Quick answer: Vitamin A and zinc support the retina, but more is not better. Preformed vitamin A above 3,000 mcg a day can harm an unborn baby and the liver; zinc above 40 mg a day long-term can lower copper. Smokers should avoid high-dose beta-carotene.
Vitamin A
Needed for night vision. The adult upper limit for preformed vitamin A (retinol) is 3,000 mcg a day. Pregnant women should be especially careful.
Beta-carotene and smokers
High-dose beta-carotene increased lung cancer risk in smokers in large trials.
Zinc
The adult upper limit is 40 mg a day. Long-term excess can cause copper deficiency.
Avoid doubling up
Add up multivitamins, fish liver oil and other eye supplements.
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General information, not medical advice. Visivra is a dietary supplement and is not intended to diagnose, treat, cure or prevent any disease.