The more you know about fat, the more capable you are to make healthy choices.
Healthy Fat vs. Unhealthy Fat? Healthy fats and unhealthy fats: what's the difference? What are healthy fats?
Research on fat is confusing, and the internet is full of conflicting suggestions.
When people generalize about the fats in their diets, a lot of confusion happens. Many weight loss books, media, and blogs talk about fat as if they were all the same.
In fact, there are dozens of common fats in your diet, each with a different role in the body, with an impact on your health. Even in saturated, unsaturated, and polyunsaturated fat groups, specific fats still have different effects.
This article will explain the differences between some of the major dietary fats and their health effects, for better or worse.
The key is to understand that each type of fat has its own unique effect on the body. Once you start thinking more specifically about fat, you'll be better equipped to make healthy eating choices.
How fat becomes a dirty word
Decades ago, common sense was to eat high-fat foods because it was the most effective way to get energy. By weight, fat contains more calories than any other nutrient.
Over time, scientists began to understand that some fats are healthier than others. In the 1930s, Russian scientists discovered that feeding animals a diet high in cholesterol cause atherosclerosis (1).
This is a condition in which plaques accumulate in the arteries, narrowing them and increasing the risk of heart disease. Atherosclerosis is the most prominent cause of heart disease and stroke (1).
In the 1940s and 1950s, heart disease decreased in several countries. Many attribute this phenomenon to wartime rationing during World War II. This has led to the belief that high levels of fat and cholesterol in restrictive foods can lead to heart disease.
The large international Seven Nations study, directed by American physiologist Ancel Keys and other international scientists, revealed several important risk factors for heart disease.
These include smoking, high blood pressure, weight gain, yo-yo dieting, and blood cholesterol (2).
The Seven Kingdoms study helps hypothesize that saturated fat increases blood cholesterol, predicting atherosclerosis and heart disease. (3）。
However, even a few decades ago, Ancel Keys recognized that not all fats are harmful. He was skeptical of the importance of dietary cholesterol and showed that unsaturated fats reduce the risk of heart disease. (4）。
Unfortunately, the science of him and other researchers have been misread a lot by policymakers, nutritionists, and journalists.
Extreme conclusions that are black and white, such as "all saturated fats are harmful" or "everyone should eat a low-fat diet," are neither helpful nor true. This article will combine old and new research to demystify the confusing literature on fat.
Summary: Since the 1930s, scientists have suspected that fat and cholesterol cause atherosclerosis, heart disease, and stroke. However, later studies have shown that judging all fats —even all saturated fats— together is an inaccurate oversimplification.
Dietary cholesterol has little effect on heart health
Cholesterol is made by the livers of humans and animals. For this reason, you can only get it from a diet of animal products.
Major sources include egg yolks, animal liver, fish or fish oil, animal fats, or oils such as butter, shellfish, meats, cheeses, and animal fats made from baked goods.
The liver adjusts the amount of cholesterol it produces based on the amount of cholesterol it consumes in the diet. When you consume a lot of cholesterol, the liver produces less cholesterol.
The cholesterol you consume has little effect on cholesterol levels in your blood. Even 50 years ago, Ancel Keys realized that the impact was insignificant for most people.
"Focusing only on [dietary cholesterol] has had little effect," Keys said (5).
According to a large study that synthesized evidence from more than 350,000 adults, dietary cholesterol was not associated with a heart attack or stroke. (6）。
However, a combination of multiple large studies found that as many as 25% of people have an above-average sensitivity to dietary cholesterol. For these people, large amounts of dietary cholesterol increase "bad" LDL and "good" HDL cholesterol (7).
Summary: According to the largest available study, dietary cholesterol does not alter most people's risk of heart disease. However, for up to a quarter of the population, high dietary cholesterol increases "bad" LDL and "good" HDL cholesterol.
Calling all saturated fats bad fat is an oversimplification
Saturated fat differs from unsaturated fat in that it does not have chemical double bonds. This makes it more stable, so it is solid at room temperature.
Saturated fat is a controversial topic, and nutrition experts don't always agree on how it affects health. There are many reasons why the study of saturated fats is confusing.
Not all saturated fats are created equal
While people who offer dietary advice often conflate saturated fats, there are many different kinds of saturated fats that have different health effects. Labeling all saturated fats as "healthy" or "unhealthy" is simplistic.
A distinguishing feature of fats is their length, which means the number of carbon atoms they contain. Fats may be short (containing less than 6 carbons), medium (6-10 carbons), long (12-22 carbons), or very long (22 or more).
Your cells handle fat very differently depending on their chain length, which means that different lengths of fat can have different effects on health.
A study of 16,000 European adults found that intake of ultra-long-chain fatty acids (VLCFAs) was associated with a reduced risk of type 2 diabetes (8).
VLCFAs are found in tree nuts, including peanut oil and rapeseed oil. The study also found that the long-chain fatty arachnid acid found in vegetable oils has a protective effect.
It also matters whether the number of carbon atoms in a saturated fat chain is even or odd.
The same study of 16,000 European adults found that saturated fatty acids with even carbon atoms were associated with type 2 diabetes, while fats of odd length were associated with a lower risk of developing the disease (8).
Isometric saturated fats include stearates, which are mainly found in meats, cheeses, and baked goods.
They also include palmitates, named after palm oil, but are also found in dairy, meat, cocoa butter, and perhydrogenated vegetable oils. Another saturated fatty myristate of even length is found in butter, coconut oil, and palm oil.
Odd saturated fats, including stevodecanoic and pentadecanthic acids, are derived primarily from beef and dairy products.
Since the effects of saturated fats on health and the way they are metabolized are so subtle, it is useless to collectively refer to them as "good" or "bad."
Difference Between Saturated Fats And Unsaturated Fats
To know more about saturated and unsaturated fats, visit BYJU’S.
People eat food, not personal nutrients
While most nutrition studies look at the effects of individual nutrients, even the same specific type of fat may have different effects depending on its source.
For example, saturated fatty palmitate from lard causes atherosclerosis in animals, but the same palmitate extracted from tallow does not (9).
In addition, the way the fats in lard are connected to each other to make it more like tallow can reverse the harmful effects of palmitate (9).
Although these differences are subtle, the conclusion is that a particular food is more important than the type of fat it contains.
For example, one avocado contains the same amount of saturated fat as three slices of bacon.
Bacon increases levels of "bad" LDL cholesterol (10).
However, according to a study of 229 adults, eating about half to 1.5 avocados a day actually lowered levels of "bad" LDL cholesterol. (11）。
This may be partly due to the different types of saturated fats in avocados and the way they are structured. However, avocados also contain healthy plant compounds that may bring other benefits.
When you decide which fats to include in your diet, choosing a variety of healthy foods that include vegetables, nuts, seeds, and fish is more important than focusing on individual fatty acids.
Other factors in the diet can alter the effects of saturated fats
When researchers looked at the association between saturated fat and health, they often assumed that saturated fat came from meat, cheese, and, other dairy products.
In fact, 15% of the saturated fat in the U.S. diet comes from high-carb desserts, including cakes, biscuits, pastries, and candy. Another 15% came from "junk" foods such as burgers, fries, pizza, and fries, and another 6% from dairy desserts (12).
When these junk foods and desserts were represented only by saturated fat content in the study, it was difficult to distinguish their health effects from other foods that also contain saturated fat.
For example, cheese saturates more Latino the Western diet than any other single food. However, the largest cheese study looked at the effects of 177,000 adults over 5-15 years and found no link between cheese and early death (13).
Another large study of hundreds of thousands of adults for 25 years found that consuming milk, cheese and yogurt did not increase the risk of heart disease, or even slightly reduce the risk of stroke. (14）。
Regarding meat, a study of more than 1.6 million adults found that those who consumed the most processed meat had about 20 percent higher risk of heart disease and all-cause death than those who consumed the least amount. (10）。
The study also found that people who ate the reddest meat had a 16 percent higher risk of dying from heart disease than those who ate the least. (10）。
However, it is important to note that people sometimes mistakenly attribute the effects of unhealthy diets to saturated fats.
Foods high in saturated fat tend to be high in calories and lead to weight gain, so it's easy to blame saturated fat for effects that may actually be caused by too many calories and weight gain.
For example, some studies have shown that heart disease is actually more closely related to extra calories and weight gain than saturated fat. (15）。
This is important because it means that many foods high in saturated fat are safe, as long as they are consumed in moderation in a diet that does not lead to weight gain.
Summary: Some saturated fats can cause heart disease. However, it is too simplistic to call all saturated fats bad fats. In fact, some saturated fats are healthy when they come from dairy and vegetables, and certain meats.
Industrial -- unnatural -- trans fats can lead to heart disease
Trans fats are made by "hydrogenating" vegetable oils in a process involving bombarding vegetable oils with hydrogen. This converts liquid unsaturated fats into solid or near-solid saturated fats and trans fats.
The most common sources of trans fat include cakes, pies, icing, cream fillings, fried foods, and biscuits and biscuits made with shortening or margarine.
"Fully hydrogenated" oils are indistinguishable from saturated fats and are considered saturated fats by the body.
However, trans fats — at least made from vegetable oils — are foreign to the body and can lead to atherosclerosis and heart disease. (16）。
A 39-month study of atherosclerosis of the heart in 50 men showed that men who consumed more trans fats worsened more quickly. (17）。
An increase in atherosclerosis increases the risk of a heart attack. A study surveyed 209 people who had recently experienced a heart attack and found that their fat cells had higher levels of trans fat than 179 adults who did not have a heart attack. (18）。
In the United States, food labels are now required to list the trans fat content of each serving. Unfortunately, if the amount per serving is less than 0.5 grams, companies can round it to zero.
Given that serving sizes are unregulated, which is especially cumbersome, companies may manipulate portion sizes to make them smaller than the amount you normally eat at one time to claim "0 grams of trans fat per serving."
To avoid this trap, look at the ingredients. If they list "partially hydrogenated", then the food contains trans fats and should be used with great caution.
While industrial or human trans fats are clearly harmful, dairy products and meat contain small amounts of natural trans fats. These natural trans fats are not related to heart disease and may actually be beneficial (19).
Summary: Industrial or human trans fats can cause heart disease. Avoid them. Even if the food label claims it contains "0 grams of trans fat," if its ingredient list says "partially hydrogenated" oil, it means it contains unhealthy industrial trans fat.
Unsaturated fats are good for heart health
Unlike saturated fats, unsaturated fats have double chemical bonds that can change the way your body stores and uses them for energy.
Unsaturated fats are good for the heart, although some are healthier than others. As with saturated fats, there are many different unsaturated fats. Their length and the number and location of the double bonds affect their role in the body.
Monounsaturated fats have one double bond, while polyunsaturated fats have two to six double bonds.
Monounsaturated fats are good
Olive oil, rapeseed oil, and avocado are rich in monounsaturated fats. They can also be found in tree nuts, including almonds, walnuts, pecans, hazelnuts, and cashews.
A 4-30-year study of 840,000 adults found that those who consumed the most monounsaturated fats had a 12% lower risk of dying from heart disease compared to those who ate the least. (20）。
Compared to other monounsaturated fat sources, this benefit of oleic acid and olive oil is strongest.
More unsaturated fats are better
Polyunsaturated fats may be better than monounsaturated fats. In one study, replacing foods rich in saturated fats with polyunsaturated fats reduced the risk of heart disease by 19% (21).
The results showed that people who consumed 5% of their calories per day from polyunsaturated fats instead of saturated fats reduced their risk of heart disease by 10%.
Polyunsaturated fats are mainly found in vegetable oils and seed oils.
Omega-3 fatty acids have many health benefits
Omega-3 fatty acids are a specific type of polyunsaturated fat found in seafood, especially fatty fish such as salmon, herring, bluefin tuna, and albacore tuna.
A study of 45,000 adults used omega-3 fatty acids in the blood and adipose tissue to estimate the amount of omega-3 in the diet. Studies have found that high omega-3 intake is associated with a 10% reduction in heart disease risk. (22）。
Not all studies have found the same benefits, and some people worry about eating fish because it can be a source of mercury that, if consumed in large enough amounts, can be toxic. (23, 24）。
The U.S. Food and Drug Administration and the Environmental Protection Agency say eating two to three servings of fish per week is the safety cap, but it depends on the type of fish (23).
They recommend against regular consumption of fish with the highest mercury levels, including larger fish such as mackerel, marlin, swordfish, and bigeye tuna.
Albacore tuna and yellowfin tuna have less mercury and are safe to eat up to once a week, while salmon, trout, and whitefish are safe to eat 2-3 times a week.
Summary: Olive oil, canola oil, and seed oil can be used in cooking and are a source of monounsaturated and polyunsaturated fats for heart health. Nuts and fish are also a source of healthy polyunsaturated fats, including omega-3s.
Conclusion
The more you know about fat, the more capable you are to make healthy choices.
The key is to understand that each particular type of fat has unique effects on the body, and these effects can be good or bad.
For example, many studies have confused all saturated fats, when in fact there are many different kinds of saturated fats, each of which has a different role in the body.
In addition, people don't eat saturated fats in isolation — they choose foods that contain multiple fats and other nutrients.
Even the same type of saturated fat has different effects, depending on how it relates to other fats and other components in the diet. For example, saturated fats in dairy, poultry, and certain vegetable oils are neutral and even for heart health.
Unsaturated fats are always good for heart health, while industrial trans fats are always bad. In contrast, small amounts of natural trans fats in dairy products are harmless, as is cholesterol in eggs and other animal products.
Overall, choose good fats, including unsaturated and saturated fats from a variety of vegetables, nuts, seeds, fish, and unprocessed meats. Avoid bad fats in processed meats, such as partially hydrogenated oils and saturated fats.
Following these guidelines will help control your risk of heart disease and extend your lifespan.
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