THE PREDIMED TRIAL
Other population-based studies have come to similar conclusions— nuts are good for you. In particular, the PREDIMED trial, a long-term trial evaluating how a Mediterranean diet may reduce risk of cardiovascular disease (diseases of the heart and blood vessels), randomly assigned 7,447 older adults (ages 55-80 years) with a high risk of developing cardiovascular disease into one of three diet groups: a Mediterranean diet plus 1 liter per week of virgin olive oil (50 ml/day), a Mediterranean diet plus 30 grams per day of mixed nuts (15 grams walnuts, 7.5 grams hazelnuts and 7.5 grams almonds) or a low-fat diet (control diet). The participants in the Mediterranean diet groups were educated on this eating pattern, which is based on consumption of fresh fruits, vegetables, legumes, fish or seafood (including at least one serving of fatty fish per week), at least one serving of nuts or seeds per week, choosing white meats versus red meats and the addition of tomatoes, garlic, onion at least twice per week while cooking. They were instructed to limit or eliminate fried foods and sweets. In addition, those in the low-fat control diet group were advised to reduce all types of fats and consume lean meats, low-fat dairy products, cereals, potatoes, rice, pasta, fruits and vegetables. All groups could consume food as they desired— they were not given a strict calorie limit to adhere to. After an average follow-up period of 4.8 years, participants who consumed the Mediterranean diet including nuts increased their nut consumption from an average baseline intake of 0.9 servings per week to six servings per week while those in the Mediterranean diet group increased their consumption of extra-virgin olive oil from a baseline intake of 32 grams per day to 50 grams per day. Both the Mediterranean diet with added extra virgin olive oil as well as the Mediterranean diet with added nuts led to a significant reduction in risk of stroke as well as a 30 percent reduction in risk of death from cardiovascular disease.
In a separate observational cohort analysis of the PREDIMED study, scientists evaluated the initial diets of 7,216 study participants and found those who consumed more than three servings of nuts (including any of the following: peanuts, almonds, hazelnuts, walnuts, pine nuts, pistachios, Brazil nuts, macadamia and cashews) per week at the start of the study had a 39 percent lower risk of death over the course of the 4.8 year follow-up period. In addition, participants in the upper category of nut consumption had a 55 percent lower risk of death from cardiovascular disease and 40 percent lower risk of death from cancer compared to those who never ate nuts over the average 4.8-year follow-up period. And though many of these participants changed to a Mediterranean diet pattern over the course of the study, this study suggests that consuming more than three servings of nuts per week adds additional benefits to a Mediterranean diet.
A UNIQUE COMPOSITION
What makes nuts so good for your body? Nuts come in tiny packages that deliver enormous nutrition benefits. They are full of healthy fats, fiber, vitamins, minerals, phytosterols and antioxidants, substances that protect the cells in your body from damage due to free radicals, Jekyll-and-Hyde-like compounds that are essential for life but can go around and wreak havoc if the body’s antioxidant capacity is too overwhelmed to suppress them from their rampage.
The unique composition of nutrients and healthy plant- based compounds found in nuts has led to a number of studies examining how eating nuts may benefit health. The Harvard study and PREDIMED trial added to previous research studies which have found a relationship between increased consumption of nuts and a decreased risk of certain types of chronic diseases including heart disease and some types of cancer. In addition, clinical trials, studies where participants consumed nuts regularly as part of a mixed diet, have found the more nuts participants ate, the more their levels of blood fats dropped. Increasing consumption of nuts resulted in decreases in total cholesterol, LDL cholesterol, triglycerides and other measures. LDL circulates in the bloodstream where it can build up on artery walls and, along with other substances, form a thick plaque that compromises artery functioning and decreases blood flow. Triglycerides are a type of fat made by the body.
Both high LDL and triglycerides are considered risk factors for heart disease. Three types of study participants benefited the most from the addition of nuts: those with high baseline levels of LDL cholesterol, adults with low body mass index and those consuming a Western diet, which is sometimes referred to as SAD, the Standard American Diet— one that contains large amounts of fried and sweet foods, processed meats and refined grains.
SMALLER WAIST AND LESS WEIGHT GAIN
If you want all of the benefits associated with nuts but you are worried about how they will affect your waistline, consider this: the Harvard study found participants who consumed nuts more frequently were not only leaner but they also had healthier lifestyle habits compared to study participants who consumed nuts less frequently. Frequent nut consumers were more likely to exercise and take a multivitamin supplement; they ate more fruits and vegetables and were less likely to smoke. Previous studies have similar findings— nut consumption is associated with less weight gain and a smaller waist. Despite their high- calorie and high-fat nutrition, snacking on various types of nuts may also lead to weight loss—a phenomenon many experts have attributed to their very filling protein and fat content. In addition to keeping you full, research on almonds and pistachios suggests that our bodies absorb less fat, and therefore calories, from nuts than other food sources.
A study conducted by the U.S. Department of Agriculture and published in the American Journal of Clinical Nutrition found that participants absorbed only 80 percent of the calories from the almonds they ate as part of a mixed diet. And therefore, one serving, or about 23 almonds, provided just 129 calories, not 160 as listed on the Nutrition Facts panel of the package. So what happened to the other 31 calories? During digestion the human body doesn’t completely break down the cell walls that surround the fat within almonds. And therefore, we cannot completely absorb the fat within the nuts.
Another study, published in the British Journal of Nutrition, found that one of the lowest calorie nuts, pistachios, might contribute fewer calories to our diets than previously thought. Over a three-week period, scientists gave study participants a measured amount of pistachios, either 0 (no pistachios), 42 grams or 84 grams of pistachios per day as part of a controlled diet. Using a crossover design, each participant had a chance to consume each level of pistachios— 0, 42 grams and 84 grams— in order to help eliminate potential individual differences from what they set out to determine: if the human body can metabolize and absorb all of the calories from pistachios. Participants absorbed 5 percent fewer calories from the pistachios due to decreased absorption of fat from the nuts. In addition, consuming pistachios lowered LDL cholesterol by 6 percent. Because both of these studies were conducted using whole nuts, the results can’t be transferred to nut butters, which are processed so the cell walls are already broken down, making it easier to absorb the calories they contain.
IN-SHELL VERSUS SHELLED PISTACHIOS
In addition, if you are watching your waistline, in-shell pistachios have an added benefit— research suggests you’ll eat fewer calories if you choose in-shell as opposed to shelled pistachios. College students at Eastern Illinois University were given a 16-ounce cup of either in-shell or shelled pistachios and asked to self-select a portion of pistachios to eat. Students offered in-shell pistachios consumed 41 percent fewer calories than students offered shelled pistachios, indicating the form of the food influenced how many calories were consumed. And though the in-shell pistachio group didn’t eat nearly as many calories as those consuming shelled pistachios, reported fullness and satisfaction ratings were not different between the groups. The study authors suggested those who ate in-shell pistachios consumed fewer calories possibly due to the time it takes to crack open the shells and because the shells are a visible reminder of how much you’ve consumed. And, this theory makes sense. Think about a good server in a bar— they immediately clear beer bottles from the table so their guests aren’t staring at a table full of empty bottles and thinking, “Gosh I better slow down, I’ve had a lot of beer already.” To get you to buy more, they clear plates and bottles off of your table as soon as possible.
GO NUTS
If there’s one step you should take today to help decrease your risk of cardiovascular disease, stroke and possibly even some types of cancers, it’s adding nuts to your diet. Despite their high calorie content for the amount of food you are getting, you probably won’t absorb all of the calories from whole nuts and study after study shows that nut eaters weigh less than those who avoid nuts. So, crack one open today.
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