Researchers who reviewed 20 years of diet history and 30 years of physical and clinical measurements found that participants who ate walnuts early in life were more likely to be more physically active, follow a higher-quality diet, and experience a better risk of heart disease when they reached puberty. From age to mid-adulthood.
These new findings come from the Coronary Artery Risk Development in Young Adults (CARDIA) study, A long-term, ongoing study supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health and aimed at examining the evolution of heart disease risk factors over time.
This study is one of the longest-running studies to suggest that the simple act of adding a little extra is heart-healthy^ Nuts in the diet are often a bridge to other health-promoting lifestyle habits later in life.
The findings also reinforce that walnuts may be an accessible and accessible food choice for improving a variety of heart disease risk factors when eaten in young to mid-adulthood.
In this recent study published in Nutrition, metabolism and cardiovascular diseaseUniversity of Minnesota School of Public Health researchers note that a possible explanation for the findings may be due to the unique combination of nutrients found in walnuts and their impact on health outcomes.
Walnuts are the only nut that is an excellent source of the plant-based omega-3 alpha-linolenic acid (2.5g/oz), which research shows may play a role in heart health, brain health, and healthy aging. Additionally, just one serving of walnuts (1 ounce), or roughly a handful, contains a variety of other important nutrients to support overall health including 4 grams of protein, 2 grams of fiber, and a good source of magnesium ( 45 milligrams). . Walnuts also offer a variety of antioxidants, including polyphenols.
According to Professor of Epidemiology and Community Health at the University of Minnesota School of Public Health and Principal Investigator at CARDIA, Lyn M. Steffen, Ph.D., MPH, RD, “Nut eaters appear to have a unique phenotype that carries with it other positive traits that affect health. Like better diet quality, especially when they start eating nuts from young to mid-adulthood — with higher risks of chronic diseases like heart disease, obesity and diabetes.”
In this longitudinal, observational study, supported in part by the California Walnut Commission, diet and health information from 3,023 healthy black and white men and women ages 18 to 30 years old was collected and analyzed at one of four field centers located in Birmingham, Alabama, Chicago, IL, Minneapolis, MN, and Oakland, CA, when the CARDIA study began in 1985-1986. Self-reported diet history was taken at three times during the study: baseline, year 7, and year 20. Physical and clinical measurements were taken in multiple tests spanning over 30 years.
Diet history was categorized into ‘nut consumers’, ‘other nut consumers’, or ‘no nut consumers’, and relationships were assessed between heart disease risk factors, including dietary intake, smoking, body composition, blood pressure, and plasma lipids (eg, triglycerides), fasting blood glucose, and insulin concentrations in 352 nut consumers, 2,494 other nut consumers, and 177 non-nut consumers.
The average nut intake during the study was about 1 ounce/day, and the intake of nuts among other nut consumers was about 1 ounce/day.
There was a good degree of diversity in terms of geographical area locations and population studied. Following these 30 years of white and black women and men provides an unparalleled study window into how lifestyle decisions in free-living environments in adulthood can impact health in midlife,” Stephen adds.
Lyn M. Steffen, Ph.D., MPH, RD, Professor of Epidemiology and Community Health, University of Minnesota School of Public Health
Study results at a glance
In general, the researchers reported the following findings:
- Physical and clinical indicators of heart disease risk after 30 years:
- Nut consumers had higher physical activity scores than other nut consumers and no nut consumers.
- Compared to other nut consumers, eating walnuts has been linked to a better heart disease risk profile:
- lower body mass index
- lower waist circumference
- lowers blood pressure
- Low levels of triglycerides in the blood
- Eating walnuts was associated with lower weight gain during the study period, and fewer participants who ate walnuts were classified as obese than other nut consumers.
- Compared with no nut consumers, nut consumers had lower fasting blood glucose concentrations while other nut consumers had higher levels of LDL cholesterol.
- Diet quality indicators after 20 years:
- Including walnuts in the diet during youth was positively associated with a higher overall diet quality score (Healthy Eating Index 2015) compared to other nut consumers.
- Compared with other nut consumers or non-nut eaters, subjects who ate walnuts had the following self-reported daily dietary intakes, including a significant correlation with higher intakes of several nutrients consumed and food groups important to overall health as shown in Diet 2020-2025 Guidelines for Americans:
“Nut consumers showed an advantage with regard to diet quality, but nut consumers appeared to have better heart disease risk factors compared to the other groups, even after taking into account overall diet quality,” Stephen said. “Sudden health shifts in the overall dietary pattern of nut consumers suggest that walnuts may serve as a bridge or ‘carrier food’ to help people form healthy eating and lifestyle habits throughout life.”
While these results are positive and confirm previous work from the CARDIA study on the health benefits of eating walnuts, randomized controlled clinical trials in other populations and settings need to be performed to confirm the observations in the current study. Observational studies cannot support cause-and-effect conclusions.
In addition, some findings of heart disease risk factors related to cholesterol and lipids in the current study are inconsistent with previous randomized controlled trials. This may be related to differences in study design, including the duration of the intervention (eg, several months to 30 years) or the amount of nut intake. Finally, the researchers did not isolate other types of nuts in their database, so the results cannot indicate that there is no benefit from other nuts.
This study is one of the longest-running to show that adding about a handful of walnuts to the diet each day and early in life can be associated with benefits for overall diet quality as a heart-healthy “vector food” for any eating occasion.
Yee, C.; , et al. (2022) Association of nut consumption with cardiovascular disease risk factors in young to middle-aged people: the Coronary Artery Risk Evolution in Young Adults (CARDIA) study. Metabolism and cardiovascular disease. doi.org/10.1016/j.numecd.2022.07.013.