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Sunday, March 18, 2012

The Truth About Fat

Fat has gotten a bad reputation, but it’s a necessary nutrient. Fats help us absorb fat-soluble vitamins and provide our bodies with energy. They protect and insulate our internal organs and regulate our digestion. Fats help build cells, tissues, organs, nerves, hormones, and chemical messengers that allow our cells to communicate with the rest of the body and with the brain. Our brains are 60 percent fat.

Fat Facts

The fats our bodies need must come from food. To distinguish the good fats in our diet from the bad, it's important to understand some basic fat facts. All fatty acids are made up chains of carbon and hydrogen atoms. When every carbon in the chain is saturated with hydrogen atoms, it’s a saturated fat. Saturated fats are stable and they have a regular structure that allows them to pack tightly together, so they're solid at room temperature. Examples include coconut oil and butter.

When fatty acids have double bonds, not all of the carbon atoms are saturated with hydrogen atoms, so we call them unsaturated. If there’s just one double bond, it’s a monounsaturated fatty acid. If there is more than one double bond, it's polyunsaturated. Because they are missing hydrogen atoms, unsaturated fatty acids are always ready to react with other molecules in order to gain them. So they're naturally unstable. The double bonds in unsaturated fats change their three-dimensional structure, so they don’t pack together as tightly. As a result, they are usually liquid at room temperature, like olive oil and vegetable oil.

Inflammatory Fats

There are two specific types of unsaturated fatty acids that are so important for good health, we call them essential: omega-3s and omega-6s. Our bodies require them but can't make them, so we must get them from food. Their names identify the location of double bonds in their chemical structure: omega-3 fatty acids have a double bond before the third-to-last carbon in the chain and omega-6s have one before the sixth-to-last carbon.

This difference in double bonds seems small, but in fact, it changes everything. Omega-3 fats and omega-6 fats have opposite actions. Omega-3s decrease inflammation in the body and omega-6s increase inflammation.

Like fat, inflammation has gotten a bad reputation, but it’s not all bad. Sometimes we need inflammation. For example, our immune systems use it to fight infections and heal injuries. But we also want to be able to turn it off once it has served its purpose. When there is too much inflammation, or if it becomes chronic, it can contribute to cardiovascular disease, depression, diabetes, autoimmune disease, dementia, and cancer. Too much inflammation is a common underlying cause of chronic illness and balancing inflammation is an important part of preventing it.

To strike a healthy balance between anti-inflammatory and pro-inflammatory activity in the body, we need both omega-3 and omega-6 fats in our diet, ideally in equal amounts. But most people are eating way too many omega-6s and far too few omega-3s. Experts estimate that most people in the US are eating up to 25 times more omega-6s than omega-3s. 

Where do these fats come from?

The parent fatty acid of the omega-3 family, alpha-linolenic acid, is the most abundant fat on the planet. It’s concentrated in green leaves because plants use it for photosynthesis. When animals eat green leafy plants (or algae and plankton in the case of fish and seafood) they become good sources of omega-3 fats themselves.

Besides green leafy vegetables, seafood, wild game, grass-fed meats, and pasture-raised eggs, other good sources of omega-3s are walnuts, ground flax seeds, and cold-pressed extra virgin olive oil.

The parent fatty acid of the omega-6 family is linoleic acid. Plants use it to store energy in their seeds, which they will later convert to alpha-linolenic acid when they germinate and begin photosynthesis. Here, the term “seeds” refers to the reproductive parts of plants, which includes grains. When we feed grains to animals, they too become sources of omega-6 fats.

Other foods high in omega-6s include oils extracted from seeds like canola oil, corn oil, cottonseed oil, peanut oil, safflower oil, soybean oil, sunflower oil, and "vegetable" oil. 

Damaged Fats

The other group of fats we should avoid is damaged fats. Unsaturated fats are most likely to become damaged because they are unstable and readily react with other molecules. During these reactions, the fats become oxidized, or damaged, and the molecules they react with become free radicals that can damage cells. Examples of oxidized fats are oils, nuts and seeds that have gone rancid.

Food production can damage fats through oxidation, by exposing them to high temperatures in the presence of oxygen, and also by altering their structure to extend shelf life. Chemical reactions like hydrogenation and inesterification change the three-dimensional structure of fats, creating  trans-fats and other unnatural forms. These fats last longer because they are less susceptible to rancidity, but the disruption to their chemical configuration disrupts the way they work inside our bodies. Damaged fats create inflammation and have been linked to cardiovascular disease, diabetes, obesity, and other chronic illnesses.

Because saturated fats are naturally stable and least likely to oxidize, they're least likely to become damaged. Saturated fats are actually healthy fats, as long as they don't come from animals fed grains or exposed pesticides, antibiotics, or hormones. Despite popular myths, studies show that saturated fats do not cause heart disease.

Good Fats

Find healthy fats in these foods:
  • Green leafy vegetables (contain very small amounts)
  • Wild game 
  • Wild fish and seafood
  • Pasture-raised and grass-fed meats, eggs, and dairy products like butter and ghee
  • Raw walnuts
  • Cold-pressed oils: extra virgin olive, walnut, coconut, and flax
  • Coconut milk
  • Avocado 
  • Olives
  • Ground raw flax seeds
  • Raw chia seeds
Because the fats in oils that are liquid at room temperature are primarily unsaturated and unstable, always store olive oil, walnut oil, and flax seed oil in the fridge and never heat them above 300 degrees Fahrenheit. For the same reason, raw walnuts and ground flax seeds should also be stored in the fridge. When cooking at high temperatures, choose stable saturated fats like coconut oil and butter or ghee from grass-fed cows.  

Meats labeled "grass-fed," "pastured," and "pasture-raised" come from animals that were allowed to forage for their food. Labels that read "free-range" mean that animals had access to pasture, but it's doesn't necessarily mean that the animals ate any green-leafy plants. Animals can have access to pasture and still eat grains.

Other misleading labels include "organic" and "vegetarian-fed." Organic meat comes from cows fed organic grains, which is better for them than non-organic grains, but in the end, they're still grains. Vegetarian-fed labels mean that the animals were not fed animal parts, but it doesn't mean that they ate grass. After all, grains are vegetarian.

Vegetarian-fed chickens were not raised on pasture because chickens are not naturally vegetarian. They eat bugs, insects, and larvae as well as grass. If the chickens were allowed to forage for their food, the farmer couldn't guarantee that they didn't eat any other creatures. 

Bad Fats

To get our bodies back in balance, we don’t just need to eat more omega-3 fats, we need to drastically reduce our intake of omega-6s. Start by avoiding these foods:
  • Grains and flours
  • Foods made from flour like pasta, cereal, bread and other baked goods
  • Grain-fed animal products like meat, eggs, and dairy products
  • Canola oil, corn oil, cottonseed oil, peanut oil, safflower oil, soybean oil, sunflower oil, vegetable oil
  • Foods made with these oils like potato chips, French fries, deep-fried foods, crackers, cookies and other fried or manufactured foods
  • Processed foods, especially those containing trans-fats or hydrogenated, partially-hydrogenated, or inesterified oils
  • Fake butter products like margarine and vegetable oil spreads and sprays
  • Roasted nuts and seeds, roasted nut butters, tahini made from roasted or toasted sesame seeds, toasted oils
If liquid oils haven't been cold-pressed, they've been extracted with chemical solvents and/or heat that can damage the fatty acids. Not only are the oils listed above pro-inflammatory because they contain too many omega-6s and not enough omega-3s, but they're likely damaged as well. But because the extraction process damages the flavor molecules too, the end product is often flavorless and odorless.

Note that all foods contain mixtures of saturated and unsaturated fats, of omega-3s and omega-6s. Whole foods aren't ever only one or the other, but to simplify the discussion, I've categorized these foods based on the types of fat that predominate.

1 comment:

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