Vitamin A and Bone Health

Vitamin A is essential for good health. It promotes growth, the immune system, reproduction, and vision. However, recent research suggests that too much vitamin A, particularly in the form of retinol, may be bad for your bones. This fact sheet explains where we get vitamin A, how much of this important vitamin we need, how it can build up in the body to excessive levels, and how you can assess your own vitamin A intake.

 What Is Vitamin A?

Vitamin A is a family of compounds that play an important role in vision, bone growth, reproduction, cell division, and cell differentiation. We get vitamin A from a variety of sources. Two of the most common are retinol and beta-carotene. Retinol is sometimes called “true” vitamin A because it is nearly ready for the body to use. Retinol is found in such animal foods as liver, eggs, and fatty fish. It can also be found in many fortified foods, such as breakfast cereals, and in dietary supplements.

Beta-carotene is a precursor for vitamin A. The body needs to convert it to retinol or vitamin A for use. Beta-carotene is found naturally in plant foods, mostly orange and dark green ones such as carrots, sweet potatoes, mangos, and kale. The body stores both retinol and beta-carotene in the liver, drawing on this store whenever more vitamin A is needed.

How Much Vitamin A Do I Need?
The Institute of Medicine developed the Recommended Dietary Allowance (RDA) for vitamin A (retinol). The recommended intakes are listed in International Units (IU) in the table, below:

The body can convert beta-carotene into vitamin A to help meet these requirements. While there is no RDA for beta-carotene, the National Institutes of Health (NIH) Office of Dietary Supplements recommends eating five or more servings of fruits and vegetables per day, including dark green and leafy vegetables and deep yellow/orange fruits to get appropriate amounts of beta-carotene.

How Does Vitamin A Affect My Bones?

Vitamin A is a family of fat-soluble compounds that play an important role in vision, bone growth, reproduction, cell division, and cell differentiation. Vitamin A is important for healthy bones. However, too much vitamin A has been linked to bone loss and an increase in the risk of hip fracture. Scientists believe that excessive amounts of vitamin A trigger an increase in osteoclasts, the cells that break down bone. They also believe that too much vitamin A may interfere with vitamin D, which plays an important role in preserving bone.

Retinol is the form of vitamin A that causes concern. In addition to getting retinol from their diets, some people may be using synthetic retinoid preparations that are chemically similar to vitamin A to treat acne, psoriasis, and other skin conditions. These preparations have been shown to have the same negative impact on bone health as dietary retinol. Use of these medications in children and teens has also been linked to delays in growth.

Beta-carotene, on the other hand, is largely considered to be safe and has not been linked to adverse effects in bone or elsewhere in the body.

How Can I Make Sure I Get the Right Amount of Vitamin A?

Most Americans are getting adequate amounts of vitamin A. The National Center for Health Statistics estimates that, on average, U.S. men and women get about 6,064 IU and 5,256 IU of vitamin A respectively each day, which is more than twice the RDA.

The Institute of Medicine cautions against daily intakes of retinol above 10,000 IU.

The chart below identifies some common food sources of retinol. Most of the reported cases of vitamin A toxicity have been blamed on the use of supplements. Healthy individuals who eat a balanced diet generally do not need a vitamin A supplement.

Plant sources of beta-carotene are not as well absorbed as the animal sources of vitamin A listed in the chart, but they are still an important source of this vitamin. Dark orange and green vegetables and fruit, including carrots, sweet potatoes, spinach, cantaloupe, and kale are excellent sources of beta-carotene. Due to concerns about the negative effects of too much retinol, some people prefer to eat more foods rich in beta-carotene to satisfy their need for vitamin A.

Are Some People At Special Risk of Getting Too Much Vitamin A?
The National Health and Nutrition Examination Survey (NHANES III) found high levels of retinol in 5 to 10 percent of the survey participants. These increased levels were more common in men over the age of 30 and women over the age of 50.

Older people who regularly take dietary supplements containing vitamin A may be at higher risk of getting too much vitamin A.

Studies suggest that taking dietary supplements is a common practice among many seniors. However, the routine use of vitamin A supplements, as well as fortified foods, in older men and women is increasingly being questioned. Older adults are at significant risk for osteoporosis and related fractures, and their serum (blood) levels of retinol increase with age. As a result, fortified foods and supplements containing vitamin A in the form of beta-carotene may be a better choice for bone health in this population.

The supplement label provides information about how much vitamin A is provided, in both International Units and as a percentage of the RDA. The list of ingredients will contain information about which forms of vitamin A are included. Other names for retinol include retinyl, palmitate, and retinyl acetate.

Where Can I Find More Information?
For additional information on bone health, visit the National Resource Center Web site at www.niams.nih.gov/bone or call 1-800-624-2663.
For additional information on vitamin A, visit the NIH Office of Dietary Supplements Web site at http://dietary-supplements.info.nih.gov or call 301-435-2920.

Facts about Vitamin C

By. Linda B. Bobroff and Isabel Valentin-Oquendo

Why do we need vitamin C?

Vitamin C, also known as ascorbic acid, has a wide variety of uses in the body. It helps slow

down or prevent cell damage. It also is needed to maintain healthy body tissues and the
immune system. Vitamin C helps the body absorb iron from plant foods.

What happens if we don’t get enough vitamin C?
Vitamin C is found in many foods we eat and deficiency is rare. Scurvy, the disease caused
by vitamin C deficiency, was common a few generations ago. It was prevalent among
seamen who lived on dried and salted foods for months at a time. Scurvy is rare in the U.S.
Still, not getting enough vitamin C can lead to anemia, bleeding gums, infections, and poor
wound healing.

How much vitamin C do we need?
The following table lists recommended daily intakes of vitamin C. People who smoke need
an additional 35 mg of vitamin C every day.

The following table lists recommended daily intakes of vitamin C:

How can we get enough vitamin C?

The best way to get enough vitamin C is through foods rather than supplements.Fruits and

vegetables are the best sources.

Here are some foods and the amount of vitamin C they contain:

What about fortified foods?
Some juices and cereals have vitamin C added. The amount of vitamin C in each product
varies. Check the nutrition label to see how much vitamin C the product contributes to
your daily need.

How should foods be prepared to retain vitamin C?
Vitamin C is easily destroyed during preparation, cooking, or storage. To retain vitamin C, follow these tips:

• Eat raw fruits and vegetables as soon aspossible after buying them.
• Cut vegetables just before eating or cooking.
• Cook vitamin C-rich foods quickly in as little water as possible.• Microwave, steam, or stir-fry to retain the
most vitamin C.

What about supplements?
Healthy individuals who eat plenty of fruits and vegetables rarely need vitamin C supplements. Taking vitamin C supplements does not prevent colds. Some studies show that vitamin C supplements may decrease the duration of a cold.

How much is too much?
If you do take a supplement, do not get more than 2000 mg/day of vitamin C from foods
and supplements. Although excess vitamin C is mostly eliminated in the urine, high doses
can cause headaches, frequent urination, diarrhea, and nausea. People with a history of
kidney stones should avoid high levels of vitamin C.

Where can I get more information?
The Family and Consumer Sciences (FCS) agent at your county Extension office may
have more written information and nutrition classes for you to attend. Also, a registered
dietitian (RD) can provide reliable information to you.Reliable nutrition information may be
found on the Internet at the following
sites:
http://fycs.ifas.ufl.edu
http://www.eatright.org
http://www.nutrition.gov

Facts about Vitamin E

By Jennifer Hillan

Why do we need vitamin E?
Vitamin E is an antioxidant that helps protect the body from the effects of free radicals. Free radicals
are substances that can damage the body’s cells. Free radicals may increase the risk for heart disease
and cancer.

What happens if we don’t get enough vitamin E?
A deficiency of vitamin E can affect the nervous system and the eyes. It also can cause a form of
anemia (“hemolytic” anemia). Vitamin E deficiency is very rare, but it can develop in people who can’t absorb fat normally. This is because vitamin E is a fat-soluble vitamin and needs dietary fat to be absorbed. People who don’t get enough vitamin E may have higher risks for heart disease and cancer.

How much vitamin E do we need?
In food, vitamin E is found in many forms. The form that is most usable in our bodies is called alpha-tocopherol. Vitamin E often is measured as milligrams (mg) of alpha-tocopherol. It also can be measured as International Units (IU). Supplements usually show vitamin E content as IU. The following table lists recommended daily intakes of vitamin E:

How can we get enough vitamin E?

Vegetable oils, salad dressings, and margarines are the richest dietary sources of vitamin E. Other good sources are nuts and green leafy vegetables. Fortified cereals also are good sources of vitamin E. Here are some foods and the amount of vitamin E they contain:

What about supplements?

Foods can supply the recommended amount of vitamin E for good health. Many people choose to take a vitamin E supplement. Recent studies do not support use of vitamin E supplements for prevention of heart disease.

Before deciding to take a supplement, talk with your doctor. He/she can tell you how much to take and if there may be interactions with other drugs or supplements that you take. For example, vitamin E supplements can be harmful if you take blood-thinning drugs like warfarin (Coumadin�), or aspirin.

How much is too much?

You should not get more than 1000 mg (1500 IU) of alpha-tocopherol per day from supplements. Doses above this amount increase the risk of bleeding problems. When bleeding occurs in the brain it can cause a hemorrhagic

stroke.

Where can I get more information?

The Family and Consumer Sciences (FCS) agent at your county Extension office may have more

written information and nutrition classes for you to attend. Also, a registered dietitian (RD) can

provide reliable information to you. Reliable nutrition information may be found on the Internet at the following

sites:

http://fycs.ifas.ufl.edu

http://www.eatright.org

http://www.nutrition.gov

http://mypyramid.gov

Vitamin A (Retinol)

Updated and revised by Jackie Mosure, Dietetic Intern, College of Human Ecology.

This fact sheet is one in a series containing information to help you select foods that provide adequate daily amounts

of vitamins, minerals, and dietary fiber. The Dietary Guidelines Advisory Committee just released the Dietary Guidelines

for Americans 2005 that convey the following nine major messages concerning these topics:

• Adequate nutrients within calorie needs

• Weight management

• Physical activity

• Food groups to encourage: fruits and vegetables, whole grains, and nonfat or low-fat milk and milk products

• Fat

• Carbohydrates

• Sodium and potassium

• Alcoholic beverages

• Food safety

What is the importance of vitamin A?

Vitamin A, a fat-soluble vitamin, plays essential roles in vision, growth, and development; the development and

maintenance of healthy skin, hair, and mucous membranes; immune functions; and reproduction.

How much do you need?

Vitamin A is also called retinol. Measurement of the amount of vitamin A is taken in retinol activity equivalents (RAE).

Carotene, an orange pigment found in food, is split by the body to become two active units of vitamin A. This is also important when calculating the amount of vitamin A in the body. The U.S. Recommended Daily Allowance (RDA) for

vitamin A is 700 RAE per day for women and 900 RAE per day for men. The U.S. RDA given is for adults and changes

for women who are pregnant or lactating; therefore, please consult your healthcare provider for differences.

A good source of vitamin A contains substantial amounts of vitamin A and/or carotene in relation to its calorie content

and contributes at least 10% of the U.S. RDA for vitamin A in a serving.

Do Americans get enough vitamin A?

According to recent surveys by the U.S. Department of Agriculture (USDA), the average intake of vitamin A (and

carotene) by an American adult is adequate.

How to get enough vitamin A.

Eating a variety of foods that contain vitamin A (and carotene) is the best way to get an adequate amount. Healthy

individuals who eat a balanced diet rarely need supplements.In fact, too much vitamin A can be toxic. Select foods that

contain excellent to good sources of vitamin A each day.

How to prepare foods to retain vitamin A.

Vitamin A can be lost from foods during preparation, cooking, or storage. To prevent loss of vitamin A:

• Use raw fruits and vegetables whenever possible.

• Keep vegetables (except sweet potatoes and winter squash) and fruits covered and refrigerated during storage.

Where to find vitamin A in the Food Guide Pyramid.

• Steam vegetables and braise, bake, or broil meats instead

of frying. Some of the vitamin A is lost in the fat during frying.

What about fortified foods?

Low-fat and skim milk are often fortified with vitamin A because it is lost during processing. Margarine is fortified to

make its vitamin A content the same as butter. Most ready-to-eat and instant prepared cereals are fortified

with vitamin A. Fortified ready-to-eat cereals usually contain at least 25% of the U.S. RDA for vitamin A. Cereals vary,

so check the label on the package for the vitamin A content for that cereal.

What is a serving?

The amount of vitamin A in a serving depends on the weight of the serving. For example, ½ cup of a cooked vegetable

contains more vitamin A than ½ cup of the same vegetable raw, because the cooked vegetable weighs more. Therefore,

the cooked vegetable provides vitamin A, just not enough in a ½-cup serving to be considered a good source.

Food companies label their products according to regulations set by the Food and Drug Administration (FDA). Terms

to define a serving of food that has 20% or more of the RDA include: “high,” “rich in,” or “excellent source of” vitamin

A. Terms to define a serving of food that contains 10% or more of the RDA include: “good,” “contains or provides”

vitamin A. Terms to define a serving of food that contains less then 10% of the RDA include: “enriched,” “fortified,”

or “added” vitamin A.

References

Browne, M. B. 1993. Label Facts for Healthful Eating. Mazer Corporation, Dayton, OH.

Federation of American Societies for Experimental Biology,Life Sciences Research Office. Prepared for the

  Interagency Board for Nutrition Monitoring and Related Research, 1995. Third Report on Nutrition Monitoring

  in the United States: Volumes 1 and 2. U.S. Government Printing Office, Washington, DC.

Subcommittee on the 10th Edition of the RDAs, Food and Nutrition Board, Commission on Life Sciences, National

  Research Council. 1987. Recommended Dietary Allowances, 10th ed. Academy Press, Washington, DC.

U.S. Department of Agriculture, U.S. Department of Health and Human Services. Your Health: Dietary Guidelines for

  Americans, 4th ed. Home and Garden Bulletin No. 232.U.S. Government Printing Office, Washington, DC.

VITAMIN D LINKED TO REDUCED MORTALITY RATE IN CHRONIC KIDNEY DISEASE

Washington, DC (Tuesday, May 6, 2008) — For patients with moderate to severe chronic kidney disease
(CKD), treatment with activated vitamin D may reduce the risk of death by approximately one-fourth,
suggests a study in the August Journal of the American Society of Nephrology.
Many patients with advanced CKD take the drug calcitriol, an oral form of activated vitamin D, to
treat elevated levels of parathyroid hormone. "Although activated vitamin D is known to influence many
biological processes, previous clinical knowledge is limited to its effect on parathyroid hormone levels,"
explains Dr. Bryan Kestenbaum of the University of Washington in Seattle, one of the study authors.
The study included 1,418 patients who had stage 3 to 4 CKD, which means moderately to severely
reduced kidney function. All patients also had high parathyroid hormone levels (hyperparathyroidism),
which can contribute to weakening of the bones in CKD. The researchers identified one group of patients
who were being treated with calcitriol to lower their parathyroid hormone levels and another group who
were not receiving calcitriol.

During a two-year follow-up period, mortality rates were compared for patients who were and were
not taking calcitriol. "We then adjusted for differences in age, kidney function, parathyroid hormone levels,
other illnesses, and other medications," says Dr. Kestenbaum.
In the adjusted analysis, the overall risk of death was about 26 percent lower for patients taking
calcitriol. Patients on calcitriol were also less likely to develop end-stage renal disease, requiring dialysis to
replace lost kidney function.

Overall, treatment with calcitriol was associated with a 20 percent reduction in the risk of either
death or dialysis. The reduction in mortality with calcitriol was unrelated to its effect on parathyroid
hormone levels.

"Recently, there has been an increased focus on the effects of vitamin D beyond those on bone
health," Dr. Kestenbaum comments. "Vitamin D deficiency has been associated with risk factors for
cardiovascular disease, such as high blood pressure, diabetes, and inflammation." Previous studies have
suggested that treatment with intravenous vitamin D can improve survival in patients on hemodialysis.
The new results suggest that treatment with oral activated vitamin D may also improve survival in
patients with CKD who do not yet require dialysis. "Randomized clinical trials are needed to test the
hypothesis that vitamin D therapy can improve cardiovascular health and survival in CKD,"
Dr. Kestenbaum adds. "Future studies should also examine the role of non-activated vitamin D, which is
less expensive and less toxic."

The study has some important limitations, including a lack of data on other factors that may have
affected survival in patients taking calcitriol. Also, since the study included mainly older, white men, the
results may not apply to younger, more ethnically diverse populations with CKD.
This study was supported by a Career Development Award (K23 DK63274-01) from the National
Institutes of Health.

Dr. Kestenbaum receives consulting fees from Abbott and Shire as well as grant support from
Amgen.

The study entitled, "Association of Oral Calcitriol with Improved Survival in Nondialyzed CKD,"
will be available online at http://jasn.asnjournals.org/ beginning on Wednesday, May 7, 2008, and in print
in the August issue of the Journal of the American Society of Nephrology (JASN).
The American Society of Nephrology (ASN) is a not-for-profit organization of 11,000 physicians
and scientists dedicated to the study of nephrology and committed to providing a forum for the
promulgation of information regarding the latest research and clinical findings on kidney diseases. ASN
publishes JASN, the Clinical Journal of the American Society of Nephrology (CJASN), and the Nephrology
Self-Assessment Program (NephSAP). In January 2009, ASN will launch a newsmagazine.