Unsaturated fats are those with a double bond in their carbon chain. This gives the molecules a pronounced kink which is characteristic of this group of fats. However, unsaturated fats are useful in human nutrition for a number of reasons beyond the elegancy of their curving structures. Firstly the essential fatty acids alpha linolenic acid and linoleic acid are required for the formation of a number of short lived cellular signal molecules called eicosanoids. Eicosanoids regulate cell function and in particular maintain the fine balance between pro- and anti-inflammatory cellular states. Unsaturated fats are also useful to cells because their kinked structures require more space to house in cell membranes. The result of this is that other molecules are pushed further away, and the membrane becomes more fluid as a result. Cells are therefore able to maintain membrane fluidity through alteration to the amount of unsaturated fat in their cell membranes. Further, polyunsaturated fatty acids are an important source of fuel for cellular metabolism.
However, the structures of the unsaturated fats that make them useful to humans for metabolic purposes also makes them susceptible to oxidation in the environment. In particular, heat and light can provide the activation energy required to oxidise the fats at their double bonds, and this results in an altered fat that is no longer healthy to humans. Plants go to great lengths to protect these fatty acids by encapsulating them in dark seeds away from light and oxygen and placing high amounts of antioxidants such as vitamin E with the fats. Removing the fats from the seeds and processing it with heat and light and other chemicals as is common in the food industry produces an oxidised and toxic oil that is then used in the preparation of foods, particularly those sorts of foods found in the Western diet. Deodorised supermarket oils are a great example of a toxic product that contains fats that often bear little resemblance to the original fats present in the seed from which it originated. Cooking with such oils exacerbates the toxicity of the oil through further oxidation.
We should eat plant oils in their natural unrefined, unheated state as this provides the fatty acids in their unaltered forms. Processing the oils creates a toxic oxidised mixture of fats and evidence in the nutritional literature is increasingly showing that regular consumption of such a product is a cause of Western lifestyle diseases such as cardiovascular disease, cancer and obesity. Once in the body such oxidised fats interfere with essential fatty acid metabolism and initiate free radical chain reactions that damage tissues and cells, leading to inflammation and disease. But it gets worse, much worse. Evidence from animal studies suggests that the toxicity of oxidised fats is so great that they can cause permanent damage to the growing foetus if consumed in the maternal diet and this can result in an increased risk of disease in the offspring during adulthood. For example,m in one study1, pregnant mice were fed oxidised frying oil and the susceptibility of the offspring to disease was subsequently assessed by feeding them a high fat diet.
The results of this study showed that although all pups were raised under identical conditions, those female offspring from mothers fed 10 % oxidised soybean oil in their diet were significantly more susceptible to diet induced obesity, compared to those fed 10 % non-oxidised soybean oil. However, this was not the case for the male offspring, because the male offspring displayed an increased expression of a transcription factor called PPARα (peroxisome proliferator-activator receptor alpha) in both the liver and white adipose tissue in response to the high fat diet. This transcription factor is important in the regulation of fat oxidation and its upregulation likely occurred in response to the high fat diet. The male mice from mothers fed the oxidised soybean oil also had increased levels of thermogenesis in their white adipose tissue. Therefore consumption of oxidised fats by mice increases the risk of female offspring becoming obese because for some reason it prevents the offspring modifying their metabolic regulation to increase the oxidation of fats under conditions of a high fat diet.
Dr Robert Barrington’s Nutritional Recommendation: This study and others show that the consumption of oxidised fats has wide reaching implications that we are only just beginning to understand. The increased susceptibility of female offspring to diet induced obesity following maternal consumption of oxidised fats is worrying because if similar patterns occur in humans then it could be assumed that consumption of a Western diet is damaging not only for an individual, but also their offspring. It is increasingly being shown that the diet of pregnant women is able to affect the health of their children not just at birth, but into adulthood as well. Oxidised fats might be one of the most dangerous foods that it is possible to eat (here) and care should be taken to eliminate it from the diet where possible. The sex differences seen in this study are not uncommon, and are likely a result of differing hormonal milieus in the growing foetuses.
RdB
