Food Groups: Nuts and Seeds

nuts seeds

Food Groups: Nuts and Seeds
Nuts and seeds are concentrated sources of a variety of substances such as protein, soluble and insoluble fibre, folic acid, arginine (an amino acid), minerals, fats (mainly monounsaturated and polyunsaturated), antioxidants and phytonutrients. However, they appear to be beneficial to human health when consumed regularly in small quantities.

NUTS
The common usage of the word ‘nut’ refers to an edible kernel surrounded by a hard shell. The nuts that we consume include almonds, cashew, walnuts, pecans, Brazil nuts, chestnuts, hazelnut (filberts), pistachios, pine nuts and macadamias.

Nuts belong to a number of different botanical families. For example, cashews and pistachios belong to the Anacardiaceae family (which also includes mangoes) whereas almonds belong to the Rosacea family (subfamily Prunoideae) (which includes plums, apricots, peaches, cherries and nectarines).

Peanuts (also called groundnuts) are not included in this chapter because they are classified botanically as legumes but their nutrient profile is generally similar to other nuts (i.e. tree nuts).

Chemistry and Health Benefits of Nuts
Nuts are a storehouse of healthy fats, fibre, phytochemicals, arginine (an amino acid), antioxidants, flavonoids and polyphenols. According to several studies, frequent nut consumption is associated with lower rates of coronary artery disease. In addition, dietary intervention trials have demonstrated that nut-rich diets improve the serum lipid profile of participants.

Because nuts are high in kilojoules and fat, there is some concern that frequent nut-eating may have a detrimental effect on body weight and insulin resistance. The evidence so far indicates that these concerns are probably not warranted but further research is needed to fully address the specific effects of nuts on satiety, energy balance, body weight and insulin resistance. There is some evidence that nuts can actually help to regulate body weight and protect against type II diabetes.

Brazil nuts can be a good source of selenium; one nut can contain between 10-100 micrograms of selenium depending on whether the soil they are grown in is selenium-rich or selenium-poor.

Healthy Fats: Nuts are a great source of healthy fats. Healthy fats are monounsaturated or polyunsaturated fats which play an important role in vascular health. Nuts high in monounsaturated fat include macadamias, cashew, almond pistachios and pecans. Nuts high in polyunsaturated fat include walnuts, hazelnut, pine nuts and Brazil nuts. Alpha-linolenic acid – a short-chain omega-3 essential fatty acid (polyunsaturated – is found in pecans, walnuts and hazelnuts. Eating a variety of nuts will help provide the right of balance of healthy fats in your daily eating plan.

Plant Sterols: Tree nuts contain plant sterols. These are substances that can reduce cholesterol absorption from the gut. Pistachios, cashews, almonds and pecans provide plant sterols.

Antioxidants: Nuts contain a variety of antioxidants including flavonoids, other phenolic compounds, vitamins C and g beta– carotene, other carotenoids and luteolin. These antioxidants have benefits for the health of blood vessels and for reducing the risk of clogged arteries and cancer. Vitamin E may have particular benefits as it has been associated with reduced risk of death from heart disease.

Arginine: Nuts contain arginine, an amino acid that helps keep blood flowing smoothly through the blood vessels. It can slow the formation of blood clots and reduce the clogging of arteries.

Folic Acid: Folic acid (or folate) is a B vitamin that helps reduce high levels of a potentially dangerous amino acid called homocysteine, which is a strong risk factor for heart disease. Cashews, chestnuts, hazelnut, pine nuts, pistachios and walnuts provide useful amounts of folic acid.

Fibre: All nuts contribute fibre to the diet. Fibre, especially soluble fibre, helps reduce excessive levels of cholesterol in the bloodstream. Fibre is a major contributor to preventing constipation.

Cautions
• Some individuals are allergic to peanuts and tree nuts and these are the commonest food cause of fatal and near-fatal anaphylactic reactions. Peanut allergy is more common than tree nut allergy, but many allergic subjects develop hypersensitivity to both peanuts and tree nuts.
• Nuts should not be given to infants and young children as they can lodge in the oesophagus and airways if not properly chewed. ln several studies of children needing to have foreign bodies removed from their airways, pieces of nuts were the most common.
• Aflatoxins are a group of toxic compounds produced by fungi, particularly by certain strains. Aflatoxins exert their toxicity primarily in the liver and are considered to be carcinogens. They are stable to heat and survive most forms of food processing.
• Individuals with sensitive digestion may find the brown skin of almonds slightly irritating. To remove the skin, soak in water overnight and peel in the morning.

Nuts in a Nutshell
Almond: Just a handful of almonds (30g, about 20 nuts) provide 85% of the RDI for vitamin E, a fat-soluble antioxidant vitamin. Bitter almonds contain prussic acid (also known as hydrogen cyanide). Extract of bitter almond was once used medicinally, but the almonds we eat are considered ‘sweet’.

Brazil Nuts: Brazil nuts are particularly rich in selenium, a vital antioxidant mineral which works with vitamin E in helping to prevent heart disease. Just two nuts per day will provide most of your selenium needs. They are called Brazil nuts because they are the seeds of a very large tree from the Amazon rainforest. Brazil nuts for international trade come entirely from wild collection rather than from cultivation. Most provide some vitamin E and B vitamins.

Cashews: The cashew is particularly a source of magnesium, needed for strong bones. Count 15 cashews in a handful. Unshelled cashews are not sold because the nut is surrounded by a double shell that contains the caustic phenolic resin, urushiol, a potent skin irritant and toxin which is also found in poison ivy.

Chestnut: Mount Olympus, home of the gods was said to have had an abundance of chestnut trees producing this sweet edible nut. Just so you know, Mount Olympus is actually in my home country: Turkey. Chestnuts have about 50% water content, are high in complex carbohydrates and contain high quality protein. Once cooked, their creamy-white flesh is similar in texture to a roast potato with a delicate, sweet flavour.

Hazelnut: The hazelnut is referred to in a manuscript found in china dating from 2838 BC. At that time the hazelnut took its place among the five sacred nourishments God bestowed on humans. Hazelnuts contain significant amounts of B-group vitamins, including folic acid and vitamin B6 and are the highest in fibre of all the nuts. An average handful is 20 hazelnuts.

Macadamia: This native Australian nut contains a large amount of healthy monounsaturated fats. Fifteen macadamias make one handful. However, macadamias are toxic to dogs.

Pecan: With a number of essential nutrients, the pecan is a great all-round snack for the health-conscious. A handful of pecans is about 15. The-pecan tree is a species of hickory native to south-eastern North America. The word ‘pecan’ is apparently from the native North American Algonquin word which literally means ‘a tough nut to crack’. Best to use a nutcracker.

Pine Nuts: Pine nuts are the edible seeds of the pine tree and are removed from pine cones. They contain useful amounts of zinc, vitamin B3, manganese and arginine. The Ancient Greeks and Romans believed that the pine nut was an aphrodisiac, and it is a standard ingredient in traditional Italian cuisine. An average serve is two tablespoons.

Pistachio: With that recognisable green colour, the pistachio is the only edible nut that does not need to be shelled before roasting. Related to the almond, they are rich in protein and contain good levels of vitamin E. About 60 pistachios make an average serve of 30g.

Walnut: Walnut is believed to have been first cultivated more than 4,000 years ago, but fossilised shells have been found in South-West France dating back 8,000 years. The modern name ‘walnut’ comes from the German wallnuss meaning foreign nut’. Walnuts contain the most omega-3 among the nuts along with good levels of vitamin E, potassium, iron and manganese. An average serve of walnuts is 10.

Buying and Storing Nuts
Nuts can be purchased in their shells or shelled and packaged as whole, slivered, chopped, blanched or ground nuts.

What to look for: Choose unsalted varieties rather than salted, preferably not roasted and as fresh as possible. For best quality, select clean nuts free from cracks and holes. Nuts in the shell should be heavy for their size, indicating a fresh, meaty kernel. Crisp, plump and meaty kernels indicate high quality. Also, clean, bright shells are more likely to contain good kernels. In their shells, nuts hold their quality longer.

How to store nuts: Nuts can become rancid quite quickly due to their lipid (fat) content especially if not protected from heat air, light and excessive moisture. They are best stored in an airtight container in a cool dry place. Remove the nuts from plastic bags and store them in an airtight container such as glass jars in the refrigerator (up to four month or the freezer (up to six month). Label the jars.

It is best to buy unshelled nuts and to store them in dark, cool, dry areas and in breathable bags and use them as needed.

SEEDS
The seeds that are commonly eaten include sunflower, sesame, pumpkin and flaxseeds (also called linseeds). Seeds such as caraway, cumin, poppy and fennel are usually classified as spices. But this is a culinary distinction rather than a botanical one. Botanically speaking, grains, legumes and nuts are ‘seeds’, and so to avoid confusion the ‘seeds’ we are discussing in this section are sometimes referred to as ‘oil seeds’. Like nuts, seeds are a lipid (fat) rich food.

nuts seeds

Seeds are an excellent source of polyunsaturated fatty acids, especially omega 6.

Seeds in a Nutshell
Flaxseeds (linseeds): Flaxseeds are the richest food source of the omega 3. One tablespoon (10 g) of flaxseed meal (ground flaxseeds) provides 2 grams of omega 3. This is the minimum recommended daily intake of omega 3 by the National Heart Foundation of Australia for prevention of cardiovascular disease. The other health benefits including lowering total cholesterol and blood pressure. Recent studies also showed positive benefits of flaxseed oil in irritable bowel disease (Crohn’s disease and colitis). Flax seed oil seems to be able to heal the inner lining of the inflamed intestines. Flaxseed oil should always be kept in the fridge and never to be heated.

Flaxseeds are also the richest food source of lignans. Like isoflavones, lignans are phytoestrogens. Breast cancer has been found to be associated with low lignan levels in studies of population groups in the USA, Finland, Sweden and Australia.

To enhance the digestibility of flaxseeds they can be soaked in water overnight, or freshly ground as needed. Ground flaxseeds are best refrigerated to prevent the polyunsaturated oils from becoming rancid.

How to store flaxseeds: Whether you purchase ground flaxseeds or grind them at home, it is important to keep them in a tightly sealed container in the refrigerator or freezer to prevent them from becoming rancid. Ground flaxseeds stored in the refrigerator in this manner will keep fresh for six months; and in the freezer, for one year.

Sesame seeds: Sesame seeds are very good sources of manganese, copper, calcium, magnesium, iron, phosphorous, vitamin B1, vitamin E, zinc and fibre. They also contain the lignans; sesamin and sesamolin. Sesamin has been found to protect the liver from oxidative damage. As discussed above, lignans are phytoestrogens and they play a significant role in preventing breast cancer.

Digestibility of sesame seeds: Different cultures have developed various methods for enhancing the digestibility of sesame seeds as they are difficult to chew. The Middle Eastern solution is to grind the sesame seeds into a paste called tahini. Gomasio is a macrobiotic condiment made from roasted sesame seeds and sea salt ground together in a suribachi (a Japanese mortar and pestle).

How to store sesame seeds: Once sesame seeds are hulled, they have to be stored in the refrigerator. If you do not plan to refrigerate your sesame seeds then keep them in airtight containers in a cool, dry place. They will stay fresh for a maximum of 3 months. You can also freeze the sesame seeds. They will last for close to a year this way.

Pumpkin seeds: Pumpkin seeds are a good source of iron, zinc, essential fatty acids, potassium and magnesium. Pumpkin seeds may also promote prostate health because components in the oil appear to interrupt the triggering of prostate-cell multiplication by testosterone and dihydrotestosterone (DHT), a metabolite of testosterone.

Sunflower seeds: Sunflower seeds are an excellent source of vitamin E and are rich in omega-6, a very good source of copper, manganese, magnesium, phosphorus, folic acid (folate), selenium and vitamin B1 and B6.

How to store sunflower seeds: Store sunflower seeds in an air-tight, non-permeable and non-reactive container such as glass jars. Keep the jars in a cool and dark place. I keep mine in the fridge however room temperature is fine if you plan to use them within 2-4 months. You could also freeze them.

References:
1. Nutrient Reference Values for Australia and New Zealand. National Health and Medical Research Council, 9 September, 2005.
1. McGee H.1992 On Food and Cooking: The Science and Lore of the Kitchen. Harper Collins U.K. page 264.
2. Brostoff J. & Gamlin L. 1992 The Complete guide to Food Allergy and Intolerance. Bloomsbury U.K. pages 303-304.
3. Pitchford P. 1993 Healing with Whole Foods: Oriental Traditions and Modern Nutrition. North Atlantic Books. U.S.A. pages 491, 528, 541.
4. Fraser G. 2000 Nut consumption, lipids, and risk of coronary event. Asia Pacific Journal of Clinical Nutrition 9(Suppl):S28-S32.
5. Garcia-Lorda P. et al 2003 Nut consumption, body weight and insulin resistance. European Journal of clinical Nutrition. S7(Suppl):S8-S11.
6. Higdon J. 2003 An Evidence-Based Approach to Vitamins and Minerals. Thieme U.S.A. pages 184-185.
7. Lee C. & Sheffer A. 2003 Peanut allergy. Allergy Asthma Proc. 24(4):259-264.
8. de Leon M. et al 3002 immunological analysis of allergenic cross-reactivity between peanuts and tree nuts. Clinical Exp, Allergy 33(9):1273-80.
9. Pogorzelski A. et al 1995 Broncho-pulmonary complications due to aspiration of foreign bodies by children. Pediatrics Pol, 70(4):325-31.
10. Becker B. & Nielsen T. ,994 Foreign bodies in the airways and oesophagus in children. Ugeskr Laeger. 1 56(30) :4336-9.
11. Peanut Company of Australia. Aflatoxin. www.pca.com.au accessed on 22/11/03.
12. Williams P. 20A2 Food toxicity and safety (Ch 23) in Essentials of Human Nutrition 2nd Edition. Mann J. & Truswell A. Oxford University Press U.S.A. page 420.
13. Australian Consumers’ Association. 1994 Peanut Butter. Choice. July pages 19-21.
14. FSANZ (undated) 19th Australian Total Diet Survey (from foods sampled throughout the 1998 calendar year). www.foodstandards.gov.au accessed on 1 8/1 0/03.
15. FSANZ (undated) 20th Australian Total Diet Survey (from foods sampled throughout the 1999 calendar year). www.foodsta.ndards.gov.au accessed on 1 B/1 0/03.
16. Cooney R.et al 2001 Effects of dietary sesame seeds on plasma tocopherol levels. Nutrition in Cancer 39(1):66-71.
17. Ratnesar S.2002 The Omega-3 Life Program. McGraw Hill Australia page 49.
18. Champ M. 2002 Non-nutrient bioactive substances of pulses. British Journal of Nutrition 88 Suppl (3):S307-S319.