Fats – the good guys and the bad guys

We’ve already discussed the importance of protein in the diet, so now we’ll move on to fats — they are energy-rich, supplying 9 calories per gram of fat. A common misconception is that eating excess fat will add fat to your belly or hips. Well, actually, that is true – but it’s true that excess calories in the form of carbs or protein will add fat as well. If you consume more calories than you burn, the excess is stored as fat.

It’s important to understand that we need to eat SOME fat. It is essential for absorbing certain vitamins (A, D, E and K) and carotenoids and lycopenes which help our bodies function and may help decrease the risk of cancer. It is essential for brain growth and development and makes up the substance of cell walls, regulating what stays in the cell and what stays out. There is ‘structural fat’ which is essential for holding organs and nerves in position, padding palms and buttocks to avoid bone injury, and helping us maintain a constant body temperature — in my case, that temperature would be permanently cold — just ask my patients! And our fat stores supply energy for long bouts of exercise.

Fats are essential – the key is to mainly consume the better fats that will not add to your risk of heart disease. If you just want to get to the bottom line about which nuts or fish to eat, just skip to the end. If you’d like to know why omega-3’s are so good for you, and why trans fats are so bad for you, let’s start with a brief look at the basic fat molecule structure. A fatty acid is a chain of an even number of carbon or C molecules, with single bonds between them, and two hydrogen or H’s on each C.

   H H H H H H H H H H
H-C-C-C-C-C-C-C-C-C-C-……….       Saturated fat – all single bonds.  Each C has 4 single bonds.
   H H H H H H H H H H

A saturated fat has all single bonds, as shown above. These are generally from animal sources (beef, chicken, fish, dairy and eggs) and are solid at room temperature. A monounsaturated (1st example below) or polyunsaturated fat has one or more double bonds. A double bond means there are 2 connections between carbons. Since each C can only have 4 bonds, 2 H’s are dropped. When the dropped H’s are on opposite sides of the fat, as in the 2nd example below, it is called a trans fat. More about that in a little bit.

       H H H H   H H H H                                                                    H     
1) H-C-C-C-C=C-C-C-C……                                           2)                 C=C
       H H H        H H H                                                                          H

 Monounsaturated fat -at least one double bond                      A trans fat has at least one trans double bond

Fats with a high percentage of mono- or poly-unsaturated fatty acids are usually liquid at room temperature and are referred to as ‘oils’. These contribute essential fatty acids and are naturally present in olive, canola, corn, peanut and sunflower oils.

Now we get to the omega-3’s – the good guys. Unsaturated fats are named by the position of the double bond nearest the end of the fatty acid. An omega-3 fatty acid has its 1st double bond at the 3rd carbon from the (methyl) end. Animals can only create double bonds as low as the 9th carbon. They must get their omega-3s from plants. Salmon are rich in omega-3s from eating marine plants. Interestingly, fish oils of cold water creatures contain highly unsaturated fatty acids because they must maintain their fats in liquid form even at low temperatures.

Omega-3’s are believed to contribute to brain function during aging, protect us from fatal irregular heart beats associated with heart disease, and reduce arthritis and inflammation. The favorable omega 3’s – EPA and DHA – are mainly found in cod liver oil, mackerel, salmon and sardines, flaxseed, canola oil and soybean oil. Although these are available in pill form, eating the fish itself is more beneficial. Only 2 servings of fish each week is enough to provide health benefits.

I’ve always been confused by recommendations about which nuts are ‘best’ nutritionally. It seemed that each list I saw had a different ‘best’ nut. I finally realized that sometimes the recommendation was based on omega 3 content, sometimes on the omega 3 to omega 6 ratio, and other times on total grams of fat. It is advisable to keep the ratio of omega 3’s to omega 6’s in the diet at about 1:2 to 1:3. In general, people get much more omega 6’s than that, and these may oppose the benefits of the omega-3’s.

Let’s get back to trans fats – the bad guys- as promised. In naturally occurring double bonds, the 2 carbons lose a hydrogen on the same side of the carbon chain. This allows the fatty acid to bend, to stay liquid. When food companies add hydrogens to form solid, stable oils with a long shelf life, they add one H on each side of the chain. These trans fatty acids (#2 above) do not bend. They are found in shortening, high-fat baked goods and, most publicized, frying fats at fast food joints. They can increase the bad LDL part of your cholesterol and decrease the good HDL. Their bad reputation is due to the associated increased risk of heart disease, cancer and diabetes. Although their presence should be listed on the nutrition label, there may still be up to 0.5 gms per serving when the label says “zero trans fats”. Check the actual ingredients for “hydrogenated” or “partially hydrogenated” fats if you want to be sure to avoid them.

Some practical points on healthier oils and fats:
1) Polyunsaturated – highest to lowest – olive, canola, peanut, safflower, soybean, corn, sesame
2) Omega 3 in fish – highest to lowest – sardines, herring, mackerel, bluefish, tuna, salmon, pompano. High cooking temperatures may destroy up to half of the omega 3 content.
3) Omega 3 in nuts – almond, peanuts, walnuts and pecans.

When preparing canned fish, consider avoiding regular mayo. Here are some comparisons:
Regular mayo: 94 calories, 10 gm fat, 1.6 gm saturated, 6 gm polyunsaturated, 2.3 gm monounsaturated
Canola mayo:100 calories,  11 gm fat, 0.5 gm saturated, 3 gm polyunsaturated, 7   gm monounsaturated
Tofu mayo:    35  calories, 3.5 gm fat, 0.5 gm saturated, 2 gm polyunsaturated, 1   gm monounsaturated

As you can see, canola mayo has as many calories and grams of fat as regular mayo, but a higher monounsaturated fat content. Tofu mayo has 1/3 the calories. I have recently used Spectrum brand Canola Mayo and Nasoya brand Tofu Mayo, and I can’t taste the difference from the real thing.

RECIPE: Use 10 oz of tuna packed in water, 1 Tbsp tofu mayo, juice of 1/2 lemon, and 1/4 cup shredded carrots. Mix together for a moist, tasty low-fat tuna salad.

For a substitute sandwich spread, consider mustard or canola or tofu mayo.

Stay tuned for an article on the third nutrient — carbs and the glycemic index.

Sources:
Modern Nutrition in Health and Disease, 11th Ed. © 2014. Lippincott Williams & Wilkins. Editiors AC Ross, B Caballero, et al.
The New Food Lovers’ Companion by Herbst and Herbst
NEJM June 23, 2011, 364:2439-2450.
www.cnpp.usda.gov/Publications/DietaryGuidelines/2010/PolicyDoc/Chapter4/pdf