Chronic excess of linoleic acid (omega 6), coupled with a deficiency in alpha-linoleic acid (omega 3), can increase obesity down the generations. The researchers exposed several generations of male and female adult and young mice to a "Western-like" diet of this type, and then assessed the consequences of such a lipid environment in the human diet. These findings are published in Journal of Lipid Research.
Omegas 6 and 3 are essential polyunsaturated fatty acids: they are indispensable to the human body, which cannot produce them itself and must therefore source them from food. Omega 6 are normally found in corn, which is itself consumed in large quantities by the farmed animals eaten by humans (half of our lipid intake comes from meat and dairy products). As for omega 3, they are mainly present in grass, linseed, rapeseed and fatty fish such as salmon, sardine or mackerel (which contain very high levels of alpha-linoleic acid).
In the past forty years, there has been a steady rise in obesity over the generations in Western societies. During the same period, the diet in industrialized countries has seen a quantitative increase in the calories ingested (lipids account for 35 to 40% of food intake), high levels of linoleic acid (omega 6) and low levels of alpha-linoleic acid (omega 3). Indeed, the amount of omega 6 consumed during the past forty years has rocketed (+250%) while that of omega 3 has fallen by 40%, thus destabilizing the omega 6/omega 3 ratio when compared with the recommended intakes. Omega 6/omega 3 ratio of between 3/1 and 5/1 is ideal, actual consumption is 15 omega 6 for 1 omega 3 in Europe. In the US, this ratio can even reach 40 omega 6 for 1 omega 3.
To perform their experiments, the researchers exposed four generations of mice to a Western-style diet, characterized by these same omega 6/omega 3 ratios. As a result, they saw a gradual increase in fat mass over several generations. They also observed the onset of metabolic disorders such as insulin resistance, which is the first step in the development of type 2 diabetes and a stimulation of the expression of the inflammatory genes involved in obesity. Thus, in a genetically-stable animal population, exposure to a diet similar to that of developed or developing countries was sufficient to cause the emergence of transgenerational obesity, in line with the data collected in humans. The agrifood industry needs to take greater account of the implications of these findings.
Courtesy of Science Daily
Bonnie - bingo! This study backs what Eaton and Cordain have said for two decades in their research. We have changed very little genetically over the last 10,000 years yet our diet has. And we are paying dearly for it.
Tuesday, July 27, 2010
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Polyunstaturated fats may cut risk of heart disease
Study compares use of staturated and unsaturated fats
Although for nearly 60 years people have been urged to decrease their consumption of saturated fats to prevent heart disease, there has been surprisingly little scientific evidence that doing so actually decreases the risk of coronary heart disease events. But a new study (available in full here) by researchers at Harvard School of Public Health (HSPH) provides the first conclusive evidence from randomized clinical trials that people who replace saturated fat in their diet with polyunsaturated fat reduce their risk of coronary heart disease by 19 percent, compared with control groups of people who do not.
By systematically reviewing a large group of randomized clinical trials and conducting a pooled meta-analysis of these studies, the HSPH team found that increasing the intake of polyunsaturated fats as a replacement for saturated fats could significantly reduce the rate of heart attacks and cardiac deaths in the population. The study appears in the March 23 issue of the open-access journal PLoS Medicine.
Currently, the Institute of Medicine guidelines recommend that a range of 5 to 10 percent in energy consumption come from polyunsaturated fats. In addition, some scientists and organizations have recently suggested that consumption of polyunsaturated fats (largely omega-6 fatty acids) should actually be reduced, due to theoretical concerns that such consumption could increase coronary heart disease risk.
The results from this study suggest that polyunsaturated fats from vegetable oils may be an optimal replacement for saturated fats, an important finding for dietary guidelines and for when food manufacturers and restaurants are making decisions on how to reduce saturated fat in their products. The findings also suggest that an upper limit of 10 percent of energy consumption from polyunsaturated fats may be too low, as the participants in these trials who reduced their risk were consuming about 15 percent of their energy from polyunsaturated fats.
For full story:
http://harvardscience.harvard.edu/medicine-health/articles/polyunstaturated-fats-may-cut-risk-heart-disease
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