The Friedewald and Iranian equations: Fasting triglycerides can seriously distort calculated LDL

This post is a revised version of a previous post. The original post has been or will be deleted, with the comments preserved. Typically this is done with posts that attract many visits at the time they are published, and whose topics become particularly relevant or need to be re-addressed at a later date.

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Standard lipid profiles provide LDL cholesterol measures based on equations that usually have the following as their inputs (or independent variables): total cholesterol, HDL cholesterol, and triglycerides.

Yes, LDL cholesterol is not measured directly in standard lipid profile tests! This is indeed surprising, since cholesterol-lowering drugs with negative side effects are usually prescribed based on estimated (or "fictitious") LDL cholesterol levels.

The most common of these equations is the Friedewald equation. Through the Friedewald equation, LDL cholesterol is calculated as follows (where TC = total cholesterol, and TG = triglycerides). The inputs and result are in mg/dl.

    LDL = TC – HDL – TG / 5

Here is one of the problems with the Friedewald equation. Let us assume that an individual has the following lipid profile numbers: TC = 200, HDL = 50, and trigs. = 150. The calculated LDL will be 120. Let us assume that this same individual reduces triglycerides to 50, from the previous 150, keeping all of the other measures constant with except of HDL, which goes up a bit to compensate for the small loss in total cholesterol associated with the decrease in triglycerides (there is always some loss, because the main carrier of triglycerides, VLDL, also carries some cholesterol). This would normally be seen as an improvement. However, the calculated LDL will now be 140, and a doctor will tell this person to consider taking statins!

There is evidence that, for individuals with low fasting triglycerides, a more precise equation is one that has come to be known as the “Iranian equation”. The equation has been proposed by Iranian researchers in an article published in the Archives of Iranian Medicine (Ahmadi et al., 2008), hence its nickname. Through the Iranian equation, LDL is calculated as follows. Again, the inputs and result are in mg/dl.

    LDL = TC / 1.19 + TG / 1.9 – HDL / 1.1 – 38

The Iranian equation is based on linear regression modeling, which is a good sign, although I would have liked it even better if it was based on nonlinear regression modeling. The reason is that relationships between variables describing health-related phenomena are often nonlinear, leading to biased linear estimations. With a good nonlinear analysis algorithm, a linear relationship will also be captured; that is, the “curve” that describes the relationship will default to a line if the relationship is truly linear (see: warppls.com).

Anyway, an online calculator that implements both equations (Friedewald and Iranian) is linked here; it was the top Google hit on a search for “Iranian equation LDL” at the time of this post’s writing.

As you will see if you try it, the online calculator linked above is useful in showing the difference in calculated LDL cholesterol, using both equations, when fasting triglycerides are very low (e.g., below 50).

The Iranian equation yields high values of LDL cholesterol when triglycerides are high; much higher than those generated by the Friedewald equation. If those are not overestimations (and there is some evidence that, if they are, it is not by much), they describe an alarming metabolic pattern, because high triglycerides are associated with small-dense LDL particles. These particles are the most potentially atherogenic of the LDL particles, in the presence of other factors such as chronic inflammation.

In other words, the Iranian equation gives a clearer idea than the Friedewald equation about the negative health effects of high triglycerides. You need a large number of small-dense LDL particles to carry a high amount of LDL cholesterol.

An even more precise measure of LDL particle configuration is the VAP test; this post has a discussion of a sample VAP test report.

Reference:

Ahmadi SA, Boroumand MA, Gohari-Moghaddam K, Tajik P, Dibaj SM. (2008). The impact of low serum triglyceride on LDL-cholesterol estimation. Archives of Iranian Medicine, 11(3), 318-21.

Does "Metabolically Healthy Obesity" Exist?

Obesity is strongly associated with metabolic alterations and negative health outcomes including diabetes, cardiovascular disease, and some types of cancer (1, 2, 3, 4).  Excess body fat is one of the primary causes of preventable health problems and mortality in the United States and many other affluent nations, ranking in importance with cigarette smoking and physical inactivity.  Obesity is thought to contribute to disease via the metabolic disturbances it causes, including excess glucose and lipids in the circulation, dysregulated hormone activity including insulin and leptin, and inflammatory effects.  This immediately raises two questions:

1. Does metabolically healthy obesity exist?
2. If so, are metabolically healthy obese people at an elevated risk of disease and death?

Does metabolically healthy obesity exist?

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Are You Drinking Enough Water?

One thing I noticed after the Thanksgiving break was that I was drinking less water because I wasn't working out and I got out of the habit of keeping my water cup full at home.  I felt like my skin was looking dull and icky, so this week, I got back on my normal water routine.  

It helps so much to have a large bottle or cup that you like to drink from near you so you remember to drink water throughout the day.  I like the insulated cups the best so they don't sweat and create a puddle on your furniture.  The one pictured on my desk is from Wal-Mart and holds 20 oz. of water.  I drink about 3 of these a day, so about 60 oz. of water.  

It used to be recommended that people drink 8, 8 ounce glasses of water a day = total 64 ounces.  But now, the Institute of Medicine sets general guidelines for total water intake and recommends that women consume a total of 91 ounces (that’s about 2.7 liters) per day – from all food and beverages combined. But, depending on your diet, about 25% of the water you consume comes from your food.  

I've read that most healthy people get enough water in the food and liquid they take in on a regular basis, but you can gague whether you're getting enough water by if you feel thirsty or your urine is dark.  

I feel better when I'm drinking water throughout the day and definitely notice a difference in my skin.  

I really like these 24-Ounce Insulated Cups.  They come in a variety of colors too for a great price.  I always prefer a lid (just in case of spills) and straw.

How much water do you drink per day?  Do you use a special cup too?  

Healthy Beef Burritos

I've often talked about one of my go-to healthy meals, Tex Mex to go, and sometimes I mix it up and make it into a healthy beef burrito.  It's super easy and delicious!

I like to make a big batch, so I start with 2 packages of Laura's lean ground round or sirloin (4% fat).  Lean beef still has plenty of flavor, try it if you typically go with something fattier.  I'd be surprised if your family even notices the difference.

Then, I add two packages of low sodium taco seasoning and mix with 1.5 cups of water and bring it to a simmer until the meat has absorbed all the seasoning.  Meanwhile, I heat up a large can of low-fat refried beans.  

For me, the key to a delicious burrito is fresh pico de gallo (salsa), which is very easy to assemble.  I make it the same way I make guacamole, just without the avocados.   Just dice up tomato, white onion, jalapeno (deseeded for milder flavor) and cilantro and toss it all together with a squeeze of lime.

When the beans are heated through and the meat is ready, I assemble my burrito on a whole wheat tortilla (that I warmed up on the stove or in the microwave) and add low-fat cheese and sour cream- just a touch. 

Let me know if you try it and how you like it. 

Healthy Hair

About a year and a half ago, I accidentally (and stupidly) fried my hair in an effort to save money and do an at-home Keratin treatment.  The Keratin treatment was supposed to turn my naturally-a-little-frizzy hair into smooth, shiny locks.  The box clearly stated NOT to use it on bleached hair (which I have), but I thought it would be okay.  Wrong!  After you put the treatment on your hair, you are supposed to comb it through very straight.  As I started combing my hair, it starting coming out in big chunks.  I quickly washed the product out of my hair, but the damage was done.  It continued to break for months after that, I had to chop it, and I've been working on growing it back out, healthy, ever since.

Of course, it looked nice chopped when it was just styled from my awesome hairdresser.  But, I have a major cowlick and could never get it to stay side swept like that.  I really don't mind the shorter length, I  just want it to be healthy!

Now, I try to wash it every other day (I can't go more than that with workouts) and only dry it with a hairdryer or use a curling iron on the first day, trying to let it air-dry as much as possible.  Then I might put it up in a top knot the next day.   

I use Kerastase oil (just on the "pony tail" so it doesn't get weighed down) and I think it's been working miracles.  It's the green one for damaged hair.  I was surprised to see that Amazon sells it- I used to have to wait until I had a hair appointment at the salon.   

I only use it a couple times a week and a tiny bit goes a long way. It makes your hair really sleek and shiny, taking out the frizz too.  It also smells divine.  I love the Kerastase shampoo and conditioner too, but it's expensive so I don't always buy it. 

I wanted to ask y'all about Biotin supplements.  I read that Biotin is often recommended for strengthening hair and nails, though scientific data supporting this outcome are weak. Nevertheless, biotin is found in many cosmetics and health products for the hair and skin.  I found this brand on Amazon and it had a lot of great reviews, but I was wondering what you think or if you've tried it.  

Let me know!

Protein IQ

How was your Thanksgiving?  I was home the whole week with my son and we also had house guests, so I didn't get in any exercise.  My body is craving a good workout, so this week it's back at it!  I can hardly believe we're in December already and it's just 3 weeks until Christmas!  Let's make these 3 weeks count so we can finish the year strong.  And so we don't add on additional weight that we have to work to lose in the new year.  You with me? 

If you can't make it to the gym and/or just don't have time to workout, you can still accomplish so much by watching what you eat.  I love this visual example of how much protein, veggies, and starches should be on our plates.

Via Lauren Conrad

And this list of proteins is pretty helpful too.  I aim for about 90 grams of lean protein a day when I'm trying to gain muscle and get lean.  I used to count and measure all my food but now I'm pretty good at estimating it.  If you want an easy way to track your calories, protein, carbs, and fat, try MyFitnessPal.com.  It's a free site and is very easy to use.

Via Women's Health

So, what are you doing to finish 2013 healthy and strong?  

Food Reward Friday

This week's lucky "winner"... Oreo cookies!!!

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