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Does changing diet to improve blood lipid levels actually reduce mortality?

Answered on August 19, 2014
Created February 22, 2013 at 8:39 PM

OK, there are always innumerable questions on PH about hacking blood test lipid values, all, I assume, posed with the expectation that improving blood lipids will improve health or mortality.

There are data like this http://renegadewellness.files.wordpress.com/2011/02/cholesterol-mortality-chart.pdf that show that a total cholesterol of about 220 is correlated with lowest overall mortality.

But this is a correlation. It doesn't tell us that getting our blood lipids into this range CAUSES reduced mortality. Is there any evidence out there that shows that moving one's blood lipids from a less optimal number to a more optimal number actually CHANGES mortality? Or, do we work to improve blood lipids purely on the hope that these changes are causal to lower mortality?

Medium avatar

(10611)

on February 23, 2013
at 04:09 AM

Lipid panels are just one marker among many. The unusual combination of high LDL and low triglycerides I've seen in many blood test panels I've seen here has to be weighed off against whether the other markers are good or bad.

Medium avatar

(10611)

on February 23, 2013
at 01:15 AM

That's the problem with a good question.

61844af1187e745e09bb394cbd28cf23

(11058)

on February 23, 2013
at 12:22 AM

Uh, no, you are going to die regardless. Life is terminal.

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6 Answers

3
A2c38be4c54c91a15071f82f14cac0b3

(12682)

on February 22, 2013
at 11:59 PM

There are just so many biological variables being affected when people make changes to their lifestyle that determining a solidly casual relationship between a blood lipid change from diet trials and mortality is damn near impossible.

Furthermore, what if you improve one blood lipid but worsen another? The recently republished Syndey Diet Heart study is a decent example of this conundrum. It found that, compared to saturated fat, feeding heart disease survivors omega-6 fats (probably with with some trans fats) lowered total cholesterol and triglycerides, but increased mortality. This is despite that group having cholesterol closer to that supposedly ideal 220 (243 vs. 266). HDL wasn't reported that for this study, but I'm almost sure it would be higher in the saturated fat group.

I guess a better litmus test would be a diet trial where only one blood lipid variable changed between two groups. The GISSI trial, is alright examples of this. Taking fish oil reduced mortality and essentially the only blood lipid that changed (other than LDL, which increased a little bit) was triglycerides, which decreased notably in the fish oil group. That's about all I can come up with.

If we look at randomized, controlled trials we can look for consistencies. A number of RCT's are consistent with the idea that lowering triglycerides lowers mortality and raising triglycerides mortality. Same with LDL (controversially). Same with HDL, except with higher being better. But it doesn't take long to find inconsistencies, primarily when one of those variables improves but others worsen.

Another important point is that things can be be going inside the body, good or bad, that aren't reflected by blood lipids, since studies like the Lyon Diet Heart trial have noted a significant reduction in mortality despite no changes in any blood lipids.

So there is decent evidence that supports the hypothesis that improving blood lipids may reduce mortality, but we really can't say for sure that improving blood lipids will always reduce mortality since we haven't and may never prove such a thing definitively.

Anyway, sorry for the lengthy answer, I just started typing and couldn't stop.

Medium avatar

(10611)

on February 23, 2013
at 01:15 AM

That's the problem with a good question.

1
5dd50f78f47b8848d93724d6eb38d4c1

on February 23, 2013
at 02:37 AM

That cholesterol mortality chart is basically useless. It doesn't account for dozens of variables and context such as low cholesterol levels due to diseases predisposing to death.

A 30 year follow up in the Framingham study, very low cholesterol levels over a lifetime seemed to increase longevity. http://www.ncbi.nlm.nih.gov/pubmed/3560398

Medium avatar

(10611)

on February 23, 2013
at 04:09 AM

Lipid panels are just one marker among many. The unusual combination of high LDL and low triglycerides I've seen in many blood test panels I've seen here has to be weighed off against whether the other markers are good or bad.

1
Medium avatar

(10611)

on February 23, 2013
at 12:12 AM

It depends on whether the diet improves the organism. If you are obese and diet reduces your weight you will probably improve several markers for health, including your lipid panel. If you're healthy it's harder to quantify an improvement in something like longevity. Still, shifting HDL up and blood pressure down have positive effects on reducing CV risk, which is tantamount to a slight longevity improvement even if you're already at low risk.

1
Cbda678b2a6bf0537d8c4ea0ce8aa9ad

(4319)

on February 22, 2013
at 09:23 PM

Causes? or reflects? What's the difference? My opinion is that whether cholesterol is cause or effect, it is a marker. Statistics show what you have written; the healthiest numbers via-a-vis mortality appear to lie between 200 and 240 with HDL/Trig ratios important.

High, or low, or medium cholesterol numbers, they appear to be a reflection of what is happening in the organism. If eating a Paleo diet (whatever that is) moves cholesterol numbers in the right direction, so be it.

0
D7cc4049bef85d1979efbd853dc07c8e

(4029)

on February 22, 2013
at 10:32 PM

Changing blood lipids does not change mortality. Changing the other underlying health that created the high blood lipids probably will though.

We know higher HDL was a sign of better health. Yet drugs that did just that, raise HDL, did nothing to improve mortality or morbidity.

0
7a6529ea25b655132fe58d793f95547a

(2030)

on February 22, 2013
at 09:51 PM

I think it has a lot to do with our ability to make better decisions in our day to day lives since lower cholesterol has been linked to depression, anxiety, and violent death from suicide and accidents.

http://arno.uvt.nl/show.cgi?fid=28060

http://www.psychosomaticmedicine.org/content/62/2/205.full.pdf+html

This is just observational but I would wager that the majority of people with higher cholesterol would have a higher paying job or at least a steady income, access to higher quality nutrition, and a broader social support system and all would contribute to a longer life.

Like anything else though there are probably other beneficial effects of having more cholesterol in the blood.

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