Results revealed that five or more servings of nuts per week was associated with lower numbers of certain inflammatory biomarkers.
This association remained significant after further adjustment for body mass index. However, no significant association was observed with tumour necrosis factor receptor 2 (TNFR2) – one of the biomarkers being tracked in the study.
In addition, substituting three servings of nuts per week for three servings of red meat, processed meat, eggs, or refined grains per week was associated with significantly lower levels of a type of biomarker known as C-reactive protein (CRP).
Nuts are one of the most nutrient-dense foods available, with an unrivalled unsaturated fatty acid, plant protein, fibre, mineral, vitamin profile. Nuts also contain other bioactive compounds such as phytosterols and phenolic antioxidants.
Human studies have provided strong evidence of their anti-inflammatory abilities with a reduced risk of cardiovascular disease (CVD) and type 2 diabetes already established.
Additional trials have evaluated nut’s positive effects on intermediate markers of cardiovascular disease risk, especially lipids with a dose-related reduction in LDL cholesterol.
There has been a wealth of investigations that have looked at nut consumption and inflammatory biomarkers. However, results have been inconsistent and restricted by small sample sizes of usually less than 50.
Trials have also been limited by short duration, targeting subjects with certain health conditions, and combined effects with other dietary factors.
This latest study looked into nut intake that included separate data on peanuts, tree nuts and peanut butter.
The associations between substituting nuts for sources of animal protein, refined grains, potatoes and potato chips with concentrations of inflammatory biomarkers were also examined.
Study cohorts
Data collected from a cross-sectional study enrolled 5013 participants who were free of diabetes.
These subjects were taken from two cohort studies: the Nurses’ Health Study (NHS), which consists of 121,700 female registered nurses aged 30–55 years.
The other cohort was the Health Professionals Follow-Up Study (HPFS), which consists of 51,529 male health professionals aged 40–75 years.
For each cohort, food frequency questionnaires were used to assess nut intake between 1986 and 1994. Here, questions on lifestyle factors and health were included with a follow-up rate exceeding 90% every two years.
Between 1989 and 1990, 32,826 women in the NHS provided a blood sample and between 1993 and 1995, 18,159 men from the HPFS provided a blood sample.
Plasma biomarkers identified included the C-reactive protein, interleukin 6 (IL-6), and TNFR2.
“Our study supports an overall healthful role for nuts in the diet and suggests reducing inflammation as a potential mechanism that may help explain the benefits of nuts on cardiometabolic diseases," said co-author Dr Ying Bao, an epidemiologist in Brigham and Women's Hospital.
“While the exact mechanism of action is unclear many components in nuts have anti-inflammatory properties. For example, polyunsaturated fatty acids, particularly a-linolenic acid, which is high in walnuts, were associated with reduced levels of CRP, IL6, and other inflammatory markers in several studies.”
“Other constituents of nuts, such as dietary fibre, vitamin E, L-arginine and phenolic compounds, have also been suggested to have anti-inflammatory effects.
Nuts an able substitute
Substituting three servings of nuts per week for three servings of red meat, processed meat, eggs, or refined grains per week was associated with significantly lower CRP and IL-6.
Lower CRP concentrations were also observed when substituting three servings of nuts per week for potatoes and potato chips. Similar results were found for peanuts and other nuts.
“At higher cooking temperatures, heterocyclic amines (HAAs) and advanced glycoxidation end-products (AGEs) are produced in red and processed meat,“ explained Bao.
“Both HAAs and AGEs increase inflammation. Refined grains also have a low fibre and micronutrient contents that have anti-inflammatory properties.”
Bao also commented that studies also show nut consumption linked to long-term weight loss despite being an energy-dense food. Weight loss is associated with a decrease in levels of inflammatory biomarkers.
Therefore these links between eating nuts and inflammatory marker numbers could be facilitated in some measure through an individual’s body mass index.
“This is yet another piece of evidence showing that people should include more nuts in their diet,” said Maureen Ternus, executive director of the International Tree Nut Council Nutrition Research & Education Foundation (INC NREF).
“Just a handful of tree nuts (1.5 ounces or 1/3 cup) every day can result in numerous health benefits.”
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.116.134205
“Associations between nut consumption and inflammatory biomarkers.”
Authors: Ying Bao et al.