Do dietary supplements prevent AMD?

Macular degeneration leads to the gradual loss of central vision. According to one common theory, light and oxygen cause substances called “free radicals” to form in the retina, where they may damage the tissue. Dietary supplements are thought to help reduce this process, preventing AMD or slowing down its progress in this way.

Some products that are marketed for the treatment of AMD contain a combination of different vitamins, such as vitamin C, vitamin E and beta-carotene. They may have copper or zinc in them too. Omega-3 fatty acids, zeaxanthin, lutein and Ginkgo biloba are also commonly recommended.

There is currently no scientific proof that these products can prevent AMD in people who have healthy retinas. Vitamin E and beta-carotene have been well studied. Studies involving over 75,000 participants have shown that these products aren't able to lower the probability of AMD developing. There are no good-quality studies on products containing omega-3 fatty acids.

This question has been looked into in studies on the substances zinc, lutein, zeaxanthin, vitamin C, vitamin E, beta-carotene, omega-3 fatty acids and Ginkgo biloba. There is no evidence to suggest that omega-3 fatty acids or Ginkgo help.

Taking one of the following combinations of nutrients daily can possibly slow down the progression of AMD:

• The “AREDS” formula, containing vitamin C (500 mg), vitamin E (400 I.U. – international units), beta-carotene (15 mg), zinc (80 mg) and copper (2 mg)
• The nearly identical “AREDS 2” formula, containing vitamin C (500 mg), vitamin E (400 I.U.), zinc (80 mg), copper (2 mg), lutein (10 mg) and zeaxanthin (2 mg)

So far, only people who have a considerably higher risk of developing late-stage AMD have been shown to benefit from the AREDS supplements. People are at higher risk if they already have many deposits in their eyes, called drusen. Regularly taking AREDS supplements lowered the risk of late-stage AMD associated with loss of vision in some of them. In order to be effective, the supplements had to be taken daily for several years.

It's important to talk with your doctor before taking these products because they aren't suitable for everyone. German health insurers don't cover the costs of the AREDS formula.

One large study known as the “AREDS study” (Age-Related Eye Disease Study), involving about 3,600 participants, suggests that the AREDS supplements have a positive effect. The study lasted 6 years. During this time, the progression of vision loss was slowed down a little in some people who used the AREDS formula, but most of them didn't benefit from taking it. Expressed in numbers:

• Without treatment: Vision worsened considerably within the six years in about 43 out of 100 participants.
• With treatment: This happened in about 37 out of 100 participants who took the AREDS formula.

In other words, 6 out of 100 people benefited from taking these supplements every day for six years.

The long-term use of dietary supplements at high doses can sometimes be harmful. Beta-carotene, for example, increases the risk of lung cancer in people who smoke or used to. The beta-carotene in the AREDS formula caused lung cancer in 1 out of 100 study participants. Nearly all of the people who developed lung cancer over the course of the study were ex-smokers.

The AREDS 2 formula, which contains lutein and zeaxanthin instead of beta-carotene, is now available. People who used to smoke, or still do, need to make sure they use a product that doesn't have beta-carotene in it.

Products containing beta-carotene caused some participants’ skin to turn yellow. There were also problems such as constipation, bloating and diarrhea.

In 3 out of 100 participants, taking supplements that only contained zinc led to urological problems requiring hospital treatment. These included problems such as bladder infections and incontinence.

Other studies have shown that high doses of vitamin E can increase the risk of death. But in the six-year study on the AREDS formula there weren't an abnormally high number of deaths in the group taking the formula.