Vitamin A - and I see... Vitamin A - Retinol, was discovered in 1916. But only 15 years later its chemical structure was determined. And it took another 15 years before we learned to produce it synthetically (in the form of acetate). It's quite rare in dietary supplement stores, which is odd because a lack of it can lead to even gray-blindness. Vitamin A is necessary for the production of rhodopsin, a visual pigment that we use in low light conditions. A deficiency of this vitamin causes poor vision in low light conditions, and a severe deficiency can lead to night blindness. First, you may notice that you have trouble driving or reading in the evening, and later you may lose your vision completely in low light. Night blindness can also be hereditary, even if it is treated with vitamin A. The recommended daily dose is 0.8 mg or 4.8 mg of betacarotene (the ratio is 1:6). Vitamin A is therefore produced by the human body itself, it must be consumed. Good sources are carrots, yellow and green leafy vegetables,