consumption. There is no adequate level, recommended daily amount or tolerable upper limit for trans fats. This is because any incremental increase in trans fat intake increases the risk of coronary artery disease. Despite this concern, the NAS dietary recommendations have not included eliminating trans fat from the diet. This is because trans fat is naturally present in many animal foods in trace quantities, and thus its removal from ordinary diets might introduce undesirable side effects and nutritional imbalances if proper nutritional planning is not undertaken. The NAS has, thus, "recommended that trans fatty acid consumption be as low as possible while consuming a nutritionally adequate diet". Like the NAS, the World Health Organization has tried to balance public health goals with a practical level of trans fat consumption, recommending in 2003 that trans fats be limited to less than 1% of overall energy intake. The US National Dairy Council has asserted that the trans fats present in foods of animal origin are of a different type than those in partially hydrogenated oils, and do not appear to exhibit the same negative effects. A scientific review agrees with the conclusion (stating that "the sum of the current evidence suggests that the Public health implications of consuming trans fats from ruminant products are relatively limited") but cautions that this may be due to the low consumption of trans fats from animal sources compared to artificial ones. A meta-analysis showed that all trans fats, regardless of natural or artificial origin equally raise LDL and lower HDL levels. Other studies though have shown different results when it comes to animal based trans fats like conjugated linoleic acid (CLA). Although CLA is known for its anticancer properties, researchers have also found that the cis-9, trans-11 form of CLA can reduce the risk for cardiovascular disease and help fight inflammation. Health risks Partially hydrogenated vegetable oils were an increasingly significant part of the human diet for about 100 years, especially after 1950 as processed food rose in popularity. The deleterious effects of trans fat consumption are scientifically accepted. Intake of dietary trans fat disrupts the body's ability to metabolize essential fatty acids (EFAs, including Omega-3) leading to changes in the phospholipid fatty acid composition of the arterial walls, thereby raising risk of coronary artery disease. While the mechanisms through which trans fatty acids contribute to coronary artery disease are understood, the mechanism for their effects