Eating a diet rich in fruits and vegetables may not, it turns out, help us enjoy a long and healthy life.

Studies over the last 15 years, The Times reported, reveal that much of our produce is low in phytonutrients, the compounds that are supposed to reduce the risk of the four diseases that plague modern life: cancer, heart disease, diabetes and dementia. And the decline in the health benefits of our food is not a recent development.

"Unwittingly, we have been stripping the phytonutrients from our diet since we stopped foraging for wild plants some 10,000 years ago," Jo Robinson wrote in The Times.

Wild dandelions have seven times the phytonutrients of spinach, which many think is a superfood; a purple potato native to Peru has 28 times more cancer-fighting anthocyanins than a common potato; one type of apple has 100 times more phytonutrients than a Golden Delicious.

When Europeans first arrived in North America, they noted that the Indians had corn of many hues. These days white sweet corn is ubiquitous, a variety higher in sugar and lower in anthocyanins. We've also discovered that blue, red and black corn is rich in anthocyanins, which "have the potential to fight cancer, calm inflammation, lower cholesterol and blood pressure, protect the aging brain and reduce the risk of obesity, diabetes and cardiovascular disease," Ms. Robinson wrote.

Of course if we don't have time to consume these superfoods, we can make sure we take our vitamins. Some experts say people get enough vitamins from a routine diet, while vitamin makers say supplements are needed.

"Most people assume that, at the very least, excess vitamins can't do any harm," Paul A. Offit wrote in The Times. But, "scientists have known for years that large quantities of supplemental vitamins can be quite harmful."

Studies have shown that supplemental vitamins A, C, E and beta carotene, and a mineral, selenium, caused higher death rates when taken to prevent intestinal cancers, Mr. Offit reported in The Times.

But help may be available from unseen allies. Recent research shows that the trillion or so bacteria living in our guts and on our skin may fight off some chronic diseases of our time. Maria Gloria Dominguez-Bello, a Venezuelan-born microbiologist at New York University, went to remote corners of the Amazon to collect samples from hunter-gatherers who have had little contact with Westerners. "We want to see how the human microbiota looks before antibiotics, before processed food, before modern birth," she told The Times.

Preliminary results indicate that a pristine microbiome features much greater diversity, and this may play a role in Amerindians' markedly lower rates of allergies, asthma, atopic disease and chronic conditions like Type 2 diabetes and cardiovascular disease, Michael Pollan reported in The Times.

The Western diet lacks fiber, and another problem is an overemphasis on hygiene, some scientist believe.

"There's a case for dirtying up your diet," the Stanford microbiologist Justin Sonnenburg told Mr. Pollan. Yet people should probably wash their produce because many times they are rinsing off pesticide residues.

"Increased exposure to environmental microbes likely decreases chance of many Western diseases, but increases pathogen exposure. Certainly the costs go up as scary antibiotic-resistant bacteria become more prevalent," Mr. Sonnenburg said in an email.

Mr. Pollan urges you to wash your hands in situations when pathogens or toxic chemicals are likely present, but maybe not after petting your dog.

Mr. Sonnenburg advises: "In terms of food, I think eating fermented foods is the answer - as opposed to not washing food, unless it is from your garden."

For comments, write to nytweekly@nytimes.com.

(China Daily 06/23/2013 page9)