Nutrition and Metabolism — MCQs

Nutrition and Metabolism Indian Medical PG Practice Questions and MCQs

Question 321: Protein quality assessment is best done by?

A. NPU (Correct Answer)
B. Biological value
C. Amino acid score
D. Digestibility coefficient

Explanation: ***NPU*** - **Net Protein Utilization (NPU)** is considered the best method for assessing protein quality because it measures the percentage of ingested protein that is actually retained and utilized by the body. - It accounts for both the **digestibility** of the protein and the **biological value** of the absorbed amino acids, providing a comprehensive assessment. *Biological value* - **Biological Value (BV)** measures the proportion of absorbed protein from food that becomes incorporated into proteins in the organism's body. - While important, BV does not account for the **digestibility** of the protein, meaning some protein may not be absorbed even if its amino acid profile is excellent. *Digestibility coefficient* - The **digestibility coefficient** measures the proportion of food protein that is absorbed from the gastrointestinal tract. - It only reflects the extent of **absorption** and does not provide information about how efficiently the absorbed amino acids are utilized once inside the body for protein synthesis. *Amino acid score* - The **amino acid score** compares the amino acid profile of a test protein with the amino acid requirements of humans. - This score identifies the **limiting amino acid** but does not factor in the protein's digestibility or how effectively the absorbed amino acids are used by the body.

Question 322: Calcium absorption is hampered by

A. Protein
B. Lactose
C. Acid
D. Phytates (Correct Answer)

Explanation: ***Phytates*** - **Phytates** (phytic acid) found in whole grains, legumes, nuts, and seeds bind to calcium, forming an insoluble complex that significantly **reduces its absorption** in the intestines. - This binding prevents the free calcium ions from crossing the intestinal wall into the bloodstream. *Protein* - **Protein** generally *enhances* calcium absorption, especially when consumed in moderate amounts, as some amino acids can form soluble calcium complexes. - However, very high protein intake, particularly from animal sources, *may* slightly increase urinary calcium excretion in the long term, but it does not directly hamper intestinal absorption. *Lactose* - **Lactose**, a sugar found in milk, is known to *enhance* calcium absorption. - It does so by creating a more acidic environment in the small intestine and by forming soluble complexes with calcium, making it more bioavailable. *Acid* - **Stomach acid** (hydrochloric acid) is crucial for calcium absorption as it helps to solubilize calcium salts from food. - A *reduced* acidic environment, such as from antacid use or certain medical conditions, would hamper calcium absorption, but acid itself is beneficial.

Question 323: Clinical effect of vitamin D is reduced by ?

A. Simultaneous ingestion of lactose
B. Simultaneous ingestion of phytates (Correct Answer)
C. None of the options
D. Acidic environment

Explanation: ***Simultaneous ingestion of phytates*** - **Phytates (phytic acid)** found in whole grains, nuts, seeds, and legumes can **reduce the clinical effect of vitamin D** through multiple mechanisms - Phytates **chelate calcium** and form insoluble calcium-phytate complexes, reducing calcium absorption - Since **vitamin D and calcium metabolism are closely linked**, impaired calcium absorption indirectly reduces vitamin D efficacy - Phytates can also **directly bind to vitamin D** in the gastrointestinal tract, reducing its bioavailability - Studies show that **high phytate intake increases vitamin D requirements** and can impair vitamin D status *Simultaneous ingestion of lactose* - Lactose does **not reduce** vitamin D absorption or efficacy - In fact, **dairy products are commonly fortified** with vitamin D, and the presence of lactose does not interfere with its beneficial effects - Lactose may actually **enhance calcium absorption**, which works synergistically with vitamin D *Acidic environment* - Vitamin D is a **fat-soluble vitamin** absorbed primarily in the small intestine - An acidic environment (stomach acid) is **not known to inhibit** vitamin D absorption - The absorption process occurs in the **alkaline environment of the small intestine** where fat-soluble vitamins are absorbed with dietary fats *None of the options* - This is **incorrect** as phytates do reduce the clinical effect of vitamin D through calcium chelation and direct binding mechanisms

Question 324: Which nut has the highest protein content among the following options?

A. Walnut
B. Coconut
C. Groundnut (Correct Answer)
D. Almond

Explanation: ***Groundnut*** - **Groundnuts** (peanuts) contain approximately **26 grams of protein per 100 grams**, which is the highest among the given options. - While botanically classified as legumes, groundnuts are commonly grouped with nuts in nutritional contexts. - They are also rich in **healthy fats**, **fiber**, and various **B vitamins**. *Almond* - **Almonds** contain about **21 grams of protein per 100 grams**, making them the second highest in protein content among the options. - They are excellent sources of **vitamin E**, **magnesium**, and **healthy monounsaturated fats**. *Walnut* - **Walnuts** contain approximately **15 grams of protein per 100 grams**, which is lower than both groundnuts and almonds. - They are notably rich in **omega-3 fatty acids** (alpha-linolenic acid). *Coconut* - **Coconut flesh** has relatively low protein content, around **3.3 grams per 100 grams**. - It is primarily known for its high content of **medium-chain triglycerides** and **saturated fats**.

Question 325: All of the following are required more during lactation as compared to pregnancy, except ?

A. Niacin
B. Energy
C. Iron (Correct Answer)
D. Vitamin A

Explanation: ***Iron*** - **Iron requirements are significantly higher during pregnancy** (~27 mg/day) due to the expansion of maternal red blood cell mass, fetal development, and placental iron needs. - During lactation, iron requirement decreases to **~9-10 mg/day**, lower than in pregnancy, as **lactational amenorrhea** (absence of menstruation) reduces iron loss. - This represents the **most significant decrease** in requirement from pregnancy to lactation among the listed nutrients. *Vitamin A* - The **recommended daily allowance (RDA) for Vitamin A is higher during lactation** (~1300 μg/day) compared to pregnancy (~800 μg/day). - This increased requirement ensures **adequate transfer to breast milk** to support infant's **vision development and immune function**. *Niacin* - **Niacin requirements during lactation** (~17 mg/day) are **similar to pregnancy** (~18 mg/day). - While lactation involves increased metabolic demands, niacin requirements do not show a marked increase compared to pregnancy, unlike Vitamin A and Energy. - This option is less clearly "required more" during lactation. *Energy* - **Energy requirements are significantly higher during lactation** to fuel milk production, which is energetically demanding. - A lactating woman typically needs an **additional 500 kcal/day**, compared to ~300 kcal/day in the 2nd/3rd trimester of pregnancy.

Question 326: In which of the following conditions is protein catabolism MOST increased?

A. Burns (Correct Answer)
B. Surgery
C. Starvation
D. Fever

Explanation: ***Burns*** - Severe burns lead to a profound **hypermetabolic state** with the highest increase in **protein catabolism** among all the options listed. - The extensive tissue damage triggers massive breakdown of muscle protein to provide amino acids for **wound healing**, **acute phase protein synthesis**, and **immune response**. - Burns can increase metabolic rate by **100-200%**, with protein catabolism far exceeding that of other stress conditions. *Starvation* - While starvation initially increases protein catabolism, the body adapts within days by shifting towards **ketone body utilization** to spare protein. - After adaptation, protein breakdown decreases to **20-30 grams per day** to preserve lean body mass. - The goal is survival through metabolic adaptation, not tissue repair. *Surgery* - Major surgery induces a **stress response** that increases protein catabolism, but it is typically less severe and shorter-lived than burns. - The degree of catabolism is proportional to the **magnitude of surgical trauma** and usually resolves within days. - Protein catabolism increases by **50-75%** in major surgery compared to **100-200%** in severe burns. *Fever* - Fever increases basal metabolic rate by approximately **13% per degree Celsius** rise in body temperature. - While metabolism is elevated, protein catabolism is **modest** compared to the massive tissue destruction and repair demands of severe burns. - The increase is primarily in energy expenditure, not protein breakdown.

Question 327: Which of the following plant components is not fermented by gastrointestinal microorganisms?

A. Lignin (Correct Answer)
B. Cellulose
C. Hemicellulose
D. Pectin

Explanation: ***Lignin*** - **Lignin** is a complex polymer found in plant cell walls that is highly resistant to degradation by digestive enzymes and microbial fermentation in the gastrointestinal tract. - Its complex, cross-linked structure makes it **non-fermentable** by the microorganisms typically present in the human gut. *Cellulose* - **Cellulose** is a major component of plant cell walls and is a type of dietary fiber that can be fermented by certain gut bacteria. - While humans lack the enzymes to digest cellulose, colonic microorganisms possess cellulases that break it down into **short-chain fatty acids (SCFAs)**. *Hemicellulose* - **Hemicellulose** is a diverse group of plant polysaccharides that are a significant source of fermentable fiber for gut microbiota. - It is readily broken down by gastrointestinal bacteria into **SCFAs** and gases, contributing to colonic health. *Pectin* - **Pectin** is a soluble dietary fiber found in fruits and vegetables, known for its gel-forming properties. - It is highly fermentable by gut microorganisms, leading to the production of **SCFAs** like butyrate, propionate, and acetate.

Question 328: Which is not a dietary fiber ?

A. Lignin
B. Pectin
C. Cellulose
D. Lactulose (Correct Answer)

Explanation: ***Lactulose*** - **Lactulose is NOT a dietary fiber** - it is a synthetic disaccharide used pharmaceutically as an osmotic laxative and for treating hepatic encephalopathy. - Unlike true dietary fibers, lactulose is a manufactured drug, not a naturally occurring food component. - While it is fermented by colonic bacteria (similar to fiber), it does not meet the definition of dietary fiber. *Lignin* - Lignin is a complex aromatic polymer that provides structural support to plant cell walls. - It is classified as a non-polysaccharide dietary fiber that is largely indigestible by human enzymes. - Contributes to fecal bulk and is considered an insoluble fiber. *Pectin* - Pectin is a soluble dietary fiber found naturally in fruits, particularly in apple peels and citrus fruits. - Forms a gel when mixed with water, slowing gastric emptying and aiding digestion. - Beneficial for gut health and blood glucose regulation. *Cellulose* - Cellulose is the most abundant dietary fiber and a major structural component of plant cell walls. - An insoluble fiber composed of β-1,4-linked glucose polymers that cannot be digested by human enzymes. - Contributes to stool bulk and promotes regular bowel movements.

Question 329: Selenium deficiency is seen in -

A. Keshan disease (Correct Answer)
B. Wilson disease
C. Acrodermatitis enteropathica
D. None of the options

Explanation: ***Keshan disease*** - **Keshan disease** is a form of **cardiomyopathy** caused by **selenium deficiency**, particularly prevalent in regions with selenium-poor soil. - It presents with **heart failure**, arrhythmias, and cardiac enlargement. *Wilson disease* - **Wilson disease** is a disorder of **copper metabolism**, leading to excessive copper accumulation in organs, primarily the liver and brain. - It is not related to selenium deficiency. *Acrodermatitis enteropathica* - **Acrodermatitis enteropathica** is a genetic disorder of **zinc deficiency**, characterized by dermatitis, diarrhea, and alopecia. - It does not involve selenium deficiency. *None of the options* - This option is incorrect because Keshan disease is directly linked to selenium deficiency.

Question 330: What is the recommended daily calcium intake for adult non-pregnant females?

A. 1000 mg (Correct Answer)
B. 1200 mg
C. 600 mg
D. 800 mg

Explanation: ***1000 mg*** - The recommended daily calcium intake for adult non-pregnant females (ages 19-50) is **1000 mg** according to **WHO and international guidelines** (US RDA/NIH) to maintain bone health and prevent osteoporosis. - This is the **standard recommendation** used in most medical textbooks and international nutritional guidelines. - Adequate calcium intake supports various bodily functions, including **nerve transmission**, **muscle contraction**, and **hormone secretion**. *1200 mg* - While 1200 mg is the recommended intake for **older women (above 50-70 years)** or during **pregnancy/lactation** per some guidelines, it is generally higher than necessary for non-pregnant adult females aged 19-50. - While not harmful, this higher dose is not specifically indicated for the general non-pregnant adult female population. *600 mg* - This amount of calcium is **lower than the internationally recommended daily allowance** for adult women (though it aligns with some regional guidelines like ICMR for sedentary women). - For optimal bone health and prevention of osteoporosis, **1000 mg is the widely accepted standard** in medical education. *800 mg* - This value is **below the internationally recommended daily intake** for adult non-pregnant females, which could lead to long-term calcium deficiency. - Insufficient calcium intake can increase the risk of conditions like **osteopenia** and **osteoporosis**.

Practice by Chapter

Macronutrients and Energy Requirements

Practice Questions

Protein Quality and Nitrogen Balance

Practice Questions

Essential Amino Acids and Proteins

Practice Questions

Essential Fatty Acids and Lipids

Practice Questions

Dietary Fiber and Complex Carbohydrates

Practice Questions

Glycemic Index and Glycemic Load

Practice Questions

Micronutrients: Vitamins and Minerals

Practice Questions

Trace Elements and Metabolism

Practice Questions

Malnutrition: Biochemical Consequences

Practice Questions

Dietary Antioxidants

Practice Questions

Functional Foods and Nutraceuticals

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Dietary Guidelines and Recommendations

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