The most frequently occurring clinical indicator of vitamin A deficiency is night-blindness, which is the earliest manifestation of xerophthalmia.
In its mild form it is generally noticeable after stress from a bright light that bleaches the rhodopsin (visual purple) found in the retina. Vitamin A deficiency prolongs the time to regenerate rhodopsin, and thus delays adaptation time in dark environments.
Night-blind young children tend to stumble when going from bright to dimly-lit areas and they, as well as night-blind mothers, tend to remain inactive at dusk and at night.
A plant-based diet is a diet of any animal (including humans) based on foods derived from plants, including vegetables, whole grains, legumes and fruits, but with few or no animal products.
"Plant-based diet" has been used to refer to the following diets:
- Vegan diet - no food from animal sources.
- Fruitarian - consists primarily of fruit.
- Raw vegan - food is uncooked and sometimes dehydrated.
- Vegetarian - plant foods, may include eggs and dairy, but no meat.
- Ovo-lacto vegetarian - includes dairy and eggs.
- Ovo vegetarian - includes eggs but no dairy.
- Lacto vegetarian - includes dairy but no eggs.
- Pescatarian - diet with eggs, dairy and seafood.
- Semi-vegetarian - with occasional inclusion of meat.