Deficiency in vitamins A and D can occur when there is insufficient intake through diet or limited sunlight exposure. Certain groups are more likely to be at risk:

People with limited sunlight exposure: Individuals who live in regions with little sunlight, especially during the winter months, or those who spend little time outdoors, may have insufficient vitamin D.

People with dietary restrictions: Those following vegan or vegetarian diets may be at risk of vitamin D and A deficiencies, as these vitamins are primarily found in animal-based foods.

Older adults: As people age, the skin becomes less efficient at producing vitamin D from sunlight. Older adults may also have a reduced ability to absorb vitamin A and D from food.

People with malabsorption conditions: Individuals with digestive disorders such as Celiac disease, Crohn's disease, or other conditions that impair fat absorption may have difficulty absorbing fat-soluble vitamins like A and D.

Infants and children: Some infants, particularly those who are breastfed and not given vitamin D supplements or fortified foods, may be at risk of vitamin D deficiency.

Note: Vitamin A toxicity can occur if taken in excessive amounts, so it’s important to follow recommended dosages and consult a healthcare provider before starting supplementation, particularly for pregnant women.