Is saturated fat back on the hook?

That pain in your neck? It might be a case of nutrition-advice whiplash.

Saturated fat, long blamed for heart disease, seemed to be exonerated last month by a large study which found no connection between saturated fat intake and heart disease. People who ate less saturated fat were just as likely to have heart disease as people who ate more. Conclusion: Saturated fat does not cause heart disease. Cue rejoicing (not to mention “I told you so’s”) from Atkins and Paleo dieters.

But now the Harvard School of Public Health is throwing a bucket of ice-water on the whole party. They did their own analysis of the relationship between fat and heart disease and found that it all depends on what you replace the saturated fat with.

The Harvard authors note that previous clinical trials aimed at reducing saturated fat had “very mixed” results, “with most showing no significant effect.”   But, they note, when health authorities started to recommend reducing saturated fat, they didn’t offer much guidance in terms of what to replace it with. Some replaced those calories with hydrogenated fats.Others replaced them with refined carbohydrates. In both cases, the benefits of reducing saturated fat may have been canceled out by the negative impact of trans fats and refined carbs.

But when saturated fats were replaced with polyunsaturated fats (yes, the much maligned PUFAs), heart disease risk declined 20%.  (Read summary of research and interview with lead authors.)

This story isn’t over yet. Those who never let go of the notion that saturated fat contributes to heart disease will now get their chance at the “I told you so’s.” Those who are wedded to the idea that saturated fat is the ideal fat or that PUFAs are the source of all evil will find grounds to question this latest analysis. (Post them below–but not before reading the rest of the post.)

Where does this leave the non-ideologue who is just trying to figure out what to eat today?  Let me try to save you some neck pain.  These ground rules are unlikely to change:

1. I think everyone can agree that too many refined carbohydrates is a big problem. Limit them.

2. Trans fats (from hydrogenated oils) are bad news. Avoid them.

3. In the context of a typical Western diet, shifting some of your fat intake from saturated fats (from animals) to polyunsaturated fats (from vegetable oils) appears to have some advantages in terms of heart health. But I would argue that monounsaturated fats (olive oil) and omega-3 fat (fish and flax) are even better replacements.

For my Paleo and Weston Price folks who are about to pop a vein (but NOT from atherosclerosis!!) let me add:

For those who have made a more radical departure from the typical Western diet, by (say) eliminating all or most grains, sugars, processed foods, etc., it may be that reducing saturated fat offers no further benefits in terms of protecting your heart. Party on.