Nuts have been consistently associated with reduced risk of coronary heart disease in epidemiological studies.1 Evidence of nuts’ cardioprotective effects were originally recognized in the early 1990s2, and since then, several human trials have documented improvements in lipid levels in response to including nuts in the diet.3 Beneficial cardiovascular effects beyond cholesterol lowering have also been identified, particularly for walnuts and almonds.
A review published recently in Archives of Internal Medicine pooled the data from 25 different clinical studies that ran for a minimum of three weeks, comparing a nut eating group to a control group. Most of the studies were done on walnuts or almonds, but studies on macadamias, pistachios, hazelnuts, pecans, and peanuts were also included in the analysis.4,5
This review confirmed that nut consumption has beneficial effects on lipid levels, and it also reached two interesting new conclusions:
1. Dose dependent effect
First, the different studies were on different quantities of nuts, and the review concluded that the cholesterol-lowering effects of nuts are dose-dependent – this means that more nuts consumed translated into greater decreases in LDL and total cholesterol:
Quantity of nuts consumed | Decrease in total cholesterol | Decrease in LDL |
1 oz. | 2.8% | 4.2% |
1.5 oz. | 3.2% | 4.9% |
2.4 oz. | 5.1% | 7.4% |
For healthy weight individuals, these results suggest that 2.4 ounces may be better than 1 ounce for cardiovascular health.4,5
2. Effects were greater in individuals with lower BMI
The researchers found that body mass index (BMI) modified the association between nut consumption and cholesterol lowering. The effects of nuts were greater in individuals with lower BMI, meaning that those who were overweight or obese saw less cholesterol-lowering benefit than healthy weight individuals.4,5
Nuts and seeds are critical components of a disease-preventing diet, and I recommend eating them daily. However, I also recommend a limit of 1 ounce of nuts and seeds per day for individuals who are overweight. The results of this study support my recommendations. For those that are overweight, nuts are beneficial, but weight loss is even more important. The primary means of decreasing cardiovascular risk in overweight individuals should be eating lots of high micronutrient, low calorie foods. For people significantly overweight, nuts should still be included, but their caloric density suggests a limit such as 1 ounce per day for women and 1.5 ounces a day for men.
Wondering how many nuts are in a 1 ounce serving? The International Tree Nut Council’s website provides aguide to 1 ounce serving sizes of several different nuts.
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