Vegetarian diets and your genes: what the FADS2 gene reveals about how we make healthy fats

The foods our ancestors ate over thousands of years have left traces in our DNA. One of the best-studied examples is a group of genes called FADS, which help the body make important fats. A study of a largely vegetarian population in India found that a version of the FADS2 gene that boosts this process is far more common there than in other parts of the world, likely because it helped people on plant-based diets make the fats that others get from meat and fish.

What are long-chain fatty acids, and where do they come from?

Long-chain polyunsaturated fatty acids include the omega-3 fats EPA and DHA and the omega-6 fat arachidonic acid. They are building blocks of cell membranes, especially in the brain and eyes, and are used to make signalling molecules involved in inflammation, blood clotting and blood pressure.

There are two ways to get them:

• From food. Fish, seafood, meat and eggs contain ready-made long-chain fatty acids.
• By making them. The body can build them from shorter plant fats, such as alpha-linolenic acid (ALA, an omega-3 found in flaxseed, chia, walnuts and canola oil) and linoleic acid (an omega-6 found in most vegetable oils).

Vegans rely almost entirely on the second route.

What do the FADS1 and FADS2 genes do?

The FADS1 and FADS2 genes carry the instructions for two enzymes, called fatty acid desaturases, that perform key steps in turning short plant fats into long-chain fatty acids. Common differences in these genes change how active the enzymes are, and they are among the strongest genetic influences on the levels of these fats in the blood.

What did the study of a vegetarian population find?

In 2016, researchers from Cornell University and the University of Pune studied a variant in the FADS2 gene called an insertion, which increases the activity of the fat-making enzymes. They compared 234 people from a largely vegetarian population in Pune, India, with 311 people from the United States.

• 68% of the Indian participants carried two copies of the insertion, compared with 18% of the American participants.
• Worldwide data from the 1000 Genomes Project showed the same pattern: two copies were found in 70% of South Asians, 53% of Africans, 29% of East Asians and 17% of Europeans.
• People with two copies had about 8% more arachidonic acid in their blood than people with no copies.
• Genetic tests for natural selection pointed to positive selection of the insertion in South Asian, African and some East Asian populations.

The authors concluded that the insertion may have given people an advantage on traditional plant-based diets. This is evolution across many generations of a population, not a change in any one person's genes: being vegetarian does not change your DNA.

Have other populations adapted differently?

Yes. Greenland Inuit, whose traditional diet is very rich in omega-3 fats from marine animals, show some of the strongest signs of natural selection in the same FADS gene cluster, with variants that change the fat composition of their cells. In Europeans, comparing ancient DNA from the Bronze Age with modern DNA showed that different FADS variants became more common after the shift to farming, which changed the types of fat people ate. These variants have the opposite effect on fatty acid levels to those selected in the Inuit. The same genes have adapted in different directions, depending on what people ate.

What does this mean for vegetarians and vegans today?

Well-planned vegetarian and vegan diets are healthful and nutritionally adequate at all stages of life, according to the Academy of Nutrition and Dietetics, although vegans need a reliable source of vitamin B12. For omega-3 fats, the body turns only small amounts of ALA from flaxseed, walnuts and other plant oils into EPA and DHA. In a review of intervention studies, ALA from nut and seed oils did not raise DHA, while oils made from microalgae did. If you follow a plant-based diet, talk with your health care provider or a dietitian about whether an algae-based omega-3 supplement makes sense for you.

Can a genetic test tell me how I process food and medications?

FADS genes are not part of pharmacogenetic testing, and there are no clinical guidelines that use FADS results to plan your diet. But the same idea, that genes change how your body processes what you take in, is well established for medications. For example, the CYP1A2 enzyme breaks down caffeine and also medications such as clozapine, olanzapine and duloxetine, and smoking speeds it up. Read more about how coffee, cigarettes and your DNA affect your medications.

How can a Pillcheck test help?

A Pillcheck test does not test FADS genes, but it reports CYP1A2 and other genes that affect how your body handles many common medications, including antidepressants, pain medications, heart medications and acid reducers. A pharmacist reviews your results together with all your medications and prepares recommendations to share with your prescriber.

Pillcheck testing is performed in CAP- and COLA-accredited clinical genetic laboratories located in Canada. Pillcheck reports on 24 genes, increasing coverage with new guidelines and drug labels (see the genes tab), and covers 355 medications, which account for over 70% of dispensed prescriptions. The Pillcheck test panel ensures high accuracy for people of non-European and admixed ancestries. Your results last a lifetime, and report updates are free of charge.

Summary

• FADS1 and FADS2 help the body make long-chain omega-3 and omega-6 fats from plant fats.
• A FADS2 insertion that boosts this process is common in South Asia (70% carry two copies) and rare in Europe (17%).
• It appears to have been favoured by natural selection in populations with traditional plant-based diets.
• Greenland Inuit and Europeans show different FADS adaptations that match their traditional diets.
• Vegans convert little ALA to DHA, and algae-based oils are a vegetarian source of DHA.
• FADS is not part of pharmacogenetic testing, but genes such as CYP1A2 affect how you process medications.

Frequently asked questions

Does being vegetarian change my genes?

No. Your DNA does not change because of what you eat. The FADS2 insertion became common over many generations in populations that traditionally ate plant-based diets.

Do vegetarians need omega-3 supplements?

Not everyone does, but the body makes only small amounts of EPA and DHA from plant omega-3s. Ask your health care provider or a dietitian whether an algae-based supplement is right for you.

Can I get tested for FADS variants?

Some research and consumer tests include FADS, but there are no clinical guidelines for using the results. FADS is not part of pharmacogenetic testing.

Which genes affect how I process medications?

Genes such as CYP2D6, CYP2C19, CYP2C9 and CYP1A2 affect how your body breaks down many common medications. A pharmacogenetic test can show how these genes may affect your medications.

References

Kothapalli KSD, Ye K, Gadgil MS, et al. Positive selection on a regulatory insertion-deletion polymorphism in FADS2 influences apparent endogenous synthesis of arachidonic acid. Mol Biol Evol. 2016;33(7):1726-1739.

He Z, Zhang R, Jiang F, et al. FADS1-FADS2 genetic polymorphisms are associated with fatty acid metabolism through changes in DNA methylation and gene expression. Clin Epigenetics. 2018;10(1):113.

Fumagalli M, Moltke I, Grarup N, et al. Greenlandic Inuit show genetic signatures of diet and climate adaptation. Science. 2015;349(6254):1343-1347.

Buckley MT, Racimo F, Allentoft ME, et al. Selection in Europeans on fatty acid desaturases associated with dietary changes. Mol Biol Evol. 2017;34(6):1307-1318.

Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: vegetarian diets. J Acad Nutr Diet. 2016;116(12):1970-1980.

Lane K, Derbyshire E, Li W, Brennan C. Bioavailability and potential uses of vegetarian sources of omega-3 fatty acids: a review of the literature. Crit Rev Food Sci Nutr. 2014;54(5):572-579.