But an update is in order. It is not that vitamin C does not do these things. Rather, it does more – much more.

It may very well help to prevent cancer, says the Committee on Diet, Nutrition, and Cancer (of the U.S.). The panel members were impressed enough with studies of vitamin C and Cancer to advise us to eat foods rich in vitamin C every day.

Scientists have found that cancers of the stomach and esophagus are less common among people who eat diets rich in vitamin C. In fact, year-round access to foods rich in vitamin C may be one explanation for the dramatic fall in stomach cancer rates in the case of the United States.

Stomach cancer was common in the United States at the turn of the 20th century, when some fruits and vegetables were available only seasonally. We now have year round access to these fruits and vegetables, and many are rich in vitamin C. And stomach cancer is no longer common. It does remain a major health problem in some parts of the world.

A few studies also tie vitamin C to lower risk of bladder and colon cancer. But there is not enough research yet to make a firm judgment about vitamin C’s  ability to protect against these two forms of cancer.

How Vitamin C Protects Us

We have a pretty good idea of how vitamin C works to prevent cancer. Substances in food called nitrites can turn into cancer-causing nitrosamines during cooking or digestion. Bacon, of course, has a particularly bad record;  nitrosamines have often been found in it after cooking.

Laboratory scientists know that nitrosamines can be created by letting certain chemicals come in contact with each other. yet when vitamin C is added to the chemical mixture that normally results in nitrosamines, fewer of them form. In some cases, vitamin C has completely blocked the formation of nitrosamines.

Can the same thing happen in our bodies? Studies around the globe suggest that the answer is yes.

In the U.S., a team of  researchers found that the chances of developing cancer of the esophagus went down as the amount of fruits and vegetables in the diet went up. Researchers also know that Americans and Western Europeans have fairly low rates of stomach cancer. These countries enjoy access to a variety of fruits and vegetables.

On the other hand, fruit and vegetable intake is low in some of the regions where stomach and esophageal cancer are rampant. Iranians living along the coast of the Caspian Sea, for instance, have alarming rates of esophageal cancer. Researchers sent to find out why noted that fruits and vegetables were almost absent from the diets of these people.

Another Role for Vitamin C

Scientists have known for decades that vitamin C can block the chemical reaction called oxidation. Oxidation is the process that causes food to become rancid. Substances that prevent oxidation are called antioxidants.

Until recently, no one realized that antioxidants might help protect against cancer. But they very well may. Scientists now believe that some chemicals cause cancer only if oxidized. By preventing oxidations, vitamin C may cut down on our exposure to cancer-causing chemicals.

The Recommendation and How to Meet It

“Eat fruits, vegetables…… daily, especially those high in vitamin C,” advises the Committee on Diet, Nutrition, and Cancer. This is going to be a popular recommendations. Almost everyone – from babies to adults – likes foods rich in vitamin C.

To follow the committee’s advice, take a look at the following chart. It rates foods as low, medium, or high in this vitamin.
How about animal foods? Animal foods are not listed because the supply less than 10 % of the vitamin C in our diet. Fruits and vegetables are the foods to depend on for this nutrient.

Vitamin C in Fruits and Vegetables

Adapted from the work of Committee on Diet, Nutrition, and Cancer, National Academy of Sciences, USA, 1989

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From all over the world have come the most exciting findings ever reported about vitamin A. More than a dozen studies have linked diets rich in vitamin A to a surprising amount of protection against some forms of cancer.

In Chicago, scientists found only two cases of lung cancer among 500 men, including some smokers, who eat many fruits and vegetables rich in vitamin A. That was only one-seventh as many lung cancer cases as were found in 500 men who ate few of these foods.

And in Norway, the findings were no different. Men who ate many vegetables rich in vitamin A had only one-third as much lung cancer as those eating little of these foods.

In Japan, the story was the same. Researches found 30 percent fewer cases of lung cancer among people who ate vegetables rich in vitamin A every day. The daily vegetable eaters also had lower rates of stomach cancer.

Cancer scientists have been so fascinated by these findings that the ability of vitamin A to protect us from cancer has become one of their top interests. Many are already convinced that we should be eating more foods rich in vitamin A. The Committee on Diet, Nutrition, and Cancer of the National academy of sciences has urged us to do so.

Studies have linked a diet rich in vitamin A to protection from cancer in eight different organs. The evidence is strongest for cancer of the lung, stomach, or esophagus.

But there is more good news. Research also ties vitamin A to protection from cancers of the mouth, colon, rectum, prostate, and bladder. There is less evidence here than for lung, stomach, and esophageal cancer. But there is enough to merit our attention.

Three Types of Vitamin A

“Vitamin A” is very general term. It refers to several substances that can take care of the body’s need for this nutrient.

For many of the body’s functions that need vitamin A, any form will do. But in cancer prevention, the picture looks different. As things stand right now, it seems that only some kinds of vitamin A in food.

• Retinol is the vitamin A in animal foods.
• Carotene, (or beta-carotene) is the main kind of vitamin A in fruits and vegetables.
• Carotenoids are other forms of vitamin A found in fruits and vegetables. They are a very minor source of vitamin A.

Of these different kids of vitamin A, carotene is linked most strongly to protection from cancer.

….carotene is linked most strongly to protection from cancer.

Vitamin A Supplements Are Different

Of course, we can also get vitamin A from pills. The form used in vitamin compounds is not carotene or retinol. It usually is a synthetic form of vitamin A called vitamin A palmitate. Little research has been done on the ability of this kind of vitamin A to protect against cancer.

For this reason, it is not good idea to rely on vitamin A pills to reduce your risk of cancer. Scientists simply don’t know if this type of vitamin A has any value in preventing cancer.

You may also be aware that the kind of vitamin A usually contained in vitamin capsules or tablets can be toxic if taken in very high doses.

Newspapers and magazines have published some articles about special forms of vitamin A that show remarkable anti-cancer potential in laboratory animals. Scientists have used these forms of vitamin A, called retinoids, to block cancers of the lung, bladder, and breast in test animals.

Retinoids may be on the drugstore shelves someday. But right now they are not for sale. Their use is strictly experimental.

The Recommendation and How to Meet It

The Committee on Diet, Nutrition, and Cancer recommends daily consumption of fruits and vegetables. The committee advises us to emphasize those fruits and vegetables that are rich in carotene, the most important kind of vitamin A in plant foods.

To help in selecting foods, the Committee prepared the following chart which classifies foods as low, medium, or high in carotene.

Carotene in Fruits and Vegetables

Note: Chart adapted from a 1989 compilation by the Committee on Diet, Nutrition,

and Cancer, National Academy of Science, U.S.A.

Before I continue to write this subject, I suggest you to find another point of view concerning the power of vitamin A in  fighting cancer, a useful  article for you posted in Blog of Health.

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