Vitamin A

Vitamin A is the general name for several compounds in plants and animals that are essential for sight, immune function, growth and many other body functions. Beta carotene and carotenoids are the plant forms of Vitamin A and are precursors of vitamin A. This means beta carotene and carotenoids can be converted to vitamin A in the body.

 

And if I don't get enough?

Vitamin A deficiency occurs mostly in children under five years who live in deprived nations. It can lead to night blindness and irreversible, total blindness.

 

And if I get too much?

Vitamin A can be stored in the body. Continued high doses, therefore, can result in toxicity. Signs of toxicity include itchy skin, headaches, nausea, and diarrhea. During pregnancy, vitamin A toxicity may also cause birth defects. In addition, excessive amounts of carotene, although not toxic, will cause the skin to turn orange.

Vitamin A is found in many foods. Here are just a few:

• Liver

• Cheddar cheese

• Broccoli

• Carrots

• Spinach

• Pumpkin

• Mangoes

• Watermelon

• Winter squash

 

Cautions

Daily doses exceeding 6,000 IU can produce growth retardation and urinary-tract malformations of fetus. Don't take megadoses. [1]

A large body of observational epidemiologic studies has consistently demonstrated that individuals who eat more fruits and vegetables, which are rich in carotenoids, and people who have higher serum beta-carotene levels have a lower risk of cancer, particularly lung cancer. In contrast to these observations, two studies that used beta-carotene supplements reported an increased risk for lung cancer among smokers [2]. The conclusion was that foods rich in beta-carotene are protective but beta-carotene supplements are risky.

Carotenoids
To date, approximately 500 carotenoids have been identified in various fruits and vegetables and recent studies have investigated their health benefits.

Lycopene
Lycopene, found in tomatoes appears to reduce the risk for breast, prostate and pancreas cancer. However, further exploration and evaluation of the biological function of lycopene alone or in combination with other chemical compounds present in foods is required before claims can be made [3].

Lutein
A study at the Health Research Center in Salt Lake City, Utah, looked at 1,993 subjects ages 30 to 79 years who had been diagnosed with colon cancer, and a control group of 2,410 people who did not have cancer. An inverse relationship between lutein intake and colon cancer was found for all subjects, meaning those who ate lutein-containing foods had a lower risk of colon cancer [4]. Lutein is found in spinach, broccoli, lettuce, tomatoes, carrots, oranges and orange juice, celery, greens and eggs.

Beta-carotene
Many epidemiological studies have found that people who have higher serum beta-carotene levels have a lower risk of cancer, particularly lung cancer. However, as noted above, two human intervention studies that used high-dose beta-carotene supplements reported an increased risk for lung cancer among smokers [5]. Beta carotene is found in carrots and other orange and dark-green fruits and vegetables.

Warning: Beta-carotene supplements can increase cancer risk.

 

References

1. Winter Griffith H: The Complete Guide to Vitamins, Minerals & Supplements. Fisher Books (1988)

2. Wang XD. Russell RM: Procarcinogenic and anticarcinogenic effects of beta-carotene. Nutrition Reviews. Vol 57(9 I) (pp 263-272), 1999.

3. Sengupta A. Das S: The anti-carcinogenic role of lycopene, abundantly present in tomato. European Journal of Cancer Prevention. Vol 8(4) (pp 325-330), 1999.

4. Rustad M.: Leutein-containing foods help prevent colon cancer. American Journal of Clinical Nutrition (2000;71:575-582).

5. Wang X-D. Russell RM: Dr. X.-D. Wang, Jean Mayer: Procarcinogenic and anticarcinogenic effects of beta-carotene. Nutrition Reviews. Vol 57(9 I) (pp 263-272), 1999