wsj: Flu Fighters in Your Food | Boost Immunity by Making Sure Your Diet Has the Right Nutrients

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The Flu Fighters---in Your Food

New Research Points to Ways to Boost Immunity by Making Sure Your Diet

Has the Right Nutrients

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While many people are still waiting for swine-flu vaccine to become

available in their area, there is a lot they can do in their own

kitchens to help fight off disease and build a strong immune system.

Scientists in the growing field of nutritional immunology are unveiling

new evidence of the complex role that nutrition plays in fighting off

infectious diseases like influenza. A diet rich in nutrients such as

vitamin A, found in colorful fruits and vegetables, and zinc, found in

seafood, nuts and whole grains, can provide the critical fuel the body

needs to fight off disease, heal injuries, and survive illness when it

does strike, experts say.

Key Ingredients

Click on the link below to see key ingredients in your food

http://s.wsj.net/public/resources/documents/wsj_informed091123.pdf

Scientists are still studying all the complex ways in which nutrients

interact with the immune system. There is still much that they don't

know about minerals such as zinc, for instance, including how they are

absorbed and all the roles they play in the body. But scientists do know

that certain vitamins and minerals can improve the body's ability to

fight off infection: Studies in healthy elderly adults, for example,

have shown an improved immune response to vaccination and fewer

infections after receiving extra doses of vitamin E.

To create immune cells to fight off a specific infection, the body has

to rapidly draw nutrients from the bloodstream, says Anuraj Shankar, a

researcher at the Harvard School of Public Health. " If you don't have an

adequate intake of vitamins and minerals, you won't be able to produce

the number of immune cells you need, and the immune cells you do produce

may be compromised, " Dr. Shankar says. That makes it impossible to mount

an effective response to infection, he says.

The benefits of good nutrition may have been recognized first by

Hippocrates, the ancient Greek physician who declared " let food be thy

medicine, and medicine be thy food. " An 18th century naval surgeon's

discovery that citrus fruits could cure scurvy in sailors was later

recognized as a vitamin C deficiency, and after the 1930s, when dairies

began to fortify milk with vitamin D, the disease known as rickets was

virtually eliminated in the U.S.

Researchers warn that malnourished people may be a breeding ground for

more dangerous infectious diseases. Animal studies at the University of

North Carolina show that in a host with poor nutrition, viruses mutate

in the face of a weak immune response to become more powerful. And once

those mutations occur, even well-nourished hosts are susceptible to the

newly virulent virus. " A lot of people may think malnutrition on the

other side of the world isn't their problem, " says Melinda A. Beck, a

researcher at the University of North Carolina, Chapel Hill. But

malnutrition " is a driving force in emerging infectious diseases that

are spreading around the world, " she says.

The human body doesn't have to be starving to suffer from malnutrition.

Studies show that obesity, in addition to its other health risks, may

also make people more susceptible to infections like the flu. A diet

heavy on processed and fast foods may be low in the vitamins and

minerals important for health. And diets that are high in saturated fat

appear to actually depress the body's immune response, increasing the

risk of infections.

Dr. Beck says studies of mice show that only 4% of lean animals infected

with the flu virus die. That compares with a death rate of between 40%

and 60% in obese mice infected with the virus. And after a small study

showed that obese people vaccinated for the flu didn't mount a strong

immune response, the University of North Carolina is expanding its

trials to compare vaccination response rates in lean and obese people.

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When obese people fall ill, " their immune function may not be strong

enough to mount an effective response, " says Hensrud, a Mayo

Clinic specialist in preventive and internal medicine and

editor-in-chief of " The Mayo Clinic Diet, " a new book promoting weight

loss through a healthy diet that allows unlimited quantities of fruits

and vegetables.

Warning on Supplements

Dr. Hensrud and other experts caution against loading up on supplements

to add vitamins and minerals to the diet. While a multivitamin is a good

addition to any balanced diet, individual supplements and vitamin pills

may not be as well absorbed by the body as nutrients in foods. Some

supplements also can have toxic effects in too-high quantities. An

excess of zinc, for example, can interfere with absorption of other

nutrients, including iron and copper. And too much of the mineral

selenium can cause nerve damage and has been linked recently to an

increased risk of diabetes.

There is no single test to measure if your body has enough vitamins and

minerals, and assays for individual nutrients are generally expensive

and unreliable. Blood tests used to screen for blood-cell abnormalities

can pick up changes that are linked to possible vitamin or mineral

deficiencies, but they can't necessarily identify the cause.

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" The key to supplements for strengthening the immune system is

time. You have to be using them for months before the infection for them

to be effective. "

--- Wayne Osedach

Scientists have long known that some vitamins, minerals and other

nutrients can play a key role in the immune system by acting as

antioxidants. These protect and repair cells from oxidative stress, the

damage caused by molecules known as free radicals.

But nutrients work in ways beyond acting as antioxidants, says Dr. Beck.

For example, vitamin A can enhance the immune system " by stimulating

specific proteins necessary for immune function by activating specific

genes, " she says. So, if vitamin A is deficient, then the immune cells

that require vitamin A to function properly won't work as efficiently.

Animal studies show that a deficiency of vitamin B-6, which helps

maintain the health of organs that make white blood cells, can decrease

antibody production and suppress the immune response. And selenium in

small amounts can help stimulate immune cells and may prevent the growth

of some tumors.

Nutritional experts generally agree that the best way to get the right

balance of nutrients is a balanced diet that includes plenty of fresh

fruits and vegetables, lean proteins and dietary fiber. The federal

Centers for Disease Control and Prevention's

www.fruitsandveggiesmatter.gov Web site offers a calculator to determine

how many servings are ideal based on calorie needs for age, sex and

activity level. Harvard's Nutrition Source Web site includes a healthy

eating pyramid based on the most up-to-date knowledge of nutrition

requirements. And the National Institutes of Health's Office of Dietary

Supplements Web site (dietary-supplements.info.nih.gov) offers detailed

information on the risks and benefits of supplements, along with tables

that list food sources for each vitamin and mineral.

A survey by the CDC in 2007 showed that the majority of adults consume

less than the government's recommended five servings of fruits and

vegetables daily. But quantity matters: A 2004 Harvard study of 110,000

men and women showed that people who averaged eight or more servings of

fruit and vegetables daily were 30% less likely to have had a heart

attack or stroke than those who had only 1.5 servings daily.

Nutrition experts say to boost immunity it is also important to avoid

processed foods, and to minimize trans fats and unhealthy saturated fats

from animal products and vegetable oils like palm and coconut. Instead,

they say, people should eat foods rich in unsaturated fats such as olive

oil.

Contradictory Advice

Some advice for a healthy diet can seem contradictory. For example,

heart-healthy diets typically include unsaturated fats such as omega-3

fatty acids, which are found in fish such as salmon and trout and in

flaxseed and walnuts. For people who don't want those foods,

nutritionists may recommend fish-oil supplements, which can be

beneficial in suppressing chronic inflammation in the body, a condition

that can lead to coronary artery disease and arthritis.

But those same anti-inflammatory properties of fish oil can also

suppress the immune responses necessary to combat an acute viral

infection. Studies at the University of North Carolina have shown that

mice fed with fish oil have an impaired resistance to infections,

including the flu. " If I suppress the immune response and get a viral

infection, I'm worse off, " says Dr. Beck, who is studying the links

between fish oil and resistance to influenza.

One nutrient hard to get in food is vitamin D. Even with the

fortification of milk, orange juice and other food products, some

experts have been sounding the alarm in recent years about wide

deficiencies, especially in children. Tests are available for about $100

to determine vitamin D levels, but their accuracy is in question. And

just how much vitamin D different people need is the subject of

considerable debate. The federal government's current recommendations

range from 200 international units daily for children to 600 IUs for

adults, with a safe upper limit of 2,000 IUs daily. The American Academy

of Pediatrics recommends 400 IUs for children, and vitamin D experts at

Oregon State University and elsewhere recommend 2,000 IUs daily for all

adults. The Institute of Medicine, a government advisory group, is

expected next year to update the recommendations.

Gombart, a researcher at Oregon State University's Linus ing

Institute, says vitamin D, in addition to building strong bones and

fighting off a variety of diseases, appears to activate proteins that

help the body fight off infection. " Vitamin D won't prevent you from

getting the flu, but it might allow you to mount an optimal immune

response, suffer less of the effects, and resolve the infection more

quickly, " says Dr. Gombart, who is researching the nutrient's role in

stimulating immune cells.

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