Fat isn’t bad.
Actually it is essential to our health and it is recommended that about 30% of our daily intake be in the form of fat. Dietary fat can be reduced below this number and our bodies can convert carbohydrates that we eat into fats but there are good reasons to keep intake around 30%. First, there are essential fats that our bodies simply can’t produce. Second, dietary fats are necessary for the absorption of the fat soluble vitamins A, D, E, and K. Third, fats are rich in energy and help with satiety, in other words, the feeling of fullness. Having healthy, natural fats as part of the diet provides essential nutrients, helps with the absorption of vitamins and helps us ‘feel’ full appropriately.
Fats are rich in energy because they are made of long carbon chains surrounded by hydrogen atoms. Each bond represents energy to be tapped into… a lot of energy! If a carbon chain is completely bonded to hydrogen atoms, it is said to be saturated. Examples of saturated fats include lard, butter, and other animal fats. As a rule of thumb these are solid at room temperature. There are also vegetable sources of saturated fat, like coconut oil. In general, these saturated fats lead to higher cholesterol and clogging of the arteries and are considered the BAD fats.
The Unsaturated Fat: A Complex Individual
Two carbon atoms can share a double bond leading to two less hydrogen atoms. This creates a fold in the fatty acid chain and creates a fat in an unsaturated state.
Unsaturated fats can be monounsaturated and polyunsaturated based on the number of double bonds. Examples of monounsaturated fats are olive oil, avocado, cashew, canola, and peanut oils. Polyunsaturated fats are things like corn oil, fish oil, sunflower oil and safflower oil.
Omega-3’s and DHA: The LCPUFA’s
LCPUFA stands for Long Chain Polyunsaturated Fatty Acid. Omega-3 fatty acids including DHA are excellent examples of LCPUFA’s that are getting a lot of press lately. Omega-3 fatty acids are found in fish like salmon and trout and also in flaxseed. Omega-3’s are thought to have significant benefit for people with heart disease and DHA has been touted for its role in early neural and retinal development for a baby in utero.
DHA is not a magic supplement that creates a baby with superior brain and eyesight. Actually the AAP has no official opinion on whether or not formula should be supplemented with DHA and ARA. That is because clinical studies are inconclusive as to whether or not it actually does anything. Yes, these LCPUFA’s are needed in development but mother’s milk has them and baby can create them with the fats available. These are good fats. Pregnant and breastfeeding mothers should be consuming two servings of fish per week (again, not big game fish like tuna… I’m talking salmon here) but beyond that, there is no evidence that fancy supplements do anything. This brings up another good point that is more of a general rule in nutrition: If a substance is beneficial for your health, it is far better to consume it in its natural form than to take a pill. Our bodies were designed to pull nutrients from real food and our supplements are notoriously bad in terms of ‘bioavailability.’ This means that the DHA obtained from eating fish is much better absorbed than from a supplement. The same goes for things like iron. The list goes on.
The Wolf in Sheep’s Clothing
So we are getting a good concept of fats, here: saturated animal fats are bad, light vegetable and fish derived unsaturated fats are good. There is however one important exception: trans fats.
Trans fats are unsaturated, meaning there is a carbon double bond in the molecule, but the three dimensional structure is different from other unsaturated fats: the bond is in trans formation, instead of cis. (cis formation has both hydrogen atoms on the same side and trans has them on opposite sides of the bond.) Trans fats are the WORST kind, in terms of health. They are just as bad if not worse than saturated fats in causing atherosclerosis and elevated cholesterol. By and large, trans fats are manmade fats, like partially hydrogenated oils. These fats are found in cookies, cakes and other packaged items. They can be found in French fries at fast food restaurants because the consistent reheating of what was once a ‘good’ oil can change cis bonds to trans bonds, making the oil more unhealthy. Avoid trans fats!
Fats are not all bad. In fact they are essential for normal growth and should make up a substantial part of our diets but we need to be selective. Meat and animal fats should be kept to a minimum. When eating meat, make sure it is lean and avoid the urge to put bacon on everything. Keep prepackaged cookies and crackers to a minimum and leave out fried fast food all together. Get your fats from fish and vegetable sources like avocados and olive oil. While LCPUFA like DHA are certainly good for your baby, the jury is still out on whether or not supplementation does any good.
Matthew Toohey, MD. February 29, 2012