Nuts and Seeds
Nuts and Seeds Help Keep Disease Away
Did you know you should go nuts over nuts and their little partners, seeds? Although they are often overlooked as important health foods, nuts and seeds are mighty warriors who pack a powerful punch in fighting diseases, including our nation’s number one killer, heart disease and, in so doing, contribute to enhanced longevity. In my book, The End of Heart Disease, I devote an entire chapter to fat, where I unravel the controversy around saturated fat, discuss cholesterol levels, and explain why you should eat nuts and seeds every day.
Nuts and seeds reduce heart disease risk
In the early 1990’s, the first research findings suggesting that nut consumption could reduce the risk of heart disease emerged.1 Eventually, the pooled results from four large prospective studies showed that eating five or more servings of nuts per week was associated with a 35 percent reduction in the risk of coronary heart disease.2
Scientists set out to find nuts’ protective mechanism on the heart and blood vessels. Early on it was established that nuts have a powerful cholesterol-lowering effect. The most recent meta-analysis on the cholesterol-lowering properties of nuts, included pooled data from sixty-one different clinical trials, was published in December 2015.
In this analysis, each daily serving of nuts was associated with a 4.7 mg/dl reduction in total cholesterol and 4.8 mg/dl reduction in LDL cholesterol, plus reductions in apolipoprotein B and triglycerides. Apolipoprotein B (ApoB) is the primary protein component of low-density lipoprotein (LDL) and is strongly associated with increased risk of developing cardiovascular disease. Higher doses of nuts (about 2 ounces per day or more) produced bigger benefits.3
Improved insulin sensitivity and endothelial cell function (the cells that form the inner lining of blood vessels) and reduced oxidative stress may also contribute to the cardiovascular benefits of nuts and seeds.4-7 Adding flaxseed to the diet has been found in many clinical trials to reduce systolic and diastolic blood pressure, and nut consumption is also linked to a lower risk of stroke.8,9
Nuts and seeds are strongly associated with longevity
In addition to reduced heart disease risk, nut consumption is now consistently linked to a longer life. Several large, long-term studies on American, European, and Asian populations have reported a lower rate of death from heart disease or from all causes in those who were eating nuts and seeds regularly. The studies included the Adventist Health Study,10 the Nurses’ Health Study, Health Professionals Follow-up Study,11,12 the Physicians’ Health Study,13 the PREDIMED study,14 and others.15-17
A meta-analysis published in 2015 pooled data from many of these studies concluded that one daily serving of nuts reduces the risk of death from all causes by 27 percent and cardiovascular death by 39 percent. A reduced risk of death from cancer was also reported.18
Of these large studies, the PREDIMED Study was particularly impressive. It incorporated participants’ habitual nut consumption and the results of a five-year intervention study, investigating three different diets: a control low-fat diet, a Mediterranean diet supplemented with olive oil, and a Mediterranean diet supplemented with mixed nuts. At the end of the five-year study, both Mediterranean groups had improved their blood pressure, blood glucose, and cholesterol, and had experienced fewer heart attacks and strokes than the low-fat diet group.19
When investigating survival, the researchers also looked at nut consumption at baseline, before the dietary intervention started. The lowest risk of death was found in the participants who were already eating three or more servings of nuts a week before the study began, and then were assigned to the mixed nuts group.14 This suggests that regular nut consumption over many years is longevity-promoting.
Now that there is more research on nuts and seeds, their benefits are coming into clearer focus, revealing it’s not just about heart disease. Nuts have many beneficial actions that may help us live longer.
Nuts and seeds linked to cancer prevention
Part of why eating nuts and seeds is connected to greater survival may be due to their cancer prevention properties. This is a newer area of study, but beneficial links have been found for a few cancers, especially in women.20 Nut consumption during adolescence was found to be associated with a lower risk of breast cancer later in life; women who ate one or more servings of nuts daily had a 24 percent reduced risk compared to those who ate less than one serving per month.21
In the Nurses’ Health Study, there was a 13 percent reduction in colorectal cancer risk and a 35 percent reduction in pancreatic cancer risk for women who ate at least two servings of nuts per week compared to those who rarely ate nuts.22,23 There was also a reduction in colorectal cancer risk in women who ate nuts regularly in the European Investigation into Cancer and Nutrition (EPIC) study.24
Phytochemicals from nuts and seeds have anti-proliferative, antioxidant and anti-inflammatory actions.25Flax, sesame, and chia seeds contain lignans, anti-estrogenic phytochemicals which have been found to protect against breast cancer, 26,27 and possibly against endometrial, ovarian, and prostate cancers.28-30
Scientists also have hypothesized that the LDL-lowering effects of nuts could potentially modulate energy metabolism in cancerous cells, which could thereby inhibit growth and proliferation, but this has not yet been investigated.25
Nuts and seeds may help with weight loss
Nut consumption is associated with a lower BMI and smaller waist circumference, and a lower likelihood of gaining weight or becoming obese.31,32 There are three ways that nuts and seeds are thought to help with weight loss and maintenance:
- The fats and fiber slow emptying of the stomach, making meals containing nuts and seeds satiating; this results in a compensatory decrease in calorie intake from other foods throughout the day.
- Studies have suggested that many of the calories in nuts do not get absorbed from the digestive tract. So an ounce of nuts, which would be listed at 150-200 calories, doesn’t truly deliver all of those calories.
- Eating nuts and seeds regularly may increase our calorie expenditure at rest, though more research is needed on this topic.33
Nuts’ significant association with longevity may in part be due to their contribution to maintaining body weight in a healthy range which helps to prevent heart disease, diabetes and cancer.
Nuts may play a significant role in brain health
The effects of nuts on cognitive function is another new area of research. Walnuts, probably because of their omega-3 ALA content, have been predominantly extensively studied so far. Animal studies suggest that walnuts and almonds could be helpful for preventing age-related cognitive decline and Alzheimer’s disease.34,35
New human data from the PREDIMED study (discussed above) found that participants in the Mediterranean diet plus nuts group were less likely to have low BDNF (brain-derived neurotrophic factor) levels compared to the olive oil and low-fat groups; 36 BDNF is important for the growth and survival of nerve cells, and altered BNDF levels are linked to neurodegenerative diseases and mood disorders.37
Also in the PREDIMED study, walnut consumption was associated with better working memory.38 In the Nurses’ Health Study, higher intake of total nuts was linked to better overall cognition in older women.39
Nuts and seeds improve glycemic load of the diet
The inclusion of nuts and seeds in a plant-rich diet lowers the glycemic load of the diet significantly, reducing insulin resistance, and offers protection against diabetes.4 Improvements in these parameters have been documented in clinical trials: replacing carbohydrate foods with mixed nuts was shown to improve HbA1c in patients with diabetes, and adding pistachios to the diet was found to reduce insulin resistance in patients with prediabetes.40,41 Lower insulin requirements are also a factor thought to promote longevity.
Nuts and seeds contribute to nutrient adequacy
Nuts and seeds provide plenty of fiber, plant protein, polyphenols, plant sterols, vitamins, and minerals.25Because of their beneficial nutritional composition, regular consumers of nuts are more likely to meet recommended intakes for vitamin A, vitamin C, folate, calcium, magnesium, zinc, potassium, and fiber.42
The antioxidant compounds in nuts help protect the polyunsaturated fats from oxidation, and the fats assist in the absorption of carotenoids in vegetables in the same meal.43,44 Individual types of nuts and seeds have distinct beneficial nutrients; for example omega-3 ALA (the precursor to DHA and EPA) in walnuts and flax, chia and hemp seeds; polyphenols in almond and walnut skins; and zinc in pumpkin seeds.
I recommend using nuts and seeds, rather than animal products and oils, as your major dietary source of fat. Have at least 1 – 2 ounces of nuts and seeds per day (more if you are slim and active), and make half of your nut and seed intake those high in omega-3s (walnuts and flax, chia, and hemp seeds). I also advise eating nuts and seeds in salads, dressings and sauces rather than out of hand, as they aid in the absorption of carotenoids and it may help to prevent overconsuming calories.
- Fraser GE, Sabate J, Beeson WL, Strahan TM. A possible protective effect of nut consumption on risk of coronary heart disease. The Adventist Health Study. Arch Intern Med 1992, 152:1416-1424.
- Kris-Etherton PM, Hu FB, Ros E, Sabate J. The role of tree nuts and peanuts in the prevention of coronary heart disease: multiple potential mechanisms. J Nutr 2008, 138:1746S-1751S.
- Del Gobbo LC, Falk MC, Feldman R, et al. Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials. Am J Clin Nutr 2015, 102:1347-1356.
- Rajaram S, Sabate J. Nuts, body weight and insulin resistance. Br J Nutr 2006, 96 Suppl 2:S79-86.
- Katz DL, Davidhi A, Ma Y, et al. Effects of walnuts on endothelial function in overweight adults with visceral obesity: a randomized, controlled, crossover trial. J Am Coll Nutr 2012, 31:415-423.
- Kris-Etherton PM. Walnuts decrease risk of cardiovascular disease: a summary of efficacy and biologic mechanisms. J Nutr 2014, 144:547S-554S.
- Bullo M, Juanola-Falgarona M, Hernandez-Alonso P, Salas-Salvado J. Nutrition attributes and health effects of pistachio nuts. Br J Nutr 2015, 113 Suppl 2:S79-93.
- Khalesi S, Irwin C, Schubert M. Flaxseed consumption may reduce blood pressure: a systematic review and meta-analysis of controlled trials. J Nutr 2015, 145:758-765.
- Zhang Z, Xu G, Wei Y, et al. Nut consumption and risk of stroke. Eur J Epidemiol 2015, 30:189-196.
- Fraser GE, Shavlik DJ. Ten years of life: Is it a matter of choice? Arch Intern Med 2001, 161:1645-1652.
- Bao Y, Han J, Hu FB, et al. Association of nut consumption with total and cause-specific mortality. N Engl J Med 2013, 369:2001-2011.
- Baer HJ, Glynn RJ, Hu FB, et al. Risk factors for mortality in the nurses' health study: a competing risks analysis. Am J Epidemiol 2011, 173:319-329.
- Hshieh TT, Petrone AB, Gaziano JM, Djousse L. Nut consumption and risk of mortality in the Physicians' Health Study. Am J Clin Nutr 2015, 101:407-412.
- Guasch-Ferre M, Bullo M, Martinez-Gonzalez MA, et al. Frequency of nut consumption and mortality risk in the PREDIMED nutrition intervention trial. BMC Med 2013, 11:164.
- Luu HN, Blot WJ, Xiang YB, et al. Prospective Evaluation of the Association of Nut/Peanut Consumption With Total and Cause-Specific Mortality. JAMA Intern Med 2015.
- van den Brandt PA, Schouten LJ. Relationship of tree nut, peanut and peanut butter intake with total and cause-specific mortality: a cohort study and meta-analysis. Int J Epidemiol 2015.
- Mayhew AJ, de Souza RJ, Meyre D, et al. A systematic review and meta-analysis of nut consumption and incident risk of CVD and all-cause mortality. Br J Nutr 2016, 115:212-225.
- Grosso G, Yang J, Marventano S, et al. Nut consumption on all-cause, cardiovascular, and cancer mortality risk: a systematic review and meta-analysis of epidemiologic studies. Am J Clin Nutr 2015, 101:783-793.
- Estruch R, Ros E, Salas-Salvado J, et al. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med 2013, 368:1279-1290.
- Wu L, Wang Z, Zhu J, et al. Nut consumption and risk of cancer and type 2 diabetes: a systematic review and meta-analysis. Nutr Rev 2015, 73:409-425.
- Liu Y, Colditz GA, Cotterchio M, et al. Adolescent dietary fiber, vegetable fat, vegetable protein, and nut intakes and breast cancer risk. Breast Cancer Res Treat 2014, 145:461-470.
- Yang M, Hu FB, Giovannucci EL, et al. Nut consumption and risk of colorectal cancer in women. Eur J Clin Nutr 2016, 70:333-337.
- Bao Y, Hu FB, Giovannucci EL, et al. Nut consumption and risk of pancreatic cancer in women. Br J Cancer 2013, 109:2911-2916.
- Jenab M, Ferrari P, Slimani N, et al. Association of nut and seed intake with colorectal cancer risk in the European Prospective Investigation into Cancer and Nutrition. Cancer Epidemiol Biomarkers Prev 2004, 13:1595-1603.
- Falasca M, Casari I, Maffucci T. Cancer chemoprevention with nuts. J Natl Cancer Inst 2014, 106.
- Thompson LU, Chen JM, Li T, et al. Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer. Clin Cancer Res 2005, 11:3828-3835.
- McCann SE, Thompson LU, Nie J, et al. Dietary lignan intakes in relation to survival among women with breast cancer: the Western New York Exposures and Breast Cancer (WEB) Study. Breast Cancer Res Treat 2010, 122:229-235.
- Higdon J: Lignans. In An Evidence-Based Approach to Dietary Phytochemicals. New York: Thieme; 2006: 155-161
- Bandera EV, King M, Chandran U, et al. Phytoestrogen consumption from foods and supplements and epithelial ovarian cancer risk: a population-based case control study. BMC Womens Health 2011, 11:40.
- Saarinen NM, Tuominen J, Pylkkanen L, Santti R. Assessment of information to substantiate a health claim on the prevention of prostate cancer by lignans. Nutrients 2010, 2:99-115.
- >O'Neil CE, Fulgoni VL, 3rd, Nicklas TA. Tree Nut consumption is associated with better adiposity measures and cardiovascular and metabolic syndrome health risk factors in U.S. Adults: NHANES 2005-2010. Nutr J 2015, 14:64.
- Jackson CL, Hu FB. Long-term associations of nut consumption with body weight and obesity. Am J Clin Nutr 2014, 100 Suppl 1:408S-411S.
- Mattes RD, Dreher ML. Nuts and healthy body weight maintenance mechanisms. Asia Pac J Clin Nutr 2010, 19:137-141.
- Pribis P, Shukitt-Hale B. Cognition: the new frontier for nuts and berries. Am J Clin Nutr 2014, 100 Suppl 1:347S-352S.
- Poulose SM, Miller MG, Shukitt-Hale B. Role of walnuts in maintaining brain health with age. J Nutr 2014, 144:561S-566S.
- Sanchez-Villegas A, Galbete C, Martinez-Gonzalez MA, et al. The effect of the Mediterranean diet on plasma brain-derived neurotrophic factor (BDNF) levels: the PREDIMED-NAVARRA randomized trial. Nutr Neurosci 2011, 14:195-201.
- Anastasia A, Hempstead BL. BDNF function in health and disease. Nature Reviews Neuroscience 2014, 15.
- Valls-Pedret C, Lamuela-Raventos RM, Medina-Remon A, et al. Polyphenol-rich foods in the Mediterranean diet are associated with better cognitive function in elderly subjects at high cardiovascular risk. J Alzheimers Dis 2012, 29:773-782.
- O'Brien J, Okereke O, Devore E, et al. Long-term intake of nuts in relation to cognitive function in older women. J Nutr Health Aging 2014, 18:496-502.
- Jenkins DJ, Kendall CW, Banach MS, et al. Nuts as a replacement for carbohydrates in the diabetic diet. Diabetes Care 2011, 34:1706-1711.
- Hernandez-Alonso P, Salas-Salvado J, Baldrich-Mora M, et al. Beneficial effect of pistachio consumption on glucose metabolism, insulin resistance, inflammation, and related metabolic risk markers: a randomized clinical trial.Diabetes Care 2014, 37:3098-3105.
- O'Neil CE, Nicklas TA, Fulgoni VL, 3rd. Tree nut consumption is associated with better nutrient adequacy and diet quality in adults: National Health and Nutrition Examination Survey 2005-2010. Nutrients 2015, 7:595-607.
- Fillon M. Nuts may lower cancer risk. J Natl Cancer Inst 2014, 106:dju102.
- Brown MJ, Ferruzzi MG, Nguyen ML, et al. Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. Am J Clin Nutr 2004, 80:396-403.