Nutrition Education

Testing Your Nutrition Knowledge: Lipids – Part 2

I promised that Part 2 would be the good stuff, so here it is:

TYPES OF FAT AND THEIR FOOD SOURCES/HEALTH IMPLICATIONS! 

Anyone else this excited when they talk about food? Yes? No? Let’s just get this show on the road.

Fats, Foods, & Health

Let’s catch up from where we were last time. I like to think of fats (the fatty acids) as being broken down into 4 groups:

  1. Saturated Fats
    • Saturated fats are fats that are generally solid (for the most part) at room temperature, because they are able to pack tightly together with their straight carbon chains. However, this is not always the case. Let’s look at rich food sources of saturated fats:
      • Animal fats (think of the marbling in red meats/bacon)
      • Butter
      • Cheese
      • Whole milk
      • Tropical oils (palm oil and coconut oil)
    • If you’re looking at this list and thinking something is odd, I’m going to guess it’s about the last one: tropical oils. One thing to realize is that, while most saturated fats are solid, they can still be liquid. The reason for this is because of the length of the carbon chain of the fatty acid. Generally, longer chains (>14 carbons) are solids, and the shorter the chain, the more liquid it becomes. For instance, milk has saturated fats, but they are mostly short chain fatty acids. In addition, coconut oil has saturated fats, but coconut oil is a rich source of medium chain fatty acids, especially myristic acid (14:0; 14 carbons, 0 double bonds). We’ll talk about the health implications of saturated fats later.
  2. Monounsaturated Fats
  3. Polyunsaturated Fats
  4. Trans Fats
    • Yikes. There are very few things that I believe have no place in our diets, but trans fats are number one on that list. HOWEVER, this is referring to industry-made trans fats. There are some natural sources of trans fats that are actually thought to hold some potential health benefits. We’ll list the ugly here:
      • Fried foods
      • Margarine 
      • Snack cakes/cookies/crackers/potato chips
    • So you might be asking, “what do you mean industry-made trans fats?”. Let me explain. Industry uses a process called hydrogenation to convert oils to solids (this helps increase shelf life of products, because unsaturated fats are prone to rancidity). For instance, ever wondered what margarine is? Margarine was at one time, an oil full of unsaturated fats. Through this process of hydrogenation (where hydrogens are added to break the double bonds in the unsaturated fat), oils become solids and voila! Margarine. However, sometimes hydrogens are not completely added to the double bonds. Instead, what happens is the cis formation of the natural double bond (that is, the hydrogens on the same side, providing the kink in structure – refer to Part 1, if needed) becomes a trans double bond. This still makes the oil become a solid, but instead of saturated fats, we now have trans fats (*gasps*). This process of partial hydrogenation creates the trans fats. 
    • Hydrogenation vs. Partial Hydrogenation
      Figure 1. Hydrogenation vs. Partial Hydrogenation. Hydrogenation of a cis double bond in an unsaturated fat, results in a saturated fat. Partial hydrogenation results in the cis double bond converting into a trans double bond, giving us a trans fat. Photo source: http://catsfork.com/Health-Diet/FatChem_Trans2-Problem_files/hydrogenation-fat.jpg

       

    • How do you know if what you’re snacking on contains Trans fats? Well, you can check the Nutrition Facts label, but know this: companies are allowed to state that their product has 0 g of Trans fat if the food contains <0.5 g Trans fat per serving. So what does that mean? That means, if you’re eating double or triple the serving size on the Nutrition Facts label, you could actually rack up the Trans fats (if they are, in fact, present). But WAIT. How do you even know if there is Trans fat in the food that they would try to hide from the customer? Check the ingredients list! If you see the words “partially hydrogenated …” you can bet that there is Trans fat in the product – it just may be below 0.5 g in the serving size. Companies will try to trick you with this, just check out this Benecol product below!
    • benecol
      Photo source: http://www.scientificpsychic.com/fitness/benecol.jpg

       

    • Another question that consumers have about Trans fats is: will frying my own food at home make Trans fats too? Yes, but if you throw out the frying oil after each batch, don’t worry. Let me explain: frying creates a natural partial hydrogenation reaction. In order for partial hydrogenation to occur, you need oil, heat, and a metal catalyst (probably the pan in which your frying). Yes, some Trans fats can result from at home frying, but probably not in high enough amounts to cause major concern (unless you have cardiovascular disease, in which, you will want to avoid Trans fats at all costs). Why? Trans fats need to accumulate in the frying oil before they can present major concern. This is why eating fried foods in restaurants is not a good idea, because it is likely that they do not change their frying oil very often. Even if they do, there is still the possibility that several other items have been fried in the oil before you get your food. If you MUST have the fried food, it is probably a better idea to make it at home, where you know you have just added the oil a few minutes beforehand.
    • FINALLY, what about those potentially healthy Trans fats? The natural Trans fats present in beef or dairy are thought to possibly possess health benefits, although further research is needed. You may have heard of CLAs (conjugated linoleic acids): these are the natural Trans fats that are actually sold as supplements. It has been shown in some animal studies that CLAs may lower the inflammatory response and atherosclerosis, and they have shown anti-cancer properties in animals, as well. In some human studies, they have been associated with a decrease in body fat and improved lean body mass. Now, the thing about scientific research is that you must take everything with a grain of salt. Just because something occurred in animal studies does not mean that it will translate over to humans. Further, just because something occurred in a few studies does not mean that it is a miracle drug for all nor does it mean that long-term consequences have been evaluated. 

Okay, so now that we’ve discussed food and types of fat, let’s talk about the health implications.

  • Saturated Fat: Has long been bashed for negative health impacts, but has recently come back into the spotlight as some research debates this classical view. It is thought that long-chain saturated fats are the bad fats and shorter-chain saturated fats may not be that bad. Longer chain saturated fats are found in animal sources, whereas shorter chains are found in some foods such as coconut oil. This is still heavily debated, but for now, I will say that the long-chain saturated fats are “bad” because they have been shown to increase your LDL levels (low-density lipoproteins, which can carry cholesterol to your blood vessels, contributing to cardiovascular disease risk). 
  • Monounsaturated Fat: Has been considered “good fats”, as they have been shown to decrease LDLs, while some evidence shows that they may also increase your HDLs (high-density lipoproteins, which pick up that deposited cholesterol in your blood vessels to help prevent cardiovascular disease).
  • Polyunsaturated Fat: Also has some positive health benefits, such as decreasing total serum triglycerides and reducing inflammation (we’ll talk more about the health effects of PUFAs in Part 3!)
  • Trans FatIs the double-whammy of negative health effects. Trans fats not only increase your LDLs, but evidence has also shown they also decrease your HDLs. This is why it is so important to avoid Trans fat if you have cardiovascular disease.

Dietary advice is to switch out the “bad fats” (Trans fats and Saturated) for the healthier fats (MUFAs and PUFAs). 

Fats and cardiovascular disease risk go hand-in-hand. To assess for cardiovascular disease risk:

  • Serum LDL levels greater than and equal to 160 mg/dL is associated with an elevated risk. Desirable LDL is less than 100 mg/dL.
  • Serum HDL levels less than 40 mg/dL is associated with an elevated risk. Desirable HDL is greater than 60 mg/dL.

If you have elevated LDL levels, it is recommended by the Therapeutic Lifestyle Changes Diet (TLC Diet) to lower your total fat intake to <30% of total calories and lower saturated fat intake to <10% of total calories. If you have experienced a cardiovascular disease event, such as a heart attack or stroke, it is recommended that saturated fat intake be lowered to <7% of total calories. 

Now that my fingers are tired from typing, we’ll end this blog on Testing Your Nutrition Knowledge. Look for Part 3 when we discuss omega-3s! 

Remember: more guacamole, less bacon.

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Photo source: https://ih1.redbubble.net/image.278891398.1320/flat,800×800,075,f.u3.jpg
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