Fat in our food gets a lot of negative press. It’s hard to believe that fat represents anything besides unwelcome calories or a risk factor for heart disease.
But fats play many important roles in human health besides providing calories. For example, your brain is actually 2/3 fat, and the protective covering surrounding nerves is 70% fat. Fatty acids are used to synthesize hormones and molecules involved with immune function and cell signaling. Fatty acids are a key part of cell membranes, and are important for hair and skin health.
Fatty acids come in many different shapes and sizes, and several specific fatty acids are essential to cell structures and metabolism. The omega-6 and omega-3 unsaturated fatty acids are known to be essential. There is a minimal Adequate Intake for both of these, as seen in the chart below. These recommended amounts are quite small. The requirement of 12 grams/day of linoleic acid for an adult woman could be met by consuming just over 1 TB of safflower oil.
The recommendation for omega-3 fats is even smaller, and is based on alpha-linolenic acid, which is the plant-source omega-3. This fatty acid must be modified in the body to the two longer omega-3 fats, EPA and DHA. You can consume those omega-3 fats directly from fish like salmon.
Many foods are high in fat, and most people consume much more than the small essential daily amount. Fat makes food taste good, and creates satiety. It also contributes calories. High fat foods are typically high calorie foods, since fat has more than twice the calories per gram as either protein or carbohydrate.
Unfortunately, when people eat too many calories, extra fat is stored. There is no way for the body to excrete excess calories or excess fat.
Recommended Dietary Allowances for Fats
Reference ranges for total fat intake (as percent of daily calories), and adequate intake for specific fatty acid types
Which Foods Are High Fat?
Foods may be naturally high fat, such as butter, or high fat due to preparation, such as fried food or high fat processed meat products like hot dogs.
Fat from animal-source foods can be high in saturated fat, which is linked to elevated blood cholesterol. Some plant foods, like coconut oil or certain nuts also contain significant saturated fat. But in general, plant fats are more unsaturated, meaning they will be liquid at room temperature. The more saturated the fat, the more solid it will be at room temperature.
Unsaturated fats can be chemically altered so that they are also solid at room temperature. While this process also protects the fats from going rancid, it results in what are called “trans” fats, a form that does not occur naturally. These are linked to increased risk for heart disease.
Many food manufacturers have changed how fats are handled to decrease or eliminate trans fats from their products. You can find information about trans fat content on food labels. In general, trans fats will not be present in any significant amount naturally. You will find them in commercial processed foods, such as stick margarine, deep fry oil or shortening and foods prepared with these fats.
Salad dressings (regular)
Nuts and nut butters
Milk and full fat dairy products like whole milk yogurt
Poultry (especially dark meat)
Which Foods Have Healthy Fat?
In general, healthy fat refers to unsaturated fats, such as the essential omega-3 and omega-6 fatty acids. The best sources of these are high fat plant foods like vegetable oils and nuts.
Other vegetable oils
Salad Dressings, especially oil-based vinaigrette varieties
What Happens If You Don’t Get Enough Fat?
Because the basic requirement for fatty acid intake is so modest, outright fatty acid deficiency is hard to find, except for extreme circumstances. People who were maintained on a fat-free tube feeding developed visible deficiency symptoms which include skin rashes and hair loss.
Deficiency in infants impacts growth. Starvation and famine also cause fatty acid deficiency, along with many other deficiency and health problems. In severe cases of anorexia, the brain actually shrinks, due at least partially to inadequate fatty acid intake.
Current research is examining whether the recommendation for omega-3 intake is too low. Some experts suggest that a higher intake, especially of EPA and DHA, would lower disease risk. Heart disease, inflammation and other chronic diseases seem to have a link to omega-3 status, but so far studies haven’t clearly established what daily intake would improve health.
For most people, the problem with fat is excess intake, not deficiency. Fatty foods taste good. Because fat is a dense food, it’s easy to overeat fatty foods and consume excess calories, leading to weight gain. There’s no need to ban all fats from your diet. That wouldn’t be healthy.
The basic rule of thumb for fats should be to focus on healthy fats, avoid trans fats and limit the amount of total fat you consume.