Nuts and Antioxidants

When I was growing up, nuts were considered a fattening food with little nutritional value. Times have changed, and the more nuts are analyzed, the more interesting they become. See Table 1.

Mixed Nuts

In review of four major epidemiological studies - the Adventist Health Study, the Iowa Women's Health Study, the Nurses' Health Study, and the Physicians' Health Study - dietary records were isolated and reviewed. The findings reveal that those who consumed nuts four times per week had a 37 percent reduced rate of heart disease, compared to those who rarely or never ate nuts. What was most impressive was in this review, each additional serving of nuts per week reduced the risk of heart disease by 8.3 percent.²

Almonds

Fifteen adults were studied on how various food combinations affected glucose, insulin and markers of postprandial oxidative stress. The addition of almonds to a base meal caused elevated serum thiol, indicating reduced oxidative damage to proteins.³ This was not seen when mashed potatoes, parboiled rice or white bread were added to the base meal.

Walnuts

Ten subjects were involved in a five-week study. After a two-week run-up period, baseline laboratory testing was performed. For the next three weeks, the subjects consumed their regular diet, with the addition of four walnuts daily. Then, their blood was retested. The findings included a doubling of alpha-linolenic acid (ALA) and close to a fourfold increase in eicosapentaenoic acid (EPA).⁵ Docosahexaenoic acid (DHA) levels were unchanged.

Pecans

Twenty-four volunteers, ranging in age from 25 to 55, were divided into a pecan-enriched diet group (20 percent of energy) or a control diet group who followed the American Heart Association's Step-One Diet. After four weeks, the subjects were crossed over for another four weeks. Testing revealed that when the subjects concluded the pecan-enrichment phase of the trial, plasma antioxidant levels were unchanged, yet a 7.4 percent reduction in thiobarbituric substances (TBARS - a marker for lipid oxidation) was noted, indicating a non-plasma antioxidant effect.⁶

Hazelnuts

In an eight-week study of 15 males (average approximate age: 48) with high cholesterol, the consumption of a hazelnut-enriched diet had the following effect (Table 2):

There was also improvement in the cholesterol/HDL ratio. The authors concluded that adding hazelnuts to a diet resulted in a significant reduction of lipids in hypercholesterolemic males.⁴

Peanuts

In a dietary study of 24,000 men and women in Taiwan, 10-year follow-up data revealed that females who ate peanuts on a regular basis had a reduced risk of colorectal cancer. Males also had a reduced risk, although the magnitude was not as great.⁷

Nut Butters

In this review, the authors found that people who consumed peanut butter or other nut butters once a week had an overall reduced rate of mortality. The death rate was further reduced as the number of servings of nut butter/peanut butter increased up to four. The specific diseases most associated were cardiovascular disease and coronary artery disease. The authors speculated that such reductions in death from cardiovascular disease and coronary artery disease may be due to the antioxidant content of nuts.⁸

Macadamia Nuts

Seventeen men with high cholesterol were given macadamia nuts equivalent to 15 percent of their daily calories for one month. Tests following the trial revealed biomarkers for both oxidative stress and inflammation were lower, leading the authors to conclude that short-term macadamia-nut consumption reduced risk factors for coronary artery disease, even though overall dietary fat intake increased.⁹

References

1. Wu X, Beecher GR, Holden JM, et al. Lipophilic and hydrophilic antioxidant capacities of common foods in the United States. J Agric Food Chem, 2004;52:4026-37.
2. Kelly JH, Sabate J. Nuts and coronary heart disease: an epidemiological perspective. Br J Nutr, 2006:96:S61-67.
3. Jenkins DJA, Kendall CWC, Josse AR, et al. Almonds decrease postprandial glycemia, insulinemia and oxidative damage in healthy individuals. J Nutr, 2006;136:2987-92.
4. Mercanligil SM, Arslan P, Alasalvar C, et al. Effects of hazelnut-enriched diet on plasma cholesterol and lipoprotein profile in hypercholesterolemic adult men. Eur J Clin Nutr, 2007;61(2):212-20.
5. Marangoni F, Colombo C, Martiello A, et al. Levels of the omega-3 fatty acid eicosapentaenoic acid in addition to those of alpha linolenic acid are significantly raised in blood lipids by the intake of four walnuts a day in humans. Nutr Metab Cardiovasc Dis, 2007;17(6):457-61.
6. Haddad E, Jambazian P, Karunia M, et al. A pecan-enriched diet increases tocopherol/cholesterol and decreases thiobarbituric acid reactive substances in plasma of adults. Nutr Res, 2006;26(8)397-402.
7. Yeh CC, You SL, Chen CJ, Sung FC. Peanut consumption and reduced risk of colorectal cancer in women: a prospective study in Taiwan. World J Gastroenterol, 2006;12(2):222-7.
8. Blomhoff R, Carlsen MH, Andersen LF, Jacobs DR. Health benefits of nuts: potential role of antioxidants. Br J Nutr, 2006;96(S2):S52-60.
9. Garg ML, Blake RJ, Wills RB, Clayton EH. Macadamia nut consumption modulates favorably risk factors for coronary artery disease in hypercholesterolemic subjects. Lipids, 2007:42(6)583-87.