Question

38. Explain the effects of skin pigmentation, latitude, sun exposure, age, and sunscreen on vitamin D production by the skin.
39. Which 2 fat soluble vitamins can most easily become toxic when consumed in amounts above the DRI’s?
40. Which fat soluble vitamin is made by the skin after exposure to sunlight?
41. Which fat soluble vitamin is made by bacteria in the small intestine? Do we still need to consume this vitamin from food?
42. What is the main symptom of vitamin K deficiency?

Answer 1

Ans8) When your skin is exposed to sunlight, it manufactures vitamin D. The sun's ultraviolet B (UVB) rays interact with a protein called 7-DHC in the skin, converting it into vitamin D3, the active form of vitamin D.

- Exposure to sunlight prompts our skin to self-manufacture vitamin D. Increased skin pigmentation lowers the rate of manufacture of vitamin D. Therefore, greater levels of skin pigmentation are considered a risk factor for vitamin D deficiency. Their levels of vitamin D were measured using blood tests.

9) The fat-soluble vitamins, A, D, E, and K, are stored in the body for long periods of time and generally pose a greater risk for toxicity than water-soluble vitamins when consumed in excess. Eating a normal, well-balanced diet will not lead to toxicity in otherwise healthy individuals.

10) Vitamin D is unique because it can be made in the skin from exposure to sunlight. Vitamin D exists in two forms. Vitamin D 2 is obtained from the UV irradiation of the yeast sterol ergosterol and is found naturally in sun-exposed mushrooms.

11) Probiotic bacteria, members of the gut microbiota, are able to synthesize vitamin K and most of the water‐soluble B vitamins, such as biotin, cobalamin, folates, nicotinic acid, panthotenic acid, pyridoxine, riboflavin, and thiamine, in humans.