Файл: Medical_Myths_Lies_and_Half-Truths_guidebook.pdf

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Lecture 7: Sugar and Hyperactivity

1. 

What is the evidence regarding the claim that eating sugar, or any food, 
makes children hyperactive?

2. 

What is the evidence to support the notion that ADHD is a 
real disorder?

    Questions to Consider

29

Antioxidants—Hype versus Reality 

Lecture 8

Basic science tells us what kind of directions we should go in with clinical 
research but ... can’t be used to make clinical claims. More often than 
not, we’re going to be wrong when we guess what the outcome should 
be based upon just our basic understanding of basic biochemistry
and biology.

T

he term “antioxidant” has become a marketing term synonymous with 
healthful. But does the hype really hold up to reality? Will that green 
tea or Acai juice make you live longer and be healthier? Let’s examine 

the biochemisty a bit. We have something called oxygen free radicals inside 
our body, going around destroying our cells and DNA. This may sound 
scary, but actually, they exist in an equilibrium. They serve some bene

¿

 cial 

effects inside our bodies. For example, they are used by some cells of the 
immune system to attack 
and destroy bacteria 
and viruses. Oxygen 
free radicals are also 
used as chemical signals 
that trigger important 
functions inside the cell. 
Therefore, you wouldn’t 
want to completely get 
rid of them. 

Because these oxygen 
free radicals are an 
unavoidable by-product 
of energy production in 
the mitochondria in all 
of our cells, it stands to 
reason we would have evolved mechanisms to sop up those oxidative free 
radicals and keep them from doing damage. Substances that do that are 
called antioxidants. There are a number of naturally occurring antioxidants 

Eating several servings per day of fruits and 
vegetables is associated with a decrease in
cancer risk.

© JupiterImages/BananaStock/Thinkstock.

30

Lecture 8: 

Antioxidants—Hype versus Reality

in the body, including vitamins E and C and many speci

¿

 c enzymes. They 

exist in part to reduce these oxygen free radicals and keep the whole system 
in equilibrium. 

What about eating antioxidants or taking supplements? Beginning in the 
1990s, the possibility arose that cellular damage from oxidative stress was 
actually the underlying cause of not only normal aging, but also many 
neurodegenerative diseases like Alzheimer’s disease, Parkinson’s disease, 
and amyotrophic lateral sclerosis (ALS). This was cutting edge and very 
interesting science. Many of us were very excited by the prospect that 
antioxidants in some dose would become very effective in slowing down 

the progression of these diseases, 
maybe even halting it.

It turns out that as we get older, 
we lose some of our naturally 
occurring antioxidant capacity. 
It makes sense that replenishing 
antioxidants would be bene

¿

 cial. 

Also, the brain is particularly 
susceptible to oxidative stress 
because the brain consumes a lot of 

oxygen. It therefore produces a correspondingly increased amount of oxygen 
free radicals. However, it’s possible—and this was raised as a cautionary 
concern—that the oxidative stress leading to cell damage may have been a 
secondary effect. It may not have been the primary underlying cause of cell 
death in these neurodegenerative diseases. In other words, it’s just one of the 
many things that happen when cells are dying, not the original or underlying 
cause of those cells dying. 

So what did that research show? For Parkinson’s disease, in human 
trials, antioxidants had no detectable bene

¿

 cial effect in preventing the 

development of the disease or slowing its progression. The story is very 
similar for Alzheimer’s disease. Human trials showed mixed results at 
best; there wasn’t any compelling evidence for bene

¿

 t even at high doses. 

For ALS, too, the results were disappointing. Studies of vitamins E and 
C, especially in high doses, did not affect the outcome of the disease. The 

The public perception that 
antioxidants are healthful 
and a net good for health has 
persisted—despite the fact that 
the scienti

¿

 c evidence just did 

not turn out that way.

31

scienti

¿

 c community was humbled by this experience. We had every reason 

to think that antioxidants were going to be a huge cure for many serious 
illnesses. Yet 15 or 20 years of clinical research completely disappointed us. 

What about cancer prevention? We think that oxidative stress may damage 
DNA, in turn leading to cancer. In fact, there is evidence that eating several 
servings per day of fruits and vegetables is associated with up to a 30% 
decrease in overall cancer risk and greater longevity. 

Fruits and vegetables contain antioxidants; eating them helps prevent cancer 
and improves longevity. However, we can’t necessarily conclude that it’s the 
antioxidants that are doing this. The exact mechanism of this clear bene

¿

 t 

from fruits and vegetables has yet to be determined. High antioxidants may 
be playing a role, but there are other variables as well. Perhaps there are 
other things in fruits and vegetables that are healthful. Perhaps people who 
eat fruits and vegetables engage in other activities that are healthful. Perhaps 
if you eat lots of fruits and vegetables, you’re not eating as much of other 
kinds of foods that may increase your risk of cancer.

There are simply too many variables to know whether it’s the antioxidants 
or what exact role the antioxidants are playing in cancer prevention. But one 
clue we have comes from antioxidant supplements. The research shows that 
taking antioxidant supplements does not decrease cancer risk. That would 
argue against antioxidants being the de

¿

 nitive factor. 

The public perception that antioxidants are healthful and a net good for 
health has persisted—despite the fact that the scienti

¿

 c evidence just 

did not turn out that way. What’s the bottom line of all this? There’s no 
evidence to support the routine use of antioxidant supplements or so-called 
superfoods—like Acai, Noni, blueberry, or pomegranate juice—that are 
loaded with antioxidants. There’s simply no evidence that taking pills or 
eating superfoods has any health bene

¿

 t. The evidence keeps leading us back 

to the common wisdom that most of us know to be true: You should eat your 
fruits and vegetables—especially your vegetables—every day. 

Ŷ

32

Lecture 8: 

Antioxidants—Hype versus Reality

Denisov and Afanas’ev, 

Oxidation and Antioxidants in Organic Chemistry 

and Biology

. 

Novella, “Antioxidant Hype and Reality.” 

1. 

What role does oxidative stress play in health and disease?

2. 

Are there any proven risks or bene

¿

 ts to foods or supplements high 

in antioxidants?

    Questions to Consider

    Suggested Reading