Healthy Fats: Types, Seed Oils and Best Sources

Written by Dr. Ryan Kneessi, ND

Quick answer: Fats store energy, help absorb vitamins A, D, E and K, make hormones, build cell membranes and support the brain. Quality matters: emphasize monounsaturated fats and omega-3s from olive oil, avocado, nuts and fatty fish, enjoy whole-food saturated fats in moderation, avoid trans fats, and limit processed foods made with refined seed oils.

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Key takeaways

Dietary fat is needed to absorb vitamins A, D, E and K and to build hormones, cell membranes and brain tissue.

The article favors whole-food fats such as olive oil, avocado, nuts and fatty fish over the refined seed oils common in packaged foods.

Omega-3 fats are built into brain and cell membranes and help the body resolve inflammation.

What fats do

Fats provide energy storage and help the body absorb vitamins A, D, E and K. They are needed for hormone production, cell membrane structure, and brain development and function, and they supply essential fatty acids (omega-3 and omega-6) that we must get from food.

Types of fat

Saturated fats

Found in meat, butter, cheese and coconut oil. Research on heart health is mixed; enjoy whole-food sources in moderation and monitor your cholesterol.

Monounsaturated fats

Olive oil, avocado and many nuts.

Polyunsaturated fats

Omega-3s (fatty fish, flax, walnuts) and omega-6s (seeds, many oils). Modern diets tend to be high in omega-6 and low in omega-3.

Trans fats

Artificial trans fats are linked with higher heart disease risk; avoid them.

Seed oils

Refined seed oils are common in fried and packaged foods. I recommend limiting the processed foods that rely on them and cooking with olive oil, avocado oil, ghee or butter.

How much fat?

Needs vary with your overall diet and goals. These ranges are general education, not a prescription; personalize them with your provider.

Best sources

Fatty fish: wild salmon, mackerel, sardines, herring
Pasture-raised eggs and grass-fed meats
Nuts and seeds: walnuts, flax, chia, pumpkin seeds
Olive oil and avocado
Ghee, grass-fed butter and coconut oil for cooking

Healthy aging lens

Omega-3s are built into brain and cell membranes and help resolve inflammation. See diet and inflammation and foods to eat.

When to see a naturopathic doctor

It may be time to see a naturopathic doctor if you have a chronic inflammatory, autoimmune or digestive condition, or if you have diabetes, kidney disease or take medications affected by diet changes. The same is true if you are pregnant, breastfeeding, or have a history of disordered eating, or if you want a plan tailored to your labs, symptoms and goals.

See a medical provider promptly for severe abdominal pain, signs of an allergic reaction such as swelling or trouble breathing, or fainting.

What the research shows

The strongest trial on dietary fat and heart health is PREDIMED, a Spanish study of 7,447 adults aged 55 to 80 at high heart risk. Participants followed a Mediterranean diet with extra olive oil, a Mediterranean diet with mixed nuts, or a low-fat control diet for about 4.8 years. Major heart events occurred in 3.8% of the olive oil group, 3.4% of the nut group and 4.4% of the control group, about a 30% lower relative risk with either added-fat diet. The original 2013 report was withdrawn because some participants were not properly randomized, and this 2018 reanalysis adjusted for that, which is an important caveat.

Omega-3 fats have been studied for mood as well as the heart. A 2019 meta-analysis by Liao and colleagues pooled 26 placebo-controlled trials with 2,160 people and found a small overall benefit for depressive symptoms. The benefit came mainly from formulas with at least 60% EPA at 1 gram a day or less, while DHA-heavy formulas did not help. The trials varied in size and population, and the authors called for more research.

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Questions to bring to your clinician

These questions can help you get the most out of your next visit.

Which fats should I emphasize or limit, given my cholesterol and heart health history?

Which fats would be best for me to cook with at home?

How much would cutting back on seed oils matter for my health?

Would my own health history change how I approach healthy fats and seed oils?

Frequently asked questions

Are fats bad for you?

No. Quality matters most.

Which fats are healthiest?

Monounsaturated fats and omega-3s.

Should I avoid seed oils?

Limiting the processed foods that use them is a good start.

Is saturated fat harmful?

Research is mixed; enjoy whole-food sources in moderation and monitor cholesterol.

Sources

Estruch R, Ros E, Salas-Salvadó J, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. N Engl J Med 2018. PMID: 29897866. https://pubmed.ncbi.nlm.nih.gov/29897866/
Liao Y, Xie B, Zhang H, et al. Efficacy of omega-3 PUFAs in depression: A meta-analysis. Transl Psychiatry 2019. PMID: 31383846. https://pubmed.ncbi.nlm.nih.gov/31383846/
de Souza RJ, et al. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ 2015. PMID: 26268692. https://pmc.ncbi.nlm.nih.gov/articles/PMC4532752/
Hooper L, et al. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev 2020. PMID: 32827219. https://pmc.ncbi.nlm.nih.gov/articles/PMC8092457/
Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother 2002. PMID: 12442909. https://pubmed.ncbi.nlm.nih.gov/12442909/
Calder PC. Omega-3 fatty acids and inflammatory processes: from molecules to man. Biochem Soc Trans 2017. PMID: 28900017. https://pubmed.ncbi.nlm.nih.gov/28900017/
MedlinePlus: Dietary Fats
NIH ODS: Omega-3 Fatty Acids

This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.