RICE AS A SOURCE OF NUTRITION AND

HEALTH

Marguerite Uphoff, MD, MPH

IV. International Rice Meeting

Havana, June 2-6-2008

Rice is the staple food for more than half of the world’s population

Worldwide, rice provides 20% of total human energy Rice consumption varies by region -- annual per

capita consumption of rice ranges from 60 kg to 220 kg in Asian countries, to 12 kg per capita in North America

Rice consumption also varies by income -- dependency on rice is very high among poor people, in parts of Asia rice provides 50 to 80% of all the calories of poor households

In Central America and Cuba, rice provides 5 to 10% of total dietary energy

Rice is more than a source of energy

the major source of energy, but also the major source of protein, and a significant source of fiber and of

essential micronutrients

When rice is a large proportion of the diet, and when the diversity of the diet is limited, as is true for many living in poverty, rice is:

How to make rice count for nutrition

1. Use of all of the nutrients that are in the rice grain

2. Choose the most nutritious varieties– traditional cultivars– conventional breeding – transgenic engineering

3. Harness better cultivation techniques to enhance nutritional value

1. Using all the nutrients: Grain composition and nutrition

Hull (Husk)—removed and discarded in initial milling

Bran: Pericarp, Aleurone, Embryo—removed in further milling and polishing

Endosperm: the white rice that remains after milling and polishing.

Milling and polishing:loss of nutritional valueWhite rice – milled and polished grains

– contains about 90-94% carbohydrates– contains 6-10% protein – contains no significant vitamins or minerals

Brown rice – minimally milled grains– retains the bran -- pericarp, aluerone, and

endosperm– contains about 75-85% carbohydrates– richer than white rice in protein, lipids, fiber, and

vitamins and minerals

Bran is the key to improving rice’s contribution to

nutrition and health All rice lipids are in the bran Rice bran oil has some unique qualities

– 80% of the lipids in rice bran are polyunsaturated fatty acids

– High levels of polyunsaturated fatty compounds are effective in lowering blood cholesterol levels.

Even a little Vitamin E is beneficial for health

– Rice bran oil is a rich available source of vitamin E -- which consists of tocopherols and tocotrienols

– Tocotrienols decrease the synthesis of cholesterol by inhibiting the activity of HMG-CoA reductase, an enzyme involved in cholesterol biosynthesis

– Tocotrienols have been shown to decrease LDL – the “bad” cholesterol -- by 42-62% in animal studies -- and in human studies by 20%

Rice bran also has value for its lipid fraction

– Rice bran oil contains linoleic acid, an essential fatty acid that must be obtained from the diet because the human body cannot synthesize it

– Linoleic acid is important for many cell functions but particularly important for the brain’s development.

Brown rice lowers the grain’s glycemic index

Brown rice has a lower glycemic index because it is digested more slowly than white rice – this is important for diabetes– Fat content in the bran slows the emptying

of the stomach and also the hydrolysis and absorption of starch

– Fiber content in the bran slows emptying time of the stomach

Brown rice can help lower blood pressure

– Brown rice diets have been known for many years to be effective in reducing hypertension.

– Rice bran has recently been shown to decrease hypertension via inhibition of an angiotensin-1 converting enyzme (ACE inhibitor).

Brown rice contributes to antioxidants

The micronutrients manganese, selenium and magnesium are found almost entirely in the bran of rice

One cup (195 grams) of cooked brown rice can provide– 66% of the daily requirement of manganese– 27% of the daily requirement of selenium– 20% of the daily requirement of magnesium

These micronutrients facilitate the synthesis of certain antioxidant enzymes that are protective for the prevention of cancer and inflammatory processes, including arteriosclerotic disease

Other benefits of consuming the whole

grain Eating whole grains such as brown rice is

linked in many studies to protection against :– Coronary artery disease and stroke – Obesity– Insulin resistance (pre-diabetes)– Type II diabetes (adult-onset diabetes)– Celiac disease (gluten intolerance)

Intriguing studies Asthma: One Dutch study found that the

probability of having asthma with bronchial hyper-responsiveness was significantly less in children who had a high intake of whole grains

Gastrointestinal cancer: A British study of gastrointestinal adenoma found that daily consumption of a high dose of stabilized rice bran was associated with an average reduction of 51% in the number of precancerous adenomas in the intestinal tract

2. Choosing the most nutritious varieties

Benefits from traditional cultivars– A study of Philippine landraces (traditional

cultivars) demonstrated average lipid content to be significantly higher than in HYVs collected in the same area – 2.1% for HYVs compared with up to 3.2% for some landrace varieties

– Some landraces had a linoleic acid content of almost 1% of the total grain so that 200 grams of such rice could supply half of an adult’s daily requirement

Traditional cultivars and protein quality

Some landraces in the Philippines have protein content up to 14%; one Chinese long-grain rice has been reported with a 16% protein content

Average protein content of HYVs is 6-11% American and Indian rice breeders recently

announced a hybrid with 12.4% protein.

Traditional cultivars and micronutrients

Commercial varieties of rice usually contain about 2 mg/kg of iron

Some selected Philippine varieties contain more than 5 mg/kg of iron

Certain colored traditional rice varieties in Philippines have 63.5 mg/kg iron.

Some highly-colored landraces in Philippines and Malaysia can contribute most, but not all, of a person’s daily requirement of vitamin A precursors

Remember: iron like other nutrients is in bran!

Bio-engineering nutrition

An transgenic rice has been developed which is iron-rich – It has an iron content of 38 mg/kg

– This iron is stored as iron-ferritin in the endosperm

Therefore, it is in principle more bio-available and is not lost with milling

Bio-engineered Iron-Rich Rice

– The grain has been engineered to have lower phytate levels

Phytates interfere with iron absorption

– The grain also has a metallothionein-like protein that enhances iron absorption

– However, field testing and human

absorption studies have yet to be done

Golden Rice Golden Rice is a transgenic engineering

accomplishment that has been heralded in the popular media as a means of combating vitamin A deficiency.

Ingo Potrykus from Zurich and Peter Beyer of Freiburg developed a biosynthetic pathway that expressed beta carotene in the rice endosperm.

The first Golden Rice (GR1) developed in 1999 contained 1.6 micrograms of beta carotene per gram– This was an order of magnitude more than

most rice but still a small contribution toward the daily requirement.

Golden Rice GR2, developed in 2005, produces up to

37 micrograms of beta carotene per gram of milled rice– This amount theoretically could meet the

daily requirement of someone whose primary source of dietary energy was rice.

However, how well the carotenoids in Golden Rice will be converted to vitamin A in the intestinal tract -- and absorbed into the blood stream -- has yet to be studied.

Golden Rice Golden Rice may make a significant

contribution to alleviating vitamin A deficiency diseases

But the contribution of Golden Rice to human nutrition and health will not be available for a number of years

3. Modifying cultivation to improve nutrition

Cultivation practices and environmental circumstances have been shown to affect the total protein content of rice

Some factors that increase the protein content of rice are:

wider spacing border effectsresponse to nitrogen fertilizervarious stresses

Cultivation practices affect the biological value (BV) of the rice protein– BV reflects the completeness of the set of amino

acids that the body needs for protein synthesis A Bulgarian research project demonstrated that

application of nitrogen-phosphorus fertilizer increased yield and total protein– But this protein had a lower biological

value because of the relative decrease in various essential amino acids: Lysine, Arginine, Threonine, Valine, Leucine and Isoleucine – by 5 to 24%

The effect of fertilizer application on amino acid composition of the rice protein varied among the cultivars evaluated

Biological Value of protein

Cultivation affects BV A study in Japan showed that application

of nitrogen fertilizer changed the free amino acid composition of brown rice

The total amount of some free amino acids (glutamic acid, aspartic acid, asparagine, glutamine and alanine) was higher in grain produced without application of nitrogen fertilizer

The BV of rice protein makes a difference

Study of nitrogen balance in poor children in Peru compared high-protein rice (11.4% protein) diet with conventional rice (7.1% protein) diet:– Children on the high-protein rice diet retained

more nitrogen in their bodies than with the lower-protein rice diet, but

– Less nitrogen was retained per gram of ingested N for high-protein rice compared with the lower-protein rice, indicating that the high-protein rice had lower BV

Rice can contribute more to health and nutrition if we:

1. Consume whole grain rice -- do not discard the most nutrient-rich part, the bran!

Rice can contribute more to health and nutrition if we:

2. Utilize the best available varieties in terms of their nutritional value:

Select and protect a biodiverse set of existing cultivars that provide positive nutritional benefit, and

Continue the breeding and

development of promising new cultivars

Rice can contribute more to health and nutrition if we:

3. Learn more about how alternative cultivation practices affect the nutrient qualities of rice, e.g. SICA

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