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, I discuss cholesterol levels, and explain why you should eat nuts and seeds every day.
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
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.
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.25 Flax, 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
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:
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.
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
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 provide plenty of fiber, plant protein, polyphenols, plant sterols, vitamins, and minerals.25 Because 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.