Why California Walnuts?
Walnuts are the only nut to contain a significant amount of the plant-based omega-3 fat called alpha-linolenic acid. Walnuts contain 2.5 grams of omega-3 fat per 30 g serving. Walnuts also contain protein and fibre, plus they are a source of iron, magnesium and zinc.
Walnuts fit well into Canada’s Food Guide, which encourages eating a variety of protein sources, including plant-based protein options such as nuts and seeds.1 The Food Guide also recommends choosing foods that contain mostly healthy fats instead of mostly saturated fats. Walnuts contain mostly polyunsaturated fat (14 out of 19 grams of total fat per 30 g serving).
A study from the Harvard T.H. Chan School of Public Health suggests that people who replace saturated fats with polyunsaturated fats may have a lower risk of heart disease.2 The study analyzed the diets of nearly 85,000 nurses and 43,000 doctors every four years over 30 years. After calculating the percentage of calories the participants received from polyunsaturated fatty acids (PUFAs), monounsaturated fatty acids (MUFAs), whole grain carbohydrates and refined carbohydrates, the study found that substituting 5 percent of the calories from saturated fat with the same amount of energy from PUFAs was associated with a 25 percent lower risk of coronary heart disease (CHD). Replacing saturated fats with equivalent energy intake from MUFAs or whole grain carbohydrates was associated with a 15 percent and 9 percent lower risk of CHD, respectively. Given this was an observational study, the findings cannot prove causality and additional research is needed to determine how these results apply to more diverse populations. Furthermore, residual confounding cannot be ruled out.
As a nutrient-dense food, walnuts can be eaten in place of less healthy choices to improve overall diet quality. A study from Yale University’s Yale-Griffin Prevention Research Center found that including walnuts in a habitual diet, with or without reduced calorie intake, significantly improved diet quality in adult men and women at high risk for diabetes.3 Diet quality was assessed using the Healthy Eating Index 2010 (HEI-2010). In this parallel design study, participants (31 men and 81 women ages 25–75) were assigned to a calorie adjusted diet or an ad libitum diet and were also randomized to two different sequences to include or exclude walnuts. Participants were provided 392 grams of walnuts per week (2 ounces per day) to include in their diet and received guidance from a dietitian while on the calorie adjusted diet. Larger studies in more diverse populations are needed to clarify the results.
Canada’s Food Guide: Eat Protein Foods. https://food-guide.canada.ca/en/healthy-eating-recommendations/make-it-a-habit-to-eat-vegetables-fruit-whole-grains-and-protein-foods/eat-protein-foods/
Li Y, Hruby A, Bernstein AM, et al. Saturated fats compared with unsaturated fats and sources of carbohydrates in relation to risk of coronary heart disease. J Am Coll Cardiol. 2015;66(14):1538-48.
Njike VY, Ayettey R, Petraro P, et al. Walnut ingestion in adults at risk for diabetes: effects on body composition, diet quality, and cardiac risk measures. BMJ Open Diabetes Res Care. 2015;3(1):e000115.