A highly publicized study released earlier this year claimed that eating meat in midlife may cause early death but eating meat later in life can protect older people from frailty. The conclusion was interesting, but the study raised a more general question: Should we eat differently at different ages? Should our diet shift, as we do, across our lifespan? 

Well, yes and no. No, because a balanced diet filled with the foods you already know are good for you — fruits and veggies, whole grains and lean meat — and light in those that aren’t — sugar, salt and processed foods — would ideally nourish people at every age. Yes, because, in reality, eating behavior changes with age and doesn’t always support our needs. Plus, certain nutrients become more or less important at different stages of life.

For example, as we age our bodies lose protein so we need to find new protein sources to stay healthy. And yet, this is a time in life when many people don’t eat enough, says Michael Roizen, chief wellness officer of the Cleveland Clinic. "When you are frail, that is, when you are older, you need a certain amount of protein, whether it is animal or vegetable protein," he says. By contrast, eating red meat when you're younger gives the animal protein time to develop into cancer and other diseases, he says. As Roizen sees it, nutritional requirements don’t dramatically change over the lifespan; but we do.

That said, Americans aren’t doing a great job of eating well at any age. The chasm between optimal and actual eating, coupled with physical inactivity, has nearly 70 percent of U.S. adults overweight or obese by the standards of the Centers for Disease Control and Prevention. Adults and children are getting so little of some nutrients — potassium, dietary fiber, calcium, and vitamin D — that it's a public health concern, according to the 2010 Dietary Guidelines for Americans.

In other words, we eat too much of the wrong foods and not enough of the right ones. How that affects us has a lot to do with the way our dietary patterns and needs evolve over time.

Youth

Until about age 14, we tend to be food phobic, says Brian Wansink, who studies eating behavior as director of Cornell University’s Food and Brand Lab. "We’re kind of scared of new foods." Our narrow range of foods can limit important nutrients. Key among them are calcium, protein and vitamin D to build bone and muscle mass. One thousand milligrams of calcium are recommended every day for children between the ages of 4 and 8, and that amount climbs to 1,300 from ages 9 to 18. But bone building remains a priority throughout the 20s, according to the American Academy of Nutrition and Dietetics, which emphasizes getting the recommended 1,000 milligrams of calcium per day through foods such as low-fat dairy, beans, leafy greens and canned salmon.

Still, young people have, well, youth on their side.

The hormones and muscle mass of youth can keep insulin sensitivity in check, explains Walter Willett, chair of the nutrition department at Harvard’s School of Public Health. "We can get away with less healthy diets without gaining weight or developing diabetes, even though it would be better to have a healthy diet even then," he says. "By middle age, these anabolic hormones are declining, our muscle mass is shrinking, and the same diet and activity pattern will lead to weight gain and metabolic abnormalities and even diabetes."

But even before the onset of middle age — generally defined as the period from the mid-40s to the mid-60s — some of youth’s resilience slips away. By the 30s, skin becomes less elastic and metabolism slows, says Jim White, a Virginia Beach-based dietitian and spokesperson for the Academy of Nutrition and Dietetics. You can boost skin health with supplements of vitamin C and omega-3 fatty acids, he says, and, meanwhile, watch the scale.  "Weight can really creep up in these years," he says. "While they’re healthy, while they’re young, this is when they want to really step up their exercise game and really stay in tune to their diet."

Women considering pregnancy will also want to get enough folic acid, a B vitamin that helps prevent severe birth defects. Because defects in brain and spinal development can form early in pregnancy — and because half of pregnancies are unplanned — women who could become pregnant should take 400 to 800 micrograms of folic acid a day, according to government recommendations. Roizen of the Cleveland Clinic says that taking a prenatal vitamin for three months before becoming pregnant reduces the risk of autism in a child by 40 percent.

Middle age

If there’s a time in life when eating habits really count, this is it. In middle age, dietary choices simply carry more weight, so to speak. So beware of the so-called "middle age spread."

Harvard’s Willett cites a 2010 study published in the New England Journal of Medicine that found links between a high body mass index (BMI) and increased risk of death. The study analyzed 1.46 million white adults and found that the lowest rates of mortality were found among those with a BMI that’s considered normal — in the range of 20 to 24.9.

Belly fat, in particular, has been shown to correlate with risk of heart disease and diabetes.

vegetables healthy eatingTo be healthy later in life, White suggests fortifying your 40s with two to four servings of fruit per day and "unrestricted veggies." You can also boost your metabolism with structured snacking and weight training to build up lean muscle, he says.

The problem is that much of what we crave during these years can derail us.

According to Wansink, during the broad swath of adulthood — from 18 through 65 — we eat too many starchy carbs like potatoes, French fries and highly processed foods. These fill us up with lots of calories but not a lot of nutrients, which is precisely the opposite prescription for this age. (By contrast, we can use the extra calories in youth, when we also crave starchy carbs, and in old age, when we happen to crave soups, he says.) Wansink also finds that men tend to consider comfort food hot, heavy meals, which are more likely to provide some nutrients, while women go for nutrient-poor snack foods.

On entering the 50s and beyond, White advocates a varied and moderate diet, steering clear of any fads that avoid entire food groups, which could lead to dangerous deficiencies. "I know moderation’s not the sexiest word, but it really gets the job done," he says. White also advises taking a multivitamin and cutting back on salt, saturated fat and added sugars to keep cholesterol and blood pressure in check.

From age 50 on, Roizen encourages taking DHA, or omega-3 fatty acids, to protect brain function and guard against the beginnings of macular degeneration. Women, meanwhile, will want to increase their calcium intake as menopause and age can bring about osteoporosis. Starting at age 51, the National Institutes of Health recommends upping daily calcium intake from 1,000 milligrams to 1,200 milligrams. Vitamin D is also recommended to aid calcium absorption.

In navigating these considerations, meal plans may take some ingenuity. So, for example, to treat her book club of women in their 50s and up, Wyoming-based dietitian Judy Barbe recently created age-appropriate refreshments: a blue-cheese spread using cottage cheese and yogurt, paired with whole-grain crackers and fruits for dipping. "They need healthier fat, and they need more calcium-rich foods, so that it could be delicious and nutritious. And it turned out it was."

Still, Barbe says, "I don’t think food can bear the burden of a healthy lifestyle. You have to be physically active to build your bones, strengthen your muscles, relieve stress and sleep better."

Older age

As people age into their 60s and beyond, they need enough protein. Starting in their 70s, men will also require more calcium, with 1,200 milligrams recommended per day for bone health. And supplements of vitamin B12, which support the brain and nervous system, may be needed because it gets harder absorbing nutrients with age.

If this all sounds complex, it doesn’t really need to be, according to Marion Nestle, professor of nutrition, food studies and public health at New York University. "Most people who take in adequate calories take in adequate protein and get enough vitamins, particularly because so many foods are vitamin fortified. The biggest risk factor for nutritional problems in aging is all the drugs people take, which affects metabolism, she says. "The more drugs, the higher the risk of nutritional problems."

So, talk with your doctor to ensure your food and medications support your nutrition. And if nothing else, try to avoid processed foods. "There are only five food felons," Roizen says, rattling them off: "saturated fat, trans fat, added sugar, added syrups and any grain that isn’t 100 percent whole grain."

Apart from that, Willett says, "In nutrition, everything is always a trade-off."

Choose wisely.

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Photo (vegetables): Yeko Photo Studio/Shutterstock