Scientific Name(s): Prunus dulcis (P. Mill) D.A. Webb
Common Name(s): Almond milk, Almond oil, Amygdale amara, Amygdalin, Bitermandel, Bitter almond, Ku wei bian tao, Laetrile, Oil of almonds, Sweet almond, Vitamin B17, Volatile almond oil
The almond, apricot, cherry, peach, and plum are members of the Rosaceae (rose) family. The almond is distinct because its seed is edible, while the outer pulp is hard, inedible, and juiceless. The genus Prunus (plum), to which the almond tree belongs, is synonymous with Amygdalus in the US Department of Agriculture's PLANTS database, but the literature remains confusing and often categorizes the sweet and bitter almond in different genera. Synonyms are Amygdalus communis L., Amygdalus dulcis P. Mill, Prunus amygdalus Batsch, Prunus communis (L.) Arcang., and Prunus dulcis (Mill.) D.A. Webb var. amara (DC.) Buchheim.1
The plant, a moderate-sized tree, was probably introduced to the United States from Eastern Europe or western Asia. The United States, especially California, is the world's major producer of almonds.2 Many varieties of the plant differ in flower color and form, as well as in the size of the fruit or shell. Plants with entirely pink flowers produce sweet almonds; those with flowers that are almost white at the tip of the petals and are red/pink at the base produce bitter almonds. When fully ripe, the green outer covering of the fruit dries and splits and the almond shell (endocarp) drops out. The almond seed is rounded at one end and pointed at the other, with a yellow, fibrous outer covering.1
References to the almond are found in Greek mythology, the Bible, and in Shakespeare's writings. In the Middle Ages, almonds already were commercially important.3
Amygdalin was isolated by French chemists in 1830, and reports of its use as an anticancer agent date back to 1845 in Russia. In the United States, records show laetrile was used as a cancer treatment in the 1920s and was patented in the 1950s as a supposedly nontoxic form of amygdalin.4
The FDA has banned the sale of laetrile as a medicinal product; however, it remains available and its use is promoted in Mexico where it often is produced.4 Sweet almond is historically described as Mistura Amygdalae, Pulvis Amygdalae Compositus, and Almond Oil in the British Herbal Pharmacopoeia.
Almond nuts have a unique fatty acid profile, largely composed of unsaturated fats, some saturated fats, and no cholesterol. In addition to the protein and carbohydrate content, almonds contain large amounts of alpha-tocopherol and arginine, as well as magnesium, potassium, and sodium. Almonds are rich in phytosterols, including beta-sitosterol, stigmasterol, and campesterol.5 The skin of the almond nut accounts for 4% of the total nut weight and is rich in polyphenols, including hydroxybenzoic acids and aldehydes, flavonol and flavanone aglycones, and glycosides.6 Other chemical compounds in the almond include betulinic, oleanic, and ursolic acids. Other acids (corosolic and maslinic) have been identified as aldehydes. Antioxidant flavonoids quercetin, isorhamnetin, quercitrin, kaempferol, and morin have been isolated. Prunasin, a cyanogenic compound, is found only in the vegetative parts of the almond plant.7, 8, 9, 10, 11, 12
Amygdalin exists in the seeds of apricots, cherries, and plums.13 Amygdalin is hydrolyzed to yield glucose, benzaldehyde, and hydrocyanic acid. The production of cyanide defines cyanogenic glycosides. Enzymatic release of cyanide can occur in the presence of beta-glucuronidase, an enzyme found in the seeds and in the human intestine.13 When the cyanide component is removed, the resulting oil is referred to as "bitter almond oil" and consists mostly of benzaldehyde. This oil is toxic when consumed in large amounts.
The term "laetrile" is often used interchangeably with amygdalin, but they are not the same chemical entity. The word was coined from laevorotatory and mandelonitrile and is used to describe a semisynthetic derivative of amygdalin. Most laetrile from Mexico is made from crushed apricot seeds and is a mixture of amygdalin and neoamygdalin, which are mandelonitrile gentiobiosides. Other laetrile products of varying composition are commercially available.14
Uses and Pharmacology
Despite promising in vitro experiments, the use of amygdalin as a cancer treatment has not been validated by any clinical trials. The National Cancer Institute sponsored phase 1 and 2 clinical trials in the 1980s but found no evidence to support the use of laetrile in the treatment of cancer.4 Because a Cochrane review found no clinical trials that met adequate methodological quality, a meta-analysis could not be conducted.14 A further review evaluated all published clinical trial data and found no basis for the health claims of laetrile use in cancer.15 Laetrile has been banned in the United States and Europe for use in cancer therapy; however, interest continues and products are sold via the Internet.14, 15, 16
The widespread consumption of nuts as part of a healthy diet and the availability of clinical data make data from animal studies largely irrelevant.
Based on observations of epidemiological data and findings from intervention studies, the AHA recommends the daily intake of nuts (28.35 to 56.7 g) as part of a healthy diet. The FDA allows a qualified claim that eating 42.52 g/day of most nuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.5, 17, 18
Specific trials evaluating the efficacy of almonds in reducing cardiovascular risk factors, including reducing hyperlipidemia, are generally lacking and limited methodologically by lack of randomization, small numbers of participants, absence of controls, short washout periods, or short duration.5, 19 A review of available trial data and a meta-analysis of 5 clinical trials found a decrease in total cholesterol with daily consumption of almonds. Trials included in the meta-analysis used a range of 25 to 168 g of almonds per day.5, 19
Almonds, rich in phytosterols, fiber, and alpha-tocopherol, may act via various mechanisms to reduce cholesterol absorption and increase elimination, as well as via interaction at the cellular level with enzymes such as HMG-CoA reductase.5 Increased fiber intake, decreased oxidative stress, decreased lipid peroxidation, and increased serum tocopherol may offer explanation for the observed cardiovascular benefits of almond consumption. Changes in the lipid profile have been demonstrated in some but not all clinical studies.5, 17, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 The reductions in total cholesterol observed in clinical trials due to almond consumption are modest in comparison with the relatively larger benefit observed in cohort studies for risk reduction of cardiovascular disease; other mechanisms may be responsible for the effect.32
The widespread consumption of nuts as part of a healthy diet makes data from animal studies largely irrelevant.
Limited studies have been conducted in healthy volunteers and patients with type 2 diabetes with equivocal results. Effects on glycemic index, fasting insulin and glucose, insulin resistance, and 24-hour urinary C-peptide output are unclear.27, 32, 33, 34, 35
The widespread consumption of nuts as part of a healthy diet makes data from animal studies largely irrelevant.
Most studies find no increase in body weight associated with increased consumption of almonds22, 31, 36 and epidemiological studies suggest an inverse association may exist between frequency of nut consumption and body mass index.37
A study evaluated the effect of dietary almonds on markers of inflammation, finding decreases in C-reactive protein but no effect on interleukin or fibrinogen. No dose response was found.38
Assessment of data from 6,705 participants without baseline atrial fibrillation in the PREDIMED trial revealed a significant relevant reduction in risk of atrial fibrillation (38%) with the Mediterranean diet supplemented with extravirgin olive oil (50 g/day or more) but not with the Mediterranean diet supplemented with nuts (almonds, hazelnuts, walnuts).44
Almond oil has been used with phenol to treat rectal prolapse in infants39 and either alone or as a carrier of other essential oils in massage therapy.
The AHA recommends the daily intake of nuts (28.35 to 56.7 g) as part of a healthy diet.17
Almonds are considered a good source of tocopherol to meet the recommended daily allowance for vitamin E, now increased to 15 mg/day.24
Pregnancy / Lactation
Consumption of bitter almond or laetrile is not recommended in pregnant or breast-feeding women because of insufficient data and a theoretical risk of birth defects.
Cyanide has not been reported as a direct cause of birth defects in humans. Birth defects, harmful effects on the reproductive system, and skeletal abnormalities have been reported in mice fed water containing sodium cyanide and in hamsters given oral laetrile.40
Children born to mothers exposed to cyanide and thiocyanate during pregnancy have exhibited thyroid disease.40
Coadministration of high-dose vitamin C and almonds may result in symptoms of cyanide toxicity.4
Allergies to nuts are common, affecting an estimated 0.5% of the US population.2, 41 Adverse reactions similar to those of cyanide poisoning have been reported.4 The protein component is primarily composed of amadin, which confers the antigenicity of the nut in IgE-mediated allergy.2
Almond-based diets are possibly deficient in selenium, riboflavin, and pantothenic and folic acids.42 Published case reports have shown that infants fed almond milk exhibited hypoalbuminemia and consequent peripheral edema, as well as deficiencies in calcium and iron.43
Cyanide poisoning and death have resulted from laetrile and bitter almond consumption.13 A minimum lethal dose of cyanide is estimated at 50 mg (or 0.5 mg/kg body weight).13 Oral amygdalin/laetrile is considered 40 times more toxic than the intravenous form because of its conversion to hydrogen cyanide by enzymes in the intestine.4, 13 Symptoms of cyanide poisoning (eg, coma, cyanosis, dizziness, headache, hypotension, nausea, neuropathy, ptosis, vomiting) may be potentiated by eating foods containing beta-glucosidase (eg, bean sprouts, carrots, celery, peaches) or by taking high doses of vitamin C.4
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