Saturated fat, as an all-inclusive category, has not yet been shown to beneficially or adversely affect heart health. That being said, polyunsaturated and monounsaturated have been shown to improve heart health. So saturated fats are worse relative to the unsaturated fats, but they are not bad at all.
All major studies on saturated fats merely look at what people ingest, which are common long chain saturated fats through common foods. It is wholly possible that some saturated fats can be beneficial for heart disease prevention and this just wouldn't show when you ask people what they eat (due to, say, low consumption of coconut oil in society)
A saturation of a fatty acid (saturated, unsaturated, polyunsaturated) simply refers to how many double bonds are in the fatty acid chain. Saturated fatty acids are 'saturated' with hydrogen atoms (and have no double bonds) whereas monounsaturated have one double bond and polyunsaturated have many.
As a class, saturated fatty acids are straight chain (as double bonds bend the structure).
Since the only factor that can distinguish one saturated fat from another is the length of the side chain, there are a limited amount of them. They tend to be grouped in accordance to whether their side chain is 'short', 'medium', 'long' or 'very long' in a somewhat arbitrary manner.
Short Chain are:
Some saturated fats may have different effects than other saturated fats, like like how some polunsaturated fats (omega3) have different effects than other polyunsaturated fats (omega6). Since 'saturated fat' is a category, it is difficult to make an ultimate conclusion that applies to all saturated fats.
Saturated fat is most looked at, in regards to health, for its influence on heart disease through interacting with cholesterol and plasma triglycerides.
Several meta-analysis have been conducted on saturated fat and risk of heart health.
Looking at reviews and meta-analysis' of controlled trials, there does not seem to be much evidence that saturated fat increases risk for Cardiovascular Diseases. However, replacing some saturated fat with polyunsaturated may reduce risk.
Ones on epidemiology find relative risk ratios (RRs) very close to a value of 1, which is no effect; this suggests that there doesn't seem to be a strong relationship between saturated fat intake and risk for various conditions such as Cardiovascular Disease, Stroke, and Coronary Heart Disease. The last study there has had its statistical analysis criticized, however.
Saturated fats do increase cholesterol levels relative to polyunsaturated fats. It should be noted that in any study done on macronutrients (fat, carbs, or protein) removal of a macronutrient must be met with inclusion of another in order to balance calories out. Many studies replace saturated fats with polyunsaturated fats, which tend to reduce cholesterol and triglyceride levels. This may lead to the conclusion that saturated fats raise them, when the possibility that they are inert is viable.
Diets high in monounsaturated fats also tend to be beneficial for certain parameters of heart health.
It should be noted that causation has not yet been placed on cholesterol for causing heart problems, it is definitely correlated, with the ratio of HDL cholesterol to Total cholesterol being the strongest predictor.
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