Although "facts" about nutrition seem to change every week, some have stood the test of time.
Here are five rules that still provide good guidance, despite continually conflicting nutrition studies.
1. Choose a variety of food.
From 1980 to 1995, the Dietary Guidelines for Americans advised, "Eat a variety of foods." The 2015 Dietary Guidelines still say to "choose a variety of nutrient-dense foods across and within all food groups."
So what about popular eating plans that cut out major food groups - such as vegans avoiding dairy and paleo dieters skipping grains? Can diets be healthy if they lack "all food groups"? Foods can be mixed and matched in many ways to create a plan providing enough variety to meet nutrient needs, but it has to be done right. Want to know whether your diet measures up? See a dietitian for an assessment to know for sure.
2. Eat your vegetables.
Since the first U.S. Agriculture Department food guide appeared in 1917, the message to eat "vegetables and fruit" has been a mainstay, and scientific research on the importance of vegetables has strengthened over time.
Studies link vegetable and fruit consumption with a reduced risk of developing Type 2 diabetes, high blood pressure, heart disease, obesity, dementia and certain types of cancer. Nutritional guidelines suggest you fill half your plate with vegetables and fruit at every meal. Plus, they are versatile and taste good.
3. Get enough fiber.
Fiber-rich foods were recommended in the 1980 Dietary Guidelines for Americans to avoid constipation and reduce colon cancer risk. Fast-forward almost 40 years, and the advice remains the same. In addition to colon health, we also know that fiber is vital to prevent heart disease and Type 2 diabetes.
Fiber-rich foods include vegetables, beans, lentils, nuts, seeds, bran cereals and whole grains. Just a cup of raspberries or a half-cup of lentils add 8 grams of fiber to your day.
4. Say no to junk food
The 1979 USDA guide "Food: The Hassle-Free Guide to a Better Diet" was the first version to add a category recommending moderation for foods that provide calories from sugar and fat but havelittle nutritional value.
A healthy diet will never be built on cake and ice cream. And other than the ridiculously named Cookie Diet (using low-calorie, specially formulated cookies), no fad diets are based on eating more junk food. Chips, candy and similar treats do not provide significant nutrients to the body, and overconsumption is linked to increased disease risk. That's not going to change.
5. Be careful with alcohol.
Since 1980, the Dietary Guidelines have advised that if you drink alcohol, do it in moderation: no more than one drink a day for women or two drinks a day for men. And no, you can't save it up and consume seven to 14 drinks on the weekend. One drink equals 12 ounces of beer, 5 ounces of wine or 1½ ounces of liquor such as vodka.
Alcohol carries the risk of dependency, and excess consumption is linked to liver damage, obesity and an increased risk of certain cancers. So if you don't drink, don't start. And if you do drink, practice moderation. As with junk food, alcohol won't ever become health food.