Question

Questions Thiamin deficiency was observed only in the Chinese community even though all three communities had the same staple (rice) diet. Explain. 1. On packages of enriched rice sold in supermarkets, the rice preparation directions state that the rice should not be washed before cooking. Explain. 2. evere metabolic acidosis caused by high levels of lactate is often associated with thiamin deficiency. Explain. 4. Provide two plausible explanations for what might cause above normal levels of pyruvate in blood 5. Why does thiamin utilization increase among cancer patients? 6. A negative correlation exists between the need for thiamin and the amount of fat in the diet. and urine. How can one determine which of the two explanations is correct? Explain.

Answer 1

1. The preference of type of rice and cooking method affects the vitamin content of rice.

Studies have shown that unpolished rice have a higher content of thiamin as compared to polished rice.

Another factor that depletes thiamine content in rice is heat. Eating of parboiled rice have a greater content of thiamine.

Thiamine is water soluble. Washing of polished rice before cooking washed away majority of thiamine content.

2. Thiamine is a water soluble vitamin. When we wash rice before cooking majority of the content of thiamine vitamin is washed away in water. This results in thiamine deficiency from the rice.

3. Thiamine is essential co-factor for the enzyme pyruvate dehydrogenase oxidizes pyruvate to acetyl CoA which enters the krebs cycle. It is a crucial step in the process of energy production through krebs cycle. In thiamine deficiency pyruvate cannot be converted to acetyl CoA impairing energy production and pyruvate is converted to lactate. This causes accumulation of lactate in the body resulting in lactic acidosis.

4. The two causes for high pyruvate levels in blood are:

- pyruvate dehydrogenase complex deficiency

- thiamine deficiency

Both pyruvate dehydrogenase lactate and thiamine are necessary for conversion of pyruvate to acetyl CoA. Deficiency of any one will lead to high levels of pyruvate.

Deficiency of one of these can be ruled out by measuring Pyruvate dehydrogenase complex activity with and without thiamine in order to detect cases of thiamine-responsive pyruvate dehydrogenase complex deficiency.