Tuesday, January 13, 2015

The US News Diet Rankings: Part 2

Health Risks

Are there health risks?
Possibly. By shunning dairy and grains, you’re at risk of missing out on a lot of nutrients. Also, if you’re not careful about making lean meat choices, you’ll quickly ratchet up your risk for heart problems.
While there are no specific dieter restrictions, you’ll want to consider talking with your doctor before making changes to your meal plans.

Calcium is probably the only nutrient in a Paleo diet* where the intake won’t meet the RDI because of the lack of dairy (meanwhile conventional dietary advice is often low in choline).  There are really no other nutrients in dairy and grains that can’t be found in meat, fruit and vegetables, which is generally true of most foods.  Most foods .  For example, despite people describing whole grains as good sources of B vitamins, meat is actually a better source of most of the B vitamins [1].

In the Paleo RCTs the Paleo diet is more nutrient dense than conventional dietary advice, which is not surprising considering that meat, fruit and vegetables is more nutrient dense per calorie than grains and dairy.

      Nutrient intake (% of RDA)                  Nutrient intake (% of RDA)**
      Average: PD 173%, DHCG 117%        Average: PD 196%, ADA 141%
      Median: PD 143%, DHCG 118%         Median: PD 156%, ADA 137%

As for calcium, there are other factors of a Paleo diet that probably makes up for the lower intake of calcium:

  • Vitamin D increases calcium absorption, and sunlight (or vitamin D supplements for those in higher latitudes) is widely recommended in the Paleo community
  • At most calcium/calcium + vitamin D supplementation reduces fracture rates by 24% [2], while vitamin K2 supplementation reduces fracture rates by 60% [3].  Conventional dietary advice recommends reducing animal fat, which probably explains how vitamin K2 is far more successful than calcium (the nutrient most of us are lacking for bone health is probably vitamin K2, not calcium)
  • By reducing grains and legumes, Paleo diets have a lower amount of phytic acid (which reduces calcium absorption) 

Lastly as for SFA and CVD, observational studies find no benefit when SFA is replaced with MUFA or carbohydrate [4] [5], and while replacing SFA with PUFA is associated with reduced CHD in observational studies [4], in the better controlled RCTs replacing SFA with PUFA results in either: lower CHD events, but not CHD mortality and total mortality [6] [7]; or higher CHD events and total mortality [7] [8] [9]

* Unless someone often regularly includes bulletproof coffee, ‘Paleo’ junk food or huge amounts of added fat in their Paleo diet, in which case all of those things would replace nutrient dense foods, thereby reducing nutrient intake.  There are bad implementations of all diets

** Nutrient intake adjusted to 2000kcal.  ‘RDA’ used came from average of men and women Australian DRI

*** In the section below they say the macronutrient ratio (P:F:C) of “a sample Paleo menu” is 38:39:23.  I don’t know where they got those figures from and I’m not too keen on 38% of calories from protein.  Cordain, et al estimated hunter-gatherers got 19-35% of calories from protein 28-48% from fat and 22-40% from carbohydrate, which averages to 27:43:31 (I know, it equals 101%)

Rankings

The first page is what you expect, a whole bunch of diets which conform to dietary guidelines, with a little variation.  Page two is where you start to see some wacky diets with gimmicks, dubious claims and/or meal replacements.  Paleo was equal last with the Dukan diet and beating Paleo was:

  • Other diets that restricted food groups like the vegetarian diet #11 and the vegan diet #19.  Because restricting food groups is bad when it’s grains, but is fine when it’s meat or all animal foods (which do have unique nutrient profile unlike grains)
  • Diets based on dubious weight loss claims or outrageous justifications such as the Flat Belly Diet #16, Abs Diet #19, Medifast Diet #26, Acid-Alkaline diet #28, the Supercharged Hormone Diet #28 and Body Reset Diet #30

The rankings lose all credibility with their fairly high ranking of Slim-Fast #13, a diet based on poor quality, highly refined meal replacements.  Slim-Fast ranks more highly than several other diets based on food such as Zone #23 and Low GI #24 and is equal #13 with the Anti-Inflammatory diet


I’ve noticed a few things on how diets get a high rank:

  • Conform to the dietary guidelines, regarding macronutrient ratios and food groups (ignore that food groups are largely a human construct and often have little to do with nutrient profiles)
  • Emphasise the importance of reducing SFA, salt and dietary cholesterol (ignore that there’s no good evidence for this)
  • Only bother doing research if you followed the previous two points, otherwise it won’t count for much and probably won’t get cited anyway.  Even if you have no research supporting your diet you can piggyback on other people’s research and say that your diet is similar to theirs
  • Promote weight loss myths that the authors believe such as eating 6 small meals a day
  • Your diet should have lots of handholding.  Meal replacements or delivering meals is preferable to your dieters having to shop and cook their own food.  And certainly don’t require that your dieters have to do something crazy like research the diet to understand it
  • Your diet should be flexible so that it’s sustainable and easy to follow (ignore that mediocre effort often just produces mediocre results).  Diets that do enough to actually be effective are definitely unsustainable and there’s no way your dieters will stick with it long term
  • Leading on from the previous point, for the long term weight loss criteria your diet’s delivered meals or meal replacements should create a minor calorie deficit like 20 calories a day, not to be that effective [10], but just to tick boxes in the rankings.

To wrap up, a positive is that I don’t expect I’ll need to respond to the rankings again.  If history is anything to go by, the rankings and their justifications won’t change that much, even with new evidence.

Sunday, January 11, 2015

The US News Diet Rankings: Part 1

The annual circus of the US News Diet Rankings is back for a repeat performance this year.  Not one to disappoint old fans, they’re performing almost the exact same act as last year.  I usually don’t deal with comedy on this blog and leave that kind of thing to The Onion.  But I’m writing about this today because some poor person might get the idea that the rankings are supported by evidence and logic, and not simply written by clowns.

In this post I’ll be discussing their representation of the research regarding the Paleo diet (see here).  In the next post I’ll discuss the rest and look where some of the diets were ranked.

There are now 4 trials comparing the Paleo diet to convention dietary advice:

·         Lindeberg, et al (2009).  Paleo vs. Mediterranean
·         Jonnson, et al (2009).  Paleo vs. American Diabetes Association
·         Mellberg, et al (2014).  Paleo vs. Nordic Nutrition Recommendations
·         Boers, et al (2014).  Paleo vs. Dutch Health Council Guidelines

There are also 4 uncontrolled Paleo trials which I won’t discuss here besides saying that the first 3 were positive and the last one was a mix, but had some issues (see here)

·         Osterdahl, et al (2007)
·         Frassetto, et al (2009)
·         Ryberg, et al (2013)
·         Smith, et al (2014)

Weight Loss

“Will you lose weight?”
“No way to tell. Paleo diets haven’t yet drawn the attention of many researchers. One tiny study that looked at weight loss found that 14 participants lost an average of about 5 pounds after three weeks on a Paleo regimen. (But even the researchers called their study “underpowered.”) Still, if you build a “calorie deficit” into your Paleo plan – eating fewer calories than your daily recommended max, or burning off extra by exercising – you should shed some pounds. How quickly and whether you keep them off is up to you.”



Paleo
Other Group
P value between groups
Lindeberg
(12 weeks)
Δ Weight (kg)
-5.0
-3.8
0.30
Δ Waist (cm)
-5.6
-2.9
0.03
Δ Fat mass (%)
-2.6
-1.6
0.30
Jonnson
(3 months)*
BMI
28
29
0.04
Waist (cm)
94
98
0.02
Mellberg
(24 months)
Δ Weight (kg)
-2.4
1.4
0.059
Δ Fat mass (kg)
-4.6
-2.9
0.095
Boers
(2 weeks)
Δ Weight (kg)
-2.7
-1.7
CI = (-2.3; -0.3)
Δ Waist (cm)
-3.1
-3.3
?
Bold: p < 0.05.  Underline: p = 0.05-0.10
* Jonnson, et al (2009) used a crossover design

The rankings mention the importance of a calorie deficit.  In the first three trials both groups spontaneously reduced calorie intake on both diets (both diets were ad libitum), though to a greater extent in the Paleo diet.  Satiety is often a limiting factor in weight loss using simple calorie restriction.  In the studies that measured satiety the Paleo diet has been found to be more satiating per calorie than the Mediterranean diet [1] and the American Diabetes Association diet [2]

The rankings misrepresent the literature on Paleo diets regarding weight loss.  They only reference one uncontrolled trial and none the four RCTs, which found: (1) you probably will lose weight on the Paleo diet; (2) the Paleo diet is equal to or better than conventional dietary advice for weight loss (etc); and (3) the Paleo diet is more satiating per calorie than conventional dietary advice

* The Boers study was different as it maintained set calorie intakes and the diets were made isocaloric

Cardiovascular Disease

“Does it have cardiovascular benefits?”
“Unknown. While some studies have linked Paleo diets with reducing blood pressure, bad “LDL” cholesterol and triglycerides (a fatty substance that can raise heart disease risk), they have been few, small and short. And all that fat would worry most experts.”



Paleo
Other Group
P value between groups
Jonnson
(3 months)*
HDL-C
1.34
1.26
0.03
LDL-C
2.7
2.8
0.5
Triglycerides
1.0
1.5
0.003
SBP
140
149
0.13
DBP
79
83
0.03
Mellberg
(24 months)
Δ HDL-C
0.16
0.18
0.896
Δ LDL-C
-0.26
-0.07
0.291
Δ Triglycerides
-0.23
-0.01
0.001
Δ SBP
-3.7
1.7
0.293
Δ DBP
-4.8
-1.5
0.349
Boers
(2 weeks)**
Δ total-C:HDL-C
-0.54
0.47
0.03
Δ Triglycerides
-0.9
0.1
0.00
Δ SBP
-9
-5
0.04
Δ DBP
-8
-3
0.09
Bold: p < 0.05.  Underline: p = 0.05-0.10
* Jonnson, et al (2009) used a crossover design
** P value after adjustment for weight loss

I would argue that the cardiovascular benefits of almost every diet ranked is unknown without long term RCTs measuring CVD events, CVD mortality and total mortality, but I’ll settle for risk factors.

Three of the controlled trials found that: (1) the Paleo diet improves blood pressure and blood lipids; and (2) the Paleo diet is equal to or better than conventional dietary advice for improving blood pressure and blood lipids.

The statement “and all that fat would worry most experts” is among the more idiotic.  Why would they be worried about a higher fat diet?  Current evidence doesn’t support higher fat being an issue for CVD or low fat diets being therapeutic.  Isocaloric replacement of carbohydrate with any fat reduces the total-C:HDL-C ratio [3], the best predictor of CHD [4].  In observational studies, total fat [5] or replacing SFA with carbohydrate has no effect on CHD risk [6] [7].  Clinical trials have found that low fat diets don’t reduce CHD [8] [9], and just to make a point: the low fat, low SFA diet in the WHI, which included more fruits and vegetables, increased the incidence of CVD events among women with pre-existing CVD (HR=1.26, CI=1.03-1.54, P<0.006) [9].  Besides, the Mediterranean diet is ~35-40% of calories from fat and Cordain, et al estimate ~28-58% of calories came from fat in hunter-gatherer diets (average of 28% and 58% = 43%) [10].  Do you think a few % of calories from fat makes a difference?  If not, no double standards please.

Diabetes

Can it prevent or control diabetes?
Unknown.
Prevention: Being overweight is one of the biggest risk factors for Type 2 diabetes. If reverting back to the Paleo era helps you lose weight and keep it off, you’ll stand a better chance of staving off the disease.
Control: One small study comparing a Paleo and a traditional diabetes diet in 13 Type 2 diabetics showed the Paleo diet resulted in lower levels of hemoglobin A1C, a measure of blood sugar over time. The approach needs to be studied more before strong conclusions can be drawn, but most diabetes experts recommend a diet that includes whole grains and dairy products.



Paleo
Other Group
P value between groups
Lindeberg
(12 weeks)
Δ HbA1c
-0.13
-0.03
0.4
Δ 30m glucose
-2.0
-0.4
0.008
Δ 120m glucose
-3.3
-0.9
0.003
Δ AUC glucose
-290
-80
0.001
Normal glucose levels***
14/14
7/15
0.0007
Diabetic glucose levels***
0/14
5/15
0.01
Δ HOMA-IR
-0.24
-0.19
0.7
Jonnson
(3 months)*
HbA1c
5.5
5.9
0.02
Fasting glucose
7.0
7.5
0.08
AUC glucose
1398
1478
0.2
HOMA IR
1.4
1.4
0.9
Diabetic OGTT (y/n)
8/5
9/4
1.0
Mellberg
(24 months)
Δ Fasting glucose
-0.04
-0.002
0.465
Δ Fasting insulin
-0.18
0.87
0.500
Boers
(2 weeks)**
Δ Fasting glucose
-0.4
-0.4
0.91
Δ Fasting insulin
-2.7
-1.4
0.44
Δ HOMA IR
-0.9
-0.5
0.41
Δ AUC glucose
-18
9
0.13
Δ AUC insulin
-1918
362
0.63
Bold: p < 0.05.  Underline: p = 0.05-0.10
* Jonnson, et al (2009) used a crossover design
** P value after adjustment for weight loss
*** No statistics on change from baseline within groups.  Paleo had 2 normal and 10 diabetic at baseline.  Mediterranean had 2 normal 9 diabetic at baseline

Weight loss is important regarding type 2 diabetes and as discussed in the first section the Paleo diet is good for weight loss, being equal to or better than conventional dietary advice.  These trials also provide a good example of how calorie intake/weight loss effects blood glucose:

·         The Lindeberg trial had more weight loss in both groups and a greater difference between the groups and consequently glucose tolerance improved and to a greater extent in the Paleo group
·         Compliance was poor in the Mellberg trial, which lead to only minor weight loss and little improvement in fasting glucose and insulin at 24 months
·         The Boers trial was isocaloric and when adjusted for weight loss there were no significant differences between the groups regarding glucose and insulin

But again the rankings only cite one trial when there are 4 controlled trials measuring glucose and insulin levels, and the one trial they cited wasn’t the more appropriate and very favourable Lindeberg trial.  Once again the controlled trials find that: (1) the Paleo diet can improve glucose levels and insulin resistance; (2) the Paleo diet is equal to or better than conventional dietary advice for improving glucose levels and insulin resistance; and (3) poor compliance = poor results, regardless of diet (the Mellberg trial)

Conclusion

The rankings consistently misrepresent the research regarding the Paleo RCTs, by citing inappropriate studies and only ever one study per section, making it seem like there’s less research on the Paleo diet than there is.  The Paleo RCTs find that the Paleo diet can promote weight loss and improve CVD risk factors, glucose levels and insulin sensitivity, and that the effect of the Paleo diet is equal to or better than conventional dietary advice.


I acknowledge that 4 RCTs with a total of 146 participants isn’t much and obviously isn’t enough justification to completely overhaul dietary guidelines, but the results of these trials should surely spark some interest and be replicated on a larger scale.