Bottomline:  People with a genetic disposition have a greater risk of having a heart attack if they eat a diet high in arachidonic acid, which is found in animal foods such as meats and eggs.
Am J Clin Nutr 2008 88: 934-940

Background:  The leukotrienes, are a group of eicosanoids that include one of the most potent inflammatory compounds made from arachidonic acid.  Leukotrienes are well known for their inflammation effect on asthma and have recently been linked to atherosclerosis.  A previous study from this group showed that people possessing a genetic polymorphism, which created more leukotrienes, also had an increased risk of clogged arteries when eating a high omega-6 diet (the classic American diet).  To build on that research, the scientists evaluated if this genetic disposition, combined with a high omega-6 fat diet, would lead to more heart attacks.

Summary: In this case-control study, researchers identified nearly 2000 Costa Ricans, that possessed a gene that increases leukotriene formation from arachidonic acid.  (Specifically, this gene increases the activity of the LOX enzyme, which is necessary for this step to occur). 

Next, they evaluated incidence of heart attacks in people with the LOX polymorphism.   Indeed, there was an increased risk of having a heart attack in this group of people, if they ate a high arachidonic acid diet (of at least 250 milligrams of arachidonic acid per day). 

Interestingly, if the diet was lower in arachidonic acid, there was a protective effect-- a phenomenon that was observed in a previous study.  The researchers believe that people with this polymorphism are sensitive to substrate availability.   Therefore this type of gene could possibly be down or up-regulated, on the basis of cellular arachidonic acid concentrations. This gene-nutrient interaction  replicates previous results with a more clinically relevant endpoint, heart attack events.

Study Quote:  “These results are consistent with the notion that certain persons could benefit more from certain dietary modifications, such as a reduction in the intake of beef and eggs (major sources of arachidonic acid)…”

Comment: 
These findings are similar to a recent study, in which women with another kind of LOX polymorphism had an increase incidence of breast cancer if they ate a high omega-6 fat diet.  Yet the risk disappeared if they ate a lower omega-6 fat diet.(See Another New Breast Cancer Study: Omega-6 Fat Increases Risk Two-fold in Large U.S. Study).

To put into context what 250 milligrams of arachidonic acid looks like, consider these amounts of arachidonic acid found in food:

• 3-ounces chicken thigh (skinless, cooked) has 120 milligrams
  
• 3-ounces dark turkey meat (skinless, cooked) has 240 milligrams 
• 3-ounces ham has 70 milligrams
• 3-ounces veal (cooked) has 90 milligrams
• 1-large egg has 70 milligrams
• 6-piece Chicken McNuggets has 50 milligrams
• 1-classic double cheeseburger (Wendy's) has 90 milligrams

Link to Source:
Allayee, H et al.
Nutrigenetic association of the 5-lipoxygenase gene with myocardial infarction Am J Clin Nutr 2008 88: 934-940