The Dangers of Lipid Peroxidation


Peroxidized Fats are endogenous or exogenous fats (Fatty Acids) that have been damaged by oxygen free radicals.

The cell membrane consists primarily of layers of phospholipids.  Free radicals can attack the cell membranes, causing lipid peroxidation of the fatty acids that compose the cell membrane, resulting in injury and eventual death of the cell.

The end products of lipid peroxidation are reactive aldehydes, such as:

  • Malondialdehyde (MDA)
  • 4-hydroxynonenal (HNE)

Malondialdehyde (MDA)

Malondialdehyde (MDA) is the organic compound with the formula CH2(CHO)2. This reactive species occurs naturally and is a marker for oxidative stress. Malonaldehyde (which comprises 50% of Lipofuscin) is formed as a breakdown product of Peroxidized Polyunsaturated Fats. This compound is a reactive aldehyde and is one of the many reactive electrophile species that cause toxic stress in cells and form covalent protein adducts referred to as advanced lipoxidation end-products (ALE), in analogy to advanced glycation end-products (AGE). Malondialdehyde is reactive and potentially mutagenic. It has been found in heated edible oils such as sunflower and palm oils.


4-Hydroxynonenal, or 4-hydroxy-2-nonenal or 4-HNE or HNE, (C9H16O2), is an α,β-unsaturated hydroxyalkenal that is produced by lipid peroxidation in cells. 4-HNE is the primary alpha,beta-unsaturated hydroxyalkenal formed in this process.

Lipid peroxidation alters the physiological functions of cell membranes and plays an important role in cellular membrane damage. Peroxidation is believed to be involved in cellular aging and in various diseases, such as Parkinson’s and Alzheimer’s disease as well as schizophrenia, atherosclerosis, inflammatory diseases, and cardiac ischemia reperfusion injury. Unsaturated lipids are easily susceptible to peroxidation. One of the most important mechanisms of membrane damage results from the action of free radicals on the unsaturated lipids in membranes. This leads to an autocatalytic chain reaction called lipid peroxidation which causes widespread damage. The cell has several important protective mechanisms against this type of injury.

Heating causes the oil to undergo a series of chemical reactions like oxidation, hydrolysis and polymerization. During this process, many oxidative products such as hydroperoxide and aldehydes are produced, which can be absorbed into the fried food.

Exposure of Fatty Acids to Light may accelerate their peroxidation.

There are certain substances that have been studied to counteract the toxic effects of lipid peroxidation.  The downloadable Table below list these substances.

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Lipid peroxidation in aging brain and Alzheimer’s disease.

Koner, B. C. (2008), Effect of Different Cooking Vessels on Heat-Induced Lipid Peroxidation of Different Edible Oils” Journal of Food Biochemistry, 32: 740–751. doi: 10.1111/j.1745-4514.2008.00195.x

Chemistry of Deep-Fat Frying Oils

Chemistry and Reactions of Reactive Oxygen Species in Foods

Repeatedly Heated Vegetable Oils and Lipid Peroxidation Kamsiah Jaarin and Yusof Kamisah Department of Pharmacology, Faculty of Medicine

Determination of lipid oxidation products in vegetable oils and marine omega-3 supplements

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