There are so many variables — living conditions, activity levels, family history, medical history, smoking, sleep habits and the list goes on — that it is nearly impossible to get accurate results.

Nutrition advice tends to change, and many recommendations conflict with each other. The problem with human nutrition research is that researchers have little control when conducting diet studies. There are so many variables — living conditions, activity levels, family history, medical history, smoking, sleep habits and the list goes on — that it is nearly impossible to get accurate results. Most findings rely on observational studies linking dietary choices to health outcomes. But these usually rely on self-reported food surveys, and that’s a problem. Responses are often incorrect because people forget what they ate or lie to make it sound better. 

Unless we start institutionalizing infants for their entire lives and feeding them a controlled diet in a controlled environment, we likely will never have true scientific findings concerning diet and links to disease. The best we can do is look at observational studies for common links. 

Unfortunately, many conclusions made this way have later been proven incorrect. Following are some of the nutrition recommendations that have changed.

Cholesterol. We now know that our body’s cholesterol levels are primarily controlled by our genes rather than by what we eat. In the 1980s, manufacturers put cholesterol-free labels on everything — even things that never had cholesterol, like peanut butter. Eggs have long been vilified for their cholesterol content. If you were watching your cholesterol, the first thing you likely cut was egg yolks. Newer studies have shown that the cholesterol in eggs doesn’t raise our cholesterol level, so there is no reason to avoid eating egg yolks. Eggs may be high in fat and cholesterol, but they are also loaded with important vitamins and minerals and are an excellent, inexpensive source of protein.

Current advice: Keep your egg intake to a moderate six or seven in a week, and avoid pairing your eggs with high-fat meats, such as bacon and sausage.

Fat. The first Dietary Guidelines for Americans was published in 1980. The recommendation to decrease fat in our diet was designed to help combat the growing problem of heart disease. Consumers followed the advice, and soon low-fat everything was all the rage. Manufacturers created a whole new category of low-fat junk foods that appeared to be healthier options. We later discovered that replacing all that fat with junky carbohydrates and sugar left us fat and in worse health. Some fat is needed by the body and too little fat in the diet can cause vitamin deficiency and a weakened immune system. We now know that eating healthy fats can help with weight loss and many fats are good for your heart.

Current advice: Your daily diet should include monounsaturated fats, which include olive oil, avocados and nuts, and omega 3 fats, found in fish.

Margarine.  First developed in the late 1800s, margarine didn’t become popular until the 1950s, when the first studies connecting saturated fat to heart disease were published and manufacturers were allowed to color the previously white margarines yellow to make them more appealing. Turns out, margarines were worse for us than butter because they were made with trans fats.  Today’s margarines contain very little, if any, trans fat and are made with heart-healthy vegetables oils. Is butter better? The verdict is still out. Butter is a saturated fat, but dairy fats are less worrisome than we once thought.

Current advice: Whichever you choose, margarine or butter, use it sparingly. Cook with oils, and use butter or margarine as flavorings.

Coffee.  Around 1900, it was believed that coffee would stunt a child’s growth. Then in the 1970s and 1980s, experts said drinking coffee would lead to high blood pressure and a greater risk of heart attack and stroke. Now, coffee is practically a health food with most experts in agreement that a moderate coffee intake may actually reduce your risk of heart disease.

Current advice: Keep your coffee intake to four cups or less per day (less if you are pregnant), and you should be fine. 

Salt. Salt is essential for life; it helps regulate our blood volume, shuttles nutrients in our bodies, and helps our muscles contract and our nerves transmit. But since the 1970s, we have been told to limit our sodium intake to between 1,500 milligrams and 2,300 milligrams per day to keep high blood pressure controlled.  In 2016, a large study published in The Lancet found that those who had a normal blood pressure and ate a diet moderate in sodium (defined as between 3,000 and 4,000 milligrams daily) had a lower risk of heart disease and stroke than those who ate either more or less sodium on average.

Current advice: If you have normal blood pressure, it is probably not beneficial to restrict your sodium intake below 3,000 milligrams per day. Keep in mind, though, that many restaurant foods and processed foods have this much sodium or more in a single serving. 

There are few certainties when it comes to nutrition, and I’m sure there will be many more recommendation changes in the coming years. All we know for sure is that we can’t live without food; if we eat too much, we will get fat; and certain vitamins and minerals found in food are essential in the prevention of disease. My best advice is to buy raw food and cook it yourself; eat lots of fruits and vegetables; and limit your intake of processed and sugary foods. And always eat in moderation. 

Anita Marlay, R.D., L.D., is a dietitian in the Cardiopulmonary Rehab department at Lake Regional Health System in Osage Beach.