Nuts consumption and weight gain

Considerable evidence from epidemiologic studies and clinical trials supports that nuts consumption is a healthy way to reduce the risk of cardiovascular disease, type 2 diabetes, and inflammation. In fact, nuts including peanuts were the first whole food that received a heart health claim by the US Food and Drug Administration. Each type of nut varies somewhat in its particular nutritional value, but, in general, nuts are energy dense and provide between 23.4 and 26.8 KJ/g. The total fat content ranges from 45% to 75% of their weight, but this is mostly unsaturated.

Maira Bes-Rastrollo University of Navarra

In this context, because nuts are fat-rich and energy-dense food, their consumption has been limited by the potential negative impact on body weight. However, the available scientific evidence shows that moderate nut consumption does not lead to weight gain. Two reviews about this topic summarized the findings of more than 15 human intervention trials that evaluated the effects of nut consumption on body weight changes [1,2] and concluded that nut consumption did not have a tendency to increase body weight. Nevertheless, these well-controlled trials were based on small numbers of subjects where in mostly of them energy intake was adjusted. In addition, the duration of the nut consumption exposure has been relatively short.

Recently, results from the Nurses’ Health Study - a prospective study among free-living populations - showed that frequent nut consumption was not associated with significantly higher body weight gain during 8 years of follow-up [3]. Even, it was observed a tendency toward less weight gain with increasing frequency of nut consumption, regardless of whether all nuts, peanuts, or tree nuts were evaluated. These findings were consistent with the results from the Spanish SUN prospective cohort conducted in a Mediterranean population of university graduates [4]. Participants who frequently consumed nuts had an average 0.42 kg less weight gain (p for trend: 0.018) than did those who rarely consumed nuts after adjustment for potential confounders.

Early results from the clinical trial PREDIMED study conducted also in Spain to assess the protective effect of a Mediterranean diet supplemented ad-libitum with olive oil or tree nuts on cardiovascular disease without constraint on energy balance showed an improvement in cardiovascular risk factors but not weight gain (0.01 kg; 95% CI: -0.40 to 0.43 kg, after 3 months in the group allocated to nuts compared with those allocated to a low-fat diet) [5].

Many mechanisms have been proposed to explain this lack of association between nut consumption and weight gain. Nuts are rich in fiber and protein, dietary factors that increase satiety. Nuts may increase resting energy expenditure because of their high-protein and unsaturated fat content. Thus, dietary compensation has been suggested to be a major reason for the lack of predicted weight gain. Fat from nuts are predominantly unsaturated. Evidence suggests that monounsaturated and polyunsaturated fatty acids are more readily oxidized than saturated fats, which will possibly lead to less fat accumulation. In addition, increased faecal losses of fat because of incomplete mastication of whole nuts may result in a loss of available energy.

In conclusion, with the available evidence so far, it is possible to promote nut consumption in place of less healthful food choices without any concern or criticism about the effects of nut consumption on weight gain. In a nutshell, health professionals can allay fears of avoiding nuts to stave off weight gain, as long as recommended that nut consumption replaces the consumption of other unhealthy snacks or desserts.

Maira Bes-Rastrollo, University of Navarra

Source:
1. García-Lorda P., Megias Rangil I., and Salas-Salvadó J. Nut consumption, body weight and insulin resistance. European Journal of Clinical Nutrition 2003:57(1);S8-S11.
2. Rajaram S, Sabate J. Nuts, body weight and insulin resistance. British Journal of Nutrition 2006:96;S79-86.
3. Bes-Rastrollo, M., Nicole, M. Wedick, M.A. Martinez-Gonzalez, T.Y. Li, S. Laura and F.B. Hu. Prospective study of nut consumption, long-term weight change and obesity risk in women. American Journal of Clinical Nutrition 2009:89;1913-9.
4. Bes-Rastrollo, M., Sabaté, J., Gómez-Gracia, E., Alonso, A., Martínez, J. A., and Martínez-González, M. A. Nut consumption and weight gain in a Mediterranean cohort: the SUN Study. Obesity Research 2007:15;107-16.
5. Estruch R, Martinez-González MA, Corella D, et al. Effects of a Mediterranean-style diet on cardiovascular risk factors. A randomized trial. Annuals of Internal Medicine 2006:145;1-11.

Nuts can have a positive impact on hypertension

Daily nut consumption can lower the risk of hypertension. However a recent study did not prove that nut consumption can prevent the occurrence of this disorder completely. The high content of magnesium, potassium and unsaturated fatty acids and the low content of sodium in raw tree nuts are factors that can be expected to play a role in this process. Therefore it is very likely that nuts can have a positive impact on the development of hypertension.

Hypertension is a major public health problem, since it is one of the underlying factors in developing cardiovascular disease. Approximately 1 billion people worldwide suffer from hypertension, and in the European countries this number is still increasing. Martínez-Lapiscina et al. analyzed the effect of nuts on the incidence of hypertension with data derived from the SUN cohort.

Self-reported data
From the 19,519 recruited subjects, 9,919 healthy subjects with a normal dietary pattern were included in this research. By means of a food-frequency questionnaire, information on the consumption of nuts (walnuts, almonds, hazelnuts and peanuts) was gathered. Subjects were classified in 4 categories based on the frequency of intake: rarely/never, one to three times per month, once per week and more than once per week. Also, the systolic and diastolic blood pressures were self-reported by the subjects. Hypertension was defined as occurring with a systolic blood pressure of ≥ 140 mm Hg and/or a diastolic blood pressure of ≥ 90 mm Hg.

No association nut consumption and hypertension
During the mean follow-up of 4.5 years the incidence of hypertension was 12.4 per 1,000 person-years. Among the total study group 542 new cases of hypertension were observed. Participants belonging to the highest category of nut consumption were likely to be men, older, non-smokers, physically more active and reported a higher frequency of hypercholesterolemia. Moreover, it seems that they had a higher intake of energy, alcohol and unsaturated fatty acids, and a lower intake of sodium and saturated fatty acid. Within the study, nut consumption was related positively to a higher intake of fruit, vegetable and fish, and inversely related to dairy and meat product intake. When taking diet, gender, age and other confounding factors into account, no association between nut consumption and the incidence of hypertension was detected.

Unsalted vs salted nuts
The authors suggested that the lack of the expected association between nut consumption and hypertension might be explained by the lack of distinction between unsalted and salted nuts. Generally, the Spanish population consumes salted nuts, thus this might interfere with the outcome of the study and negate the potential benefits of nuts. Further research on this topic is necessary to establish an answer as to whether nuts are beneficial in preventing the incidence of hypertension.

Source:
Martínez-Lapiscina E.H., Pimenta A.M., Beunza J.J., Bes-Rastrollo M., Martínez J.A., and Martínez-González M.A. Nut consumption and incidence of hypertension: The SUN prospective cohort. Nutrition, Metabolism and Cardiovascular Diseases; in press.

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Eating nuts and fruits linked to less depression

A healthy Mediterranean-like diet may reduce the risk of the development of depression. This was concluded by a recent Spanish study, where a high adherence to the Mediterranean diet was associated with the chance of developing clinical depression being reduced by 40 to 50%. A mean fruits and nuts intake of 264 grams per day or more was linked to a 30 to 40% risk reduction.

Researchers used data derived from the Spanish SUN cohort. The important separate characteristics of the Mediterranean diet, such as a high consumption of nuts, fruit, fish and vegetables were determined and scored against the regular eating habits of 10,094 Spanish study participants. All participants were free from depression at the start of the study. After a median follow up of 4.4 years, 480 new cases of depression were identified.

Eat nuts to overcome a depression
After adjustment for confounding factors, such as gender, smoking and employment status, the study data showed that people that scored highly on overall adherence to a Mediterranean diet had a significant 40 to 50% lower risk of developing clinical depression. Taking the figures for the consumption of fruit and nuts separately, a significant 30 to almost 40% reduced risk of the occurrence of depression was observed for the higher fruits and nuts intake categories.

Nuts in a healthy diet achieves more success
Although the mechanisms behind this possible protective effect on depression are not clear, the researchers suggest that the effect of a combination of the different components of the Mediterranean diet may be more important than one component in particular. The Mediterranean diet provides a multiplicity of beneficial nutrients, such as omega-3 fatty acids, a relatively large amount of unsaturated fats, antioxidants from nuts, fish and olive oils, together with vitamins and minerals from fruits, nuts and other plant foods. This mix may work in combination in the prevention of mental health problems.

Third most important cause of premature death and disability
Preventing depression is of key importance, as the prevalence of depression in the Western world is high. Depression is the third most important cause of premature death and disability in the developed world. Incorporating dietary strategies would be a relatively new way of tackling this mental health problem.

Source:
Sánchez-Villegas A., Delgado-Rodríguez M., Alonso A., Schlatter J., Lahortiga F., Majem L., Martínez-González MA. Association of the Mediterranean dietary pattern with the incidence of depression: the Seguimiento Universidad de Navarra/University of Navarra follow-up (SUN) cohort.Arch Gen Psychiatry. 2009; 66(10):1090-8.

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Intersnack Group, Düsseldorf
Schuttelaar & Partners, The Hague

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Schuttelaar & Partners, The Hague

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