A diet that includes excess amounts of fat is one of the major causes of disease and premature death in modern societies. High fat intake is being associated with the current epidemic levels of CVD, stroke, diabetes, and several types of cancer (breast, prostate, colon). There are also fats that are essential for good health, the essential fatty acids. Thus, a healthy diet must contain adequate amounts of the essential fatty acids while still avoiding excess fat intake.

Fat is in itself not bad; it depends on the source. Fat from whole plant foods like avocados, nuts, and seeds are considered healthy sources of fat as they come together in a package with vitamins, minerals, fibre, antioxidants, and other beneficial nutrients, that can neutralize the harmful effects of fat.

Oils are refined fats stripped from most other nutrients, and even unrefined, cold-pressed, organic oils pale in comparison to the whole foods from which they are extracted in nutritional value. Oils are very high in calories without adding volume to a meal. One tablespoon of oil contains 120 Calories, which will not fill your stomach. Therefore, oils make it very easy to overconsume calories, leading to weight gain.

Oils or fats used for frying also tend to go rancid. Rancidity is the natural spoilage of fats that occurs under the influence of heat, moisture, oxygen and bacteria. When oils become rancid, the triglycerides are broken down, which creates undesirable flavours and free radicals that can cause cell damage. Stripped from the antioxidants of the whole food that can neutralize these free radicals, frying oils are strongly linked to adverse health effects.

Other types of fat strongly linked to adverse effects are trans-fat and saturated fat, the healthier choices being mono- and poly-unsaturated fats. All oils and fats are a mixture of saturated and unsaturated fats. Whereas animal foods generally have a higher proportion of saturated fat, plant foods are higher in unsaturated fats.

Trans-fat

Trans-fats are a type of fat found in processed foods and meat and milk from ruminant animals (cows, sheep, goats). Hydrogenation is the process used by the industry to turn liquid oils into solid, spreadable fat. This process also increases the shelf-life, but trans-fats are also created. These products were developed to replace butter, which is high in saturated fat, but it turned out that these trans-fats were even worse for our health than the butter they were trying to replace.

Industrial trans-fats are now being phased out, with governments putting regulations in place limiting the amount of trans-fat a processed food may contain. Before, around 80% of the trans-fat in our diet came from these industrial trans-fats. While these are phased out, our diet’s primary source of trans fat is meat and milk from ruminant animals. On average, 5% of the fat content from these products is trans-fat. These trans-fats have a similar detrimental effect on our health as the industrial ones.

Saturated fat

A diet high in saturated fat is almost always high in animal-derived foods, as these are the primary source of saturated fat. The other main source are tropical oils made from coconut or palm kernel trees. All foods naturally containing fat have some saturated fats, the richest sources being eggs and full-fat dairy products such as butter and cheese.

There is strong evidence that saturated fat raises your blood cholesterol and leads to atherosclerosis. Saturated fat is also associated with insulin resistance, inflammation, and several cancers. There is much debate about the leading cause of the adverse health effects of animal-derived foods, saturated fat, or animal protein.

Fatty acids can be defined according to the length of their fatty acid chain. There are short-chain fatty acids produced by our beneficial gut bacteria, with a chain length of no longer than five fatty acids. Medium-chain fatty acids have a length of 6-10 fatty acids, and long-chain fatty acids are longer than 10. Short and medium-chain fatty acids are directly absorbed into your bloodstream using the same pathway as most other nutrients. Long-chain fatty acids are first broken down before being absorbed and reassembled into triglycerides, which are coated with cholesterol and protein to form chylomicrons. Long-chain fatty acids are the most abundant fatty acids in our diet. These fat particles go first through the lymphatic system and enter the bloodstream in the heart region. Triglycerides are three fatty acids bound to a glycerol backbone, the main configuration of fat found in plants and animals, stored in adipose tissue, and circulating through the bloodstream.

The medium-chain saturated fatty acid with a chain length of 12 carbons, lauric acid, can either be classified as a medium- or a long-chain fatty acid. Medium-chain fatty acids are more soluble in water, which is why they get absorbed faster from the digestive tract. This stark difference in solubility occurs at chain lengths of 10 or less, excluding lauric acid. Consequently, around three-quarters of lauric acid is absorbed with chylomicrons, similarly to long-chain fatty acids.

Lauric acid is the most prevalent fatty acid in coconut oil, accounting for about half of the fatty acids in coconut oil. This has fuelled numerous claims that coconut oil is healthy and can reduce risk factors for cardiovascular disease. However, most lauric acid behaves as a long-chain fatty acid, and the medium-chain fatty acids with a chain length below ten only make up about 10% of coconut oil. Therefore, this tropical oil is a source of saturated fat that cannot be viewed differently from other sources of saturated fat, with similar detrimental effects.

When coconut products that contain fibre, such as coconut flour and coconut flesh, are consumed in an overall healthy dietary pattern, they do not pose a risk for heart disease. In contrast, using coconut oil as the primary source of fat in a typical Western diet produces effects similar to those of other saturated fats.