The Science Behind Plant-Based Omega-3 ALA

By Kristin Kirkpatrick, MS, RDN

A patient of mine came in with the goal of improving her health through a plant-based, whole foods diet. When I suggested she increase her consumption of omega-3 fatty acids, she told me it might be a challenge since she didn’t eat fish and had assumed fish was the best and only way to get in the omega-3s. This assumption could not have been further from the truth. While fatty fish are known for providing omega-3s, there are also plant-based food sources that should be considered and consumed. In fact, recent studies offer exciting data showing the health benefits of omega-3 consumed from plant-based sources.

Let’s start with an omega-3 fatty acids tutorial. Omega-3s are essential fatty acids. That means our body does not make them on its own, so we need to obtain them through diet. There are three forms of omega-3s. ALA (alpha-linolenic acid) comes from plant-based sources such as walnuts, chia seed, flaxseed, and vegetable oils such as flaxseed, soybean, and canola oils. ALA can also be obtained from consuming animals that feed on ALA abundant grasses. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) come from marine-based sources, like salmon, mackerel, and trout. Studies have shown the benefit of following plant-based dietary patterns on the reduction of chronic disease as well as a potential to be linked with a decrease in overall mortality.1 Although cause and effect cannot be determined, one study suggests that the intake of plant-based protein in particular was linked with a lower risk of death from all causes and death from heart disease.2 The study was a meta-analysis and systematic review of over 700,000 adults spanning anywhere from 3.5 to 32 years.

As plant-forward diets continue to trend as a popular eating pattern,3  a handful of walnuts are a powerful plant-based food to eat on the go, or as an ingredient to include in a snack or meal. Walnuts provide a rich source of essential omega-3 ALA (2.5g/oz) and good plant-based fats and protein.

ALA and Heart Health

A 2014 study from Advances in Nutrition found that ALA may help improve heart health just as we have seen in studies focused on EPA and DHA.4 Now, a 2022 paper has updated the evidence from that original paper and found that given the accumulating evidence on dietary ALA and cardiovascular-related outcomes, food sources high in ALA should be included as part of a heart-healthy dietary patten.5 The authors of the paper suggest that the evidence at this point does support current dietary guidance around ALA, which is set at intakes of 1.1 grams and 1.6 grams per day of ALA for women and men, respectively. As one of the best plant food sources of omega-3s, a handful of walnuts is an easy, versatile and tasty way to meet daily ALA recommendations (2.5 grams of ALA is provided in a one-ounce serving of walnuts). 

A 2021 BMJ systematic review and meta-analysis found that ALA intakes between 1 and 2.5 grams per day were best for the prevention of heart disease, and every 1-gram increase of ALA was linked with a 5% decrease in death from all causes and from cardiovascular disease.6

How does an additional gram per day of ALA translate to a typical plant-based diet?

Since 1/4 cup of walnuts (12-14 halves or 1 ounce) have approximately 2.5 grams of plant-based omega-3 ALA,7 having just a handful of walnuts alone as a snack, or as a topping to salads, yogurt or oatmeal is a simple way to increase your intake of ALA.

ALA and Brain Health

review study from Progress in Lipid Research assessed the tissue levels of omega-3 DHA formed from ALA.2 They reported several important findings. The first was that ALA leads to the synthesis of EPA in some cases, and in particular, may contribute to DHA levels in the brain. Evidence from cell, animal, and human studies suggests dietary ALA may be able to fulfill the human requirement for DHA in the body when higher levels of ALA (at least 1.2g) are consumed. Assessing the synthesis of EPA and DHA from ALA in humans is limited to blood level measurements. Thus, researchers relied on a variety of measurement methods used in cell, animal, and human studies to review the science. The takeaway from this study is that through its conversion process, ALA may play a role in maintaining DHA levels in important tissues such as the brain. But more research is needed to fully understand the effect of this process in the body.

ALA and Overall Mortality

Research from one of the largest clinical trials looking at the benefits of a Mediterranean diet suggested older Spanish individuals (ages 55-80) with a high cardiac risk who supplemented a high fish diet with dietary ALA saw a reduced risk of all-cause mortality.3 Specifically, study participants who consumed at least 0.7% of their daily calorie intake from ALA had a 28% reduced risk of all-cause mortality. Whereas consuming at least 500mg of omega-3s from seafood was associated with a reduced risk of heart-related fatalities from sudden cardiac death, cardiovascular disease, and coronary heart disease by 52%, 39% and 46%, respectively. The greatest protective effects were seen when people included both marine and plant-based sources of omega-3s.

In this study, published in the Journal of the American Heart Association, participants were randomly assigned into one of three groups: Mediterranean diet supplemented with mixed nuts (15g walnuts, 7.5g almonds, and 7.5g hazelnuts), Mediterranean diet supplemented with extra virgin olive oil, and a low-fat control group. An important factor in this study was that consuming sources of ALA still had additional benefits even when people were consuming sufficient amounts of EPA and DHA from seafood. Thus, this study provides even more reason to include a variety of omega-3 sources when planning your diet.

In the recent BMJ study cited above,6 there were also benefits seen for reductions in early death. Specifically, higher blood levels of ALA were associated with a reduced risk of all causes of mortality.

Every study has limitations and it’s always good to take that into consideration.

  • The review studies4,8 included evidence from human, animal, and cell studies. Results from animal and cell studies provide great background for future research, but more is needed to confirm the effects on humans. Additionally, narrative reviews are mainly descriptive.4,5 More well-designed studies are needed in order to establish specific dietary ALA intake recommendations for chronic disease risk reduction.
  • Review studies4,5,8 provide a comprehensive look at findings among populations of varying backgrounds. However, they can be limited by the methods, reported outcomes, and quality of the individual studies involved.
  • For the aforementioned study on the Mediterranean diet9, these results cannot be applied widely given that participants were older persons at high cardiovascular risk living in a Mediterranean country, so larger and longer-term studies are needed in geographically diverse populations.
  • In the meta-analysis and systematic review,6 the studies included were observational so cause and effect cannot be determined. Walnuts were also not the only source of dietary ALA reviewed in this study, so the findings alone cannot be extrapolated to represent only ALA from walnuts and impact on health. Further research is needed to explore these results in the context of more diverse settings and populations as most of the studies used were identified from Western nations. 

Putting the Research to Work on Your Plate

All omega-3s provide benefits, so it’s important to get these good fats from a variety of sources. As the only nut significantly high in omega-3 ALA (2.5g per one ounce),10 a simple way to get more ALA into your diet is to start with walnuts. How about a  Strawberry Walnut and Date Smoothie for breakfast, a Walnut Balsamic Spinach Salad for lunch or  Walnut Mexican Street Corn Tacos for dinner? You can top salads, soups, or morning oatmeal with walnuts as well. Finally, the versatility and deliciousness of walnuts make it a wonderful on-the-go snack in trail mix or simply eaten alone.

  • 1Fadnes LT, Økland JM, Haaland ØA, Johansson KA. Estimating impact of food choices on life expectancy: A modeling study. PLOS Medicine. 2022;19(2):e1003889. doi.org/10.1371/journal.pmed.1003889.

    2Naghshi S, Sadeghi O, Willett WC, Esmaillzadeh A. Dietary intake of total, animal, and plant proteins and risk of all cause, cardiovascular, and cancer mortality: Systematic review and dose-response meta-analysis of prospective cohort studies. BMJ. 2020;370:m2412. doi.org/10.1136/bmj.m2412.

    3Webster A. IFIC survey: Consumer viewpoints and purchasing behaviors regarding plant and animal protein. Food Insight website. Published January 26, 2021. Retrieved March 1, 2022.

    4Fleming JA, Kris-Etherton PM. The evidence for α-linolenic acid and cardiovascular disease benefits: comparisons with eicosapentaenoic acid and docosahexaenoic acid. Adv Nutr. 2014;5(6):863S-76S. doi.org/10.3945/an.114.005850.

    5Sala-Vila A, Fleming J, Kris-Etherton P, Ros E. Impact of alpha-linolenic acid, the vegetable omega-3 fatty acid, on cardiovascular disease and cognition [published ahead of print February 16, 2022]. Advances in Nutrition. doi.org/10.1093/advances/nmac016.

    6Naghshi S, Aune D, Beyene J, et al. Dietary intake and biomarkers of alpha linolenic acid and risk of all cause, cardiovascular, and cancer mortality: Systematic review and dose-response meta-analysis of cohort studies. BMJ. 2021;375:n2213. doi:10.1136/bmj.n2213.

    7U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019. fdc.nal.usda.gov.

    8Barceló-Coblijn G, Murphy EJ. Alpha-linolenic acid and its conversion to longer chain n3 fatty acids: Benefits for human health and a role in maintaining tissue n-3 fatty acid levels. Prog Lipid Res. 2009;48(6):355-74. doi.org/10.1016/j.plipres.2009.07.002.

    9Sala-Vila A, Guasch-Ferré M, Hu FB, et al. Dietary α-linolenic acid, marine ω-3 fatty acids, and mortality in a population with high fish consumption: Findings from the PREvención con DIeta MEDiterránea (PREDIMED) study. J Am Heart Assoc. 2016;5(1):e002543. doi.org/10.1161/JAHA.

    10Alpha-linolenic acid. California Walnuts website. https://walnuts.org/nutrition/nutrition-info/alpha-linolenic-acid/. Retrieved March 1, 2022.

     

     

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