If you’re hearing about saturated fat in the news, it’s likely to be related to how they clog up arteries, increase risk of heart disease and generally make us all die! But is all this bad press fair? Why precisely do we avoid saturated fats? What are the facts?
This four part series of articles aims to put saturated fats under the magnifying glass as we find out exactly what saturated fats are, whether there are any benefits to eating saturated fats, why we all think that saturated fats are bad for us, and what the bottom line conclusion on saturated fats is regarding whether they are good for us or not.
Let’s start off with fats in general: What is a fat?
Fats are basically molecules that are made up of carbon, hydrogen and oxygen atoms. If you stick these chemical atoms together, it doesn’t automatically make them a fat. Case in point: these same chemical ingredients also make up carbohydrates. So what makes them become fats? The way they join up together makes the difference between carbohydrates and fats.
There are different types of fat, but most fats in the human body are made up of molecules that join up in chains called fatty acid chains. The way in which carbon hydrogen and oxygen atoms join together in fatty acid chains looks a bit like this:
It’s called a fatty ACID because of the way the oxygen binds at the end, in a formation that is known as a “carboxylic acid” group (also known as the -COOH group). The fatty acid molecules are acidic, particularly when the carbon chain is short. For example the shortest chain saturated fatty acid, acetic acid, is responsible for making vinegar acidic. (Yep! Vinegar has saturated fat in it!) The longer the chain, the more diluted the acidic carboxylic acid end so that long chain fatty acids aren’t very acidic at all.
The number of carbons in the chain varies, which means there are a lot of different types of fatty acids, depending on how long the chain is. In most foods, the chain length varies from a 2 carbon chain (acetic acid, as is found in vinegar), to 16-18 carbon atoms, and foods may even contain some fatty acids with 20-30 carbon atoms in their chains, although these very long chain fatty acids are rare and found in very small amounts in food. The top 4 most abundant fatty acid chain lengths in food are the 16-carbon (palmitic acid) which usually forms the major saturated fat in foods, 18-carbon (stearic acid), 14-carbon (myristic acid) and 12-carbon (lauric acid). Chain length drastically affects the health effects of a fatty acid. (As will be seen in Benefits of saturated fats and Why saturated fats are bad).
Looking at these individual chains a little more closely will reveal what determines whether a fat is classified as a saturated fat or not.
What is a saturated fat? In other words, what makes a fat saturated?
Very basic chemistry reveals that each carbon atom has four open positions through which it can bond with other atoms. When all four of these carbon bonding spots are occupied, the carbon in said to be “saturated” or full. If less than four atoms are joining onto a carbon atom, then you get spare bonds. What do these spare bonds do? They attach to existing bonds to form double bonds. Because there is a free bond in a carbon with a double bond, the carbon is said to be “unsaturated”.
In a fatty acid chain if all the carbon bonding spots are occupied, the fatty acid chain is said to be saturated, and this makes it a saturated fat.
Ok, but what does it mean if a fat is saturated in terms of how it looks outside of the microscope? Can I tell what it looks like when I look at food?
The answer to this question is: Sometimes. It can be hard to tell if a food contains saturated fat by just looking at it, unless you’re looking at food that is mostly made up of saturated fat, like:
- Coconut oil, where 86.5% of its fat content is saturated
- Palm kernel oil where 72% of its fat content is saturated
- Cheese, where about 65% of its fat content is saturated
- Butter, where about 63% of its fat content is saturated
- Cocoa butter where 59.7% of its fat content is saturated
- (Lard and animal fat have about 39% of it as fat content is saturated)
(I calculated these figures using the USDA National Nutrient Database)
So are there general trends in what these high saturated fat foods look like? Yes. These are as follows:
a.) Usually foods high in saturated fats are solid at room temperature
In foods that are composed largely of saturated fat and little else (i.e. little carbohydrates, protein or water content), the clues that it contains saturated fat are in its consistency. Butter, lard, cocoa butter and coconut oil are all solid at average room temperature. However it is not a rule that saturated fats are always solid at room temperature. Short chain fatty acids for example are liquid at room temperature and it is only the medium and long chains that are solid.
When saturated fats are mixed into food, and are diluted with water and other food molecules, their solid-like state is far harder to detect. It is however often part of what thickens creamy desserts, sauces, pates, spreads and ice cream, and what gives chocolate, cheese, nut butters, cookies, and creamy candies their firmness. Not everything that is firm and hard however is a sign of saturated fat. For example crunchy vegetables are extremely low in fat. Perhaps a good indicator of saturated fat is a thick firmness together with a creamy texture.
b.) Usually if you’re eating animal flesh, it’s safe to say it contains saturated fat
All animals are made up of carbohydrates, proteins and fat amongst other building blocks. Saturated fats are very common in animals, making up 10-40% of the fat content. Any fat that comes from an animal, including milk fat and meat fat, contains saturated fats. Even fish and fish oil, usually touted for their high omega 3 levels, contain some saturated fat.
Although virtually all animal products contain saturated fat to some degree, some non-animal foods also contain saturated fats. The most common of these are the tropical oils, namely coconut oil (aka coconut butter) and palm oil (aka palm butter), and also cocoa butter. Nuts also contain some saturated fats, though in far lower levels.
For an ordered list of foods that are highest in saturated fat, you can click here: Saturated Fats in Foods: A Saturated Fat Food List
c.) Usually saturated fats are insoluble in water
For those who like playing with their food, if you chuck a knob of butter in a glass of water, you’ll notice that it floats on top when solid or when melted. This is because most fats are insoluble in water (as well as being less dense than water). Having said that, short chain fatty acids are small enough to be soluble in water.
Saturated Fats in Food: How can I find out exactly how much saturated fat is in my food?
For those of you who like a hard paper copy to rifle through rather than an internet search you can buy a copy of McCance and Widdowson’s The Composition of Foods
Type in the food you’re interested in, e.g. “haddock”, and click submit. The database will give you a list of foods similar to your entry, and you can choose the form of the food that matches your query most closely. E.g. “Fish, haddock, cooked, dry heat”. When the food composition comes up, scroll down to “Lipids” and “Fatty acids, total saturated”. This gives you the total amount of saturated fat in the food. For example the haddock entry has 0.111g saturated fat in 100g of fish. You’ll notice that below “Fatty acids, total saturated” in the table, are a bunch of numbers: e.g. 4:0, 6:0, 8:0 etc. These numbers relate to the chain length of the fatty acid.
4:0 has 4 carbon atoms in the fatty acid chain (and the zero denotes that it has zero “spare” bonds. Ie. It denotes that the fat is saturated).
6:0 has 6 carbon atoms in the fatty acid chain.. and so on.
Seeing what type of chain-length saturated fat is in your food becomes important when looking at the hot topic of which saturated-fat-foods are bad for your health. By the time you finish reading this four part article, you should be able to tell which saturated-fat-foods are good or bad for you yourself by looking at the amount of different chain-lengths of fatty acids in your food.
Click here for part 2 of this article series which discusses why some saturated fats are good for you: Benefits of saturated fats.