The Truth About Fat

Mar 30, 2022
The Truth About Fat

Having lived through the 1980s and 1990s, I vividly remember being told that fat is bad and should be avoided.  I was told in health class that eating fat “raised cholesterol and would lead to heart disease.”  However, we now know that not all fats are equal, and in fact we need some fat to maintain our health.  Furthermore, the link to heart disease has not proven to hold true.

What is fat?

Dietary fat is a macronutrient found in both animals and plants.  It plays many essential roles including helping to maintain the health of cells, absorption of fat-soluble vitamins, regulating immune system, and helping you to stay full longer.  Healthy fats are typically monounsaturated or polyunsaturated; human made trans fats are unhealthy.  The healthfulness of saturated fats, which have had a bad reputation, remain an open question.

What are “good fats?”

Many of the healthiest fats come from vegetables, nuts, and seeds.  Good sources include monounsaturated fats (olive oil, avocados, nuts) and polyunsaturated fats which include Omega 3 fatty acids (fatty fish, dairy, and meat from grass-fed animals, flaxseed, walnuts) and Omega 6 fatty acids (walnuts, hemp and sunflower seeds, peanut butter, and eggs).  It is a good goal to achieve a balance of omega-3 and omega-6 fats.

What is Saturated fat?

Saturated fats are solid at room temperature. Common sources of saturated fat include red meat, whole milk, and other whole-milk dairy foods, cheese, and many processed foods.

Unfortunately, there are confusing and conflicting reports about an association of saturated fats with heart disease. A recent meta-analysis of 21 studies found that there is insufficient evidence to conclude that saturated fat increases the risk of heart disease, but the authors suggest that replacing saturated fat with polyunsaturated fat may improve health. Other recent studies suggest that that replacing saturated fat with polyunsaturated fats like vegetable oils or high-fiber carbohydrates may reduce the risk of heart disease, but replacing saturated fat with highly processed carbohydrates is worse for health.

What types of fat should I avoid?

I recommend completely avoiding trans-fats (or partially hydrogenated oils).  They are banned in Europe and are in the process of being removed from the US food supply by 2021. Trans-fats cause inflammation, which can contribute to insulin resistance, heart disease, and stroke. For every 2% of calories from trans-fat consumed daily, heart disease risk increases by 23%.

Processed vegetable and seed oils, although polyunsaturated, also seem to have potential negative health impacts. Even though the jury is still out that vegetable or seed oils are harmful to health, sticking with more natural fats and minimizing the use of most highly processed vegetable oils could be more beneficial to your health.  

What fat should I use to cook at higher temperatures?

Saturated fats are resistant to heat and don’t oxidize at high temperatures, as the less stable polyunsaturated fats in vegetable and seed oils do. Some monounsaturated fats like olive oil are also good choices for cooking at high temperatures because they remain pretty stable when heated, but I would avoid high-polyunsaturated vegetable oils when cooking at high temperatures because they are more likely to become oxidized or damaged.

There is still a lot we are learning about fats and our health.  I would recommend trying to eat whole foods and limit highly processed foods.  When it comes to fats, the less processed the better.


DISCLAIMER: Sarah Smith MD is a medical doctor, but she is not your doctor, and she is not offering medical advice on this website. If you are in need of professional advice or medical care, you must seek out the services of your own doctor or health care professional.