HUMAN NUTRITION - Sheet1 Flashcards
What are the two subgroups of the vitamin E family, and how are they named?
The vitamin E family consists of two subgroups—tocopherols and tocotrienols. The members are designated by letters of the Greek alphabet (alpha, beta, gamma, and delta).
Why is alpha-tocopherol the only member of the vitamin E family that is maintained in the body to meet its needs?
Alpha-tocopherol is the only member maintained because the other members are not converted to alpha-tocopherol in the body, and they are not recognized by its transport protein.
What is the main action of vitamin E as an antioxidant?
Vitamin E’s main action is to stop the chain reaction of free radicals, preventing the production of more free radicals and protecting cell components and membranes from destruction.
How may tocotrienols contribute to health besides preventing cancer?
Tocotrienols may also protect against osteoporosis, diabetes, heart disease, and neurological disorders.
What is the primary deficiency of vitamin E associated with, and what is a classic sign of this deficiency?
The primary deficiency of vitamin E is associated with diseases of fat malabsorption, such as cystic fibrosis. A classic sign is erythrocyte hemolysis, seen in premature infants.
What is the role of vitamin E in reducing the risk of heart disease?
Vitamin E may reduce the risk of heart disease by protecting low-density lipoproteins (LDL) against oxidation and reducing inflammation.
What is the UL for vitamin E, and what can extremely high doses of vitamin E potentially cause?
The UL for vitamin E is 1000 milligrams. Extremely high doses may interfere with the blood-clotting action of vitamin K and enhance the effects of anti-clotting drugs, causing hemorrhage.
Why is the RDA for vitamin E based only on alpha-tocopherol?
The RDA is based only on alpha-tocopherol because the other tocopherols and tocotrienols cannot be converted to alpha-tocopherol, and they do not perform the same metabolic roles.
In which foods is vitamin E found, and why is the intake of polyunsaturated fatty acids related to vitamin E needs?
Vitamin E is found in vegetable oils, margarine, salad dressings, and wheat germ oil. Higher intake of polyunsaturated fatty acids requires more vitamin E, and fortunately, they often occur together in the same foods.
What are the primary roles of vitamin K in the body?
Vitamin K is essential for blood clotting and is involved in the metabolism of bone proteins, including osteocalcin. It may also be associated with a reduced risk of heart disease and some cancers.
Under what circumstances may a secondary deficiency of vitamin K occur?
A secondary deficiency of vitamin K may occur when fat absorption falters (as in bile production failure) or due to certain drugs disrupting vitamin K synthesis and action.
How do vitamin K and vitamin D interact in relation to bone health?
Vitamin K helps synthesize a specific bone protein, and vitamin D regulates that synthesis. Both vitamins, along with vitamin A, play important roles in bone growth and remodeling.
What is the primary dietary source of vitamin K, and what are the forms of vitamin K found in foods?
Leafy green vegetables such as spinach and kale, fruits like avocado and kiwi, and some vegetable oils like soybean oil are primary sources. Phylloquinone and menaquinone are the two forms of vitamin K found in foods.
Why is it important for individuals on anticoagulant drugs to monitor their vitamin K intake?
High doses of vitamin K can reduce the effectiveness of anticoagulant drugs, so individuals on these drugs should maintain a consistent intake of vitamin K-rich foods and monitor their blood clotting times regularly.
What motivates supplement manufacturers to introduce new supplements?
he day’s hot topics in nutrition and emerging research news lead supplement manufacturers to develop new supplements. Terms like antioxidants and lycopene become popular, and commercials claim magic in fighting aging and disease.
What is a free radical, and how does it become unstable?
A free radical is a molecule with one or more unpaired electrons. An electron without a partner makes the molecule unstable and highly reactive. To regain stability, a free radical steals an electron from a stable but vulnerable compound, initiating a chain reaction.
How do antioxidants neutralize free radicals, and why don’t they become free radicals themselves?
Antioxidants neutralize free radicals by donating one of their own electrons, ending the chain reaction. Antioxidants do not become free radicals because they remain stable in either form.
What role do free radicals play in the immune system?
Cells of the immune system use free radicals in an “oxidative burst” to demolish disease-causing viruses and bacteria. However, free-radical attacks most often cause widespread damage, contributing to cell damage, disease progression, and aging.
What minerals and vitamins act as defense against free-radical damage?
Enzymes dependent on selenium, copper, manganese, and zinc, along with antioxidant vitamins (vitamin E, beta-carotene, and vitamin C), defend against free-radical damage.
How might antioxidants reduce the risk of cancer?
Antioxidants may reduce cancer risks by protecting DNA from free-radical damage. Diets rich in fruits and vegetables, especially those containing vitamin C, beta-carotene, and carotenoids, are associated with lower cancer rates.
How does oxidative stress contribute to atherosclerosis, and how can antioxidants protect against heart disease?
Oxidative stress contributes to atherosclerosis by oxidizing LDL cholesterol. Antioxidants, especially vitamin E and vitamin C, protect against LDL oxidation, inflammation, and arterial injuries, potentially reducing the risk of heart disease.
According to the passage, what dietary strategies are most effective in preventing heart disease?
Effective strategies include using unsaturated fats, selecting foods rich in omega-3 fatty acids, and consuming a diet high in fruits, vegetables, nuts, and whole grains while low in refined grain products.
Should antioxidants be replenished from foods or supplements, according to the passage?
The passage emphasizes that antioxidants are best obtained from foods, especially fruits and vegetables, which offer a range of nutrients and phytochemicals. Taking supplements is not recommended for disease prevention.
What does the passage suggest about the use of antioxidant supplements for cancer prevention?
The passage suggests that antioxidant supplements may not provide the same benefits as a diet rich in fruits and vegetables. Some studies even indicate potential risks associated with certain supplements, such as increased mortality.
What are the main roles of zinc in the body?
Zinc supports the work of proteins in metabolic processes, stabilizes cell membranes and DNA, strengthens antioxidant defenses, assists in immune function, growth, and development. It participates in hormone synthesis, blood clotting, thyroid function, and influences behavior and learning.
How does zinc absorption vary with dietary intake?
The rate of zinc absorption varies from 15 to 40 percent. As zinc intake increases, the absorption rate decreases, and as zinc intake decreases, the absorption rate increases. Dietary factors like phytates can influence absorption, limiting bioavailability.
What is the enteropancreatic circulation of zinc?
After absorption, zinc circulates between the small intestine and the pancreas. Some zinc reaches the pancreas to be incorporated into digestive enzymes, providing a dual source of zinc for the small intestine. This circulation is known as the enteropancreatic circulation of zinc.
What are the symptoms of zinc deficiency?
Zinc deficiency can lead to impaired growth, immature sexual development, digestion issues, diarrhea, compromised immune response, central nervous system damage, poor motor development, cognitive performance, altered taste, loss of appetite, and slowed wound healing.
What are the potential side effects of zinc toxicity?
High doses of zinc (more than 50 milligrams) can cause vomiting, diarrhea, headaches, exhaustion, and interfere with copper metabolism, leading to heart muscle degeneration. The UL for adults is set at 40 milligrams.
In which foods is zinc most abundant?
Zinc is highest in protein-rich foods such as shellfish (especially oysters), meats, poultry, milk, and cheese. Plant-based diets tend to be low in zinc, but legumes and whole-grain products can be good sources if consumed in large quantities.
What essential role does iodine play in the body?
Iodine is integral to thyroid hormones that regulate body temperature, metabolic rate, reproduction, growth, blood cell production, nerve and muscle function. It influences energy expenditure during basal metabolism by controlling cellular oxygen use.
What is the primary cause of goiter?
Goiter is primarily caused by iodine deficiency. In iodine deficiency, the thyroid gland enlarges as it attempts to trap more iodine. Some foods containing goitrogens, like collards and kale, can also contribute to goiter by interfering with iodine uptake by the thyroid.
How does iodine deficiency impact mental health?
Iodine deficiency is the most common cause of preventable mental impairment. It can lead to poor performance in school, and severe deficiency during pregnancy can result in irreversible mental impairment and stunted physical growth, known as cretinism.
What is the UL for iodine intake in adults?
The UL for iodine intake in adults is 1100 micrograms per day. Excessive iodine intake during pregnancy can be especially damaging to the developing infant, potentially causing goiter severe enough to block airways and lead to suffocation.
What are the major sources of selenium in the diet?
Selenium is found in soil and crops, with reliable sources being meats, milk, and eggs. Eating as few as two Brazil nuts a day can effectively improve selenium status. Average intakes in the United States exceed the RDA, which is based on maximizing glutathione peroxidase activity.
What are the roles of copper in the body?
Copper serves as a constituent of enzymes involved in various metabolic roles, including iron metabolism, collagen manufacturing, inactivation of histamine, degradation of serotonin, and participation in energy metabolism reactions.
How can copper deficiency and toxicity occur?
Copper deficiency is rare in typical US diets and is associated with genetic disorders. Excessive copper intake from foods is unlikely, but supplements may cause liver damage. Genetic disorders like Menkes disease and Wilson’s disease can lead to copper deficiency or toxicity.
What is the role of manganese in the body?
Manganese acts as a cofactor for enzymes facilitating carbohydrate, lipid, and amino acid metabolism. It is essential for bone formation, the conversion of pyruvate to a TCA cycle compound, and maintaining healthy nerves.
How does fluoride contribute to oral health?
Fluoride, by forming fluorapatite in teeth, strengthens enamel and makes teeth more resistant to decay. Drinking water, usually the best source of fluoride, helps protect against dental caries. However, excessive fluoride intake can lead to fluorosis, causing tooth damage.
How much magnesium is present in a 132-pound person’s body?
About 1 ounce of magnesium.
Where is more than half of the body’s magnesium located?
In the bones.
What are the primary roles of magnesium in the body?
Maintaining bone health, forming part of the protein-making machinery, necessary for energy metabolism, participating in hundreds of enzyme systems.
What is the major role of magnesium in ATP synthesis?
Acting as a catalyst in the reaction that adds the last phosphate to ATP.
What is the dynamic interaction between magnesium and calcium in muscle contraction and blood clotting?
Calcium promotes the processes, while magnesium inhibits them.
What are significant dietary sources of magnesium?
Legumes, nuts, seeds, dark green leafy vegetables, and mineral water in areas with hard water.
What chronic diseases may be linked to magnesium deficiency?
Heart disease, stroke, hypertension, diabetes, and cancer.
How does magnesium contribute to heart health?
It is critical to heart function, protects against hypertension, and supports heart health.
What is the bioavailability of magnesium from mineral water, and how can it be improved?
About 50%; it improves when consumed with a meal.
What is the rare but potentially fatal side effect of magnesium intake from nonfood sources?
Magnesium toxicity.
What is sulfate?
The oxidized form of the mineral sulfur.
How is the body’s need for sulfate met?
Through a variety of foods, beverages, and sulfur-containing amino acids found in dietary proteins (methionine and cysteine).
What is the role of sulfur-containing amino acids in protein molecules?
They help determine the contour of protein molecules by forming disulfide bridges that stabilize the protein structure.
Why is there no recommended intake for sulfate?
Because the body’s sulfate needs are easily met with normal protein intakes, and deficiencies do not occur with adequate protein consumption.
What factors contribute to bone health besides calcium and phosphate?
Adequate protein intake, vitamin D activation, sunlight exposure, hormones (parathyroid hormone, calcitonin, estrogen, testosterone), physical activity, and body weight.
How does physical activity support bone growth during adolescence?
Active adolescents have stronger bones in adulthood as muscle strength and bone strength are interconnected.
Why is calcium nutrition during the growing years essential?
It is crucial for achieving optimal peak bone mass, and inadequate calcium intake during childhood can lead to suboptimal bone density in adulthood.
What are some nutrients, besides calcium, that support bone health?
Adequate protein, vitamin D, vitamin K, vitamin C, magnesium, potassium, vitamin A (in moderation), carotenoids, omega-3 fatty acids.
What is a perspective on calcium supplements for bone health?
While foods are generally the best source of nutrients, calcium supplements may be beneficial for those unable to consume enough calcium-rich foods. The choice of supplement type, dose, absorption, and timing should be considered for effectiveness.
What are the two compartments of bone?
Cortical bone (outer, hard shell) and trabecular bone (inner, lacy matrix).
How do trabecular and cortical bone handle calcium differently?
Trabecular bone readily gives up minerals to the blood when calcium is needed, while cortical bone gives up calcium slowly and steadily.
At what age do trabecular bone losses start becoming significant?
In the 30s for both men and women.
How does bone loss contribute to osteoporosis?
As bone density declines, bones become fragile, leading to fractures, particularly in the hip.
What is the major risk factor for osteoporosis that cannot be changed?
Age.
How does gender influence the development of osteoporosis?
Women generally experience greater bone losses than men, especially after menopause.
What are some strategies for preventing osteoporosis?
Ensure optimal peak bone mass during childhood and adolescence, maintain a healthy diet and activity habits in early adulthood, avoid smoking and use alcohol moderately, minimize bone loss in later life through nutrition, exercise, and medical consultation.
What factors influence the trace mineral contents of foods?
The trace mineral contents of foods depend on soil and water composition, food processing, diet, and the body’s bioavailability.
Why is assessing trace mineral status challenging?
Assessing trace mineral status is challenging due to the complexity of their roles, difficulty in diagnosing deficiencies, and the potential for mild deficiencies to be overlooked.
Explain the importance of avoiding excessive intake of trace minerals.
Most trace minerals can be toxic at intakes only two and a half to eleven times above current recommendations. Exceeding the Upper Level (UL) can lead to adverse effects, and dietary supplements make it easy to surpass recommended intakes.
What role do interactions among trace minerals play in the body?
Interactions among trace minerals are common and can be well-coordinated to meet the body’s needs, supporting various physiological functions. However, imbalances or excesses of one mineral can lead to deficiencies or toxicities of others.
Why is research on nonessential trace minerals challenging?
Research on nonessential trace minerals like nickel, bromine, vanadium, cobalt, and boron is challenging due to their small quantities in the body and the lack of clear understanding of their functions and deficiencies in humans.
What are the two ionic states of iron, and how do they function in the body?
on has two ionic states—ferrous iron (reduced state) and ferric iron (oxidized state). These states allow iron to serve as a cofactor for enzymes involved in oxidation-reduction reactions and as part of electron carriers in the electron transport chain.
How does the body regulate iron absorption and maintain balance?
The body regulates iron absorption primarily through ferritin and transferrin. Ferritin captures and stores iron in the cells of the small intestine, releasing it when needed. Transferrin transports iron to various tissues, and the body adapts absorption based on iron stores.
What are the dietary factors that enhance or inhibit nonheme iron absorption?
Factors that enhance nonheme iron absorption include vitamin C, MFP factor (found in meat, fish, and poultry), acids, and certain sugars. Inhibitors include phytates, vegetable proteins, calcium, and polyphenols.
Why is iron deficiency a significant concern worldwide?
on deficiency is the most common nutrient deficiency globally, affecting over 2 billion people. It can lead to anemia, particularly in preschool children and pregnant women.
What are the stages of iron deficiency, and how is it assessed?
Iron deficiency progresses through stages of diminishing iron stores, decreased transport iron, and limited hemoglobin production. Assessment involves measuring serum ferritin, transferrin, transferrin saturation, and erythrocyte protoporphyrin.
How does iron deficiency differ from iron-deficiency anemia?
Iron deficiency refers to depleted iron stores, while iron-deficiency anemia is a severe depletion that results in low hemoglobin concentration, leading to symptoms such as fatigue, weakness, and pale skin.
Why do premenopausal women often face challenges in meeting their iron needs?
Premenopausal women have higher iron needs but lower energy needs, making it challenging to obtain enough iron from their diets. They may need to consciously choose iron-rich foods at each meal.
What are some good sources of iron in the diet?
Meats, fish, poultry, legumes, eggs, fortified grains, and dark greens are good sources of iron. Enriched or fortified foods, especially in the form of bread and cereals, contribute significantly to iron intake.
What are the potential health risks associated with iron overload?
Iron overload can lead to toxic accumulation in tissues, causing free-radical damage, infections, cirrhosis, liver cancer, heart failure, and arthritis. Excess iron in the diet or supplements can contribute to iron overload.
What factors should be considered when recommending iron supplements?
Iron supplements should be prescribed by a physician after assessing iron deficiency. The dose, formulation, and schedule should be individualized, and supplements should be taken with consideration of potential side effects, such as constipation.
What is the role of chromium in the body?
hromium participates in carbohydrate and lipid metabolism.
How does chromium help maintain glucose homeostasis?
Chromium enhances the activity of the hormone insulin.
What happens when chromium is lacking in the diet?
A diabetes-like condition may develop, characterized by elevated blood glucose, impaired glucose tolerance, insulin response, and glucagon response.
