Matt Metzgar

Your Genes on a Diet

Here's a nice commentary on a recent study that looked at diet and gene expression.  In this study in the American Journal of Clinical Nutrition, researchers were able to study how various genes responded to different types of dietary carbohydrate.

Two types of carbohydrate were studied: a high insulin response food group and a low insulin response food group.  In the high insulin group, 62 genes in subcutaneous fat showed increased expression and none showed decreased expression.  In the low insulin group, 71 genes showed decreased expression and none showed increased expression.

You know science is getting pretty good when it can track gene expression from eating different foods.  In my mind, this type of science is very beneficial and will help point the way to an optimal diet.  It may also help strengthen the case for the Paleo diet due to its fit with our genetic heritage. 

How Many Sets?

The debate over whether those engaging in resistance training should use one set or multiple sets has been going on for many years.  The results are somewhat conflicting, though my opinion is that one set is normally sufficient to stimulate muscle growth.

This new study may help explain why there are often conflicting results.  Researchers measured muscle growth separately in the upper body and lower body for either a single set or three sets per exercise.  The authors found that for the upper body, there was no difference in strength and mass for either 1 or 3 sets.

For the lower body, the 3 set protocol produced greater strength and muscle mass than the 1 set routine.  Therefore, it may pay to treat the upper and lower body differently in terms of sets.

Dark Chocolate and Insulin Sensitivity

Here's a study from a couple of years ago about dark chocolate and insulin sensitivity.  The authors found that dark chocolate, but not white chocolate, improved insulin sensitivity and decreased blood pressure.

That's good news for all the chocolate lovers out there.  For me personally, I've found that the darker the chocolate, the more satisfying it is.  I usually buy the 85% cocoa dark chocolate and have a few squares from time to time.

Beware of Your Mouthwash II

My last post on different mouthwashes generated a lot of comments.  For some time, I have been looking for an alternative to the "big two": Listerine and Crest Pro-Health. 

I came across this research abstract(pdf) presented by the "Tom's of Maine" company.  Tom's compared their natural toothpaste to other natural toothpastes along with major brands.  The clear winner to me was "Listerine Essential Care", a toothpaste I'd never even heard of. 

Listerine mouthwash uses a combination of four essential oils that has been proven to exhibit antiplaque and antigingivitis properties.  But the whole solution contains alochol, the use of which has been connected to oral cancer.  But this Listerine toothpaste seems to solve the problem: it contains the four essential oils, no alcohol, and also contains fluoride like a regular toothpaste.

Lately, I've been experimenting with just using the Listerine toothpaste only and no mouthwash.  So far, it seems to be working pretty well, so I will continue using this product for now. 

Gray Hair

I've been doing a bit more research into gray hair lately (since like most men, I want to avoid it!).  Here's a summary of a neat paper that proposes a "free radical theory of graying".  In essence, the authors believe that just as damage from free radicals contributes to aging in general, damage from free radicals also contributes to gray hair.

To me, this theory rings true.  I have seen other research which shows that smokers have more gray hair than non-smokers.  I've also seen research where drug addicts show more gray hair than normal people.  So it makes sense to me that oxidative stress is a major factor in gray hair.  Certainly there is a genetic component as well, but at least the oxidative stress component can possibly be controlled/delayed.

For some more supplemental evidence, here is a recent study that looked at graying in a mouse model.  For this experiement, the researchers applied a superoxide dismutase (SOD) gel (a topical antioxidant) on one side of the mice and then exposed both sides to oxidative damage.  When the hair grew back, the side that was treated with the SOD gel was black, while the other side was gray.

This use of a topical antioxidant is in line with the recommendations put forth in the first paper I mentioned.  The authors believe that proper "strategies will involve endo- and exogenous protection from oxidative stress-induced apoptosis by stimulation of the endogenous antioxidative capacity or by treatment with exogenous antioxidants".  In other words, someone wanting to fight gray hair should focus on 1) getting enough antioxidants through diet and supplements, and 2) the application of topical antioxidants to the hair itself.

As far as I know, there are no effective topical antioxidant treatments currently on the market for gray hair.  There are supplements that may claim this, but there is no clinical proof that I've seen.  I bet that some of the bigger cosmetics manufacturers are working on something like this right now.  Until then, getting a solid amount of antioxidants through diet and supplementation is the key. 

Low-Carb Diets and Mortality

Here's another strike against low-carb diets.  This study was published just last month shows a relationship between low-carb diets and increased mortality.  The study surveyed over 22,000 people over a ten-year period.

The results showed that prolonged consumption of a diet low in carbohydrates and high in protein was associated with an increase in mortality.

Low-Carb Diets

Though it seems like the Atkins craze is dying down, there is still a great deal of misinformation with regards to low-carbohydrate diets.  The first issue is weight loss.  Low-carb diets often produce rapid initial weight loss compared to ther diets.  But does this weight loss last over the long-term?

The short answer is no.  There are a number of studies on this, but here is one and here is another.  Almost all diets, whether they are low-carb, low-fat, or other types, usually fail to show any significant long-term weight loss because they focus on energy intake and not energy expenditure.  Exercise is needed for any real long-term weight loss.

What about low-carb diets and cholesterol?  Here is nice meta-analysis on the subject.  Low-carb diets lead to lower triglycerides and higher HDL (good) cholesterol, but more LDL (bad) cholesterol than low-fat diets.  And if you look deeper, you'll find that "Mediterranean" diets outperform both the low-fat and low-carb approaches in terms of cholesterol imrpovements.

Another topic is whether low-carb diets offer any special benefits as far as preventing (or treating) diabetes.  If someone has diabetes, then by definition they have trouble processing carbohydrates.  An obvious solution would be to just limit the amount of total carbohydrate that's consumed.

But this is too simplistic in my view.  As discussed in an earlier post, the problem is not the total amount of carbohydrate but the type.  Moving a person from a high-glycemic diet to a low-carbohydrate diet would certainly improve their diabetes status, but is that the optimal treatment?  In my opinion, no - they are better off having a normal amount of "good" carbohydrates in their diet instead.

For example, in this study increasing the amount of carbohydrate from 40% of total calories to 55% led to improvements in insulin sensitivity.  You can also look at long-term eating patterns and see this, as for example this study showing vegetarians have higher insulin sensitivity than omnivores.

In summary, there is no reason in terms of health to follow a low-carb diet: 1) it doesn't lead to significant weight loss, 2) it doesn't lead to optimal cholesterol levels, and 3) it isn't the best treatment for diabetes.  A Paleo or Mediterranean diet (with moderate fat and quality slow-release carbs) is a much better dietary model and fits with our genetic heritage.

Carbohydrates and Body Weight

I came across this nice study the other day.  The authors looked to see if there were any relationships between carbohydrate intake and body weight.  Several factors were studied including carbohydrate amount, glycemic index, and glycemic load.

Controlling for the various factors, they found that daily carbohydrate intake and percentage of calories from carbohydrates were not related to body weight.  They did find that the glycemic index of carbohydrates consumed was related to body weight.  Again, it seems that it's the type of carbohydrate (those with a high-glycemic index), not the total amount consumed, that leads to health problems. 

Carbohydrates and Diabetes

Here's a good paper on the relationship between carbohydrate intake over time and diabetes.  The authors tracked both the quantity and quality of carbohydrates over the 20th century.  At first glance, there is a correlation between carbohydrate intake (grams per day) and the prevalence of diabetes over the past 20 years.  But the authors looked deeper and found that it was really the type of carbohydrate being consumed that has driven the increase in diabetes.

The research points out two major factors: corn syrup and refined cereals.  The consumption of these two items correlates directly with the rate of diabetes.

The daily amount of carbohydrate turned out not to be a key factor in this analysis.  In fact, people were consuming about the same amount of carbohydrates per day (500 grams) in 1909 as they were in 1994.  But back in 1909, much of this intake was in the form of whole grains.  Today this intake is more often in the form of refined grains such as flour, white bread, etc., - all foods that lower insulin sensitivity and increase the risk of diabetes.

Google Search

I replaced the Blogbar search with a Google site search on the right menu.  This should make searching the content of this site easier.