Trans fats are everywhere.  Go to your cupboards, grab any packaged food products like crackers or cereal and you will probably find the words “partially hydrogenated” in the ingredients list.  So, what are trans fats? and how bad are they?

There are two types of fatty acids: saturated (no double bonds) and unsaturated (1 or more double bonds).  Fatty acids can be relatively straight molecules, except double bonds in the “cis” configuration put a “kink” in them.  “Cis” is the opposite of “trans;” saturated fats are neither cis nor trans because they don’t have any double bonds.  See below.

Trans fats are exactly like unsaturated fats except the kink is straightened out a bit, so now they have 1 or more double bond, like unsaturated fats, but are relatively straight, like saturated fats:

It’s kind of amazing that these molecules are so similar, yet you can eat 150 grams of saturated + cis-unsaturated fat every day and live a long healthy life, or eat 5 grams of trans fats, become obese and die prematurely.

Trans fats start out as liquid cis-unsaturated fats in vegetable oils (e.g., soybean oil, canola oil, etc.).  From a manufacturing standpoint, cis-unsaturated fats are too soft and unstable.  So to put them into foods would result in a messy product that melted at room temperature and then goes rancid.  That is not exactly what you think of when you picture a delicious warm muffin, or some crispy crackers, or an oreo cookie.  Converting cis-unsaturated fats into trans-unsaturated fats is what makes the difference.  Now your favorite processed food products have the perfect consistency, taste delicious, and don’t go stale.  From the perspective of the food company, people will buy more because it tastes better, and they don’t have to worry about it going bad if there is a slump in sales.  Win-win.

The melting point of the 18-carbon saturated fatty acid “stearic acid” is ~70F (mostly solid at room temperature; e.g., steak fat).   The melting point of the 18-carbon monounsaturated fatty acid “oleic acid” is ~56 F (mostly liquid at room temperature; e.g., olive oil).  The melting point of the 18-carbon monounsaturated trans-fatty acid “elaidic acid” is 113 F (almost always solid; e.g., Crisco is still solid after sitting out in the Southern California sun all day).   FTR, room temperature is 68 – 84F

Stearic acid is pretty much always solid.  It is found in steak.  Picture the white marbling in a thick cut of beef; it is solid.  Unlike oleic acid, which is found in olive oil.  Olive oil is usually a liquid, but will solidify if you put it in the fridge for a few hours.  Oils high in elaidic acid are almost as solid as stearic acid; elaidic and stearic acids can be solid at body temperature; this is highly favorable for food companies.  That is a key temperature that is important for the deliciousness of processed foods; they melt in your mouth not in your hands

Moving on to the data:  The first paper is another seminal manuscript from the infamous Nurses’ Health Study.  In brief, the Nurses’ Health Study began in the mid-70’s and has been steadily collecting data on over 100,000 women.  This particular analysis includes a sample size of ~80,000 (for the record, that is an enormous amount of people to study).

Dietary fat intake and the risk of coronary heart disease in women. (Hu et al., 1997 NEJM)

Nurses’ Health Study

Table 1.  top half of the figure, “Mean intake.”   On average, in this population of ~80,000 women in the United States, 2.2% of total calories came from trans fat.  That’s about 5 grams on a 2,000 kcal diet.  Their average total fat intake was 37.1% , or 82 grams per day. Thus, trans fats comprise about 6 % of the total fat ingested.

bottom half of the figure “Correlation.”   Trans fat intake correlates better with PUFA & MUFA (0.55 & 0.59) than with SFA (0.30).  This is half expected and half surprising.  It’s half expected because, as stated above, trans fats are unsaturated fats, so by definition if you’re eating more trans fat then you’re eating more unsaturated fats.  It’s half surprising because you might think unhealthy people eat a lot of saturated fat and trans fat, so those two things should correlate well.  But they don’t.  It appears as though there are some people who eat vegetable oils and trans fats while others who eat saturated fats.  There is of course much overlap, but thats the gist of Table 1.

Table 2.  What are people eating?

Table 2.  I love these kinds of tables; they look busy but really aren’t.  There are 4 super-columns: Saturated fat, monounsaturated fat, polyunsaturated fat, and trans unsaturated fat.  Each super-column is divided into three sub-columns: low, intermediate, and high intake levels.  For example, check out the 1st three columns in the 3rd row:  people with low saturated fat intake drink 9 grams of alcohol per day (~1 drink), people with high saturated fat intake drink less (5 grams or about a half a drink).

Now for the fun part:  cholesterol (in the red box).  Cholesterol and saturated fats are virtually always found in the same foods, so you can see that the people who ate the least saturated fat also ate the least cholesterol (red circle, 183 mg/1000kcal), and people who ate the most saturated fat also ate the most cholesterol (245 mg). Trans fats are primarily made out of vegetable oils, and there is no cholesterol in vegetable oils. People who ate the least trans fats also ate the most cholesterol (218 mg), and people who ate the most trans fat also ate the least cholesterol (206 mg).  These tables have the kind of stuff that becomes common sense but only after you think about it for a while.

Back to the half surprising point from above; maybe it should have been only 25% surprising. Healthy people try to avoid both saturated and trans fats, and healthy people who eat the least SFA or trans fat also eat the most fiber (last row in Table 2).  So all those things group together and can be seen in the table.  The advantage of this kind of table is that it independently breaks down each nutrient.  The disadvantage is that sometimes the common sense stuff doesn’t become common sense until you’ve thought about it for a long time, but I guess that’s true with a lot of things.

Moving on, to the bottom half of table 2:

similar trends…  People who eat the least saturated or trans fats also exercise the most, smoke the least, etc.  Where do you fit in?

Below is Table 3 in its entirety, but don’t worry we will not be considering very much of it.

Divide and conquer.

Of all the variables on that table, Trans fats carry the highest relative risk for CHD:  

For the highest quintile of trans fat intake compared to the lowest, relative risk is 1.53, or people who consume 2.9% of total calories as trans fats (~8 grams) have a 53% greater chance of developing coronary heart disease than people who consume 1.3% of total calories as trans fats (~2.9 grams).  A difference of only 5 grams per day can increase your risk by half!  Where can you find 5 grams of trans fat ?  I thought you’d never ask:

Holy sh!t 9 grams of trans fat in a bag of microwave popcorn?!?  So microwave popcorn causes irreversible lung damage and heart disease too?

(Note the absence of real food on those two charts)

Back to the data:  Furthermore, the Nurses’ Health Study seems to exonerate saturated fats a little.  The age-adjusted risk for the highest saturated fat intake (18.8% of total calories or 41 grams) compared to the lowest (10.7% or 24 grams per day) is pretty high: 1.38 or 38% greater risk of CHD.  Well, back to that ‘common sense’ theme, unhealthy people eat a lot of saturated fat and trans fats.  Trans fat is the real bad guy, so when the data are controlled for trans fats, the risk of eating a lot of saturated fat completely went away (see red circle).

The relative risk is “1.07,” which would mean a 7% increased risk for CHD.  BUT:  The numbers in paranthesis after the relative risk are the confidence interval.  In brief, when the confidence interval includes “1.0” as it does here (1.0 is between 0.77 and 1.48), there is no longer a statistically significant association.

And the same thing happened to animal fat:

The adjusted risk for eating 36.4% (81 grams) compared to 17.4% (39 grams) of total calories from animal fat is “0.97” which would mean there is a 3% reduced risk for CHD if you ate more animal fats.  BUT the confidence interval includes “1” so there is no statistically significant association.

In the Nurses’ Health Study of ~80,000 women in the United States, CHD risk was not associated with intake of saturated fat, animal fat (or cholesterol), and was significantly associated with trans fat.  My take?  If you are at risk for CHD, avoid trans fats like the plague.  And microwave popcorn.

calories proper

Influence of individual and combined health behaviors on total and cause-specific mortality in men and women: the United Kingdom health and lifestyle survey. (Kvaavik et al., 2010 Archives of Internal Medicine)

The United Kingdom Health and Lifestyle Survey looked at the relationship between mortality and the following four variables:

Smoking (never, former, current);

fruits and vegetables (> or < 3x per day);

physical activity (> or < 2 hours per week); and

alcohol consumption (> or <  2/d for women or 3/d for men)

Importantly, the analysis was designed to specifically address poor behaviors; it wasn’t how many vegetables you ate; it’s whether you eat more or less than 3 servings per day.  This simplifies things statistically, but it kind of excludes healthy people.  In other words, this study cannot tell you if 8 servings of veggies per day are better than 5 (a question that would be relevant to healthy people), it can only tell you if it’s bad to have less than 3 (a question that’s really only relevant to unhealthy people).  And this study says nothing about ‘what’s the worst thing for you;’ keep in mind that it only says how bad for you are those 4 pre-specified variables.

Data were collected in 1984 on ~5,000 people in the UK who were born before 1966 (they were at least 18 years old), and follow-up lasted until 2005.

Pretty much, the whole story is summarized in Table 1.

??

Lies, damned lies, and statistics.

Divide and conquer.

The hazard ratio is calculated as follows: take the first group, smoking, “never smokers.” Of the 1,591 people who never smoked, 214 died during the study.  The rate of death among never smokers is therefore: 214 / 1591 = 0.13.  Of the 2,124 people who were current smokers when the study began, 497 died.  The death rate for smokers is 497 / 2124 = 0.23.  The hazard ratio for smoking is 0.13 / 0.23 = 1.74; current smokers had 74% increased risk of dying compared to never smokers.  For former smokers, the risk was actually much worse; they had a 134% increased risk of dying.  NOTE: that is not because quitting smoking is bad for you.  Former smokers have already done a lot of damage to their health by smoking, and smokers who are very sick are very likely quit smoking but are also still very likely to die.  These are correlations not causations.   In any case, the reason why my numbers don’t match the table is because their data are “statistically adjusted.”

Going by their hazard ratios, of the 4 poor habits in question, being a current smoker is the worst (83% increased risk of dying compared to never smokers).  In terms of mortality risk, smoking is worse than regularly drinking in excess, getting less than 15 minutes of physical activity per week, and eating zero fruits or vegetables.  Nutrition is important, but not as important as not smoking.

The next worst factor was getting less than 15 minutes of physical activity per week. OK, so nutrition is important, just not as important as exercise and not smoking.  Actually, their nutrition variable had pretty much no significant correlation with all-cause mortality.

Moving on, Table 2. All cause and cause specific mortality

Again, the worst risk factor is current smoker, which was strongly associated with cancer mortality; getting < 2 hours of physical activity per week was strongly associated with CVD and all-cause mortality.

So if someone has all 4 poor behaviors, they should 1) stop smoking, 2) exercise just a little bit, 3) drink less alcohol, and 4) eat more fruits and vegetables.  If they only have 1 poor behavior it doesn’t really matter that much.

IMHO if someone asked what I considered a poor nutrition behavior, it wouldn’t be “too few fruits and vegetables.” People don’t get sick because of eating too few of anything, they get sick from eating too much.  I would have said a poor nutrition behavior is something like “> 3 servings of processed foods per day” or “too much damn sugar” because obesity and obesity-related disorders are the number one causes of death and those two behaviors do far more harm than fruit does good.  (too much processed foods and sugars can cause obesity; too little fruit cannot)

jump back over the pond to:  Risk Factors for Mortality in the Nurses’ Health Study: A Competing Risks Analysis (Baer et al., 2010 American Journal of Epidemiology)

The Nurses’ Health Study is one of the biggest epidemiological investigations of all time.  This study included young and middle aged nurses who completed multiple questionnaires about diet and lifestyle in 1980, 1984, and 1986.

The basic outline is similar to the UK study, and according to the table above, smoking triumphed again as the worst.  But wait, table 2 continued:

A Ha! diabetes is worse than smoking.

So perhaps eating more than 3 servings of vegetables per day isn’t as good as never smoking, but being diabetes-free is the best.  However, there is one important caveat.  This view of the data doesn’t exclude a relatively extreme interpretation.  I.e., eat as much junk food as you’d like and as long as you don’t develop diabetes, your lifespan won’t be affected.  A better interpretation needs to exclude that possibility because, unfortunately, people cannot eat as much junk food as they’d like and not get diabetes.

However, this study wasn’t about what led to the leading causes of death, it was about the leading causes of death.  It’s a bit cryptic, but I think it means 1) don’t smoke and 2) don’t do anything that causes diabetes…

“glycemic load”  shows a pretty good correlation with all-cause mortality.  Glycemic load is basically how much your diet increases your blood sugar.

Glycemic load is increased by:

1)       eating a greater quantity carbohydrates; or

2)       eating higher glycemic index carbohydrates

We know a high glycemic load contributes to diabetes from an earlier publication on the Nurses’ Health Study

the 800 pound gorilla, no pun intended..  is it too much of a stretch to say your best chance of dying is:

“glycemic load –> diabetes –> mortality”

?

more thoughts about the data: Having a drink a day (~10% reduced risk vs. teatotallers) or getting a little bit of exercise (13% reduced risk) were good for you, but not good enough to compensate for smoking (>100% increased risk) or a carbohydrate-rich diet (22% increased risk due to glycemic load; >100% increased risk for diabetes).  I’m usually very nutritionally biased; for example, the cause of everything can be traced to nutrition.  In the UK study they didn’t ask about glycemic load or diabetes, but they said smoking carried the greatest risk for all-cause mortality.  In the Nurses’ Health Study, smoking was bad but diabetes was worse.  I imagine the findings about diabetes would have been similar in the UK study had they asked.  So my conclusion from these studies is that the universal order of things (or just how the majority of us will go) is most likely: “glycemic load –> diabetes –> mortality”

One more study, from the National Center for Health Statistics

The preventable causes of death in the United States: comparative risk assessment of dietary, lifestyle, and metabolic risk factors (Danaei et al., 2009 PLOS Medicine)

Briefly, these authors made a death-rank chart to display the 12 quantitatively biggest contributors to mortality in the United States.  Nutrition isn’t number one, but it did capture ~10 of the top 12.

calories proper

the mice got fatter without a positive energy balance.

There was  a lot of good feedback from the post about 5% calorie restriction, but it has left people wondering,  how could this happen?

Truthfully, I have no clue. But since First Amendment Rights apply in the blogosphere, I am free to speculate.  However, for anyone with proper training in nutrition and or energy balance, this may seem like shouting fire in a crowded auditorium, so please forgo this post.

Divide and conquer.

Energy balance MUST AND WILL BE MAINTAINED.

For starters, lean mass (muscle) was lost, which might be indirectly caused by the reduction in food intake.  Muscle is the major contributor to energy expenditure.  If food intake declines, and muscle is lost in order to reduce energy expenditure, energy balance could be in fact maintained.  The only strange part of that conclusion is that it states that muscle was lost in order to reduce energy expenditure.  Why would muscle do this?  Perhaps it is due to a novel variation of the “use it or lose it” principle.  “Use it or lose it” refers to the decline in skeletal muscle that occurs during extended periods of disuse (think of someone’s arm after it spent 2 months in a cast).

When calorie intake is reduced, leptin levels decline rapidly signaling “starvation” mode to the brain.  This causes a large reduction in energy expenditure in order to preserve energy stores.  Previously, the decline in energy expenditure would have been predicted to occur by decreased physical activity.  And reduced physical activity could cause muscle loss due to the “use it or lose it” principle.  BUT physical activity was unchanged.  Therefore, it is possible that the decline in metabolic rate was manifested by processes other than physical activity in muscle tissue.  This means that “use it or lose it” could apply to functions (“using it”) that occur while we are resting.  Clearly, this is a marked deviation from the energy balance dogma.  And it has kept me up at nights.

What processes could these be?  None were measured or even suggested by the authors of the study, but I suppose some possibilities could be reduced activity of sodium potassium ion channels or possibly reduced futile cycling.  This is interesting, indeed.  More research is severely warranted.

So muscle was lost in order to balance the reduced food intake.  OK, so where did the energy come from to build fat mass?  This may have already been explained… if metabolic rate was reduced down to match food intake, energy balance would be maintained.  If metabolic rate was reduced even further, it would produce a relative energy surplus.  Perhaps this is precisely what occurred.  Thus, muscle was lost in order to balance the reduced food intake, and metabolic rate declined in order to create a relative positive energy balance selectively to the fat tissue.  Why would something like this occur?  It is very strange, to be sure, but may have had something to do with the stress of the feeding regimen. The body thinks it is starving, so preserving fat mass becomes a priority.  Maybe the systems that work to preserve fat mass during starvation are the same as those that build fat mass during energy surplus.

For now, trying to explain these findings without defying the laws of energy balance caused gray hairs to appear in my beard.   I’ll try to figure out the why later.

The mice got fatter without a positive energy balance.  Can this happen to us?  Does it matter?  These results suggest that fat tissue has a propensity to grow regardless of energy balance.  In the abovementioned study, the trigger may have been the hormonal response to a stressful feeding regimen.  Type I diabetics are usually very thin but develop fat deposits in their insulin injection sites; thus, in type I diabetics, the trigger is insulin.  In both situations, fat mass grew because of the hormonal milieu, not an energy surplus.

calories, proper

United States v. Forty Barrels and Twenty Kegs of Coca-Cola

flashback 1916
Coca-Cola busted for being adulterated with an ingredient known to be harmful to health.  Caffeine!!!  lol

HFCS you’re next.

You can find 100 of them in conveniently packaged snacks, our bodies burn them all the time, and yet they can be neither seen nor touched. That is because a calorie is technically a unit of heat. Just like how feet and meters are ways to quantify distance, calories quantify heat. More specifically, a calorie is the amount of heat required to raise the temperature of one gram of water (~1 mL) from 14.5°C to 15.5°C. Another popular unit used to quantify heat is the joule, which is equal to approximately 0.239 calories. When expressed as a unit of mechanical energy, 1 calorie = 4.2 joules. Lastly, a British Thermal Unit (BTU), more famous for measuring the cooling capacity of air conditioners, is the amount of heat required to warm a gallon of water by 1°F. The important point to remember is simply that a calorie is, albeit somewhat abstract, a unit of heat. Knowing that calories are a measure of heat is important, although less useful than knowing about the calories in food, and how they are handled by the body. Calories, whether those in food or those expended by the human body, are measured by a procedure known as calorimetry.