PDA

View Full Version : oxidative stress



steveo
September 25th, 2003, 11:34 AM
I have always been involed with sports.I would like to do a triathon next summer/fall . I read an article about oxidative stress and the damage it can do. My question is would it help we take a elite athete multivitamin or just plan good whole food. {pulled a calf muscle}. Thanks for any help . Steveo http://www.runnertriathletenews.com/news/coopercomplete.html
and Complete Triathon Book

mattson
September 25th, 2003, 12:33 PM
The book on my shelf is Haas's "Eat to Win". Yes, it is 20 years old, but it is easy to read. I believe that his section on free radicals and antioxidants is still valid science. (I'm sure that other people will list more current articles of equal merit.)

Don't be caught up in the idea that "a little is good, more must be better". Whenever I hear about the ill side effects of mega doses of vitamins (like 10-100 times daily requirement), I wonder if the user remembers the meaning of the word "supplement". Also, you will want to see if you fall into the two categories of people that need multivitamin/multimineral supplements:
1) Unbalanced diet
2) Exercising at such a high level, that you cannot take in the required nutrients with your normal calorie load

If you have a balanced well-rounded diet, then most likely you don't need any supplements. (I eat too much junk food. :p I like to use Centrum, because it is easy to break the pills in half, to dilute the supplement levels.)

u352
September 25th, 2003, 04:01 PM
I agree that supplements should just be that, a supllement to healthy eating but as an athlete we do need more of the good stuff which is less and less present in our foods for various reasons. a good multivitamin is a start but I would recommend supplementing that with vitamins that athletes need more of.

For example-this summer I did the Bay Bridge swim and during my training I took 1g of vitamin C, Vitamin B, Chromium Cod oil (rather than just vit E) and some other amino acids. I learned this at a conference last summer and i have to say that I always felt good during my training. That was my strategy that i learned from a PHD of nutrition from U of New Mexico. The bottom line though is that everyone has an opinion and everyone's body is different so you need to do what is right for you amd your needs.

What worked for me may not work for you. It is though an important part of the equation that shouldn't be overlooked.

Mattson is right-Remember that is a supplement.

gull
September 25th, 2003, 07:33 PM
Unfortunately no study to date has proven the effectiveness of antioxidants. No one disputes the harmful effects of free radicals, however.

u352
September 26th, 2003, 08:08 AM
I saw this article from the afpafitness.com web site. They seem to have a good handle on this stuff. Enjoy;

Vitamins and Minerals:Bottled Health or Rip-Off?

By the rows of bottles of vitamins and minerals in drug stores, supermarkets, and health food stores, you can see these products are big business. Public health experts insist if you eat a diet with plenty of fresh fruits and vegetables you don't need vitamin supplements. But it turns out quite a number of these experts take supplements themselves. So is public health policy lagging science? Let's take a look.

Why Are They Important?

Vitamins were once called accessory food factors. This reflected the fact that although they didn't contribute to energy or tissue growth, they were necessary in human diets to prevent certain diseases, called deficiency diseases. These diseases include scurvy from a lack of vitamin C, a bone disease called rickets from a lack of vitamin D, and night blindness from a lack of vitamin A.

The role of minerals is more complex. Some are needed in relatively large amounts, such as calcium and phosphorus for building bones. Others are needed in trace amounts, such as selenium and copper. The purpose of some minerals is reasonably clear. For example, iron transports oxygen. But the function of others, such as copper, are not completely understood.

As we have learned more about nutrients, our views of the roles of vitamins and minerals have expanded. We now know they are more important than just preventing deficiency diseases. For example, some of them function as antioxidants. Part of the oxygen you breathe in produces very active compounds called free radicals. These can wander around your body damaging tissues and genetic material. Some free radicals may be connected with diseases, including cancer and heart disease. Antioxidants found in your food can mop up free radicals and reduce risks of disease. Antioxidants receiving the most attention are vitamin C, vitamin E, and betacarotene (which is converted to vitamin A in your body).

There are now consistent studies on a variety of populations that link diets high in fruits and vegetables and low in fat with reduced risk of disease, compared to populations that eat less fruits and vegetables. One link that leads to less disease seems to be antioxidants in fruits and vegetables, especially the antioxidant vitamins just mentioned.


--------------------------------------------------------------------------------



SupplementsóYes or No?

If vitamins lead to lower disease risks, why not just take vitamin supplements? The public health organizations fear that a reliance on supplements will encourage many people to ignore proper dietary guidelines. (What you eat affects your health in more ways than just by providing vitamins and minerals.) Therefore the official position is that there is no convincing evidence that extra vitamins have health benefits, beyond those provided by the recommended dietary allowances (RDAs) obtained from a proper diet.

But there is evidence that extra vitamin C can reduce cancer risk, and vitamin E may reduce heart disease risk. Other studies on supplements suggest benefits such as a reduction in free radical damage caused by a single bout of exercise. But most supplement studies have been short term, and sometimes the experimental design of the study made the conclusions ambiguous.

An ideal study would use a double blind crossover method to compare the test compound to a placebo. The diet would also have to be controlled, so that you would know how much and what kind of nutrients were ingested from both the diet and the test compound. But this kind of study is extremely difficult and expensive to conduct because the subjects would have to be confined so that everything they ate and drank could be monitored for accuracy (self reported data are notoriously inaccurate). What we really need are rigorously designed, long-term studies on the use of supplements, and we really don't have any, so far. But some have been started in recent years.

Another argument against supplements is that it is widely believed that nutrients in foods are absorbed by our bodies more effectively than the same nutrients in supplements. However, this is not always true. Absorption varies case by case, says Gladys Block, Ph.D., at the University of California, Berkeley. Block says that equivalent amounts of vitamin C from food and supplement may cause the same increase in blood levels of this vitamin. Betacarotene capsules, however, can give a higher increase in blood levels of this antioxidant than the same amount from foods.

In spite of the lack of clear evidence in favor of supplements, obviously they are selling well. And it is not only the general public that favors them. Those of us who served on the Food and Nutrition Board of the National Research Council had a bias against vitamin supplements, but we are changing our view, says biochemist Max Horwitz, Ph.D., at the St. Louis School of Medicine in Missouri. Horwitz polled his colleagues at scientific meetings and found a significant number, including himself, take supplements, especially vitamin E. This is one vitamin that can fall short of the dietary recommendations when eating a low-fat diet because the best sources are vegetable oils.

The AR&FA Editorial Board members also are cautiously on the side of supplements, but not as substitutes for proper diet. Of those polled, 83% use vitamin and/or mineral supplements. I eat well and have a well-balanced diet, but I continue to take a multivitamin with minerals, an extra 500 milligrams of vitamin C, and 400 I.U. of vitamin E. I'm familiar with the research and I know I probably don't need them, but I figure it can't hurt,' says Paul Taylor, D.P.M.

I follow the same advice I give my patients and students, says Sarah Harding Laidlaw, M.S., R.D. “If you want a little extra insurance, take a one-a-day multivitamin that contains no more than 100% of the RDA of each nutrient. I also take additional vitamin E because of its antioxidant properties. She quickly adds, And I make sure to eat plenty of fruits and vegetables, and have been adding more soy products to my diet. Supplements are not a substitute for food.


--------------------------------------------------------------------------------



A Changing Scene

If you eat a diet that provides the energy you need for your active lifestyle, and balance it in the way suggested by the US Department of Agriculture's Food Guide Pyramid you should get plenty of vitamins and minerals.

To date public health authorities have decided the evidence for additional health benefits from supplements is not firm. But many scientists believe changes will come as more long-term data accumulate. Then why wait? As we have seen, many health researchers and providers take supplements as enthusiastically as the rest of the population.

Great changes in understanding have occurred since the roles of vitamins and minerals were first discussed. For example, at first vitamin C was believed to be needed just to avoid scurvy (characterized by bleeding gums, anemia, bleeding skin, and loss of muscle and cartilage).

Then Nobel Laureate Linus Pauling, Ph.D., promoted the use of large quantities of this vitamin to prevent and treat the common cold. Many published studies failed to support Pauling's view, although few researchers used the large doses Pauling recommended (about 15 grams, or more). Later, Pauling became even more controversial by reporting some slowing or shrinking of tumor growth in cancer patients taking vitamin C.

In the last few years, antioxidant research has taken off, and one of the chief therapeutic compounds identified is vitamin C. This compound is now being associated with the control of blood pressure, heart disease, cancer, and cataracts. Some scientists are now thinking more kindly about Pauling’s efforts. Pauling continued to take 18 grams of vitamin C a day into his 90s, until he succumbed to cancer. It is fascinating to note that only humans and guinea pigs are so dependent on vitamin C from food. All other mammals manufacture their own in their bodies.

In general, public health policy does tend to lag behind science, because government officials protect public health by accumulating overwhelming evidence before they take a position. It may well be that vitamin and mineral supplements will prove to be an example of a lag in policy.

We do not know for sure that these compounds taken in accord with Laidlaw's suggestions will give health benefits in addition to those obtained from a well balanced diet. But they just might, and there is no firm evidence that at the modest levels of the RDAs they can do harm.

(You can find good nutritional information at the National Agricultural Library's Website, www.nal.usda.gov/fnic/fpyr. At www.produceoasis.com you'll find information on fresh produce, fruits, and herbs. It also has nutrition tips, trivia, and tips for buying fruits and vegetables.)

gull
September 26th, 2003, 11:31 AM
A daily multivitamin probably does no harm but is of uncertain benefit if you eat a "balanced" diet. Megadoses of specific vitamins are another story. Supplement advocates argue that the medical establishment is conspiring against the health food industry on principle, and seem unconcerned by the lack of scientific evidence. Yet many of these same individuals are suspicious of conventional FDA-approved treatments that have been validated by multiple large scale double blind randomized placebo-controlled studies. What seems intuitive (free radicals are harmful, certain vitamins have antioxidant properties, therefore megadoses should be beneficial) may be entirely wrong. A case in point--after a heart attack, patients may exhibit frequent irregular heart beats which can indicate a poor prognosis. So the thinking (in the 80's) was that eliminating these irregular beats with drugs would be a good thing. In fact the drugs themselves killed people (by precipitating lethal arrhythmias), and the study was stopped early. Today these patients receive an implantable defibrillator.