratory infections. The weight of evidence suggests there is little or no benefit. It is possible that vitamin C or multivitamin supplements may be helpful in specific people, such as those who are vitamin deficient or who have medical problems that impair their immune system.

Eye Disorder

Cataracts and Macular Degeneration. Oxygen-free radicals play a role in cataract formation and age-related macular degeneration, the most common cause of irreversible blindness in the elderly.

A low level of vitamin C in the lens of the eye has been a particularly strong predictor of cataracts. People with cataracts are frequently deficient in vitamin A, the carotenes, lutein, and zeaxanthin. Studies on protection against cataracts using antioxidant supplements have been mixed. Vitamin C currently has the strongest evidence for protection, but even with this antioxidant, studies are not consistent.

A combination of zinc and antioxidants, including vitamins C and E, may slow the progression of macular degeneration. It will not, however, prevent macular degeneration from developing in the first place. (Vitamin E alone does not appear to be protective.)

Several studies report that the consumption of antioxidant-rich foods is associated with a decreased risk for cataracts. Carotenoids, especially lutein, lycopene, and zeaxanthin, are especially eye-protective and may help prevent cataracts and macular degeneration. A vitamin formula containing vitamin C, vitamin E, beta-carotene, and zinc has been shown to reduce the risk of macular degeneration in the other eye by 25%. A diet high in lutein and zeaxanthin may also help reduce the risk of advanced age-related macular degeneration.

Several studies report that the consumption of antioxidant-rich foods is associated with a decreased risk for cataracts. Carotenoids, especially lutein, lycopene, and zeaxanthin, are especially eye-protective and may help prevent cataracts and macular degeneration.

Osteoporosis

Vitamin D. A combination of calcium and vitamin D can reduce the risk of osteoporosis. (For strong bones, people need enough of both calcium and vitamin D.) The National Osteoporosis Foundation (NOF) recommends:

• Adults under age 50 should have 1,000 mg of calcium and 400 - 800 IU of vitamin D daily.
• Adults age 50 and older should have 1,200 mg of calcium and 800 - 1,000 IU of vitamin D daily (or as much as 2,000 IU if they already have osteoporosis).

Menstrual Disorders

Vitamin B6. Limited clinical evidence suggests that vitamin B6 may be beneficial in reducing premenstrual symptoms, including depression. Typically, women take 100 mg per day, although one study suggested that a lower dose (50 mg) may have the same effect.