Since keratosis pilaris is caused by a vitamin a deficiency, would eating food with vitamin a clear it?

Not really. Pilaris is caused by building up of keratin. You need local exfoliating agents, retin a, (tretinoin) steroids.
Keratosis pilaris. Keratosis pilaris (kp, also follicular keratosis or chicken skin is a common, autosomal dominant, genetic follicular condition that is manifested by the appearance of rough slightly red in color, bumps on the skin. It most often appears on the back and outer sides of the arm (though the forearm can also be affected), and can also occur on the thighs, hands, and tops of legs, sides, buttocks.

Related Questions

How can I treat a vitamin a deficiency, night blindness, xerophthalmia, and follicular keratosis?

Look for cause. If you're eating a varied diet and are not restricting yellow vegetables, it is surprising that you are vitamin A deficient. You may want to be evaluated for malabsorption. Read more...