FSHN 120 Lecture Notes - Lecture 11: Vitamin D Deficiency, Vitamin K Deficiency, Cod Liver Oil

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Published on 11 Dec 2016
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Chapter 9: Nutrients Involved in Bone Health
1. How Do Our Bodies Maintain Bone Health?
a. The composition of bone provides strength and flexibility
i. About 65% of bone tissue is made up of minerals
1. Calcium and phosphorus are the most abundant minerals in bone
ii. About 35% of bone tissue is made up of organic substances
1. Collagen is a protein that forms strong fibers in bone and
connective tissue
iii. There are two types of bone
1. Cortical bone is very dense and comprises 80% of our skeleton
2. Trabecular bone is porous bone tissue that makes up 20% of our
skeleton
b. The constant activity of bone tissue promotes bone health
i. Bone growth and modeling determine the size and shape of our bones
1. The size of our bones increases through the process of bone growth
2. Bone modeling determines the shape of our bones
3. Bone density continues to develop into early adulthood
a. Peak bone density is achieved before age 30
ii. Bone remodeling maintains a balance between breakdown and repair
1. Bone mass is regularly recycled through remodeling
a. Resorption involves the action of osteoclasts
b. Bone formation involves the action of osteoblasts
2. How Do We Assess Bone Health?
a. Dual energy x-ray absorptiometry (DEXA) provides a measure of bone density
i. A normal DEXA t-score is between +1 and -1 of the value for a 30-year-
old healthy adult
b. Other bone density measurement tools have been developed, such as ultrasound
and different forms of x-ray technology
3. A Profile of Nutrients That Maintain Bone Health
a. Calcium is the most abundant mineral in our bodies
i. Calcium has many functions
1. Calcium provides structure to bones and teeth
2. Calcium assists with acid-base balance
3. Parathyroid hormone (PTH) raises blood calcium levels
4. Calcitonin inhibits the actions of vitamin D, causing a decrease in
blood calcium levels
5. Calcium is critical for normal transmission of nerve impulses
6. Calcium assists in muscle contraction
7. Calcium helps to maintain healthy blood pressure
8. Calcium initiates blood clotting
9. Calcium regulates various hormones and enzymes
ii. How much calcium should we consume?
1. Calcium requirements vary with age and gender
a. The bioavailability of calcium depends on our age, need for
calcium, how much is consumed at one time, and dietary
factors
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iii. Foods rich in calcium include dairy, greens, and more
1. Dairy products are the most common sources of calcium in the US
diet
2. Green leafy vegetables are good sources of calcium
3. Many packaged foods are fortified with calcium
iv. What happens if we consume too much calcium?
1. Consuming excess calcium can interfere with absorption of other
minerals
2. Hypercalcemia can be a result of an inability to regulate blood
calcium
v. What happens if we don’t consume enough calcium?
1. There are no short-term symptoms associated with consuming too
little calcium as our bodies will remove calcium from bone if
necessary
2. The long-term repercussion of low calcium intake is osteoporosis
3. Hypocalcemia is caused by various diseases including kidney
disease, vitamin D deficiency, and diseases that inhibit the
production of PTH
b. Vitamin D is a fat-soluble vitamin and a hormone
i. Vitamin D can be made in the skin when exposed to UV light
ii. Vitamin D has several functions
1. Vitamin D works with PTH and calcitonin to regulate blood
calcium levels
a. They regulate absorption of calcium and phosphorus from
the small intestine
b. They signal the kidneys to excrete more or less calcium in
urine
c. Vitamin D and PTH stimulate osteoclasts when calcium is
needed elsewhere in the body
2. Normal calcification of bone requires vitamin D
3. Vitamin D may decrease the formation of some cancerous tumors
iii. How much vitamin D should we consume?
1. The RDA is based on the assumption that an individual does not
get adequate sun exposure
a. Latitude and time of the year have the most significant
impact on ability to synthesize vitamin D
b. Other factors influencing vitamin D synthesis include time
of day, skin color, age, and body weight status
c. Vitamin D is obtained primarily from fish, fortified foods,
supplements, or sunlight
i. Vitamin D2 (ergocalciferol) is found in plant foods
ii. Vitamin D3 (cholecalciferol) is found in animal
foods
iii. Fatty fish and cod liver oil are good sources of
vitamin D
iv. Milk is fortified with vitamin D
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