Thread: The Gallon a Day Diet
1/24/2010 8:40am, #91
- Join Date
- Dec 2008
1/24/2010 1:04pm, #92
I think the source of confusion is along these lines:
When we eat something, it releases chemical energy in a particular amount and pattern. The amounts and patterns of different foods are... not well-understood, but understood to some extent. This is how "a calorie is (basically) a calorie" - once we've got chemical energy, it's basically fungible - convertible between locations and forms.
But food that we eat can also do a bunch of other things, such as:
-provide micronutrients (vitamins, minerals, etc.) or antinutrients (lectins)
-be chemically transformed by gut microflora (fibers and resistant starches)
-affect hormone levels (insulin, leptin, testosterone)
-modulate the paracrine and autocrine systems (eicosanoids)
Reasoning about the latter are where claims of "good calories" and "bad calories" come from. Most of these claims are based on woefully-incomplete understandings, though.
3/05/2010 10:44pm, #93
Here's a bit of follow-up.
Mensink and Katan, "Effect of dietary fatty acids on serum lipids and lipoproteins. A meta-analysis of 27 trials" broke down the influence of various fat-carbohydrate substitutions on lipid profile. They couldn't split omega-3 and omega-6, but they did exclude studies involving long-chain omega-3s, so it's reasonable to assume that their PUFA numbers are all omega-6. Here's the results of replacing a percentage of energy intake from carbohydrates with various types of fat (in mmol/L):
HDL = 0.012x(sat) + 0.009x(mono) + 0.007x(poly)
LDL = 0.033x(sat) - 0.006x(mono) - 0.014x(poly)
Total = 0.039x(sat) - 0.003x(mono) - 0.015x(poly)
Triglycerides = -0.025x(sat) - 0.022x(mono) - 0.028x(poly)
HDL:LDL = 0.000x(sat) + 0.003x(mono) + 0.005x(poly)
So that's an interesting set of results. Odd how they never mention the last two lines in discussions on the subject.
Surprisingly, our regression equation would predict that replacement of saturates by carbohydrates yields little if any improvement in coronary risk. This is in obvious disagreement with a large body of epidemiological evidence that shows that low-fat diets are associated with low risk for coronary heart disease.