Polyunsaturated Fatty Acids - What Are They?
Fats are essential to our bodies and cannot be completely removed from our diet. But too much fat or the wrong type of fat can be harmful to us, especially our hearts. However, there are “good” fats that offer health benefits.
All fats are made up of carbon and hydrogen atoms. The arrangement and the number of hydrogen atoms are what makes them “good” or “bad.” The good fats are called unsaturated fats, while bad fats are called saturated fats. Good fats have fewer hydrogen atoms than bad fats. Another difference that can be noticed is the state (liquid, solid, or gas) at which they are present at room temperature. Good fats are usually present in liquid form at room temperature and harden when chilled.
Polyunsaturated fatty acids or PUFA are a type of good fats. They are mostly found in plant-based oils like vegetable oils or seed oils, fatty fish, and nuts. There are two major classes of PUFA - omega-3 fatty acids and omega-6 fatty acids. Our body cannot produce these fats, and hence we must include them in our diet.
Is There A Relationship Between PUFA And Body Weight?
Omega-3 fatty acid: Animal studies reveal that omega-3 fatty acids (also known as n-3 PUFA) reduce body fat accumulation. Consumption of n-3 PUFA by pregnant and lactating women has a beneficial effect on birth weight and the growth of the infant. In studies that involved adult men and women, no significant gain in body weight was seen due to the consumption of omega-3 fatty acids. On the contrary, the same study observed weight loss in patients who were given fish oil.
Omega-6 fatty acid: For a long time in human history, there was a balance in omega-3 and omega-6 fatty acids consumption. Recently the intake of omega-6 fatty (also known as n-6 PUFA) acids has spiked up. A study showed that high omega-6 fatty acid intake induced weight gain in both animals and humans. The same study concluded that a high intake of n-6 PUFA during pregnancy resulted in fat accumulation across generations.
We need to ensure that we consume omega-3 and omega-6 fatty acids adequately. Neither of them should be ignored completely or over consumed. The ratio of consumption of omega-6 to omega-3 fatty acids must ideally be 1:1 (equal quantities of both).
However, recent studies that analyzed the intake levels revealed that an average American consumed omega fatty acids in the ratio of 17:1. This is extremely unhealthy and may put your health at risk by causing heart diseases and diabetes.
Importance Of Polyunsaturated Fatty Acids
Consuming PUFA instead of saturated or trans fat can have various health benefits:
- They help in maintaining the cholesterol levels in our body. Accumulation of bad cholesterol can lead to various heart diseases and strokes. PUFA consumption, at the recommended amount, can help reduce bad cholesterol and increase the amount of good cholesterol.
- They are a good source of vitamin E as well. Vitamin E helps us keep our skin and hair healthy. Moreover, studies have found that they help in hardening the arteries and improve our heart health.
Studies show that omega-3 and omega-6 fatty acids play a crucial role in the development and functioning of the brain. Any deficiency or imbalance in omega-3 fatty acids during the developmental or adulting phase can significantly affect brain function. Some of the brain disorders that are associated with a lack of omega-3 fatty acids include:
- Attention-deficit hyperactivity disorder (ADHD)
- Dyslexia
- Dyspraxia
- Autism spectrum disorders
Recommended PUFA Intake
According to the European Scientific Committee on Food (SCF), 2% of daily energy must be derived from omega-6 fatty (n-6 PUFA) acids, and 0.5% of total energy must come from omega-3 fatty acids (n-3 PUFA). This means a typical adult man must consume 6 g of PUFA per day with 5 g of n-6 PUFA and 1 g of n-3 PUFA. Whereas for a woman, the RDA (Recommended Dietary Allowance) is 8 g or PUFA per day - 6.4 g of n-6 PUFA and 1.6 g of n-3 PUFA.
The World Health Organization (WHO) recommends that over 2.5%-9% of the daily energy must be derived from omega-6 PUFA, and over 0.5%-2% of the daily energy must be derived from omega-3 PUFA.
This difference in the recommendation is attributed to the different nutritional goals of the two organizations. While the SCF focuses on correcting PUFA deficiency, the WHO recommends PUFA intake considering its benefits on brain and heart health
Genetics Behind PUFA Intake and Weight Gain
BDNF Gene
The BDNF gene encodes Brain-Derived Neurotrophic Factor, which is a protein found in the brain and spinal cord. This protein plays a role in the development, maturation, and maintenance of cells called neurons.
The BDNF protein is also specifically found in the regions of the brain that control eating, drinking, and body weight.
rs6265
rs6265, also known as Val66Met, is a Single Nucleotide Polymorphism (SNP) in the BDNF gene. A study carried out a detailed examination of eating behavior in persons with different Val66Met types (Val-Val or GG, Val-Met or AG, and Met-Met or AA). It was discovered that women with GG genotype had lower BMI and hip circumference than A allele carriers when on high-PUFA diet.
Effects of Excess PUFA Intake
Over-consumption of PUFA can lead to the following:
- Inflammation: Omega-6 fatty acids are pro-inflammatory; that is, they induce inflammation. While inflammation is our body’s natural response to injuries, it is also the root cause of obesity, diabetes, and heart diseases.
- Calorie buildup: In our bodies, one gram of fats provides us with nine calories - this is more than the calories provided by the other two macros (carbohydrates and protein) per gram. For this reason, even though PUFAs are healthy, it is important to stay within your calorie needs.
Apart from health risks, polyunsaturated fatty acids are generally unstable and get spoilt easily.
This is due to their chemical structures (that have double bonds). They react with the oxygen present in the surroundings, and this oxidized form of PUFA is unhealthy. They also smoke easily, and residuals of the smoke have been linked to neurological diseases and cancer in some animal studies.
Effects of PUFA Deficiency
Lack of adequate omega-3 fatty acids can cause:
- Fatigue and depression
- Poor memory
- Dry skin
- High blood pressure
- Susceptible to infections
Lack of omega-6 fatty acids in our diet can have a negative effect on our skin. A study from the University of Illinois found that omega-6 fatty acid is important for our skin. According to this study, a type of omega-6 acid (arachidonic acid) plays a role in the development of dermatitis (an itchy inflammation of the skin). The study observed that the absence of this acid in mice resulted in severe dermatitis, which could be reversed by feeding them with an omega-6-rich diet.
Dietary Sources Of PUFA
Maintaining a healthy ratio of omega-6 fatty acids and omega-3 fatty acids is important.
Plant Sources of Omega-3 Fatty Acids
- Flaxseeds
- Chia seeds
- Brussel sprouts
- Walnuts
- Hemp seed
- Algal oil
- Perilla oil
Animal Sources of Omega-3 Fatty Acids
- Mackerel
- Salmon
- Cod liver oil
- Oysters
- Anchovies
- Caviar
Plant Sources of Omega-6 Fatty Acids
- Safflower oil
- Tofu
- Peanut butter
- Avocado oil
- Almonds
- Cashews
Animal Sources of Omega-6 Fatty Acids
- Chicken
- Eggs
Summary
- Polyunsaturated fats (PUFAs) are a type of healthy fat that includes omega-3 and omega-6 fatty acids.
- PUFA is a brain-food that is involved in regulating the development and functioning of the brain.
- A region, rs6525 in the BDNF gene regulates your weight on PUFA intake - people with the AA type of rs6525 tend to have a lower BMI on PUDA intake than the AG and GG types.
- Some recommended food sources of PUFA include flaxseeds, tofu, and seafood.
References
https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good
https://www.healthline.com/health/all-about-vitamin-e#more-research
https://pubmed.ncbi.nlm.nih.gov/19672626/
https://pubmed.ncbi.nlm.nih.gov/22591885/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808858/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3335257/
https://en.wikipedia.org/wiki/Brain-derived_neurotrophic_factor
https://pubmed.ncbi.nlm.nih.gov/16707914/
https://www.ncbi.nlm.nih.gov/pubmed/29610056
https://pubmed.ncbi.nlm.nih.gov/23527564/
https://pubmed.ncbi.nlm.nih.gov/19925718/
https://www.sciencedaily.com/releases/2010/04/100412121022.htm
