Browse
Health Pages
Categories
Menu

Antioxidants: Not Always What They Are Made Out To Be?

by — 2015-12-01 in Nutrition & Dieting
Supplement manufacturers and food companies maintain antioxidants will help to prevent a host of diseases and medical conditions. But research findings are inconclusive, and there is evidence that antioxidant supplements do not provide health benefits.

Less than two decades ago antioxidants were hailed as the new hope for better health. Claims were that they could minimize the risks of chronic conditions and diseases including atherosclerosis and cancer. Health pundits urged the population to eat foods that were high in antioxidants, and supplements high in antioxidants were touted as the best way to slow disease and age-related degeneration.

Then the clinical trials began, with researchers testing realities. Like most research studies, there have been mixed results, but overall the evidence is that antioxidant supplements are not effective in protecting against cancer, heart disease or any other chronic medical conditions. Some trials have simply been inconclusive while others have reported negative rather than positive effects. While most researchers agree that fruit, vegetables and whole grains rich in antioxidants should be included in a healthy diet, because they do seem to help prevent some chronic diseases, they concur that other natural substances including minerals and fiber also play an important role – not just the antioxidant content.

The National Institutes of Health (NIH) acknowledges that there is ample evidence that eating a diet with lots of fruit and vegetables is healthy and that it will lower the risk of some diseases. But they question whether this is because of the antioxidants they contain or because of other factors. 

Additionally, the NIH warns that high-dose antioxidant supplements might carry a health risk, particularly of some types of cancer and stroke. Antioxidants can also interact with some medicines, which can also be dangerous.

What Are Antioxidants?

Simplistically, an antioxidant is a substance (or molecule) that is able to inhibit oxidization and remove potentially damaging oxidizing agents from living organisms (including food.) There are thought to be thousands of different substances that act as antioxidants, including vitamins C and E, certain minerals including manganese and selenium, beta-carotene and a few related carotenoids, as well as flavonoids, phenols, polyphenols, glutathione, lipoic acid, and coenzyme Q10.

Antioxidants occur naturally in some fruits and vegetables, and some are manufactured so that they can be taken in the form of supplement. But as the experts at Harvard’s School of Public Health point out, antioxidants are not a regular single substance. They all have their own unique chemical behavior and biological properties, and some act as electron donors (or “electron grabbers.”) What this means in reality is that one antioxidant is not the same as another, and so the claim that antioxidants (in general) do good is in a way nonsensical.

However, the generalization is that “antioxidants” can fight the free radicals that threaten our health.

Adding to the antioxidant puzzle, free radicals are described by the Harvard team as “nasty chemicals” that have the ability to damage cells and genetic material in the body. They come from food we eat and air we breathe, even from the effect of sunlight on our skin and eyes. Some free radicals are generated as byproducts when our bodies turn food into energy. An alarming effect is that it encourages so-called “bad” cholesterol – low-density lipoprotein (LDL) – into the bloodstream and it then runs the risk of getting trapped in the walls of the arteries. It can also alter the membrane of cells.

Antioxidants first made headlines in the 1990s when scientists found that early stages of atherosclerosis (caused by arteries becoming clogged), was related to free radical damage. They also linked free radical damage to a number of other chronic conditions including cancer, heart disease, Alzheimer’s, and loss of vision. Early studies showed that people who did not consume antioxidant-rich fruit and veg were more likely to develop these chronic conditions than those who did.

Today the antioxidant industry is worth millions of dollars. The antioxidant supplement industry alone is worth more than $500 million, and it keeps growing, in spite of the fact that there is no proof they do what the manufacturers claim. Instead, say the experts at Harvard, their “claims have stretched and distorted the data.”

But it hasn’t only been the “industry” that has promoted the idea that antioxidants can reverse the effects of free radicals on the body. 

In November 2007 the US Department of Agriculture (USDA) released a comprehensive database for the oxygen radical absorbance capacity (ORAC) of 277 items of food. This database was updated in May 2010, bringing the total of foods to 326. Additions included acai, goji berries and maple syrup. Foods with the highest ORAC scores were:

  • Ground cinnamon, cloves and turmeric
  • Dried oregano, rosemary, sage and thyme
  • Acai
  • Rosehip
  • Black and hi-tannin sorghum bran

READ Antioxidants-Your Defense Against Free Radicals

However the ORAC list did not include data that indicated whether the antioxidants played any biological role. It was simply a list of foods that could be used as a guide to antioxidants.

Two years later, in 2012, the USDA withdrew the database stating that while antioxidant molecules have a wide range of functions in food, many of these “are unrelated to the ability to absorb free radicals.” Further, they stated that companies manufacturing food and dietary supplements had been routinely misusing the ORAC values to promote their products. 

Lack of Evidence to Support Claims That Antioxidants Prevent Disease

Most clinical trials have tested the impact of single antioxidant “substances” like vitamins E and C, and beta-carotene – and the results have mostly been negative. There have also been some studies that involved combinations of different types of antioxidant supplements, and these results have also been inconclusive.

One six-year study into age-related eye disease did find that a combination of vitamins C and E, beta-carotene, and zinc helped protect against macular degeneration in older people. It is thought lutein, that a natural carotenoid (a type of antioxidant) found in dark green, leafy vegetables including kale and spinach might have the same effect, but there is no real evidence to support the belief.

While there is lots of evidence that it is beneficial to our health to eat fruit and veg and whole grains that are rich in antioxidants, there is no convincing evidence that antioxidant supplements have any real impact on disease prevention. Also, while it is known that free radicals and oxidative stress contribute to aging and a number of chronic diseases, it doesn’t follow that substances (or molecules) with antioxidant properties are going to fix the problem. 

What Clinical Trials Have Revealed

Clinical trials over the years have focused on the relationship between antioxidants and heart disease and stroke, lung function, cancer, and age-related eye disease.

While my no means comprehensive, here are some examples:

  • An early study in China, published in 1993, looked at the effects of antioxidant supplements in relation to risks of cancer. It found that while the antioxidants didn’t lower the risks of developing cancer, or from death as a result of esophageal cancer, they did lower the risks of death as a result of gastric cancer. This positive finding was negated in 2009 when additional deaths were reported.
  • In Harvard Medical School’s landmark Women’s Health Study that began in 1993, there was no difference in the rate of cancer and major cardiovascular events between women taking vitamin E and those taking a placebo.
  • A US cancer study report published in 1996 found that beta-carotene supplements had no effect on the incidence or mortality of cancer over a 12-year period. Smoking did not have an effect on the outcomes either.
  • A German study published in 1997 examined the value of antioxidants and vitamins in the prevention and therapy of cardiovascular disease. It found that low-dose supplementation of antioxidant vitamins for primary prevention seemed feasible, high-dose intervention in secondary prevention needed further study.
  • A Swedish study published in 2002 that also considered the role of antioxidant vitamins in preventing cardiovascular disease, took food and supplements into account. This found that increased antioxidant vitamins did lower the risk of stroke and myocardial infarction in people who generally consumed few antioxidants. However it also found that when given in the form of food supplements they had no beneficial effects, and reported that “serious adverse effects” had been reported.
  • A Canadian study published in 2005 examined the effects of vitamin E supplements taken long-term on cancer and cardiovascular events. Their finding was that it did not prevent these diseases and might even increase the risk of heart failure.
  • Noting in 2007 that previous clinical trials had failed to show that vitamin E reduced the risk of cardiovascular events, an Israeli team of researchers found that it did appear to reduce risks in middle-aged people with type 2 diabetes, who also had a common genetic predisposition that related to oxidative stress.
  • A US study report published in 2009 revealed that neither vitamin C or E had make any difference to the incidence of cancer (including prostate cancer) in physicians aged 50 and more.

READ Antioxidants, Such as Vitamin E and Zinc, May Improve Male Fertility Four-Fold

Dr Gitte Jensen, founder and research director of the Oregon-based NIS Labs (Natural Immune Systems) is one person who still believes that antioxidants do have value in terms of human health and disease prevention. However she has urged those in the industry to “use our tests and data properly” and to develop improved testing methods. This, she believes could result in the USDA being persuaded to re-open its data banks as a public resource.

Harmful Effects Of Antioxidants

In addition to some of the harmful effects mentioned above, there is a growing body of evidence that shows antioxidants fuel cancer.

At least two studies involving heavy smokers that were carried out to see if beta-carotene could reduce the risks of lung cancer had the opposite effect. A trial in Finland was stopped early when researchers found the group taking the supplement had a higher incidence of lung cancer compared to those in the group taking a placebo. Similarly, research published in 2007 showed that women taking antioxidant supplements had an increased risk of skin cancer – though men didn’t.

According to the NIH National Cancer Institute that recently reviewed antioxidants and cancer prevention, it is not uncommon for people who take antioxidant supplements while they are having cancer therapy to have “worse outcomes.” Smokers, they say are most at risk.

It seems that instead of neutralizing free radicals and lowering the risks of cancer, antioxidants can protect some cancer cells from free radicals. For this reason many medics advise those with cancer – particularly lung cancer – to avoid taking extra antioxidants.

Ongoing Research On Antioxidants

Researchers haven’t given up on antioxidants yet and the NIH and its National Center for Complementary and Integrative Health (NCCIH) continue to support studies. Recent topics include:

  • Effects of antioxidants on Alzheimer’s
  • How oxidation and antioxidants affect risks of breast cancer
  • Effects of antioxidants found in pomegranates in the prevention and treatment of prostate cancer
  • Whether antioxidants from berries (specifically anthocyanins) can prevent esophageal cancer
  • How chemical forms of vitamin E affect inflammation

Ultimately, as the NIH NCCIH points out, concerns do not relate to antioxidants that are found naturally in certain foods, but rather to manmade supplements. As they say, antioxidant supplements should never be used to replace conventional medical care or a healthy diet. 

Sources & Links

  • Important notification about information and brand names http://www.steadyhealth.com/polices/terms-of-use#copyright

Post a comment