Micronutrients and Nutrient Metabolism:

• Vitamins and Minerals:

Functions, sources, and recommended intake levels of vitamins and minerals

Recommended intake levels: 

* These are the recommended intake levels in general. The numbers may be different for each individual.

* Statistics from Harvard T.H. School of Public Health

1. Vitamin A

Functions: Essential for vision, immune function, skin health, and cell growth

Sources: Liver, fish liver oils, dairy products, eggs, orange and yellow fruits and vegetables (carrots, sweet potatoes, mangoes), leafy greens

Recommended intake levels:

• Women: 700 micrograms (2,333 IU)
• Men: 900 micrograms (3,000 IU)

2. Vitamin C

Functions: An antioxidant, supports immune function, helps collagen synthesis, and enhances iron absorption

Sources: Citrus fruits (oranges, lemons), strawberries, kiwi, bell peppers, broccoli, tomatoes

Recommended intake levels:

• Women: 75 milligrams
• Men: 95 milligrams
• Those who smoke should add 35 milligrams to the recommended intake

3. Vitamin D

Functions: Promotes calcium absorption and bone health, supports immune function, and may have beneficial effects on various tissues

Sources: Sunlight exposure, fatty fish (salmon and mackerel), fortified dairy and plant-based milk, eggs, mushrooms

Recommended intake levels:

• Women: some text
  • Ages 19 - 51: 15 micrograms (600 IU)
  • Ages 51 - 70: 15 micrograms (600 IU)
  • Ages 71+: 20 micrograms (800 IU)
• Men:some text
  • Ages 19 - 51: 15 micrograms (600 IU)
  • Ages 51 - 70: 15 micrograms (600 IU)
  • Ages 71+: 20 micrograms (800 IU)

4. Vitamin E

Functions: An antioxidant, protects cell membranes from damage and supports immune function and skin health.

Sources: Nuts (almonds and hazelnuts), seeds (sunflower seeds and pumpkin seeds), vegetable oils (sunflower oil, wheat germ oil), leafy greens

Recommended intake levels:

• Women: 15 milligrams
• Men: 15 milligrams

5. Vitamin K

Functions: Essential for blood clotting, bone metabolism, and cardiovascular health

Sources: Leafy greens, broccoli, Brussels sprouts, cabbage, and parsley

Recommended intake levels:

• Women: 90 micrograms
• Men: 120 micrograms

6. Vitamin B12

Functions: Helps with the formation of red blood cells, maintain energy levels, brain health, and cell metabolism

Sources: Meat, fish, eggs, and milk

Recommended intake levels:

• Women: 2.4 micrograms
• Men: 2.4 micrograms

7. Calcium

Functions: Supports bone and teeth health, muscle function, nerve transmission, and blood clotting.

Sources: Dairy products (milk, cheese, and yogurt), leafy greens, tofu, almonds, sesame seeds

Recommended intake levels:

• Women:some text
  • Ages 31 - 50: 1,000 milligrams
  • Ages 51+: 1,200 milligrams  
• Men:some text
  • Ages 31 - 50: 1,000 milligrams
  • Ages 51+: 1,200 milligrams  

8. Potassium 

Functions: Helps maintain fluid balance, supports muscle function, regulates blood pressure, and assists in nerve transmission

Sources: Fruits (bananas, oranges, and kiwi), vegetables (potatoes, spinach, and tomatoes), dairy products, legumes, nuts, seeds

• Women: some text
  • Ages 14 - 18: 2,300 milligrams
  • Ages 19+: 2,600 milligrams 
• Men:some text
  • Ages 14 - 18: 3,000 milligrams
  • Ages 19+: 3,400 milligrams 

9. Magnesium

Functions: Involved in enzymatic reactions, supports muscle and nerve function, regulates blood sugar and blood pressure, and contributes to bone health

Sources: Nuts, seeds, whole grains, leafy greens, legumes, tofu 

Recommended intake levels:

• Women:some text
  • Ages: 19 - 30: 310 milligrams
  • Ages 31 - 70+: 320 milligrams
• Men:some text
  • Ages: 19 - 30: 400 milligrams
  • Ages 31 - 70+: 420 milligrams

10. Iron

Functions: Oxygen transport, energy production, and immune function

Sources: Red meat, poultry, fish, lentils, beans, tofu, fortified cereals, spinach, quinoa

Recommended intake levels:

• Women:some text
  • Ages 31 - 50: 8 milligrams
  • Ages 51+: 8 milligrams
• Men:some text
  • Ages 31 - 50: 8 milligrams
  • Ages 51+: 8 milligrams

11. Zinc

Functions: Supports immune function, wound healing, DNA synthesis, and growth and development

Sources: Red meat, poultry, seafood, dairy products, whole grains, nuts, seeds, legumes

Recommended intake levels:

• Women: 8 milligrams
• Men: 11 milligrams

Micronutrient deficiencies and toxicities

Micronutrient deficiencies and toxicities can occur due to inadequate amounts of micronutrients or the overconsumption of micronutrients. These are some common micronutrient deficiencies and toxicities:

1. Iron deficiency: Iron deficiency is one of the most common micronutrient deficiencies worldwide, especially among women and children. It can lead to anemia, “a condition in which the body does not have enough healthy red blood cells.”
2. Vitamin D deficiency: Vitamin D deficiency is common in regions with limited sunlight exposure or among individuals with dark skin, older adults, or inadequate dietary intake. It can lead to weakened bones, muscle weakness, increased risk of fractures, and poor immune function.
3. Calcium deficiency: Calcium deficiency or hypocalcemia is inadequate calcium intake that can lead to weakened bones (osteopenia or osteoporosis), increased risk of fractures, and impaired muscle function.
4. Sodium toxicity: Excessive sodium intake is usually due to the consumption of processed and fast foods. This toxicity can lead to high blood pressure, cardiovascular disease, stroke, and kidney damage.
5. Vitamin A toxicity: Vitamin A toxicity or hypervitaminosis A can occur from excessive intake of supplements or animal-derived foods rich in preformed vitamin A. It can lead to symptoms such as nausea, vomiting, headache, dizziness, and liver damage.
6. Selenium toxicity: “Selenium toxicity can occur with acute or chronic ingestion of excess selenium. Symptoms of selenium toxicity include nausea; vomiting; nail discoloration, brittleness, and loss; hair loss; fatigue; irritability; and foul breath odor (often described as ‘garlic breath’).”

Role of vitamins and minerals in metabolic pathways and physiological processes

Vitamins and minerals are essential in metabolic pathways and physiological processes.

Metabolic pathways: 

1. Glycolysis is a catabolic pathway that breaks down complex compounds into simpler compounds. This degradation of complex compounds releases chemical energy found in the bonds of the molecule. Glycolysis “splits glucose into two pyruvate molecules” or a three-carbon acid that is formed during glycosis. However, vitamins and minerals are essential because they help with the functioning of enzymes (calcium, zinc, and copper) and cofactors (magnesium and vitamin B) that break apart glucose. 
2. Fatty acid oxidation, or beta-oxidation, is another catabolic pathway. Fatty acid oxidation is when fatty acids are broken down into metabolites and also to produce energy. Like glycolysis, vitamin Bs’ and minerals (magnesium, iron, and copper) help break down the fatty acids.
3. The Citric Acid Cycle, or Krebs Cycle, is an amphibolic pathway, a combination of both catabolic and anabolic processes. The Kreb’s Cycle is “a chain of reactions occurring in the mitochondria, through which almost all living cells produce energy in aerobic respiration.” The role of vitamins and minerals, especially vitamin Bs’, magnesium, copper, iron, and zinc, during Kreb’s Cycle is to maintain the cycle’s functionality. 

Physiological processes: 

1.  Movement

The ability to move is a physiological process that requires different organ systems to produce motion. In addition, vitamins and minerals help with energy production, muscle function, and bone health. Movement requires energy, and the process of converting nutrients into energy relies on various metabolic pathways, including glycolysis and the Krebs cycle. To produce energy, vitamin Bs’  and magnesium are crucial for converting carbohydrates, proteins, and fat into energy sources. On the other hand, vitamins and minerals such as calcium, magnesium, and potassium help with muscle contraction and relaxation. Finally, calcium and vitamin D ensure bone health. 

2.  Digestion

Vitamins and minerals like vitamin C, zinc, and sodium are vital for digestion. Vitamin C supports digestion by promoting the absorption of iron from plant-based foods and enhances the production of collagen. This protein forms the structural framework of connective tissues in the digestive tract. Additionally, zinc is involved in the synthesis of digestive enzymes, which break down proteins, fats, and carbohydrates. Lastly, sodium absorbs nutrients like glucose and amino acids in the small intestine.

3. Circulation

Vitamins and minerals help transport oxygen, nutrients, hormones, and waste products throughout the body via the bloodstream. Some examples of essential vitamins and minerals are vitamin C, vitamin E, and iron. Firstly, vitamin C is essential for the synthesis of collagen, a structural protein found in blood vessels, capillaries, and connective tissues. Then, vitamin E is an antioxidant that helps protect cell membranes and red blood cells from oxidative damage (heat shock). Finally, iron is a component of hemoglobin, a protein in red blood cells that binds to oxygen and transports it from the lungs to tissues throughout the body. Healthy iron levels also prevent anemia and maintain blood oxygen.

• Nutrient Absorption and Bioavailability:

Digestion, absorption, and transport of nutrients

To gain the benefits of consuming nutrients, they need to be digested, absorbed, and transported. Digestion starts in the mouth because the action of chewing breaks food into smaller pieces. Then, the food travels down the esophagus to the stomach. The stomach digests the food with the help of enzymes and strong acids. Next, the food goes to the small intestines for nutrient absorption. Once absorbed, nutrients enter the bloodstream or lymphatic system for transport to cells throughout the body. 

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Factors influencing nutrient bioavailability

Bioavailability is “the ability of a drug or other substance to be absorbed and used by the body.” Moreover, some factors that affect nutrient bioavailability are genetics, age, health, and cooking.

1. Genetics: Genetic variations can influence individual differences in nutrient absorption and metabolism, “such as increased iron absorption in hemochromatosis, a condition where the body's iron levels build up and overload.” 
2. Age/Health: Age and health status can affect nutrient bioavailability. Infants, children, pregnant women, and older adults may have different nutrient requirements and absorption capacities. Certain health conditions, such as gastrointestinal diseases, metabolic disorders, or nutrient deficiencies, can also impact nutrient bioavailability
3. Cooking: Cooking can break down cell walls and denature proteins, making nutrients more accessible for absorption. However, excessive heat can destroy nutrients in food.

Nutrient interactions and their impact on absorption and utilization

1. Vitamin D supports the absorption of calcium from the intestines. While calcium is essential for the activation of vitamin D in the body. When the nutrients combine, these nutrients are crucial in maintaining bone health and preventing conditions like osteoporosis.
2. Vitamin C enhances the absorption of non-heme iron (the type of iron found in plant-based foods) by converting it into a more absorbable form. Consuming vitamin C-rich foods, such as citrus fruits or bell peppers, and iron-rich foods can improve iron absorption and help prevent iron deficiency anemia.
3. Sodium and potassium regulate fluid balance and maintain proper nerve and muscle function. 
4. Fat-soluble vitamins (A, D, E, and K) require dietary fat for absorption. Consuming these vitamins with a source of dietary fat enhances their absorption. 

Question: 

1. What is micronutrient toxicity or deficiency? 
2. What is bioavailability and how are nutrients involved?
3. How are nutrients transported throughout the body?

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