Oxidative stress: symptoms, causes and protection

Oxidative stress: causes

Oxidative stress and ROS

During metabolic reactions, the body naturally produces reactive oxygen species (ROS) (1), better known as free radicals. These include the superoxide radical O₂•⁻ and the hydroxyl radical •OH.

With one or more ‘unpaired’ electrons on their outer shells, these ROS are highly unstable: they seek other atoms or molecules to bond to, causing these to become unstable too. Having said that, the formation of ROS is not in itself pathological. It occurs in all aerobic organisms and can even be useful in cell signalling (2).

What’s more, we have a strong arsenal of weapons with which to neutralise them. The body’s first line of defence consists of endogenous antioxidants (those we produce ourselves), made up of antioxidant enzymes, cofactors and proteins (3). Then come the vitamins provided by food, followed by DNA repair mechanisms. In this way, we’re able to maintain a redox balance.

Oxidative stress occurs when there’s animbalance between the generation of free radicals and the ability of antioxidants to neutralise them (4). When our defence mechanisms become overloaded, they can no longer combat oxidation effectively. This compromises cellular integrity, potentially damaging every component of a living organism.

Origin of oxidative stress

Oxidative stress is primarily induced by various exogenous factors: a poor diet with too few fruits and vegetables, smoking, alcohol, medications, pesticides, air pollution, prolonged exposure to the sun, radiation, as well as certain pathogenic infections (5).

Is there a link between psychological stress and oxidative stress?

Oxidative stress is distinct from psychological stress, the former occurring at a cellular level and the latter on a systemic scale. However, there may be an interaction between the two: a study of people with depression suggests that chronic stress contributes to the development of oxidative stress in certain areas of the brain (6).

Oxidative stress: symptoms

Oxidative stress is considered to be one of the main causes of ageing. Clinically, it is implicated in the development of various metabolic diseases (diabetes, atherosclerosis…), as well as respiratory, digestive, neurodegenerative and joint diseases (7).

Oxidative stress assessments are offered by some laboratories which test blood and/or urine for biomarkers of the body’s oxidative load and antioxidant defence status. These should not, however, be interpreted as definitive.

Oxidative stress: consequences

Oxidative stress and inflammation

The body’s immune system perceives excess levels of free radicals as aggressors, and will therefore try to eliminate them by initiating an inflammatory response (8).

If this proves unsuccessful, chronic (or low grade) inflammation sets in over a period of a few weeks to several years. It’s now acknowledged that this prolonged inflammatory state paves the way for auto-immune and cardiovascular diseases as well as chronic inflammatory bowel diseases (CIBD) (9-10).

Oxidative stress and uncontrolled proliferation

There may also be a slight link between oxidative stress and proliferation of abnormal cells. It seems likely that oxidative stress activates various transcription factors (NF-κB, AP-1, p53, HIF-1α, PPAR-γ, β-catenin/Wnt and Nrf2) leading to the abnormal expression of certain genes, including those governing growth factors, inflammatory cytokines and cell cycle regulatory molecules (11).

Oxidative stress and memory

Many studies point to the role of oxidative stress in age-related cognitive decline. In ageing animal models, there appears to be a correlation between changes in temporal and spatial memory, learning and information retention, and increases in oxidative species (12). Research also suggest that free radicals disrupt mitochondrial metabolism and play a part in neuron degeneration (13).

Oxidative stress and the eyes

As delicate organs, our eyes are especially vulnerable to free radical attack. The lens (involved in filtering and directing light) and the retina (responsible for converting light into nerve signals) are among the worst-affected. Oxidative stress may actually promote the onset of eye diseases such as cataracts and AMD (Age-related Macular Degeneration) (14-15).

Oxidative stress and the skin

Oxidative stress also attacks skin cells. It accelerates protein and lipid breakdown, as well as the destruction of collagen and elastin which provide tone and suppleness to the skin. It thus promotes ageing of the skin (by photoxicity in particular) and the premature appearance of wrinkles (16).

Oxidative stress and hair

By weakening the hair bulb, free radicals may accelerate hair loss and contribute to greying of the hair (17).

Oxidative stress: prevention and supplements

‘Common sense’ preventive measures, such as a healthy lifestyle that avoids the above-mentioned risk factors as much as possible, will help to minimise oxidative stress.

A varied, and preferably organic, diet seems to afford better protection against free radicals. More specifically, certain foods offer strong antioxidant potency: fresh, highly-coloured fruits and vegetables (rich in carotenoids and polyphenols), spices, oilseeds and aromatic herbs (18).

It can help to check a food’s ORAC score (oxygen radical absorbance capacity): the higher the figure, the greater its antioxidant potential (19). For example, per 100g, green tea has a score of 1250, walnuts 13,541 and cloves… 290,283!

Some of these super-ingredients are combined in synergistic supplements (the ultra-powerful Antioxidant Synergy contains, amongst others, green tea, grape seed and turmeric, as well as the patented compound Vitaberry® rich in polyphenols and anthocyanins) (20).

Vitamins C and E help protect cells against oxidative stress (21-22). Dietary sources include citrus fruit, peppers, kiwi fruit, almonds and vegetable oils. Vitamin E features in the supplement Astaxanthin, an excellent pink-red pigment from the carotenoid family, extensively studied by anti-ageing researchers.

Trace elements to prioritise include zinc and selenium, key cofactors of enzymes that catalyse oxidation-reduction reactions (23).

Present in almost all living cells, glutathione is one of our most powerful endogenous defence weapons (24). But blood levels decline after the age of 50, so taking a supplement (such as Reduced Glutathione, the only bioactive form, or Perlingual glutathione in the form of suckable tablets for fast administration) can help increase intake (25).

It has been found that the organs most subject to oxidative stress (such as the liver, heart, kidneys, skin and red blood cells) have a high content of L-ergothioneine, an amino acid which is now extracted from mushrooms to produce cutting-edge supplements (the formulation L-Ergothioneine has a half-life of 30 days compared with between 30 seconds and 30 minutes for conventional antioxidants) (26).

Known as BHT, butylated hydroxytoluene is popular in the agro-food sector for its ability to prevent oxidation and rancidity of fats. Scientists are now showing a keen interest in the potential human health applications of this fat-soluble aromatic compound (the main ingredient in BHT which offers an optimal dose of 300mg per capsule).