Published On: Fri, Aug 16th, 2013

How walnut lowers cholesterol levels, boosts fertility

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(By Temitope Obayendo)


  Looking for a natural way to reduce your cholesterol level, boosts sperm count, and ease your menstrual flow, then a daily intake of African Walnuts may be all you need to solve all these problems.

Walnuts do not only taste great but are a rich source of heart-healthy monounsaturated fats and an excellent source of those hard to find omega-3 fatty acids. Like most nuts, they can easily be added to your healthiest way of eating. Just chop and add to your favourite salad, vegetable dish, fruit or dessert.

Scientists have discovered how walnut trees respond to stress, cancer and heart condition by producing significant amounts of a chemical form of aspirin, antioxidants and essential fatty acids. They have also found that extracts of walnut tree are effective anti-microbial agents, could be used to boost sperm count, fertility, menstrual flow, treat uterine fibroids, and bring relief in hiccups.

Botanically called Tetracarpidium conophorum or Plukenetia conophora, African walnut belongs to the family Euphorbiaceae. In Nigeria, it is called Asala or Awusa in Yoruba; Ukpa in Ibo; and Okhue or Okwe in Edo.

For years, scientists have known that plants in a laboratory may produce methyl salicylate, which is a chemical form of acetylsalicylic acid, or aspirin. But researchers had never before detected methyl salicylate in an ecosystem or verified that plants emit the chemical in significant quantities into the atmosphere.

The team of scientists reported its findings few years back in the journal Biogeoscience. The research was funded by the United States National Science Foundation (NSF), the sponsors of the National Center for Atmospheric Research (NCAR).

The finding by scientists at NCAR in Boulder, Colorado, United States, opens up new avenues of research into the behaviour of plants and their impacts on air quality, and also has the potential to give farmers an early warning signal about crops that are failing.

According to the Medicinal Plants of Nigeria – South West Nigeria Volume 1 compiled and published by Nigeria Natural Medicine Development Agency (NNMDA), Victoria Island, Lagos, walnut seeds are used in the treatment of fibroid. The leaf juice is drunk to mitigate prolonged and /or constant hiccups. Seeds are chewed to improve sperm count in men. The leaf juice is used to improve fertility in women and also to regulate menstrual flow.

In southern Nigerian ethnomedicine, African walnut is used as a male fertility agent and the leaves are used for the treatment of dysentery and to improve fertility in males. The oil from the nut has found use in the formulation of wood varnish, stand oil, vulcanised oil for rubber and leather substitute. Most of the studies on the plant have been on the nutritive value of the seeds, which is a snack and delicacy.

According to The Useful Plants of Tropical West Africa by H. M. Burkill, the plant is a woody liane to over 30 metres long, of the bushy savanna. The leaves are considered a headache cure in Southern Nigeria, and have magical use to wash children to cause their mothers to conceive; the Igbo name meaning babies call babies. In Gabon, consumption of the seeds by husbands of wives already pregnant is believed to mitigate the risk of miscarriage. Nigerian material has been screened for alkaloids, a trace of which is recorded in the bark.

The fruit is a capsule six to 10 centimetres long by 3 to 11 centimetres wide containing sub-globular seeds two to 2.5 centimetres long with a thin brown shell resembling the temperate walnut, hence the English name.

The seed kernel is edible. Eaten raw, they have a bitter flavor, not unlike the kola nut and are considered to be tonic and aphrodisiac. Usually the kernels are roasted and eaten in the general diet or added to cakes. The kernels are oil-bearing yielding 48 to 60 per cent of a light golden coloured oil with a taste resembling linseed oil.

Composition is linolenic acid 64 per cent, palmitic and stearic acids 15 per cent, oleic acid 11 per cent and linoleic acid 10 per cent. This is conophor oil, or in the paint and varnish trade awusa or n’gart. It is edible and could be used in food preparations. It is unsuitable for soap-manufacture and, being quick drying, it is certainly usable in the paint industry, provided there is a certain supply and the kernels are free from excessive free fatty acids. Fresh oil has an iodine value of 190, which is excellent for a drying oil; but the seeds do not store well and deterioration caused by enzymatic action needs to be prevented at the time of collection by heat-treatment.

Nutritional Profile

Walnuts are an excellent source of anti-inflammatory omega-3 essential fatty acids, in the form of alpha-linolenic acid (ALA). Walnuts are also rich in antioxidants, including being a very good source of manganese and a good source of copper. Many other minerals are provided by walnuts in valuable amounts. These minerals include calcium, chromium, iron, magnesium, phosphorus, potassium, selenium, vanadium and zinc. Vitamin B6, while not especially concentrated in walnuts, may be more bioavailable in this food. In terms of phytonutrients, walnuts contain antioxidant and anti-inflammatory compounds, including more than a dozen phenolic acids, numerous tannins (especially ellagitannins, including tellimagrandins), and a wide variety of flavonoids. The vitamin E composition of walnuts is also of special mention, since there is an unusual concentration of the gamma-tocopherol form of vitamin E in this tree nut.

The oil has medicinal use in Nigeria in massages. The cake left after expression of the oil contains 45 per cent protein. It has local uses for food and is obviously a good source of protein. It can safely be fed to stock. The plant, presumably the kernel, is a good source of vitamins.

Results of a Nigerian study have shown that Tetracarpidium conophorum has a high potential, as an anti-microbial medicinal plant. It is reported to be useful in the folklore in the treatment of dysentery. This investigation therefore justifies its ethno-medical use, having displayed activities with the human pathogenic microorganisms that were used in this study.

Following the need for development of newer anti-microbial chemotherapeutic agents because there is increasing treatment failure rates of microbial infections, due to drug-resistant antibiotics, the most active fraction in the current study, the ethyl acetate fraction of the leaf methanol extract, has a very high potential as a source for drug discovery for anti-microbial agents.

The study, ‘anti-microbial potential of extracts and fractions of the African walnut – Tetracarpidium conophorum’ was published in African Journal of Biotechnology by E. O. Ajaiyeoba and D. A. Fadare of the Department of Pharmacognosy, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria.

Extracts and fractions were tested against four clinical strains of two Gram positive, two Gram negative bacteria and two of fungi. They exhibited concentration-dependent anti-microbial properties. The extracts displayed higher activities to the Gram positive organisms.

Gram positive bacteria includes many well-known genera such as Bacillus, Listeria, Staphylococcus, Streptococcus, Enterococcus, and Clostridium.

Preliminary phytochemical screening of the plant parts for secondary metabolites, showed the presence of saponins, alkaloids, tannins and anthraquinones in the plant samples. The concentration of these metabolites was higher in the leaves. Cardiac glycosides were not detected in leaf, stem bark, roots and kernel of T. conophorum. Percentage yields of extracts were determined after removal of solvents respectively.

The root extract displayed intrinsic antibacterial properties. Of the six microorganisms used, Staphylococus aureus was most sensitive to the root and stem bark extracts. Both extracts did not show any anti-fungal property in the current study. The leaf extract exhibited the highest activities with all the micro-organisms investigated. The leaf extract also showed anti-fungal properties, inhibiting the growth of the Aspergillus niger, a normally resistant mold, much more than the reference drug, tioconazole.

The kernel did not show any activity with the microorganisms used in this study. The hexane, chloroform, ethyl acetate and methanol fractions of the leaf extracts displayed good anti-microbial activities, which were concentration-dependent. Pseudomomas aeruginosa and Candida albicans were most sensitive to the extracts. The most sensitive bacteria to the four fractions were Pseudomonas aeruginosa. The ethyl acetate fraction was the most active extract, while the hexane fraction showed least activity.

The edible part of the plant, the kernel did not show any anti-microbial property in the assay. However, T. comophorum is an economic plant and it is widely cultivated for production of the nuts, which are delicacies snack food.

Researchers have also shown that eating snack-sized quantities of walnuts could slow the growth of cancer. The study by Dr. Elaine Hardman of Marshall’s Joan C. Edwards School of Medicine, near Huntington New York, United States, determined that mice that got part of their calories by eating walnuts had slower bosom cancer growth, and found that cancer in the walnut-fed group took twice as long to double in size as cancer in the control group.

The study published in the peer-reviewed journal, “Nutrition and Cancer”, made the mice ate a diet in which 18.5 per cent of the daily calories – the equivalent of two servings for humans – came from walnuts.

Walnuts have at least three components that could account for their cancer-slowing effect. They are high in Omega-3 fatty acids, which have been shown to slow cancer growth. They also include antioxidants and components called phytosterols, both of which have shown cancer-slowing effects in other studies.


Other Health Benefits


Cardiovascular Health

The form of vitamin E found in walnuts is somewhat unusual, and particularly beneficial. Instead of having most of its vitamin E present in the alpha-tocopherol form, walnuts provide an unusually high level of vitamin E in the form of gamma-tocopherol. Particularly in studies on the cardiovascular health of men, this gamma-tocopherol form of vitamin E has been found to provide significant protection from heart problems.


Walnuts Help Reduce Problems in Metabolic Syndrome

In the United States, as many as 1 in 4 adults may be eligible for diagnosis with Metabolic Syndrome (MetS). MetS is not so much a “disease” as a constellation of problematic and overlapping metabolic problems including excessive blood fats (triglycerides), high blood pressure, inadequate HDL cholesterol, and obesity (as measured by waist circumference, and/or body mass index). Recent studies have shown that approximately one ounce of walnuts daily over a period of 2-3 months can help reduce several of these MetS-related problems. In addition, addition of walnuts to participant diets has also been shown to decrease “abdominal adiposity”—the technical term for the depositing of fat around the mid-section. Importantly, the MetS benefits of added walnuts have been achieved without causing weight gain in any the studies we have seen to date.


Helps in Treatment of Type 2 Diabetes

Although we think about type 2 diabetes as a problem primarily related to blood sugar control and insulin metabolism, persons diagnosed with type 2 diabetes typically have health problems in other related systems, and are at special risk for cardiovascular problems. An important part of the goal in designing a diet plan for persons with type 2 diabetes is lowering the risk of future cardiovascular problems. In this context, consumption of walnuts is establishing a more and more impressive research track record. Increased flexibility in the response of the cardiovascular system following meals has been a repeated finding in research on walnuts. A variety of different measurements on blood vessel functioning (including their measurement by ultrasound) show a relatively small amount of daily walnut intake (1-2 ounces) to provide significant benefits in this area for persons with type 2 diabetes. Better blood fat composition (including less LDL cholesterol and less total cholesterol) has also been demonstrated in persons with type 2 diabetes.


Anti-Cancer Agent

Given the wide variety antioxidant and anti-inflammatory nutrients found in walnuts, it is not surprising to see research on this tree nut showing measurable anti-cancer benefits. The antioxidant properties of walnuts help lower risk of chronic oxidative stress, and the anti-inflammatory properties help lower risk of chronic inflammation; and it is precisely these two types of risk, that, when combined, pose the greatest threat for cancer development. Prostate cancer and breast cancer are the best-studied types of cancer with respect to walnut intake, and their risk has been found to be reduced by fairly large amounts of walnut consumption. (Large in this case means approximately 3 ounces per day.) For prostate cancer, the evidence is somewhat stronger, and more studies have involved human subjects. For breast cancer, most of the evidence has been based on studies of rats and mice.


Enhances weight loss

Walnuts have also produced a good track record in the research as a desirable food for support of weight loss and for prevention of obesity. That finding often surprises people because they think of high-fat, high-calorie foods as a primary contributing factor to obesity and to weight gain. In general, overconsumption of high-fat, high-calorie foods is a primary contributing factor to obesity and weight gain. However, obesity has also been clearly identified by researchers as involving chronic, unwanted inflammation. Walnuts are unique in their collection of anti-inflammatory nutrients. These nutrients include omega-3 fatty acids; phytonutrients including tannins, phenolic acids, and flavonoids; quinones like juglone; and other anti-inflammatory phytonutrients. These anti-inflammatory benefits can overshadow the high-calorie and high-fat risk posed by walnuts.

Improves Bone Health

The anti-inflammatory nutrients in walnuts may play a special role in support of bone health. A recent study has shown that large amounts of walnuts decrease blood levels of N-telopeptides of type 1 collagen (NTx). These collagen components provide a good indicator of bone turnover, and their decreased blood level in response to walnut intake is an indication of better bone stability and less mineral loss from the bone. “Large amounts” of walnuts (in this study, actually raw walnuts plus walnut oil) translated into 50 per cent of total dietary fat. In an everyday diet that provided 2,000 calories and 30 per cent of those calories from fat, this 50 per cent standard for walnuts would mean about 67 grams of fat from walnuts or 4 ounces of this tree nut on a daily basis. While this amount is more than most people would ordinarily consume, we expect the health benefits of walnuts for bone health to be demonstrated in future studies at substantially lower levels of intake.


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  1. titilayo says:

    please where are the refrences for this article. it is necessary to have refrences for further research

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How walnut lowers cholesterol levels, boosts fertility