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Essential fruit, vegetables, and lists for health

BMJ 2014; 349 doi: https://doi.org/10.1136/bmj.g4906 (Published 31 July 2014) Cite this as: BMJ 2014;349:g4906

Which nuts for health ?

The importance of nuts in health is gradually being realized through studies both in the laboratory and in the population. Though the nutritional values of the nuts are available, there has been no such population based studies indicating the supremacy of one nut over the other in maintaining health of the individuals. Studies have tried to find out the health benefits of one or more tree fruits such as walnuts, almonds, pistachio, or other nuts. However, there is no comprehensive report on their role in various chronic diseases except for few in relation to coronary heart diseases, diabetes or related metabolic syndrome.

Nuts are considered to be healthy. Besides providing calories, protein, fibres, plant sterols, and fats (less of saturated than unsaturated or good fats), nuts contain healthful ingredients such as copper, fiber, folate, and vitamin E. They have lots of arginine, an amino acid which is used by the body to make nitric oxide. Nitric oxide relaxes blood vessels so as to allow easy blood flow. An ounce of most varieties of nuts has about 10%–20% of the recommended daily intake of magnesium (1,2).

As per United States Department of Agriculture database, almonds have slightly more vitamin E than walnuts, and much more magnesium. Walnuts, is the only nut with an appreciable amount of alpha-linolenic acid, an omega-3 fat found in a plant-based food besides a rich source of vitamin E. Research has suggested that ALA may help heart arrhythmias, and it is suggested that walnuts were as effective as olive oil at reducing inflammation and oxidation in the arteries after eating a fatty meal. Peanuts are rich in folate and good for brain development. Cashews have more magnesium than almonds (83 milligrams per ounce vs. 73) but they lag behind in vitamin E. For men’s health, Brazil nuts are rich in selenium, which has a protective action against prostate cancer(1,2). One ounce of Brazil nut has almost 10 times the Recommended Dietary Allowance (RDA) of 55 micrograms of selenium. Macadamia nuts comes lower in the list of healthy nuts because of their high saturated fat (3.4 grams per ounce) compared with other nuts (1).

A comparison of nutritional values in terms of calories and fat content of the nuts is shown in table 1. There are variations in calories ranging from 69 in chestnuts to 204 in macadamia nuts (dry, roasted or raw) per 1 ounce, or 28.4 grams (g), of unsalted nuts. The saturated fat content is also low for chestnuts (0.1 g/ounce) and highest for raw Brazil nuts (4.3 g/ ounce). However, except for chestnuts, all the nuts are rich in unsaturated fats, more so for pecans (dry roasted).

Table 1: Calories and fat content of nuts (1)

Type of nut Calories Total fat(saturated/unsaturated fat)*
Almonds, dry-roasted 169 15 g (1.1 g/12.9 g)
Almonds, raw 163 14 g (1.1 g/12.2 g)
Brazil nuts, raw 186 19 g (4.3 g/12.8 g)
Cashews, dry-roasted 163 13.1 g (2.6 g/10 g)
Chestnuts, roasted 69 0.6 g (0.1 g/0.5 g)
Hazelnuts (filberts), dry-roasted 183 17.7 g (1.3 g/15.6 g)
Hazelnuts (filberts), raw 178 17 g (1.3 g/15.2 g)
Macadamia nuts, dry roasted 204 21.6 g (3.4 g/17.2 g)
Macadamia nuts, raw 204 21.5 g (3.4 g/17.1 g)
Peanuts, dry roasted 166 14 g (2g/11.4 g)
Pecans, dry roasted 201 21 g (1.8 g/18.3 g)
Pistachios, dry roasted 161 12.7 g (1.6 g/10.5 g)
Walnuts, halved 185 18.5 g (1.7 g/15.9 g)
* Total does not match because of fat value includes other non fatty acid material such as sugar or phosphates

There is lack of information on a comprehensive side-by-side comparison of the cholesterol-lowering effect of nuts. Similarly, we also don’t have adequate information on the differences in the health benefits of eating the nuts in various forms such as raw, dry, roasted, salted, fried, soaking in water or milk etc. so as to recommend which is the best form of eating the nuts.

The usual forms of eating nuts are in raw form, roasted (dry or in oil or with salt) or after soaking in water or milk. Roasting may destroy some of the nutrients, and addition of salt or oil is bad for the hypertensive or those with coronary heart diseases. The ideal would be in raw form. There are limitations to eating raw form in some nuts such as cashew, almond etc.

It is generally believed that almonds are better digested and absorbed when soaked in water overnight. It contains phytic acid and enzyme inhibitors of the gut, which is removed after soaking (3). Thus, soaking could be a better way to eat almonds. Similarly, we need to find out which form would be the best way to eat from the point of bioavailability, absorption and maintaining the optimum nutritional value.

References

1. http://www.mayoclinic.org/diseases-conditions/heart-disease/in-depth/nut... (accessed on 6th August 2014).
2. http://www.health.harvard.edu/fhg/updates/update1004d.shtml(accessed on 6th August 2014)
3. http://asianheartinstitute.wordpress.com/2012/07/10/almonds-soaking-wet/ (accessed on 6th August 2014).

Competing interests: No competing interests

06 August 2014
Mongjam Meghachandra Singh
Professor,
Reeta Devi
Maulana Azad Medical College, New Delhi; co-author-Indira Gandhi National Open University, New Delhi
Department of Community Medicine, MAMC, New Delhi and School of Health Sciences, IGNOU, New Delhi