The Truth About Fats: Unfiltered!

By Fayyaz Alam Coconut, Cod-liver, Cold-pressed, Fats, Hemp Seed, Hydrogenation, Krill Oil, Olive, Saturated Fat, Unsaturated Fat 0 Comments Like: 0

With so many standpoints on dietary fats going around these days, it can be difficult to make sense of truth and myth about fats. Fat is an integral part of any animal’s survival and plays an important role in the body’s energy supply. Fat even helps to keep the membranes of our cells intact.^1,2 Recent surveys in the United States have shown that around 95% of the population surveyed know the importance of getting enough vitamins in their diets. However, only 41% knew that certain fats are essential nutrients.³Diets during the 1980s promoted low-fat diets, using research of the time to state that fat is bad.³ There are many new research available to prove the opposite, but convincing the consumer still seems to be the hardest task.

So why is fat still getting a bad rap, and why are some healthcare organizations singing its praises?¹ The answer to the question is easy. It’s all about the different types of fat. Once you learn which ones are good or bad for you, you will be amazed at how they can transform your overall health.

In this article we will look at the following aspects of dietary fats:

The good: unsaturated fats
The moderately good: saturated fats
The bad: trans fats

We will also look at what foods contain the highest concentrations of good fats and which foods you should avoid. The general rule is to go for organic, sustainably sourced, grass-fed, non-GMO sources.

Different types of fats

The chemical structure of fat consists of hydrogen atoms bonded to a chain of carbon atoms. The length and shape of the carbon chain and the number of hydrogen atoms bonded to it, is what gives each fat its different characteristics.²

Dietary fat recommendations according to the World Health Organization is about 20–35% of your total calorie intake.³Your fat intake can then be subdivided into amounts of the three different types of fats.

1. Unsaturated fat

Unsaturated fats are generally labelled as the good fats. They are predominantly present in the vegetables, fruits, nuts, seeds, and fish we consume. Unsaturated fats are usually liquid at room temperature (think olive oil) and have less hydrogen bonds than saturated fats.²

Unsaturated fats can be divided into two classes: 1) Monounsaturated fats (MUFAs), 2) Polyunsaturated fats (PUFAs).

MUFAs are present in foods like olive oil, peanut oil, canola oil, avocados and nuts. Studies have shown that daily avocado consumption by obese patients following cholesterol lowering diets had a reduction in their bad cholesterol levels.³ Oleic acid is one of the abundant MUFAs present in foods.

PUFAs are essential fats, necessary for bodily function. Because your body can’t make your own, you need to consume foods containing PUFAs.² PUFAs can further be divided into two types of fatty acids: omega-3 fatty acids and omega-6 fatty acids.

Omega-3 fatty acids²^,4
- Omega-3 fatty acids contain more than one double bond in their chemical structure.
- The most abundant omega-3 fatty acids found in foods are alpha-linoleic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)
- Present in foods like green leafy vegetables, chia seeds, flax seeds, oily fish, krill oil, walnuts, non-hydrogenated soybean oil
- EPA+DHA has proven effects on reducing cardio risk and daily recommended intake is 250–500 mg of combined intake
Omega-6 fatty acids²^,4,5
- Omega-6 fatty acids have more than one double bond in their chemical structure
- Humans tend to get enough omega-6 from their diets
- Types of omega-6 fatty acids include linoleic acid, arachidonic acid, gamma linoleic acid
- Foods high in omega-6 are safflower oil, non-hydrogenated soybean oil, walnuts, hemp seed oil, grapeseed oil, sesame oil, spirulina, poppy seeds

Dietary recommendations suggest that we should take a balanced intake of omega-6 and omega-3 oils, one study suggests lower the omega 6 to omega 3 ratio, the better. In fact, as low as 2:1. It is also recommended to substitute your bad fatty intake with good unsaturated fats.³^,4

Benefits of healthy unsaturated fats:

Lowers bad cholesterol
Boosts brain function
Has anti-inflammatory effects that helps to reduce pain in diseases like rheumatoid arthritis
Reduces blood pressure
Lowers risk of heart disease
Supports bone health
May fight symptoms of depression, ADHD, anxiety, Alzheimer’s
Can help prevent autoimmune disease
Can lower cancer risk
Help reduce menstrual pain

2. Saturated fat

Saturated fat is labelled the ‘in-between’ fat because of the controversy surrounding it. Saturated fat chains are straight and holds as many hydrogen atoms as possible.²^,8 This causes them to be solid at room temperature, like butter or animal fats. We get our saturated fats from foods like meat, dairy products and coconut oil.

So, what is the issue with saturated fats? In the early 1960s research evidenced that consuming too much saturated fats are one of the main causes of coronary heart disease and can considerably raise cholesterol. This is still reflected in the guidelines of official organizations today.¹ Dietary recommendations for saturated fats are between 5–10% of your total fat intake.¹^,2

However, new studies are working to debunk this theory.⁶^,7 A review of 21 previous studies showed that there are no actual raised CVD risks that can be contributed to healthy saturated fats.⁷ Another article in the British Journal for Sports Medicine has claimed that saturated fats do not clog arteries, and that coronary heart disease is an inflammatory disease where many other factors need to be considered.⁶ The studies do indicate that a diet high in saturated fats and refined and processed carbohydrates can increase your chances of heart disease, whereas a diet with moderate amounts of saturated fats and PUFAs can decrease it.⁷

Studies of the traditional diets of native Indian tribes and other tribes across the world by Weston A. Price, have shown that these tribes traditionally relied on diets high in saturated fats, whether derived from coconut oil (high in saturated fat) or animal or marine fats (moderate in saturated fats).⁸ The sources of fats were important – these tribes were hunter gatherers that ate only grazing (grass-fed) animals that were not affected by any harmful food processing or additives. The studies also show that once these tribes shifted to the American diet high in carbohydrates and trans fats, diseases like obesity and diabetes were quick to set in.⁹

The main types of saturated fats are stearic acid and palmitic acid. Some of the benefits of eating saturated fat includes keeping cell membrane integrity intact, aids calcium absorption for better bones, short and medium fatty acids have antimicrobial properties, enhance immune system and aids the absorption of omega-3 fatty acids.¹⁰

3. Trans fats

Trans fats are fats formed as the byproduct of hydrogenation. Hydrogenation is a process used to make good fats (plant fats) solid and more stable at room temperature. Trans fats have no health benefits, are extremely bad for you and have been recognized as unsafe in the United States.²Some animals are able to produce trans fats, but the amounts are miniscule compared to that found in processed trans fats.

Trans fats are used in mass produced confectionaries and fast foods (cookies, donuts, pizza, hamburgers, sweets). They can raise your bad cholesterol levels and reduce your good cholesterol. Trans fats are known for causing chronic inflammation in the body and attacks the good bacteria in your gut. This can raise your chance of developing autoimmune diseases, diabetes and chronic inflammatory conditions.²

Methods of extraction

The way a fat product is processed or extracted can have an effect on its benefits and nutrients. For instance, when healthy unsaturated oils are heated for cooking, they lose their beneficial properties and produce free radicals that causes oxidative stress in the body.¹⁰

Cold-pressed

Extraction methods that damage the carbon bonds in the oil, making them loose their beneficial properties and harmful for consumption, are those used in mass production. This includes extraction by crushing and heating the oils, and further extraction using harmful hexane as a solvent.¹⁰

The safest method of extraction is the expeller-pressed method or the cold-pressed method. Where low to medium is used for oil extraction and as well in the case of cooking. These oils should remain in darkly colored bottles to stop them from oxidizing.¹⁰

General rule is smoke-point. If a given oil reaches to a level of smoke, then rancidity and toxicity and nutrient degradation becomes an issue. Use of appropriate oil dependent on the type of cooking is extremely important.

Hydrogenation

Soluble plant oils are turned into solid forms like margarine using hydrogenation. Cheaper, GMO produced plant oils are used (soy, canola) and additives like metal particles, emulsifiers, bleaches are added during the process to force the oils into solid form and to resemble the look and feel of butter. Products containing large amounts of hydrogenated fats are unhealthy and can be harmful to your health.¹⁰

Three main sources of fat

Overly processed vegetable oils, too much omega-6 from grain-fed chicken eggs and farmed fish, GMO grain-fed animal meat are all examples of good fats having their beneficial health properties reduced, and denatured. This can be harmful to your health.¹⁰ Always opt for organic, grass-fed, free range, sustainably caught and mercury-free sources of fats to gain all their health benefits.

1. Plant fats

Olive oil

Olive oil is one of the healthiest plant fats (MUFAs). Evidence has shown that daily intake of olive oil (non-heated extra virgin) can significantly reduce your chances of heart disease, lower bad cholesterol and blood pressure.³^,4,11 Olive oil has been present in the diet of Mediterranean countries for centuries. The Mediterranean diet is one of the healthiest diet plans to follow, and is high in fresh fruits and vegetables, plant-based oils and low in carbohydrates.⁴

Olive oil contains 75% monosaturated fat, 13% saturated fat, 10% omega-6 and 2% omega-3.¹⁰ Olive oil is rich in vitamin E and vitamin K and contains phytonutrients that gives it antioxidant effects.

Always buy pure, cold-pressed virgin olive oil. Do not buy olive oil blends or non-virgin as it may lack the nutritional benefits.

Black seed oil

Black seed oil is extracted from black cumin seeds (nigella sativa) and has been studied widely for is health benefits. Black seed oil has anti-inflammatory, anti-cancer, antibacterial and antioxidant properties and can be used in a wide variety of disease areas such as rheumatoid arthritis, diabetes, asthma and cancer.¹²

Black seed oil is high in vitamin E, unsaturated fats like linoleic an oleic acids, and contains palmitic acid (saturated fat).¹³ It also contains active phytochemical compounds, thymol, thymoquinone and thymohydroquinone, that gives the oil its potent anti-inflammatory, anticancer and antibacterial properties.¹²^,13 The benefits of these phytochemicals coupled with the health benefits of unsaturated plant fats, makes this one of the healthiest oils to consume.

Hemp seed oil

Hemp seed oil is extracted from the small seeds of the Cannabis Sativa plant. Hemp oil is high in PUFAs with a good balance of omega-6 and omega-3 fatty acids.¹⁴ It is also widely used in cosmetic products. The quality of hemp seed oil differs depending on the strains used, extraction method and if it is non-organic.¹⁴

Hemp seed oil also contains protein (all 20 amino acids), dietary fiber, vitamins and minerals and has recently been identified as a functional food.¹⁵

Benefits:

Helps with arthritis and joint pain
Can help with dermatological conditions like acne, eczema
Fights heart disease
Can help you lose weight
Reduces inflammation
Beneficial for hair and nails
Excellent skin emollient

Coconut oil

Coconut oil is rich in medium chain fatty acids and is one of the plant oils with the highest concentration of saturated fats, 82%. It is safe to cook with and easy to digest. The medium fatty acid chains allow it to be converted to energy, not fat, and can be used immediately.¹⁰

Coconut oil contains lauric acid, the same type of fatty acid found in breast milk and has antifungal and antimicrobial properties. Studies have proven that the saturated fat content in coconut oil actually raises good cholesterol levels and can benefit heart health.¹⁶

Other benefits of coconut oil include boosting brain function, anti-inflammatory, helps you to feel fuller, aids weight loss.

Make sure you buy coconut oil that are expeller or cold pressed and usually have the term ‘virgin’ or ‘extra virgin’ on the label. Products that do not state this are mass manufactured and refined and does not contain all the nutrients and benefits of coconut oil. Be especially careful not to buy products that contain hydrogenated or refined coconut oils as they can be harmful to your health.¹⁷

Plant oils to avoid: Unfortunately, plant oils that are mass produced using cheap GMO crops and harmful production methods are all around us. Be on the lookout for products containing canola, soy, sunflower or peanut oils as these are plant oils that are usually refined and possibly GMO-based. While these fats/oils are useful and beneficial in their own right, read your labels and evaluate your trust in the given manufacturer. Always buy organic, cold or expeller pressed oils, when possible.

2. Animal fats

Grass-fed butter products

Butter, ghee and butter oil are products made from dairy. They are high in essential fatty acids (omega-3 and omega-6), contain saturated fats and fat-soluble vitamin A, D, K and E.¹⁰ Ancestral diets show that people made their own butter from the milk of cows grazing on green grass. The product produced is a rich yellow color packed with nutrients.¹⁰ Research has shown that the high concentration of fat-soluble vitamins in butter help build healthy bones and teeth.¹⁰

The saturated oils in butter are short to medium chain fatty acids. This means that they are ready to use as energy and does not get stored away as fat. These types of fatty acids are known to support the immune system and has anti-inflammatory, antimicrobial and antitumor properties.¹⁰

Ghee (clarified butter) and butter oil are products produced when the milk proteins are removed by simmering the butter and bringing it up to smoking point. These products are a good alternative for people with lactose or casein allergies.¹⁰

Because of butter’s low melting point, it’s best not to use it for cooking. Rather use it as a spread. Meanwhile, ghee can used for high heat cooking, such as searing a steak.

Butter from GMO-fed confined animals will not have the same quality nutrients of those from animals grazing on grass. Confined animals are also injected with antibiotics and release stress hormones. Environmental toxins, toxins on grains and in water are also picked up by the animals. These toxins can contaminate meat and dairy products the animals produce, and are then ingested by humans, causing harm within our bodies.¹⁰

Grass-fed tallow and suet

Tallow is rendered fat that comes from slow cooking a piece of meat and leaving it to harden afterwards. Suet is raw hard fat that comes from beef or mutton. These fats are very stable and can be heated to high temperatures, which make them great for cooking. Tallow is about 55% saturated fat and 40% MUFAs, and suet contains up to 80% saturated fat.¹⁰ Traditionally these products were used for frying and baking and nomadic tribes valued them for their health benefits (fat-soluble vitamins) and energy properties.¹⁰

Tallow and suet are affected by the same environmental concerns as mentioned above for butter. Make sure you buy grass-fed products, or render your own tallow using organic grass-fed meat.

Pasture raised duck and chicken fat

Chicken, duck and goose fats are another source of healthy animal saturated fats. The important point here is to make sure the chicken and duck you buy are free range and pasture raised.

Chicken and duck have relatively balanced profiles of saturated fats, MUFAs and PUFAs, with duck slightly lower in PUFAs. The omega-3 content can actually be raised if you feed your chickens some flaxseeds or fish meal.¹⁰

3. Marine fats

Fish oils

Fatty fish species are known to be good sources of long chain omega-3 fatty acids. This include fish like wild caught salmon, tuna, mackerel, sardines, herring and anchovies. Fish oils are especially high in EPA and DHA.¹⁸ Fish oil comes with all the benefits of omega-3 like lowered cholesterol, lowered heart disease risk, protection against neurodegenerative diseases, anti-inflammatory effects and more.¹⁹

What about farmed fish and mercury content?

The problem with eating fish and fish oil supplements is that it can be contaminated with environmental toxins and waste products present in the ocean. One of the biggest concerns is mercury content as it can be highly neuro-, cardio- and immunotoxic.²⁰Mercury is converted into methylmercury and fish can ingest this when they eat plants, other fish and by just passing the water through their gills. The mercury levels start to build up in their flesh but does not affect them. Fish and fish oils produced from sources contaminated with mercury can be dangerous for consumption.²⁰

Consumption of farmed fish is another ongoing debate. Commercial fishing productions are stripping our ocean stocks, so fish farms seem like a logical solution. However, as with any mass-produced food supply, it comes with negatives such as crowded living conditions for the fish and antibiotic use to control parasites. Farmed fish are fed GMO corn and soy, and this can reduce the amount of omega-3 fatty acids present in the fish. They can also spread disease and antibiotic resistance to wild fish populations if they manage to escape.

What is the solution?

Source your fish from sustainable wild sources and opt for fish supplements where the manufacture has labelled it as mercury-free. Most reputable supplement companies will try to remove traces of mercury from their fish oils. If you decide to eat farmed fish, make sure you know the origin of the farm and if it is a humane and eco-friendly establishment, that use organic and non-gmo feed.

Cod-liver oil

Cod liver oil is one of the oldest fish-derived omega-3 sources around. People in the Northern countries have been using it for centuries against the cold, dark winters and achy body pains.²¹ Cod liver oil is high in DHA and EPA fatty acids, and fat-soluble vitamin D and vitamin A. It’s the high vitamin D concentration that makes it stand out against other fish oils, and it is still regarded as one of the best vitamin D sources today.²²

Benefits of cod liver oil:^22,23

High omega-3 content makes it anti-inflammatory
Helps against the development of Rickets in children
Can reduce chronic pain and rheumatoid arthritis symptoms
The high concentration of vitamin A can help fight eye diseases like glaucoma

Krill oil

Krill oil is a marine oil derived from small shrimp-like crustaceans. It has similar benefits to fish oil, but is seen as a more sustainable, bioavailable and less toxic source of healthy omega-3.²⁴ Krill is also high in healthy protein, low in fat and has higher antioxidant levels than fish.²⁵ The main fat composition of krill is high in PUFAs and lower in MUFAs and saturated fats.

Main differences between the benefits of krill oil and fish oil:^24,25

Krill is available in all oceans worldwide and is easy to harvest in large quantities
Krill is a sustainable source of omega-3 fatty acids
Krill contains astaxanthin, a potent carotenoid-type antioxidant that can help fight chronic inflammation
Krill contains phospholipid-derived fatty acids that can cause a more potent delivery of EPA and DPA because of increased absorption
Krill oil soft gels are smaller and easier to swallow
The mercury and heavy metal content of krill oil is much lower than that of fish. Krill is at the bottom of the food chain, so they are not alive long enough to accumulate mercury in their systems and they live from algae, not other fish.
Krill contains higher vitamin A, vitamin E, vitamin B12 and folate concentrations than fish

There are some instances where fish oil may have a benefit over krill oil. The potency and nutritional value of krill oil can vary depending on the time and location of the harvest, so all krill oil supplements are not equal.²⁴ Krill oil capsules may be easier to swallow because of their size, but this means they contain a lower dose of omega-3 compared to fish oil soft gels.²⁴ Krill oil formulations can also be more expensive than fish oil formulations. If you have a shellfish allergy, you should avoid using krill oil supplements.

Conclusion

Unsaturated fats from plant and fish sources are healthy and have proven cardiovascular, neurological and anti-inflammatory benefits
Saturated fats sourced from grass-fed organic sources are healthy and contains essential fat-soluble vitamins
Fats are extremely important for hormone regulation and specifically testosterone production
Trans fats should be avoided
A healthy diet consists of unsaturated fats, saturated fats from both plants and animals, contains no trans fats, with moderate protein and healthy carbohydrate intake
Sources and methods of fat production have an influence on their nutritional profile and pay attention to smoke-points and cooking method
Always looked for virgin, cold or expeller pressed, grass-fed and free-range sources
Krill oil can be used as an alternative to fish oils to avoid mercury intake and the benefit of antioxidant, astaxanthin

References:

American Heart Association (2019). Dietary Fats. [online] www.heart.org. Available at: https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/dietary-fats [Accessed 17 Nov. 2019].
Harvard Publishing (2019). The truth about fats: the good, the bad, and the in-between – Harvard Health. [online] Harvard Health. Available at: https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good [Accessed 17 Nov. 2019].
Liu, A. G., Ford, N. A., Hu, F. B., Zelman, K. M., Mozaffarian, D., & Kris-Etherton, P. M. (2017). A healthy approach to dietary fats: understanding the science and taking action to reduce consumer confusion. Nutrition journal, 16(1), 53. doi:10.1186/s12937-017-0271-4 Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577766/ [Accessed: 17 Nov. 2019].
Kris-Etherton, P. M., & Fleming, J. A. (2015). Emerging nutrition science on fatty acids and cardiovascular disease: nutritionists’ perspectives. Advances in nutrition (Bethesda, Md.), 6(3), 326S–37S. doi:10.3945/an.114.006981. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4424771/ [Accessed: 17 Nov. 2019].
Food Data Central (2019). Foods highest in total omega-6 fatty acids. Food Data Central. Available at: https://nutritiondata.self.com/foods-000141000000000000000-w.html [Accessed 18 Nov. 2019].
Malhotra, A., Redberg, R. and Meier, P. (2017). Saturated fat does not clog the arteries: coronary heart disease is a chronic inflammatory condition, the risk of which can be effectively reduced from healthy lifestyle interventions. [online] British Journal of Sports Medicine. Available at: https://bjsm.bmj.com/content/51/15/1111 [Accessed 17 Nov. 2019]. sat fat not clogging
Siri-Tarino, P., Sun, Q., Hu, F. and Krauss, R. (2010). Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. The American Journal of Clinical Nutrition, [online] 91(3), pp.535-546. Available at: https://academic.oup.com/ajcn/article/91/3/535/4597110 [Accessed 18 Nov. 2019].
Masterjohn, C. (2016). Saturated Fat Does a Body Good – The Weston A. Price Foundation. [online] The Weston A. Price Foundation. Available at: https://www.westonaprice.org/health-topics/abcs-of-nutrition/saturated-fat-body-good/ [Accessed 18 Nov. 2019].
Fallon, S. and Enig, M. (2000). Guts and Grease: The Diet of Native Americans – The Weston A. Price Foundation. [online] The Weston A. Price Foundation. Available at: https://www.westonaprice.org/health-topics/traditional-diets/guts-and-grease-the-diet-of-native-americans/ [Accessed 18 Nov. 2019].
Enig, M. and Fallon, S. (2019). The Skinny on Fats – The Weston A. Price Foundation. [online] The Weston A. Price Foundation. Available at: https://www.westonaprice.org/health-topics/know-your-fats/the-skinny-on-fats/ [Accessed 18 Nov. 2019].
Forouhi, N. G., Krauss, R. M., Taubes, G., & Willett, W. (2018). Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ (Clinical research ed.), 361, k2139. doi:10.1136/bmj.k2139. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6053258/ [Accessed: 18 Nov. 2019].
Woo CC et al. (2012). Abstract: Thymoquinone: potential cure for inflammatory disorders and cancer. – PubMed – NCBI. [online] Ncbi.nlm.nih.gov. Available at: https://www.ncbi.nlm.nih.gov/pubmed/22005518 [Accessed 18 Nov. 2019].
Nasuti, C., Fedeli, D., Bordoni, L., Piangerelli, M., Servili, M., Selvaggini, R., & Gabbianelli, R. (2019). Anti-Inflammatory, Anti-Arthritic and Anti-Nociceptive Activities of Nigella sativa Oil in a Rat Model of Arthritis. Antioxidants (Basel, Switzerland), 8(9), 342. doi:10.3390/antiox8090342. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6769720/ [Accessed: 18 Nov. 2019].
Citti, C., Linciano, P., Panseri, S., Vezzalini, F., Forni, F., Vandelli, M. A., & Cannazza, G. (2019). Cannabinoid Profiling of Hemp Seed Oil by Liquid Chromatography Coupled to High-Resolution Mass Spectrometry. Frontiers in plant science, 10, 120. doi:10.3389/fpls.2019.00120. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6381057/ [Accessed: 18 Nov. 2019].
Callaway, J. (2004). Hempseed as a nutritional resource: An overview. [online] Available at: https://link.springer.com/article/10.1007%2Fs10681-004-4811-6 [Accessed 18 Nov. 2019].
Hayes, J., & Benson, G. (2016). What the Latest Evidence Tells Us About Fat and Cardiovascular Health. Diabetes spectrum : a publication of the American Diabetes Association, 29(3), 171–175. doi:10.2337/diaspect.29.3.171. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5001225/ [Accessed: 18 Nov. 2019].
Harvard TH Chan (2019). Coconut Oil. [online] The Nutrition Source. Available at: https://www.hsph.harvard.edu/nutritionsource/food-features/coconut-oil/ [Accessed 18 Nov. 2019].
Goel, A., Pothineni, N. V., Singhal, M., Paydak, H., Saldeen, T., & Mehta, J. L. (2018). Fish, Fish Oils and Cardioprotection: Promise or Fish Tale?. International journal of molecular sciences, 19(12), 3703. doi:10.3390/ijms19123703. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6321588/ [Accessed: 18 Nov. 2019].
de Magalhães, J. P., Müller, M., Rainger, G. E., & Steegenga, W. (2016). Fish oil supplements, longevity and aging. Aging, 8(8), 1578–1582. doi:10.18632/aging.101021. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5032683/ [Accessed: 18 Nov. 2019].
Gribble, M. O., Karimi, R., Feingold, B. J., Nyland, J. F., O’Hara, T. M., Gladyshev, M. I., & Chen, C. Y. (2016). Mercury, selenium and fish oils in marine food webs and implications for human health. Journal of the Marine Biological Association of the United Kingdom. Marine Biological Association of the United Kingdom, 96(1), 43–59. doi:10.1017/S0025315415001356. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4720108/ [Accessed: 18 Nov. 2019]
Griffing G. T. (2008). Mother was right about cod liver oil. Medscape journal of medicine, 10(1), 8. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258476/ [Accessed: 18 Nov. 2019].
Ross, C. (2005). Fish Oil versus Cod Liver Oil: Is Vitamin D a Reason to Go Back to the Future. The Journal of the American Board of Family Medicine, [online] 18(5), pp.445-446. Available at: https://www.jabfm.org/content/18/5/445.1.long [Accessed 18 Nov. 2019].
Huang, W. B., Fan, Q., & Zhang, X. L. (2011). Cod liver oil: a potential protective supplement for human glaucoma. International journal of ophthalmology, 4(6), 648–651. doi:10.3980/j.issn.2222-3959.2011.06.15. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3340802/ [Accessed: 18 Nov. 2019].
Backes, J. M., & Howard, P. A. (2014). Krill oil for cardiovascular risk prevention: is it for real?. Hospital pharmacy, 49(10), 907–912. doi:10.1310/hpj4910-907. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4252213/ [Accessed: 18 Nov. 2019].
Tou, J., Jaczynski, J. and Chen, Y. (2008). Krill for Human Consumption: Nutritional Value and Potential Health Benefits. Nutrition Reviews, [online] 65(2), pp.63-77. Available at: https://academic.oup.com/nutritionreviews/article/65/2/63/1878678 [Accessed 18 Nov. 2019].