Nuts and seeds are rich in nutrients and phytochemicals. But, they are also high in fat. So, many people avoid nut consumption out of fear that it will counteract their efforts to achieve or maintain their ideal body weight. But, large population studies have shown that the people who consumed the most nuts were less obese. A possible explanation is that the nuts produced two key effects that help fight obesity:
- They promote satiety, the feeling of appetite satisfaction.
- They increase the action of the hormone insulin, thereby improving blood sugar control, appetite regulation, and metabolism.
Numerous large studies have found that higher nut consumption is also associated with a protective effect against cardiovascular disease and type 2 diabetes.
The traditional Mediterranean diet reflects food patterns typical of some Mediterranean regions in the early 1960s, such as Crete, parts of the rest of Greece, and southern Italy. The traditional Mediterranean diet has shown tremendous benefit in preventing and even reversing heart disease and cancer as well as diabetes. It has the following characteristics:
- Olive oil is the principal source of fat.
- An abundance of plant food (fruit, vegetables, breads, pasta, potatoes, beans, nuts, and seeds).
- Foods are minimally processed, and there is a focus on seasonally fresh and locally grown foods.
- Fresh fruit is the typical daily dessert, sweets containing concentrated sugars or honey being consumed a few times per week at the most.
- Dairy products (principally cheese and yogurt) are consumed daily in low to moderate amounts.
- Fish is consumed on a regular basis.
- Poultry and eggs are consumed in moderate amounts (1-4 times weekly) or not at all.
- Red meat is consumed in low amounts.
- Wine is consumed in low to moderate amounts, normally with meals.
One of the key components of the Mediterranean diet is olive oil which consists not only of the monounsaturated fatty acid oleic acid; but also contains several antioxidant agents that may also account for some of its health benefits. Olive oil is particularly valued for its protection against heart disease.
To gauge the impact of nut consumption within the Mediterranean diet, a total of 7,447 older participants (men aged 55–80 years and women 60–80 years) were assigned to 1 of 3 interventions: a Mediterranean diet enriched with extra-virgin olive oil (EVOO), a Mediterranean diet supplemented with mixed nuts, or advice on a low-fat diet (control diet).
Although participants had no cardiovascular disease (CVD) at enrollment, they were at high cardiovascular risk because of the presence of type 2 diabetes or at least 3 of the following risk factors:
- Current smoking
- High blood pressure
- Elevated blood total blood cholesterol levels
- Low levels of high-density lipoprotein (HDL) cholesterol
- Overweight or obesity
- Family history of premature CVD.
After excluding people with extreme calorie intake or incomplete dietary data, 7,216 individuals completed the analysis.
Nut consumption of participants was evaluated at baseline using a 137-item semi-quantitative food frequency questionnaire administered in face-to-face interviews by dieticians. Information on self-reported nut intake in general and walnut intake specifically was obtained. Participants reported the frequency and quantity of nut (and specifically walnut) consumption. For the purpose of this study, 28 grams of nuts was considered to be one serving.
During a median follow-up of 4.8 years, nut consumption was associated with a significantly reduced risk of all-cause mortality. Compared to non-consumers, subjects consuming nuts at a level of >3 servings/week (32% of the study group) had a 39% lower mortality risk. Furthermore, participants following the Mediterranean diet who consumed nuts >3 servings/week at baseline had the lowest total mortality risk – a whopping 63% reduced risk.
In regards to cancer risk, consuming >3 servings per week of walnuts was associated with a greater than 50% reduced risk of dying from cancer.
These results highlight the benefits of eating nuts in combination with the Mediterranean diet. They also raise a serious question on the wisdom of low fat diets that avoid nut consumption because of their fat content.
Despite the benefits of frequent nut consumption, many people avoid eating nuts because of their high fat content. The key is quality and portion control. Choose lightly dry roasted or raw nuts and seeds – avoid the chocolate covered peanuts, nuts roasted in oil and salt, and other unhealthy choices.
Are walnuts the best choice? Not necessarily. A possible explanation that may account for the inverse relationship between walnuts and cancer mortality but not with other nuts could be that walnuts are more likely to be consumed raw. And, in their raw state, walnuts are not only an excellent source of alpha-linolenic acid – an omega-3 fatty acid – they are also higher in anti-cancer polyphenols and antioxidant activity than all the other nuts. Roasting nuts, including walnuts, can cause a reduction in the polyphenol content as well as the overall antioxidant activity.
Key takeaway point – eat a moderate amount of nuts each day. About ¼ of a cup or a small handful is all that you need to see the health benefits.
Guasch-Ferré M, Bulló M, Martínez-González MA, et al. Frequency of nut consumption and mortality risk in the PREDIMED nutrition intervention trial. BMC Med. 2013 Jul 16;11:164.