Final answer:
Lowered production of stomach acid and reduced output of intrinsic factor lead to decreased absorption of nutrients, particularly vitamin B12, which is necessary for red blood cell production and neurological function.
Step-by-step explanation:
The effects of lowered production of stomach acid and reduced output of intrinsic factor include decreased absorption of nutrients, especially vitamin B12, which is vital for the production of mature red blood cells and normal neurological functioning. Intrinsic factor is necessary for the intestinal absorption of vitamin B12. If intrinsic factor is lacking, as in the condition known as pernicious anemia or after total gastrectomy, vitamin B12 cannot be absorbed effectively, leading to vitamin deficiencies.
Additionally, stomach acid is important for the initial digestion of food, and a reduction in stomach acid can impair the digestion and subsequent absorption of a variety of nutrients. Hence, the correct answer to the effects of lowered production of stomach acid and reduced output of intrinsic factor is a decreased absorption of nutrients.