You need to get nutty about nuts!

Worldwide, 1.9 million people are obese because of high energy dense, processed foods and a lack of physical exercise. Obesity is a significant determinant for non-communicable diseases (NCD) such as T2DM, CVD and cancer. The prevalence of obesity and NCD is rising at a considerable rate. When nuts are consumed within a varied and healthy diet, they have been shown to reduce obesity.

Tree nuts have high concentrations of monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), proteins and dietary fibre. Nuts also contain the important bioactive components vitamins, minerals, phytosterols and antioxidants like arginine. There are numerous health benefits from consuming nuts which include; a reduction in risk of cardiovascular disease (CVD), cancer, inflammatory markers and type 2 diabetes mellitus (T2DM). Despite these benefits, nut consumption is low, only 29% of New Zealanders eat nuts, with a mean intake of only 5g per day.

Confusion over the benefits of nuts, from health professionals, public, global variation in guidelines, rising obesity prevalence and possible allergic reactions, may be contributing to this low consumption.

The total fat in nuts is around 43 – 67% of weight, mainly unsaturated fats of MUFA and PUFA with a small amount of saturated fats (4-5%). Saturated fats affect glucose metabolism by altering cell membrane. This change in cell membrane affects insulin action, increasing blood glucose and can result in T2DM. Replacing saturated fatty acids with MUFA or PUFA, reduced incidences of T2DM. The nutrients in nuts have been shown to promote weight loss. Nuts provide considerable amounts of fibre, protein and fatty acids that may increase satiety, causing a lower total energy consumption. The increase in satiety is due to delayed gastro emptying, allowing more absorption of nutrients, resulting in suppressed hunger.

Brazil nuts contain the highest amount of MUFA (24.30 g/100g). MUFA positively affect insulin concentration and have a hypolipidemic effect. They also conserve high-density lipoproteins (HDL) which is why LDL is reduced. HDL have a protective effect and have anti-atherogenic properties. A low plasma HDL level can increase the risk of CVD.

Walnuts have a substantially higher amount of PUFA (47.18 g/100g) and a low amount of SFA (5.99 g/100g). Long chain PUFA’s reduce the number of triglycerides in the body. A high intake of PUFA, at the expense of SFA, has shown to reduce total plasma cholesterol and low-density lipoproteins (LDL). Likewise, high intakes of n-3 fatty acids, long chain PUFA’s, can reduce the number of triglycerides within the body. LDL carry triglycerides and cholesterol around the body and form plaques in blood vessels, causing strokes and heart attacks.

When consumed as part of a varied diet, 75g/d of walnuts reduced total energy intake, suggesting that walnuts contribute to energy displacement. Further studies have shown 43g/d of walnut consumption, displaced 19% of total energy from other food sources. Furthermore, 42g/d of hazelnuts, demonstrated an improvement in diet quality, significantly lowering carbohydrates and saturated fat and increasing MUFA and vitamin E. It was noted that consuming hazelnuts increased the percentage of energy from total fats and 95% compensation for fibre, which is linked to a reduced BMI.

Nuts are a reliable source of soluble and insoluble dietary fibre and can adjust the microbiome to enable a possible anti-diabetic effect and better lipid profile. Dietary fibre ferments in the colon which produces short-chain fatty acids. These short-chain fatty acids reduce the synthesis of cholesterol, a cause of CVD. A lack of fibre, as seen in 95% of Western diets, can adversely affect health outcomes. Low fibre diets contribute to obesity, cancer, cardiovascular disease and type 2 diabetes. Fibre is required by the body to assist the passage of food through the gut and increases satiety, fibre assists in weight regulation, glucose metabolism, reduced inflammation and lipid levels.

Whilst most data from studies report health advantages, there are a small few that disagree. However, confusing and inconsistent results could be attributed to varying nut contents linked to pre-and post-harvest conditions, storage conditions, soil quality and gene make-up. With a growing population of obese individuals, the correct message needs to be communicated. This message being nut consumption assists weight loss, preventing NCD. Combining nuts with a diet like the Mediterranean diet, will provide all the essential amino acids needed by the body. Only one question hangs over recommending nuts as part of a healthy diet. Allergies to nuts can be life threatening and care must be taken when advising to include/increase nut consumption. If nut allergies are not present, then >25g serving of nuts per day, will provide many benefits and aid in the reduction of obesity, which leads to NCD.