Fats and Oil

Fat is one of the three main energy sources, along with carbohydrate and protein. Fats are also essential for organs to maintain and develop normal functions. In American diet, most fats consumed are added in the cooking process.

All fats including oils and solid fats are a mixture of fatty acids. Oils specially refer to the fats are liquid at room temperature, such as vegetable oils, peanut oils, and fish oils.  Solid fats refer to the fats that are solid at room temperature, such as beef fat, butter, and shortening. 

Types of fatty acids

There are 3 types of fatty acids: saturated, unsaturated, and trans. When consuming fats, we prefer unsaturated to saturated and want to avoid trans.

  • Unsaturated fats are healthy fats. Scientific researches have confirmed the benefits of unsaturated fatty acids on heart disease, diabetes, cancer, inflammatory conditions, fetus and infant development, reproductive health, and cognitive functions.
  • Saturated fats are neutral fats. They don’t provide protective benefits like unsaturated fatty acids and are not harmful like trans-fats.
  • Trans-fats are bad fats. Scientific studies have linked trans-fats to heart disease, type 2 diabetes, and pro-inflammatory states.  Infertility is also found to associate with trans-fats intake.

Unsaturated fatty acids

Unsaturated fatty acids include monounsaturated and polyunsaturated fats. We have discussed mono-unsaturated fats in Fruits and Vegetables. Most studied beneficial polyunsaturated fatty acids are Omega-3 and Omega-6.


Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA) and alpha-linolenic acid (ALA) are major forms of Omega-3 fatty acids in human body. All 3 forms of omega-3 play important roles in the maintenance of optimal health. EPA and DHA are long chain unsaturated fatty acids, which long been known to support brain functions and neurodevelopment, boost immune system, reduce the risk of heart disease and cancer. ALA, a short chain unsaturated fatty acid, is a precursor to EPA and DHA.

Human reproductive health has a close relation to Omega-3

Long chain omega-3 fatty acids could promote male fertility. A study of fatty acid composition in sperm found that sperm carries high concentration of DHA; normal sperms with higher fertility ability contain a higher level of DHA than unhealthy sperms, suggesting that DHA are important for the viability, maturity, and functional characteristics of sperm. A study evaluated polyunsaturated fatty acid (PUFA) composition of the blood plasma and spermatozoa in infertile men with idiopathic oligoasthenoteratozoospermia and found that fertile men have higher blood and spermatozoa levels of omega-3 compared with the infertile male.

Besides the benefits for male fertility, long chain omega-3 intake may boost female reproductive health.  A 2012 study demonstrated significant positive associations between omega-3 Long chain PUFA intake and women hormone levels, number of follicles and embryo morphology. Furthermore, a 2017 study tested fatty acids levels in serum for infertile women before intracytoplasmic sperm injection, and found the patients became pregnant had higher unsaturated fatty acids and omega-3 fatty acid than others.

Long chain omega-3s are beneficial for fetus development and pregnancy health. Omega-3 is a critical component of brain and is crucial for neurodevelopment of fetus. Numerous studies have also shown that getting enough omega-3 reduces the risk of early preterm delivery, one of the leading causes of infant mortality worldwide. Similarly, recent research found the live birth rate for assisted reproduction has a positive relation to serum levels of DHA+EPA.

Long chain omega-3 is helpful for mental health, which is important for reproductive health. DHA is found in high concentrations in the nervous system and the brain. One research studied associations between dietary omega 3 intake and depression. Dietary EPA+DHA intake was significantly associated with fewer depressive symptoms, which is a common symptom of pregnancy and postnatal period. 

Short chain omega-3 – alpha-linolenic acid (ALA) does not provide much health benefits like the long chain omega-3s. In opposite, elevated ALA intake was found to associate negatively with women reproductive health in one study.  It is crucial to keep balanced omega-3 levels in the body.

Plant omega-3 vs animal omega-3

Omega-3 are available in both plant-based and animal-based foods. However, it is important to realize that omega-3s from these two different sources are not interchangeable.

Although ALA can be converted to EPA and DHA, the conversions are greatly limited in the human body (conversion rates are less than 10%). It is important to consume sufficient DHA and EPA from food and/or supplements. Both animal-based and plant-based foods are good sources of ALA, but EPA and DHA mainly exist in animal-based food sources. Including animal-based foods in the diet is necessary to maintain healthy EPA and DHA levels. 

Getting adequate dietary long chain omega-3

Scientific researches discussed above illustrate the importance of omega-3, but most of American do not get enough omega-3 through diet source. The fats American consume are mostly from the oils and fats added in the cooking process, most of which contain no or low level of long chain omega-3.

Fish and fish oils are the best food sources of long chain omega-3 especially DHA and EPA. USDA recommends consuming 2 servings of fish every week. According to USDA National Nutrient Database for Standard Reference Release 28, Mackerel, roe, shad, salmon, sablefish, whitefish, anchovy, and tuna contain high levels of omega-3.

To be continued

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