Types of Millets and It’s Importance

Dr. Utpal Giri, Dr. Saurav Das, Prof. Debashish Sen and Paramita Lodh

College of Agriculture, Tripura.

Millets are a group of highly variable small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Millets are important crops in the semi-arid tropics of Asia and Africa (especially in India and Nigeria), with 97% of millet production in developing countries. The crop is favoured due to its productivity and short growing season under dry, high-temperature conditions. The most widely grown millet is pearl millet, which is an important crop in India and parts of Africa. Finger millet, Proso millet, and Foxtail millet are also important crop species.

Millets have been important food staples in human history, particularly in Asia and Africa. They have been in cultivation in East Asia for the last 10,000 years. These crops are still the principal sources of energy, protein, vitamins and minerals for millions of the poorest people in these regions. Sorghum and millets are grown in harsh environments where other crops grow or yield poorly. They are grown with limited water resources and usually without the application of any fertilizers or other inputs by a multitude of small-holder farmers in many countries. Therefore, they are mostly consumed by disadvantaged groups; they are often referred to as “coarse grain” or “poor people’s crops”. They are not usually traded in the international markets or even in local markets in many countries. The farmers seldom, therefore, have an assured market in the event of surplus production.

DISTRIBUTION OF MILLETS IN INDIA

India is the top producer of millets followed by Nigeria for the years 2000 and 2009. In India, eight millet species (Sorghum, Pearl millet, Finger millet, Foxtail millet, Kodo millet, Proso millet, Barnyard millet and Little millet) are commonly cultivated under rain-fed conditions. Further, in each of the millet growing areas, at least 4 to 5 species are cultivated either as primary or allied crops in combination with pulses, oilseeds, spices and condiments. For instance, while pearl millet and sorghum are primary crops and allied crops respectively in the desert regions of Rajasthan, in the eastern parts of Rajasthan and Gujarat it is the opposite. Similarly, sorghum is sown as a major crop in Telangana, Andhra Pradesh, Maharashtra and parts of Central India, while it is considered a fodder crop in some of the Southern regions. Likewise, Finger millet is a primary crop in Tamil Nadu and Gujarat, while the same is a minor crop in Telangana.

Hence, the spatial distribution of millets either as a primary crop or as allied crops largely depends on the growing habitat and the amount of rainfall the region receives. While sorghum predominates in areas receiving annual rainfall beyond 400 mm, pearl millet rivals it in areas with annual rainfall of 350 mm. Further, the small millets like finger millet, foxtail millet, barnyard millet, little millet and proso millet are found in most of the southern and central states in India especially wherever annual rainfall is below 350 mm, perhaps where no other cereal crop can grow under such moisture stress.

India ranks first in the area, production and productivity of finger millet, little millet, kodo millet and barnyard millet.

Table -1: Area, Production, Productivity of small millets in India during 2016

(Source: Estimates based on data from FAO, UN and Directorate of Economics and Statistics, Dept. of Agriculture & Cooperation, Govt. of India)

The state-wise area, production and productivity data for the year 2018-19 is given in Table- 2.The state Karnataka ranks first in terms of area (527000 ha), production (677000 tonnes) and productivity (1285 kg/ha) in India. Maharashtra ranks third in terms of area (80300 ha.), production (93500 tonnes) and productivity (1164 kg/ha.).  The highest productivity (3257 kg/ha.) is observed in state Tamil nadu.

Table-2: State-wise Area, Production, Productivity of small millets in India during 2018-19

Table-3: MILLETS CROPS

The list of all millets crops is as below

1. a) Sorghum:

Sorghum(Sorghum bicolor (L.) Moench) is a warm-season crop, intolerant of low temperatures but fairly resistant to serious pests and diseases. It is known by a variety of names (such as great millet and guinea corn in West Africa, Asia and parts of the Middle East). Most of the sorghum produced in North and Central America, South America and Oceania is used for animal feed (FAO, 1995). The grain consists of naked caryopsis, made up of a pericarp, endosperm and germ. Although there is a huge range of physical diversity, sorghum are classed into four groups: (1) grain sorghum, (2) forage sorghum glum; (3) grass sorghum; or (4) Sudan sorghums and broomcorn (Macraeet al., 1993). Sorghums are grouped using the following characteristics

• The colour of the pericarp (white, yellow or red)
• Presence or absence of pigmented testa (with/without tannins)
• Pericarp thickness
• Endosperm colour (white, hetero yellow or yellow)
• Endosperm type (normal, hetero waxy or waxy)

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  2) Finger Millet:

  Finger millet (Eleusinecoracana (L.) Gaertn) is a cereal grass grown mostly for its grain. Finger millet is a robust, tufted, tillering annual grass, up to 170 cm high (FAO, 2012). The inflorescence is a panicle with 4-19 finger-like spikes that resemble a fist when mature, hence the name finger millet (de Wet, 2006; Quattrocchi, 2006). The spikes bear up to 70 alternate spikelets, carrying 4 to 7 small seeds (Dida et al., 2006). The seed pericarp is independent of the kernel and can be easily removed from the seed coat (FAO, 2012). Finger millet is a staple food in many African and South Asian countries. It is also considered a helpful famine crop as it is easily stored for lean years (FAO, 2012). The grain is readily digestible, highly nutritious and versatile, and can be cooked like rice, ground to make porridge or flour, or used to make cakes (De Wet, 2006). Sprouted grains are recommended for infants and elderly people. Finger millet is also used to make liquor (arake or areki in Ethiopia) and beer, which yields by-products used for livestock feeding (FAO, 2012). Finger millet grain is not widely used for livestock: it is primarily a food grain, but it is of lesser quality for livestock than maize, sorghum and pearl millet. In India, it is sometimes used for feeding infant calves, growing animals, as well as sick and convalescing animals (Sampath, 1986).

   

   

  3) Pearl Millet:

  Pearl millet (Pennisetumglaucum (L.) R. Br.)originated in Central tropical Africa and is widely distributed in the drier tropics and India. It was introduced into the Western state in the 1850’s and became established as a minor forage in the Southeast and Gulf Coast states. The plant was probably domesticated as a food crop some 4000 to 5000 years ago along the Southern margins of the Central highlands of the Sahara. It has since become widely distributed across the semiarid tropics of Africa and Asia. Pearl millet has traditionally been an important grain, forage, and stover crop primarily in the arid and subtropical regions of many developing countries. As pearl millet cultivation expands into non-traditional areas in temperate and developed countries, production constraints from diseases are assuming greater importance. Dissemination of accurate information on diseases of the crop has not kept pace with the increased interest in pearl millet as a viable crop in non-traditional areas. Pearl millet is well adapted to growing areas characterized by drought, low soil fertility, and high temperature. It performs well in soils with high salinity or low pH. Because of its tolerance to difficult growing conditions, it can be grown in areas where other cereal crops, such as maize or wheat, would not survive.

   

   

   

   

   

  4) Proso Millet:

  Proso millet (Panicummiliaceum (L.)) is an annual grass, growing from seed each year. Its origin goes back in history at least as far as 2000 B.C. when it is reported to have been grown in the Central regions of Europe. This plant is especially well suited to dry climates such as Central Russia, the Middle East, Northern India, Africa, Manchuria, and the Great Plains area of North America. Proso millet was first introduced to Canada in the 17th century and was used in a limited way as a forage crop in the early 1900s. Proso millet is a relatively low-demanding crop and diseases aren’t known. That’s why Proso millet is often used in organic farming systems in Europe. In the United States, it is often used as an intercrop. Thereby, Proso millet can help to avoid a summer fallow, and continuous crop rotation can be achieved. Its superficial root system and its resistance to atrazine residue make Proso millet a good intercrop between two water and pesticide-demanding crops. The stubbles of the last crop, by allowing more heat into the soil, resulting in a faster and earlier millet growth.

   

  5) Kodo Millet:

  Kodo millet (Paspalumscrobiculatum (L.)) is widely distributed in damp habitats across the tropics and subtropics of the world. It is an indigenous cereal of India and is grown today in Uttar Pradesh in the North and Kerala and Tamilnadu in the South. This cereal is also known as varagu, haraka and arakalu. It forms the mainstay of the dietary nutritional requirements. It has high protein content (11%), low fat (4.2%) and very high fibre content (14.3%). Kodo millet is very easy to digest, it contains a high amount of lecithin and is excellent for strengthening the nervous system. Kodo millets are rich in B vitamins, especially niacin, B6 and folic acid, as well as minerals such as calcium, iron, potassium, magnesium and zinc. Kodo millet contains no gluten and is good for people who are gluten intolerant. Regular consumption of Kodo millet is very beneficial for postmenopausal women suffering from signs of cardiovascular disease, like high blood pressure and high cholesterol levels.

   

  6) Foxtail Millet:

  Foxtail millet (Setariaitalica (L.) P. Beauvois) is regarded as a native of China, it is one of the world’s oldest cultivated crops. Foxtail millet ranks second in the total world production of millets and continues to have an important place in world agriculture providing approximately six million tons of food to millions of people, mainly on poor or marginal soils in southern Europe and in temperate, subtropical and tropical Asia. It will grow in altitudes from sea level to 2000 m. It cannot tolerate water logging. Foxtail millet is fairly tolerant of drought; it can escape some droughts because of early maturity. Due to its quick growth, it can be grown as a short-term catch crop. It is adapted to a wide range of elevations, soils and temperatures. Its grain is used for human consumption and as feed for poultry and cage birds.

  7) Barnyard Millet:

  Barnyard millet (Echinochloacrusgalli (L.) P. Beauvois) is a multi-purpose crop which is cultivated for food and fodder. It is also called by several other names viz., Japanese barnyard millet, ooda, oodalu, sawan, sanwa and sanwank. Nutritionally too, it is a good source of protein, which is highly digestible and is an excellent source of dietary fiber with a good amount of soluble and insoluble fractions. The carbohydrate content of barnyard millet is low and slowly digestible, which makes the barnyard millet a natural gift for modern mankind who is engaged in sedentary activities. In barnyard millet, the major fatty acid is linoleic acid followed by palmitic and oleic acid. It also shows a high degree of retrogradation of amylase, which facilitates the formation of higher amounts of resistant starches. Hence it can be potentially recommended for patients with cardiovascular disease and diabetes mellitus. Barnyard millet is most effective in reducing blood glucose and lipid levels.

   

   

   

   

   

   

   

   

   

   

  8) Little Millet:

  Little millet (Panicumsumatrense) was domesticated in India. It has grown throughout India to a limited extent up to altitudes of 2100 m but is of little importance elsewhere. The seeds of little millet are smaller than those of common millet. This species of cereal is similar in habit to the proso millet except that it is smaller. It is an annual herbaceous plant, which grows straight or with folded blades to a height of 30 cm to 1 m. The leaves are linear, sometimes with hairy lamina and membranous hairy ligules. The panicles are from 4 to 15 cm in length with 2 to 3.5 mm long awn. The grain is round and smooth, 1.8 to 1.9 mm long. It can withstand both drought and waterlogging. It can be cultivated up to 2000 m above sea level. Little millet is another reliable catch crop in view of its earliness and resistance to adverse agro-climatic conditions. The stover is good fodder for cattle.

   

   

  NUTRITIONAL IMPORTANCE OF MILLETS

  Sorghum and millets namely, Pearl millet, Finger millet, Kodo millet, Proso millet, Foxtail millet, Little millet, and Barnyard millet are important staples to millions of people worldwide. Generally, these are rain-fed crops grown in areas with low rainfall and thus resume greater importance for sustained agriculture and food security. Almost all the millets are used for human consumption in most of the developing countries but their use has been primarily restricted to animal feed in developed countries. Millets are nutritionally comparable to major cereals and serve as good sources of protein, micronutrients and phytochemicals. Processing methods like soaking, malting, decortications, and cooking affect the anti-oxidant content and activity (Saleh et al., 2013).

   

   

  Nutritional contents of millets:

  Table -4: Proximate composition and dietary fibre in millets and major cereals (per 100 g)

  Sr. no.	Crop	Carbo hydrates (g)	Protein (g)	Fat (g)	Energy (K Cal)	Dietary fibre (g)
  1	Finger millet	66.8	7.1	1.92	320.7	11.2
  2	Kodo millet	66.1	8.9	2.55	331.7	6.4
  3	Proso millet	70.4	12.5	1.10	341.1	—
  4	Foxtail millet	60.0	12.3	4.30	331.0	—
  5	Little millet	65.5	10.1	3.89	346.3	7.7
  6	Barnyard millet	65.5	6.2	2.20	307.1	—
  7	Sorghum	67.6	9.9	1.73	334.1	10.2
  8	Pearl millet	61.7	10.9	5.43	347.9	11.5
  9	Wheat	64.7	10.6	1.47	321.9	11.2
  10	Rice	78.2	7.9	0.52	356.4	2.8
  Ref: www.millets.res.in

   

  While sorghum and most of the millets contain about 10% protein and 3.5% lipids, finger millet contains 12-16% protein and 2-5% lipids. Sorghum and millets are very good sources of micronutrients such as vitamins and minerals. A major portion of sorghum protein is prolamin (kaffirin) which has a unique feature of lowering digestibility upon cooking whereas, the millets have a better amino acid profile. It has been reported that sorghum proteins upon cooking are significantly less digestible than other cereal proteins, which might be a health benefit for certain dietary groups. On the other hand, millets contain fewer cross-linked prolamins, which may be an additional factor contributing to the higher digestibility of the millet proteins. The average nutrient composition of some millet grains and other grains is summarized in Table 1. About 5-8% of protein is present in finger millet, 65-75% carbohydrates, 15-20% dietary fiber and 2.5-3.5% minerals (Chethan and Malleshi, 2007a). The Naked caryopsis of finger millet with brick red coloured seed coat is generally used in the form of a whole meal in traditional food preparations such as roti, muddle and ambali (thin porridge). Regular consumption of whole grain cereals and their products have shown in epidemiological studies that they can protect against the risk of diabetes mellitus, gastrointestinal diseases and cardiovascular risks (McKeown, 2002). The use of millets as whole grain makes the essential nutrients such as dietary fiber, minerals, phenolics and vitamins concentrated in the outer layer of the grain or the seed coat form part of the food and offer their nutritional and health benefits (Antony et al., 1996).The minerals and various water soluble vitamins profile in millets is given in Table 2.

  Table-5: Minerals & water soluble vitamins profile in millets and major cereals. (per 100 g)

  Sr. no.	Crop	Ca (mg)	P (mg)	Mg (mg)	Zn (mg)	Fe (mg)	Thiamin B-1 (mg)	Riboflavin B-2 (mg)	Niacin B-3 (mg)	Folic acid B-9 (mg)
  1	Finger millet	364.0	210	146	2.53	4.62	0.37	0.17	1.34	34.66
  2	Kodo millet	15.3	101	122	1.65	2.34	0.29	0.20	1.49	39.43
  3	Proso millet	14.0	206	153	1.40	0.80	0.41	0.28	4.50	—
  4	Foxtail millet	31.0	188	81.0	2.40	2.80	0.59	0.11	3.20	15.00
  5	Little millet	16.1	130	91.4	1.82	1.26	0.26	0.05	1.29	36.20
  6	Barnyard millet	20.0	280	82.0	3.0	5.0	0.33	0.10	4.20	—
  7	Sorghum	27.6	274	133	1.96	3.95	0.35	0.14	210	39.42
  8	Pearl millet	27.3	289	124	2.76	6.42	0.25	0.20	0.86	36.11
  9	Wheat	39.4	315	125	2.85	3.97	0.46	0.15	2.68	30.09
  10	Rice	7.5	96	19.0	1.21	0.65	0.05	0.05	1.69	9.32
  Ref: www.millets.res.in

   

  Millets are not only comparable to major cereals with respect to their nutritional features but are very good sources of carbohydrates, micronutrients and phytochemicals with nutraceutical properties. The millets contain 7-12% protein, 2-5% fat, 65-75% carbohydrates and 15-20% dietary fibre. Among them, pearl millet contains a considerably high proportion of proteins (12-16%) as well as lipids (4-6%) whereas; finger millet contains lower levels of protein (6-8%) and fat (1.5-2%). The essential amino acid profiles of the millet protein are better than maize. The niacin content in pearl millet is higher than all other cereals whereas, finger millet proteins are unique because of the sulphur-rich amino acid contents. Similar to cereal proteins, the millet proteins are poor sources of lysine, but they complement well with lysine-rich vegetable (leguminous) and animal proteins to form nutritionally balanced composites of high biological value. Small millets are more nutritious compared to fine cereals. Finger millet is the richest source of calcium (300-350 mg/100 g) and other small millets are good sources of phosphorous and iron.

   

  Nutrient Composition:

  The millet grain contains about 65% carbohydrate, a high proportion of which is in the form of non-starchy polysaccharides and dietary fibre which help in the prevention of constipation, lowering of blood cholesterol and slow release of glucose to the bloodstream during digestion. Lower incidences of cardiovascular diseases, duodenal ulcers and hyperglycemia (diabetes) are reported among regular millet consumers. Millet grains are also rich in important vitamins viz., Thiamine, riboflavin, folic acid and niacin. Millets are comparable to rice and wheat or rich in some of the minerals as well as fatty acids.

   

  HEALTH BENEFITS OF MILLETS

  Millets have potential health benefits and epidemiological studies have shown that consumption of millets reduces the risk of heart disease, protects from diabetes, improves the digestive system, lowers the risk of cancer, detoxifies the body, increases immunity in respiratory health, increases energy levels and improves muscular and neural systems.

  1. a) Cardiovascular Diseases:Being rich sources of magnesium, millets help in reducing blood pressure and risk of heart strokes, especially in atherosclerosis. Also, the potassium present in millets helps in keeping blood pressure low by acting as a vasodilator and helping to reduce cardiovascular risk. Also, the plant lignans present in millets have the ability to convert into animal lignans in the presence of microflora in the digestive system and protect against certain cancers and heart disease. The high fiber present in millets plays a major role in cholesterol-lowering eliminating LDL from the system and increasing the effects of HDL. The finger millets and proso millets have also been shown to lower significantly the concentrations of serum triglycerides than white rice and sorghum-fed rats. Finger millet and proso millet may prevent cardiovascular disease by reducing plasma triglycerides in hyperlipidemic rats (Lee et al., 2010)
  2. b) Diabetes Mellitus:Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycemia with alterations in carbohydrate, protein, and lipid metabolism. It is considered the most common endocrine disorder and results in deficient insulin production (type 1) or combined resistance to insulin action and the insulin-secretory response (type 2) (Saleh et al., 2013). The efficiency of insulin and glucose receptors in the body is increased by the significant levels of magnesium content present in millets which help in preventing diabetes. Finger millet-based diets have shown lower glycemic response due to high fiber content and also alpha-amylase inhibition properties which are known to reduce starch digestibility and absorption (Kumari and Sumathi, 2002).
  3. c) Gastrointestinal Disorders:Regulating the digestive process can increase nutrient retention and reduce the chances of more serious gastrointestinal conditions like gastric ulcers or colon cancer. Fiber content in millets helps in eliminating disorders like constipation, excess gas, bloating and cramping. An immune-mediated enteropathic disease called celiac disease is usually triggered by the ingestion of gluten in susceptible individuals (Catassi and Fasano, 2008). A gluten-free diet primarily plays a major role in affecting food consumption in the grain food group. As millets are gluten-free, they have considerable potential in foods and beverages can meet the growing demand for gluten-free foods and will be suitable for individuals suffering from celiac disease. (Taylor et al., 2006; Taylor and Emmambux, 2008; Chandrasekara and Shahidi, 2011b and 2011c
  4. d) Cancer:Millet grains based on literature values are known to be rich in phenolic acids, tannins, and phytate (Thompson, 1993). These nutrients reduce the risk of colon and breast cancer in animals (Graf and Eaton, 1990). The fibre present in sorghum and millet and also the phenolic has been attributed to a lower incidence of oesophagal cancer than those consuming wheat or maize (Van Rensburg, 1981). Recent research has revealed that fiber is one of the best and easiest ways to prevent the onset of breast cancer in women. They can reduce their chances of breast cancer by more than 50% by eating more than 30 gm of fiber every day.
  5. e) Detoxification (Anti-oxidant Properties):Many of the antioxidants found in millet have beneficial impact on neutralizing the free radicals, which can cause cancer and clean up other toxins from the body such as those in the kidney and liver. Quercetin, curcumin, ellagic acid and various other beneficial catechins can help to clear the system of any foreign agents and toxins by promoting proper excretion and neutralizing enzymatic activity in those organs. Therefore, tremendous attention has been given to polyphenols due to their roles in human health (Tsao R, 2010).

   

  REFERENCES:

   

  Antony et al., 1996. Antony, U., Sripriya, G. and Chandra, T.S. (1996): Effect of fermentation on the primary nutrients in finger millet (Eleusinecoracana). Journal of Agricultural and Food Chemistry. 44: 2616-2618.

  Catassi, C. and Fasano, A. (2008): Celiac disease. In: Gallagher E, editor. Gluten-free cereal products and beverages. Burlington, MA: Elsevier. Pp: 1-27.

  Chandrasekara, A. and Shahidi, F. (2011b): Antioxidant phenolics of millet control lipid peroxidation in human low density lipoproteins cholesterol and food systems. Journal of American Oil Chemists Society DOI: 10.1007/s11746-011-1918-5. Available from Springer [http://www.springerlink.com]. Posted August 20, 2012.

  Chandrasekara, A. and Shahidi, F. (2011c): Anti proliferative potential and DNA scission inhibitory activity of phenolics from whole millet grains. Journal of Functional Foods. 3:159-170.

  Chethan, S. and Malleshi, N.G. (2007): Finger millet polyphenols: optimization of extraction and the effect of pH on their stability. Food Chemistry. 105:862-870

  de Wet, J.M.J. (2006):Eleusinecoracana (L.) Gaertn.. Record from Protabase. Brink, M. and Belay, G. (ed). PROTA (Plant Resources of Tropical Africa / Ressourcesvégétales de l’Afriquetropicale), Wageningen, Netherlands

  FAO (1995): Sorghum and Millets in Human Nutrition. FAO, Rome.

  FAO (2012): Grassland Index. A searchable catalogue of grass and forage legumes. FAO, Rome, Italy.

  Graf, E. and Eaton, J.W. (1990). Antioxidant functions of phytic acid. Free Radical Biology and Medicine. 8(1):61-79

  Kumari PL and Sumathi S (2002): Effect of consumption of finger millet on hyperglycemia in non-insulin dependent diabetes mellitus (NIDDM) subjects. Plant Foods for Human Nutrition, 57: 205-213.

  Lee SH, Chung IM, Cha YS and Parka Y (2010): Millet consumption decreased serum concentration of triglyceride and C-reactive protein but not oxidative status in hyperlipidemic rats. Nutrition Research, 30: 290-296

  Macrae, R., Robinson, R.K., and Sadler, M.J. (1993): Encyclopedia of Food Science, Food Technology and Nutrition. Academic Press, London.

  McKeown, N.M., Meigs, J.B., Liu. S., Wilson, P.W. and Jacques, P.F. (2002): Whole-grain intake is favorably associated with metabolic risk factors for type 2 diabetes and cardiovascular disease in the Framingham Offspring Study. American Journal of Clinical Nutrition. 76(2): 390-398

  Quattrocchi, U. (2006): CRC World dictionary of grasses: common names, scientific names, eponyms, synonyms, and etymology. CRC Press, Taylor and Francis Group, Boca Raton, USA.

  Saleh, A.S.M., Zhang, Q., Chen, J. and Shen. Q. (2013): Millet grains: Nutritional Quality, Processing, and Potential Health Benefits. Comprehensive Reviews in Food Science and Food Safety. 12: 281-295

  Sampath, S. R. (1986): Scope for using small millets as forage in India. In: Seetharam, A., Riley, K.W. and Harinarayana, G. (ed). Small millets in global agriculture. Proceedings of the 1st International Small Millets Workshop Bangalore, India, October 29-November 2, 1986

  Taylor, J.R.N., Emmambux, M.N. (2008): Gluten-free foods and beverages from millets. In: Gallagher E, editor. Gluten-free cereal products and beverages. Burlington, MA: Elsevier. pp: 1-27

  Taylor, J.R.N., Schober, T.J. and Bean, S.R. (2006): Novel food and non-food uses for sorghum and millets. Journal of Cereal Science. 44(30): 252-271

  Thompson, L.U. (1993): Potential health benefits and problems associated with anti nutrients in foods. Food Research International Journal. 26: 131-149

  Tsao, R. (2010): Chemistry and biochemistry of dietary polyphenols. Nutrients. 2: 123-146

  Van Rensburg, S.J. (1981): Epidemiological and dietary evidence for a specific nutritional predisposition to esophageal cancer. Journal of the National Cancer Institute. 67: 243-251