[Rhonda]: What about carbohydrates, processed, refined carbohydrates and their effect on
small, dense LDL particles?
You're talking about context with the food.
[Ron]: Right, that's right.
So that takes me back to the nutrition committee again.
So, I started...
I said I'd been involved in lipoprotein research for a long time, and dietary effects on lipoproteins
is part of our program.
And I got into the American Heart Association nutrition activity, really, as a result of
that interest.
And in addition to inheriting this confusion between dietary cholesterol and blood cholesterol
in the general public, I also inherited from my colleagues and predecessors in the field
the mantra that we should be going for low-fat diets.
There was a very strong campaign to keep the message simple and stay away from fat, and
there were a lot of forces in society as well as in the academic and industrial worlds that
had an interest in pushing that message as a way to keep the public focused on what they
felt was the most important thing they should be doing, which is restricting fat and saturated
fat in particular.
But what nobody really thought about seriously was the unintended consequence that that message,
which the food industry responded to in a very responsible way, they said, "Well, experts
in the field are telling us to use low-fat products, so we're going to make low-fat foods.
We're going to make low-fat cookies.
We're going to make low-fat Snackwell's brownies."
[Rhonda]: And butter and cooking oil.
[Ron]: And so there was this tremendous response, which led to a reduction in fat intake and
saturated fat levels did go down in the diet.
But the tradeoff was an increase in carbohydrates.
So, getting back to your question, we became very interested in studying the effects of
a low-fat diet on lipoprotein metabolism.
And so the very first study I did when I came here to Berkeley and started to do some dietary
work was to test the effects of a low-fat diet, the traditional low-fat diet.
This is, again, when I was trying to get involved with the Heart Association.
I was still in that mode.
I was thinking, "Well, low-fat diets are good.
This is what my predecessors had said, and so, maybe that's what we should be studying."
And the hypothesis was that people with small LDL would have a good response, that we'd
put them on a low-fat diet, their heart disease risk should go down.
Well, it turned out that it was actually the opposite.
We had a completely contrary result.
We found that people who started off with large LDL, when they're put on a low-fat diet,
actually made their LDL smaller.
So it went exactly the opposite direction.
And that was, like, an eye-opener to me, and I think it's still sort of somewhere percolating
through the nutritional world.
Not everybody has really understood the implications of this.
But what we've found shortly thereafter is it wasn't so much of the low-fat aspect of
the diet that was causing this to happen, it was the fact that we were substituting
carbohydrates.
High-carbohydrate diets can promote the production of these VLDL particles from the liver that
makes small LDL.
So high carbohydrates clearly push the lipoprotein metabolism in the direction of atherogenic
dyslipidemia, all the features, high triglycerides, small LDL, and to some extents, a lower HDL.
And so we've tried to sort of break down the dietary response into a more specific role
of particular carbohydrates.
As you know, carbohydrates cover a wide range of food substances, ranging from simple sugars,
like fructose and glucose, to complex starches and fiber that are less easily metabolized
and do not raise blood sugar levels the way processed starches do.
So we had been very interested in narrowing that down, and we and others have pretty much
come to the conclusion that probably the chief culprits in the production of this atherogenic
dyslipidemic trait, low-fat, high-carbohydrate diets, are probably the simple sugars, and
fructose in particular among them, which is, of course, a component of table sugar and
added sugars, half of that is fructose, the other half is glucose.
So we think all carbohydrates have this potential for pushing lipid metabolism in that direction,
but sugars, and particularly fructose, we think are the most potent, and this has flown
in with a huge popular attention.
Now, people really do understand, I think for the most part, that dietary added sugars
have adverse effects, not just on lipids or heart disease risk, but on many aspects of
health and obesity, for example, being perhaps the biggest public health issue that has been
associated with added sugars, particularly from liquids.