Nuts and Seeds

Nuts are mature dry fruits obtained from few specific trees, containing hard ovary wall and a seed. Nuts are nutrient dense plant products. Nuts itself is a staple food, and usually, people love to eat nutty snacks or as a dessert item. However, different recipes like sauces, pastries, ice creams, spreads and baked goods contain nuts. Compared to other dietary nutrients, nut consumption is less, but gradually people became aware of health benefits of nuts. US Food and Drug Administration (FDA) issued a claim that an increased consumption of nuts reduces the risk of Coronary heart disease (CHD) by maintaining blood cholesterol level. [1] These health benefits are achieved due to all the bioactive compounds present in the nuts as they have a synergistic effect and yield favorable health effect. Most of us have the misconception that a regular consumption of nuts provides some negative effect including obesity and increased risk of diabetes. However, research experts showed that high energy source of nut obtained from its fat content is mostly unsaturated fatty acids, which does not cause health hazardous; but are essential for normal physiology. [1]  

 

The nutrient composition of nuts

The nutritional status of whole raw, unpeeled and unprocessed nuts may make them a natural health capsules. Nuts are an abundant source of dietary fiber, and variety of vitamins like folic acid, niacin, tocopherols, and vitamin B6, and different trace minerals such as calcium, magnesium, potassium. The nuts are a very good source of fats. But interestingly, very little amount of saturated fatty acids (4 to 16 percent) are present in nuts. Mostly, the fat contents in nuts are made up of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA). However, the unsaturated fat distribution varies from nuts to nuts.

L-arginine is one of the major amino acid present in nuts that serves as an excellent source of protein. Nuts also fulfill 5–10% daily requirement of dietary fibers. The different bioactive constituents, including phytosterols and phenolic compounds are present in nuts. [1]

 

Phytochemical status of nuts

The different phytochemicals present in nuts are phenolic acids, flavonoids, stilbenes, lignans; naphthoquinones; hydrolysable tannins, condensed tannins, proanthocyanidins; ellagic acid; phenolic aldehydes; alkaloids; coumestan; phytates; terpenes; phytoestrogens. In addition of phytosterols, MUFA, PUFA, other fat-soluble bioactive components are monoacylglycerols, diacylglycerols, TAG, phospholipids, sterol esters, tocopherols, tocotrienols, phytosterols, squalene, terpenoids, sphingolipids, carotenoids, chlorophylls, alkyl phenols and essential oils are present in nuts.

  • Galic acid is one of the primary phenol content in nuts.
  • A-type and B-type proanthocyanidins are present as major polyphenols; However, B-type is mostly present in all the nuts; but almond, peanut, and hazelnut also contain A-type.
  • Gallotannins and ellagitannins are two hydrolyzable tannins, which produce gallic acid and hexahydroxydiphenic acid.
  • Different types of flavonoids are present in nuts; like catechins are present in almond, hazelnut, pistachio and pecan, naringenin, quercetin, and kaempferol are also present in almond as glycosides. Gallocatechins are present in hazelnut and pecan. Pistachio is a good source of flavanone, flavone polyphenols and gallocatechins.
  • Highest phenolic acids are present in walnut and Brazil nut; however, almond, chestnut, pecan are also significant sources of phenolic acids.
  • Almond, peanut and pistachio nut skin contains stilbenes.
  • Dietary fiber, lignins of the nuts have bound phenolics.
  • Phytates are present in nuts; almond and hazelnut contain inositol phosphate ranges from 1 to 6. [2]

 

Health benefits of Nuts

Since ages nuts were known to boost immunity, improve digestion, accelerate wound healing and promote circulation. Nut are also used as analgesics. The following are some evidence-based health benefits of nuts and seeds: [2]

Natural Antioxidant

Free radical accumulation causes different degenerative conditions. Vitamin E and selenium are the two established nutrients that have antioxidant property.  Nuts specifically, almond and hazelnut are excellent source of vitamin E, which possess potent antioxidant property. Whereas, Brazil nut is a good source of selenium. Among the different varieties of nuts, walnut possess the highest antioxidant activity due to presence of polyphenols. However, cashew, hazelnut, pecan, almond, macadamia, pistachio, Brazil nut and peanut contain polyphenols and also have natural antioxidant property. They have oxyradical scavenging capacity. [2]

 

Cardioprotective

Nuts are the exclusive source of MUFAs, but walnut mainly contains PUFAs. These unsaturated fatty acids can lower the LDL level and reduce the risk of cardiac diseases. Apart from this mechanism, nuts are also effective to reduce oxidative stress, improve endothelial functioning and provide anti-inflammatory property. Altogether these activities are beneficial for heart health. [1, 3]

Physicians’ Health Study report revealed that nut consumption is inversely associated with total CHD mortality. The study result found that increased nut consumption reduces sudden cardiac death. This result was independent of gender, age, body mass index, alcohol use, other nutritional characteristics or presence of cardiovascular risk factors.

Peanut and peanut products including peanut butter is a good option to decrease the risk of cardiac heart disease (CHD) and effective to control diabetes associated CHD. The reduction of C-reactive protein (CRP), interleukin-6 (IL-6) and fibrinogen level in association with increased nut consumption provide an anti-inflammatory effect. In addition, the cardioprotective effect of nuts is due to the adiponectin plasma enhancement level, which has anti-inflammatory and anti-atherosclerotic properties. [4]

 

Diabetes risk reductions

The hyperglycemic condition is a primary sign of diabetes. Several clinical trials are conducted to check the efficacy of nuts to reduce the risk diabetes, and the study findings showed the positive result.  Many research evidence showed peanut, walnut and peanut butter can reduce type 2 diabetes. Walnut is more powerful to reduce the risk of diabetes in patients with controlled BMI. [1] Nut reduce the risk of diabetes, especially in pre-diabetic individuals. American Diabetes Association also recommended energy obtained from nut diets, especially almond can reduce insulin resistance. Almond diet also reduces urinary C-peptide output in hyperlipidemic men and postmenopausal women. The benefits of nuts in improving postprandial glycemia and diabetes risk are significant and do not causes any adverse effect. A research study conducted by providing the study subjects Mediterranean diet with walnuts, almonds, and hazelnuts showed a lower diabetes incidence without altering body weight and physical activities. Not only nuts, but peanut butter also has the potency to reduce the risk of diabetes. However, age, BMI, family history of diabetes, physical activity, smoking status, alcohol consumption and dietary pattern are important factors require adjusting to get the benefits of nut in the reduction of diabetes risk. Particularly walnut consumption provides the best outcome in terms of type 2 diabetes risk reduction, as they contain much higher amounts of both n–6 and n–3 PUFAs. [4] Apart from walnuts following nuts like almond and pistachio also have a beneficial effect to control diabetes. Consumption of almond improves glucose control in pre-diabetic individuals and also lower postprandial glycemia in type 2 diabetic patients. Consumption of pistachio improves glycemic status in type 2 diabetic patients and also in healthy young men. [3]

 

Weight management

There is a misconception that fat rich nut eating habit may increase our weight. Although research evidence showed that there is no co-relation with nut consumption and weight gain, but it is significantly associated with reduced risk of weight gain. Protein and dietary fiber-rich nuts provide satiety effect; whereas unsaturated fibers in nuts decrease fat accumulation in the body by increasing fat oxidation.  In addition, these three nutrients together may increase thermogenesis and release excess energy and high fiber reduce hunger by delaying the gastric emptying. Thus, nut help to manage the body weight. [5] This description may alter the misconception of nut intake related to weight gain. But it is obvious that raw and unroasted nuts are mainly considered in weight management benefits of nuts. Obesity management depends upon the type of food we eat. Research evidence showed that almond is more effective than complex carbohydrate in the reduction of BMI, waist circumference and fat mass.    [1]

BMI and waist circumference are the two parameters to check the body weight.  Several studies showed there is no association of nut consumption with BMI, body weight, and waist circumference. This is an interesting fact that long-term nut consumption in higher quantity associated with low weight gain. Research evidence support that both, peanut and tree nut reduce weight gain. Weight gain is inversely proportional to the nut consumption. [3]

 

Hypertension

As per common belief, nut consumption increases hypertension, but there is no such association found through different research. Moreover, individuals with lean body have decreased the risk of hypertension with increasing nut consumption. Almonds, walnuts, hazelnuts, pistachios, cashews, and mixed nuts containing diet can reduce the systolic and diastolic blood pressure in individuals with higher risk of CVD. [4]

Nuts consumption improves endothelial functioning in the blood vessel, as nuts are enriched with n-3 PUFA, antioxidants, vitamins and phenolic compounds, and L-arginine endothelial function.  Walnut may be one of the best options to improve endothelial functioning due to their high ALA content along with antioxidants and L-arginine profile. [3]    

Positive effect on HDL-cholesterol or triglyceride

Few research studies showed that nut consumption decreases LDL level. However, the effect of HDL and triglyceride level is unchanged with walnut consumption; even nut consumption does not affect HDL and triglyceride level in normotriglyceridemic individuals. Although, nut consumption increase HDL and decrease triglycerides level in individuals with hypertriglyceridemia. [4]    

 

Nuts are a rich source of a variety of vitamins, minerals, phytoesterols, and antioxidants and may have the potential benefits to prevent multiple chronic diseases. [4] But in regards to a safety concern, some individuals may have food allergy with nuts and they should avoid nut consumption. [1]

 

References

  • Emilio Ros. Health Benefits of Nut Consumption. Nutrients 2010, 2, 652-682; doi:10.3390/nu2070652
  • Cesarettin Alasalvar1, Bradley W. Bolling. Review of nut phytochemicals, fat-soluble bioactives, antioxidant components and health effects. British Journal of Nutrition (2015), 113, S68–S78 doi:10.1017/S0007114514003729
  • Yoona Kim, Jennifer B. Keogh and Peter M. Clifton. Benefits of Nut Consumption on Insulin Resistance and Cardiovascular Risk Factors: Multiple Potential Mechanisms of Actions. Nutrients 2017, 9, 1271; doi:10.3390/nu9111271
  • Jordi Salas-Salvado´, Marta Guasch-Ferre´, Mo`nica Bullo´, Joan Sabate´. Nuts in the prevention and treatment of metabolic syndrome. Am J Clin Nutr 2014;100(suppl):399S–407S

Chandra L Jackson, Frank B Hu. Long-term associations of nut consumption with body weight and obesity. Am J Clin Nutr 2014;100(suppl):408S–11S.