CHAPTER 11 BONE HEALTH

Occurs During Times of Low Blood Calcium

- increased production of PTH stimulates activation of vitamin D - Parathyroid glands increase secretion of PTH - PTH and vitamin D stimulate increased breakdown of bone

Occurs During Times of High Blood Calcium

- parathyroid glands decrease secretion of PTH - less calcium is reabsorbed by the kidneys - osteoclasts are inhibited, leading to decreased breakdown of bone.

It is important to understand where to find calcium in food, but there are a variety of factors that can interfere with the absorption of even the best sources of calcium. Which of these statements describe ways calcium bioavailability or absorption may be reduced?

-choosing calcium sources high in oxalates, like spinach -consuming large amounts of calcium at one time

Ultraviolet rays react with _____ in the skin to begin the process of forming vitamin D.

7-dehydrocholesterol Ultraviolet rays react with 7-dehydrocholesterol in the skin. This is the first step in the formation of vitamin D.

Calcium supplements are recommended for many individuals. However, effectiveness of these supplements can vary based on factors like quantity consumed, intake of other foods and supplements, and time of day the supplement is taken. This section will address these factors. Choose the correct statement about calcium supplements.

All calcium supplements should be consumed in amounts of 500 mg or less per dose. Understanding the factors that increase and decrease effectiveness of calcium supplements can help you choose wisely for yourself or a family member.

Which statement regarding calcium is FALSE?

Approximately 50 percent of calcium is found in the blood. This is the false statement. Calcium makes up approximately 2 percent of our body weight. Of that, 99 percent is found in the bones and teeth as part of the hydroxyapatite crystal. The remaining 1 percent is found in the blood and soft tissues. When too little calcium comes from food, our bodies reabsorb it from our bones. If this situation is prolonged, bone density will decrease.

Which of the following is the active form of vitamin D?

CALCITRIOL

The most abundant mineral in the human body is __________.

CALCIUM

Of the following foods, which has the highest bioavailability of calcium

COOKED KALE

Carol is a vegan and does not eat dairy foods. Is it possible for her to obtain the daily recommended amount of calcium from a diet without taking supplements?

Carol can easily obtain adequate amounts of calcium from natural foods, even if she is a vegan. Green leafy vegetables such as kale, collard greens or cabbage, and beans are excellent sources of calcium.

Bone density is measured using __________.

DXA OR DEXA DEXA is considered the most accurate assessment tool for measuring bone density.

Edgar does not like drinking milk but likes cheese, yogurt, and ice cream. What can you tell about Edgar's calcium intake?

Edgar is getting adequate calcium from his diet. Cheese, yogurt, and ice cream are good sources of calcium. All milk products are good sources of calcium. Calcium is not lost when milk is processed.

Select four foods that are fair sources of calcium

Fair sources of calcium include fruits, green vegetables, and ice cream. raw broccoli ice cream corn tortilla fresh orange juice Fair Source of Calcium (50-80mg per serving)

The Dairy Group is the only food group with a significant amount of calcium.

False Green leafy vegetables and fish with the bones left in (canned salmon or sardines) have significant amounts of calcium.

Rich Sources of Calcium

Fortified orange juice fortified soy milk milk yogurt fortified tofu mozzarella cheese Rich Source of Calcium (200-300mg per serving)

Your friend Mary, who is 21 years old, is concerned because both her mother and grandmother have osteoporosis. She mentions that she is considering a jazz dance class to decrease her risk. What statement provides the best advice to Mary?

Her idea is a good one because working the muscles places stress on bones, which promotes bone density.

The body's supply of vitamin K comes from dietary sources and is also produced in the

LARGE INTESTINE

Which of the following organs are both involved in the synthesis of vitamin D?

LIVER & KIDEYS

Which of the following foods is the best source of calcium?

Milk Milk and milk products are rich in calcium

Which statement(s) correctly describe(s) the role of hormones in calcium metabolism? Be aware that all statements may be correct.

Parathyroid hormone is released when dietary calcium levels are low. When a diet is low in calcium, blood calcium levels fall, signalling the parathyroid gland to release another hormone known as parathyroid hormone, or PTH. This hormone stimulates the activation of vitamin D in the kidneys. The activation of vitamin D promotes reabsorption of calcium by the kidney, increases calcium absorption in the intestine, and stimulates osteoclasts to resorb calcium from bone.

Which form of treatment cures osteoporosis?

There is no cure for osteoporosis.

A nutrient that assists with blood calcium regulation is __________.

VITAMIN D

Which of the following individuals would be most at risk of vitamin D deficiency?

a middle-aged woman living in Alaska

Which is NOT a function of calcium?

acting as a component of both DNA and RNA

Which is NOT a function of bone?

acting as a reservoir for enzymes and hormones

Vitamin K plays a role in maintaining bone health by __________.

acting as an enzyme important to the synthesis of two bone proteins

The ____ of calcium can depend on a person's age and calcium needs.

bioavailability

Calcium is found in a wide range of foods and food groups in varying amounts. However, the bioavailability of calcium, or percentage that can be accessed, absorbed, and used by the body, can differ greatly among foods. Which of the foods below have the highest absorption rate of calcium (above 50%%)?

broccoli and kale Not all calcium sources are created equal, so it is important to consider the absorption rate when assessing the calcium content of your meals over the course of the entire day and think about how you combine ingredients in a single meal. Bear in mind, however, that there are other nutrients to consider when putting together meals. Altogether avoiding whole-grains and spinach, which are high in other important nutrients, is not a good idea.

The active form of vitamin D, also known as a hormone, is called _____.

calcitriol Calcitriol is the active form of vitamin D, which acts as a hormone in stimulating calcium absorption. Activation reactions in both the liver and kidneys are required for the formation of calcitriol from its precursors. Calcitriol, also known as active vitamin D, plays significant roles in the prevention of rickets in children, regulation of blood pressure and the immune system, and the prevention of some cancers. Vitamin D is essential in the regulation of calcium stores at recommended levels but dangerous when taken in excess, as with vitamin supplements. Moderate sun exposure and vitamin D-rich foods (dairy products, certain fish, and fortified soy products) are the best means of assuring adequate stores of this very important vitamin.

Over 99% of the body's ______ is in the bones and teeth. is in the bones and teeth.

calcium

Low calcium can lead to muscle twitching and spasms, a condition known as

calcium tetany

Two foods that are good sources of calcium

cottage cheese low fat cheddar cheese Good Source of Calcium (90-180mg per serving)

Your friend Mike tells you that he doesn't trust the quality of his municipal water and thus gives his children only bottled water to drink. What disorder could result from this decision?

dental caries

Fluoride functions to develop and maintain healthy teeth by __________.

enhancing tooth mineralization

Once absorbed into the blood, the cholecalciferol travels to the kidney for the final step in activation.

false

Good food sources of magnesium include __________.

green, leafy vegetables

Which factor is NOT associated with an increased risk of osteoporosis?

high body weight

Too much calcium in the blood, or ____ can lead to impaired kidneys and calcium deposits in the body.

hypercalcemia

Does Not Occur DuringRegulation of Blood Calcium

increased vitamin D activation leads to decreased calcium absorption from the intestines.

_____ break down bone when calcium levels are low.

osteoclasts

Certain foods like spinach are high in ______ which can interfere with absorption of certain minerals.

oxalates

Erin does not consume adequate dietary calcium or take a calcium supplement. Which of the following factors is most responsible for Erin maintaining blood calcium levels in the normal range?

parathyroid hormone

When blood calcium is low, the parathyroid glands stimulate the production of

parathyroid hormone (PTH)

Which is NOT a function of magnesium in the body?

protecting teeth from acid-forming bacteria

One cup of skim milk has approximately 80 kcal. One ounce of low-fat cheddar cheese has approximately 50 kcal. How many kilocalories would need to be consumed to get approximately 300 mg of calcium from each of these two sources individually?

skim milk-80 kcal; low-fat cheddar cheese-125 kcal One cup of skim milk and 2.5 ounces of low-fat cheddar cheese provide approximately the same amount of calcium.

Most vitamin K is stored in

the liver

The process of bone resorption is associated with __________.

the release of calcium into the bloodstream

The bioavailability of calcium is affected by each of the following factors EXCEPT __________.

the time of day

Calcium is actively absorbed in the upper small intestine with the aid of 1, 25 dihydroxyvitamin D.

true The active absorption of calcium occurs across the cell membranes of the upper small intestine, where the environment is more acidic. This requires active vitamin D, also known as 1, 25 dihydroxyvitamin D.

The thyroid hormone calcitonin inhibits the effects of vitamin D on calcium metabolism and works to lower calcium levels in the blood.

true Thyroid hormone inhibits the effects of vitamin D, resulting in decreased reabsorption of calcium by the kidney, limited calcium absorption in the intestines, and inhibition of osteoclast cells in the bone. All of these effects work to lower calcium levels in the blood.

Her idea is a good one because working the muscles places stress on bones, which promotes bone density.

vitamin D and calcium