Abstract
Objective
To investigate the impact of a Westernizing diet on fat intake, red blood cell fatty acid composition, and health risks among Yup’ik Eskimos living in rural Alaskan Native communities.
Design
Diet data and blood specimens were collected from 530 Yup’ik Eskimos aged 14 to 94 years old. Height, weight, and waist circumference were measured.
Statistical analyses
Comparisons of select fatty acid intake between participants in quintiles of traditional food intake (percent energy) were made using analyses of variance and post hoc Bonferroni tests. General linear models were used to determine the association between traditional food intake and health outcomes.
Results
Fatty acid composition of the diet differed according to the level of traditional food intake. Traditional food intake was positively associated with higher total fat, eicosapentaenoic acid, and docosahexaenoic acid intake. No association was observed between traditional food intake and saturated fatty acid intake; indeed, participants consuming more traditional foods derived a substantially smaller proportion of their dietary fatty acids from saturated fatty acids (P<0.001). Analyses of red blood cell fatty acid composition supported these findings. After multivariable adjustment, traditional food intake was significantly positively associated with high-density lipoprotein cholesterol concentration and significantly negatively associated with triglyceride concentration (P<0.001).
Conclusions
Diets emphasizing traditional Alaskan Native foods were associated with a fatty acid profile promoting greater cardiovascular health than diets emphasizing Western foods. Further research needs to evaluate the effects of a Westernizing diet on the overall diet of Alaskan Natives.
Intake of specific fatty acids may play a greater role in development of chronic diseases than total fat intake (1–4). Although neither an adequate intake nor Recommended Dietary Allowance for total fat intake has been established, an acceptable macronutrient distribution range has been set at between 20% to 35% of energy (5). This range is based primarily on evidence for increased risk of obesity, metabolic abnormalities, and cardiovascular disease at a level of fat intake outside this range.
The traditional diet of Alaskan Natives is remarkably high in fat, although its emphasis on marine sources of fatty acids is thought to contribute to the historically low prevalence of chronic diseases observed in this population (6–8). A shift away from adherence to a traditional subsistence diet toward an increasingly commercially based Western diet over the past several decades, however, has resulted in a macronutrient distribution that is more representative of that observed in a national sample (9–11). Worldwide, the replacement of traditional diets with Western diets has increased the burden of certain chronic diseases, including obesity, cardiovascular disease, and type 2 diabetes (12). A similar experience is hypothesized to be occurring among Alaskan Natives. Coincident with a change in dietary patterns, the prevalence of cardiovascular comorbidities, including obesity has increased and may even be higher among Alaskan Natives than non-Alaskan Natives (13,14).
The benefits of a traditional subsistence diet among Alaskan Natives are poorly understood, particularly given an absence of long-term prospective studies. Westernization over the past century has precipitated major changes in food sources and intake of numerous nutrients among Alaskan Natives. Nevertheless, communities in Southwestern Alaska were among the last to experience Western influence (15), and retain a mixed traditional-Western diet. This situation provides a valuable context for examining the contribution of a traditional diet to nutrient intake and the development of chronic diseases.
While several articles to date have discussed the implications of a Westernizing diet on the nutrient intake, none that we are aware of have focused on the impact of this type of diet change on fatty acid intake and health parameters. Alaskan Native populations living in remote communities offer a unique perspective on the metabolic and dietary consequences of a Westernizing diet, particularly as it relates to fatty acid intake. We hypothesized that a decline in traditional food intake would partially explain a shift in the specific fatty acid composition of the diet, which is reflected in red blood cell membrane fatty acid composition, to one promoting increased risk of chronic diseases.
The objectives of the present study were to: (a) determine the association between degree of adherence to the traditional Alaskan Native diet and dietary and red blood cell fatty acid composition and (b) to investigate the association between dietary fatty acid composition and chronic disease risk factors.
METHODS
The study population was composed of male (n=230) and female (n=301) participants in the Center for Alaska Native Health Study, an interdisciplinary study investigating genetic, nutritional, and behavioral risk factors for chronic diseases among Alaskan Natives. The study protocol has been published previously (16). Briefly, residents of six remote communities and one town in the Yukon Kuskokwim River Delta, Alaska were recruited to participate in the study via flyers, word of mouth, and the locally popular Very High Frequency radio. A local native field assistant was hired to assist in the recruitment process in each community. Interested residents were invited to the local tribal council office or municipal hall, where the interviews were conducted. The research team spent up to 10 days in each community. The researchers introduced themselves, provided a brief explanation of the study, and verified eligibility. All male and nonpregnant female Yup’ik Eskimos aged 14 years or older were eligible to participate. Fully informed written consent, and assent required for minors, was obtained from all participants. Recruitment for the study continues and this article presents findings from data collected between December 2003 and March 2005. The University of Alaska at Fairbanks, the University of California at Davis, and the Yukon Kuskokwim Health Corporation Institutional Review Boards approved the study protocol.
The Yukon Kuskokwim River Delta is located in south-western Alaska, and is home to approximately 16,500 Alaskan Natives living predominantly in remote communities (population <500). Communities are served primarily by local air service companies, and occasionally by barge in the summer months. According to Census 2000 data, the median age in the census area was 25.3 years old, compared to 35.3 in the US population. Average per capita income is $12,603, and 18.7% of families are below the national poverty level (17). The majority of the population, particularly the younger generation, is bilingual, speaking both Yup’ik and English; 65.6% reported that a language other than English was spoken at home.
Dietary Assessment
Diet was assessed using interviewer administered 24-hour recall; a subsample of participants (n=312) also completed a 3-day food record. Dietary assessment methodologies were pilot-tested in three communities in September 2003, and were found to be feasible and well-accepted by participants. Pearson partial correlation coefficients for energy, total fat, carbohydrate, and protein estimated by 24-hour recall and 3-day food records were 0.42, 0.45, 0.39, and 0.28 respectively (P≤0.05, unpublished data), which suggested that agreement between the two methodologies was reasonable.
Diet data were collected from each participant by certified interviewers using a computer assisted 24-hour recall (Nutrition Data System for Research [NDS-R], software version 4.06, 2003, Regents of the University of Minnesota, Minneapolis). Participants were asked to recall all food and beverages consumed over a 24-hour period using a multiple-pass approach that is built into the software to minimize recall bias. Although the majority of participants were bilingual, a native Yup’ik speaker, also trained in the use of NDS-R software, assisted non-English speakers. For quality control, the lead nutritionist reviewed all recalls; subsequent testing found no significant differences in results among interviewers.
Due to an already high participant burden, the 3-day food record was not mandatory, although it was offered to all participants. Fifty-four percent elected to complete the 3-day food record for 3 nonconsecutive days (2 weekdays and 1 weekend day). Participants were instructed to maintain their usual eating habits. The 24-hour recall served to teach participants the level of detail needed to complete the 3-day food record, including details of food type, preparation methods, along with the portion size consumed. Portion sizes for both the 3-day food record and 24-hour recall were estimated using a booklet developed by the Fred Hutchison Cancer Research Center. A research team member reviewed all 3-day food records for completeness. The 3-day food record’s were entered by certified researchers using NDS-R software. For quality assurance, a second researcher reviewed all entries for accuracy.
Nutrient calculations for both the 24-hour recall and 3-day food record were performed using the NDS-R Food and Nutrient Database (18). Many Alaskan Native foods are found in the database. Foods missing from the database were either substituted for similar food items when appropriate or the food was added to the database by request. Most communities in the Yukon Kuskokwim River delta prohibit use and possession of alcoholic beverages, thus alcohol intake was not recorded. Use of vitamin and mineral supplements were rare in this population and were not included in analysis. Because data from the 3-day food record and 24-hour recall were collected using different methodologies, nutrient estimations from each were standardized and then combined to yield a single value. Data from participants without a 3-day food record was used as is.
The contribution of traditional foods to mean energy was calculated. Traditional foods were defined as those foods harvested from the local environment, and included berries, marine mammals, fish, game animals, and wild greens (19).
Anthropometric Assessment
Waist circumference was measured twice, directly on the skin at a level immediately below the lowest lateral portion of the rib cage (the end of the 10th rib) using a Gulick II 150-cm tape measure with a tensioning device. If the difference exceeded 2.0 cm a third measurement was taken. Weight to the nearest 0.1 kg and percent body fat were assessed once by bioelectrical impedance (Tanita TBF-200, Tanita Corporation, Tokyo, Japan). Repeated standing height measurements were taken to the nearest 1/8 inch using a portable stadiometer. Participants removed their shoes and wore paper gowns while measurements were taken by trained technicians. Body mass index (BMI) was calculated as kg/m2.
Biochemical Assessment
Blood specimens were collected by venipuncture after at least 8 hours of fasting and were analyzed for total cholesterol, high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol, triglycerides, plasma glucose, and glycosylated hemoglobin (HbA1c). Analyses were performed in the field using a lipid and glucose analyzer (Cholestech LDX, Hayward, CA) and an HbA1c analyzer (Bayer HbA1c DCA 2000+, Tarrytown, NY).
Total red blood cell fatty acids were extracted with isopropanol and chloroform by the method of Rose and Oklander (20) and fatty acid methyl esters were analyzed by gas-liquid chromatography as described previously (21).
Statistical Analyses
Comparisons of select fatty acid intake between participants in quintiles of traditional food intake (percent energy) were made using analysis of variance and post hoc Bonferroni tests. General linear models were used to determine the association between traditional food intake, as a categorical variable (quintile), and health outcomes. Covariates used in analyses included age, sex, and BMI, as appropriate. All statistical tests were performed using SPSS software (version 13.0, SPSS, Inc, Chicago, IL). A P value of ≤0.05 was considered statistically significant.
Although significant differences in total fat intake were observed between sexes, neither the fat composition of the diet nor traditional food intake differed. Because the latter two factors were the variables of interest, results are presented pooled for both sexes.
RESULTS
Participant characteristics are presented by sex in Table 1. Although BMI and percent body fat were significantly higher among women, many of the health characteristics, including HDL cholesterol, low-density lipoprotein cholesterol, cholesterol-to-HDL cholesterol ratio, and systolic blood pressure, favored women. Health characteristics that did not differ significantly by sex included waist/hip ratio, triglyceride concentration, HbA1c, and diastolic blood pressure.
Table 1.
Health characteristics of participants from the Center for Alaska Native Health Research study, by sex
| Men (n=230) |
Women (n=301) |
|
|---|---|---|
 |
||
| Age (y) | 39.5±18.1 | 38.8±17 |
| BMIa | 25.9±4.5 | 29.1±6.8** |
| Body fat (%) | 21.0±8 | 35.8±8.8** |
| Waist circumference (cm) | 89.7±13.1 | 90.2±17.7 |
| Triglyceride (mg/dL)b | 88.1±49.6 | 90.1±43.2 |
| High-density lipoprotein cholesterol (mg/dL)c | 58±15.8 | 65.5±15.6** |
| Low-density lipoprotein cholesterol (mg/dL)c | 129.1±41.8 | 121.8±34.7* |
| Cholesterol:high-density lipoprotein cholesterol | 3.7±1.2 | 3.3±0.9** |
| Glucose (mg/dL)d | 95.6±10.8 | 93.3±10.9* |
| Hemoglobin A1c (%) | 5.5±0.4 | 5.5±0.5 |
| Systolic blood pressure (mm Hg) | 125.4±13.5 | 119.8±16.6** |
| Diastolic blood pressure (mm Hg) | 72.2±9.3 | 71.2±10.7 |
BMI=body mass index; calculated as kg/m2.
To convert mg/dL triglyceride to mmol/L, multiply mg/dL by 0.0113. To convert mmol/L triglyceride to mg/dL, multiply mmol/L by 88.6. Triglyceride of 159 mg/dL=1.80 mmol/L.
To convert mg/dL cholesterol to mmol/L, multiply mg/dL by 0.0259. To convert mmol/L cholesterol to mg/dL, multiply mmol/L by 38.7. Cholesterol of 193 mg/dL=5.00 mmol/L.
To convert mg/dL glucose to mmol/L, multiply mg/dL by 0.0555. To convert mmol/L glucose to to mg/dL, multiply mmol/L by 18.0. Glucose of 108 mg/dL=6.0 mmol/L.
P<0.05.
P<0.001.
Traditional Food Intake and Nutrient Intake Trends
A mean age difference of 20.9±2.1 years was observed between participants in the lowest and highest quintile of traditional food intake (Table 2). No difference in energy intake was observed between quintiles. Significant trends were observed across quintiles for decreasing carbohydrate intake, and increased protein and fat intake with increasing percent energy from traditional food intake. Although neither total saturated fat nor specific saturated fatty acids (SFAs) differed across quintiles, there were significant trends for differences in polyunsaturated fatty acid (PUFA) intake (P<0.001). The trend for linoleic acid intake decreased with increased traditional intake, while the trends for eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and the PUFA:SFA ratio all increased with increased traditional intake. The trend for α-linolenic acid was not significant.
Table 2.
Select dietary fatty acid intake of the Center for Alaska Native Health Research study participants by quintile of traditional food intake
| Traditional Food Intake Quintile (% Energy) |
P Value | |||||
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | ||
| <13% | 13 to <16% | 16 to <21% | 21 to <32% | ≥32% | ||
| Sex (% male) | 42 | 43 | 44 | 40 | 46 | |
 |
||||||
| Age (y) | 31.6±14.5yz | 29.6±14.3z | 37.2±14.8y | 45.1±16.9x | 52.4±16.1w | |
| Traditional food energy (kcal) | 6.2±5.8 | 14.6±0.8 | 19.0±1.5 | 25.7±3.2 | 53.0±17.7 | <0.001 |
| Energy (kcal/d) | 2,034.7±877.7 | 2,078.7±677.4 | 2,017.9±674.0 | 1,947.5±881.5 | 1,867.9±1,057.5 | 0.398 |
| Fat (%) | 32.3±8.8z | 35.6±7.4yx | 35.3±7.3yz | 37.2±9.8y | 44±11.7x | <0.001 |
| Carbohydrate (%) | 55.6±11z | 50.9±8.5y | 47.9±8.3y | 43.3±9x | 27.3±11.9w | <0.001 |
| Protein (%) | 13.2±4.1z | 14.6±3.9z | 17.4±4.2y | 20.2±4.6x | 28.8±9.5w | <0.001 |
| SFAb (%) | 10.4±3.3 | 11.2±2.7 | 10.8±2.6 | 10.2±2.6 | 10.4±3.2 | 0.130 |
| PUFAc (%) | 6.5±3.3z | 7.6±2.9yz | 7.7±2.6yz | 8.4±3.2y | 10.6±3.5x | <0.001 |
| Total fat (g/d) | 74±38.5z | 84.3±39.5yz | 82.7±36.8yz | 85.6±53.9yz | 96.5±69.6y | <0.001 |
| Total SFA (g/d) | 24±13.2 | 26.5±12.5 | 25.2±12.2 | 23.5±14.6 | 22.7±17.4 | 0.339 |
| Myrisitc (14:0)(g/d) | 1.9±1.4 | 2.2±1.5 | 2.1±1.7 | 2.2±1.9 | 2.4±1.8 | 0.256 |
| Palmitic (16:0) (g/d) | 12.6±6.9 | 14±6.1 | 13.4±5.9 | 12.8±7.8 | 12.6±8 | 0.531 |
| Stearic (18:0) (g/d) | 6.7±3.5z | 7.2±3.3z | 6.9±3.1z | 6.3±3.9yz | 5.1±3.6y | <0.001 |
| Total PUFA (g/d) | 15.1±10.3z | 17.9±9.4z | 17.9±9z | 19.3±13yz | 23±16.6y | <0.001 |
| LAd (18:2 n6) (g/d) | 13.2±9.7z | 14.9±7.9z | 13.6±7.4z | 12.5±9.2yz | 9.8±9.1y | <0.001 |
| ALAe (18:3 n3) (g/d) | 1±0.6 | 1.2±0.6 | 1.2±0.6 | 1.1±0.8 | 1.1±1 | 0.283 |
| EPAf (20:5 n3) (g/d) | 0.2±0.5z | 0.5±0.7yz | 0.9±1y | 1.8±2x | 3.6±3.1w | <0.001 |
| DHAg (22:6 n3) (g/d) | 0.2±0.2z | 0.2±0.1yz | 0.3±0.2y | 0.4±0.3y | 0.7±0.6y | <0.001 |
| PUFA:SFA ratio | 0.69±0.40z | 0.77±0.41yz | 0.80±0.34yz | 0.87±0.30y | 1.09±0.41x | 0.001 |
Means without a common superscript are significantly different, P<0.05 (Bonferroni’s post hoc test).
SFA=saturated fatty acid.
PUFA=polyunsaturated fatty acid.
LA=linoleic acid.
ALA=α-linolenic acid.
EPA=eicosapentaenoic acid.
DHA=docosahexaenoic acid.
Participants in the highest quintile of traditional food intake (≥32% of energy) derived a significantly greater proportion of energy from fat and protein than participants in the lowest quintile (<13% of energy). Interestingly, neither the saturated fatty acid proportion of the diet nor total saturated fatty acid intake differed between the quintiles of traditional food intake, despite increasing total fat with traditional food intake. Furthermore, mean PUFA:SFA ratio increased significantly across quintiles of traditional food intake.
Given the importance of the n-6 to n-3 ratio on health (22,23), the relative contribution of specific types of PUFAs were evaluated (Figure 1). The n-6 to n-3 ratio decreased with increasing quintile of traditional food intake. Compared with participants in the highest quintile, linoleic acid (18:2 n-6) comprised a greater proportion of total PUFA intake among participants in the lowest quintile (46% vs 86% respectively; P<0.001). Although no difference was observed in percent of linolenic acid (18:3 n-3) contributing to total PUFA intake, the percentage of EPA and DHA combined in the diet was significantly higher among participants in the highest (36.8%) vs lowest (3.9%) quintile (P<0.001).
Figure. 1.
Dietary n-6 to n-3 polyunsaturated fatty acid ratio for the Center for Alaska Native Health Research study participants by quintile of traditional food intake. PUFA=polyunsaturated fatty acid; DHA=docosahexaenoic acid; EPA=eicosapentaenoic acid; ALA=α-linolenic acid; LA=linoleic acid.
Traditional Food Intake and Red Blood Cell Membrane Fatty Acid Trends
The relationship between traditional food intake and red blood cell membrane fatty acid composition was investigated to confirm the observed association between traditional food intake and dietary fatty acid intake (Table 3). A similar trend in dietary fatty acid composition was observed in the red blood cell membrane. Palmitic (16:0) and stearic (18:0) fatty acids represented approximately 13% and 19% of fatty acids in the red blood cell, regardless of the level of traditional food intake. Compared with participants in the lowest quintile of traditional food intake, the red blood cell membrane of participants in the highest quintile was characterized by significantly higher eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) concentration, adjusting for age, sex, BMI, and smoking status.
Table 3.
Relative concentration of fatty acids in red blood cell membranes in the Center for Alaska Native Health Research study participants by quintile of traditional food intake
| Traditional Food Intake Quintile (% Energy) |
P value | |||||
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | ||
| <13% | 13 to <16% | 16 to <21% | 21 to <32% | ≥32% | ||
 |
||||||
| Palmitic (16:0) | 19.09±0.07z | 19.1±0.07z | 19.21±0.07z | 19.11±0.07z | 19.39±0.08z | 0.030 |
| Stearic (18:0) | 13.08±0.05z | 13.01±0.06yz | 13.09±0.05z | 13.03±0.06yz | 12.81±0.06y | 0.011 |
| LAb (18:2n6) | 13.09±0.19z | 12.97±0.2z | 12.61±0.2z | 11.67±0.2y | 10.72±0.23x | <0.001 |
| AAc (20:4n6) | 9.35±0.15z | 9.2±0.16yz | 8.95±0.15xyz | 8.65±0.15xy | 8.38±0.18x | 0.001 |
| ALAd (18:3n3) | 0.23±0.01z | 0.25±0.01z | 0.24±0.01z | 0.26±0.01z | 0.26±0.01z | 0.060 |
| EPAe (20:5n3) | 1.75±0.13z | 1.88±0.13z | 2.18±0.13z | 3.03±0.13y | 3.68±0.15x | <0.001 |
| DHAf (22:6n3) | 5.72±0.14z | 5.96±0.14yz | 6.38±0.14y | 7.01±0.14x | 7.19±0.16x | <0.001 |
Means without a common superscript are significantly different, adjusted for age, sex, body mass index, and smoking status (yes/no).
LA=linoleic acid.
AA=arachadonic acid.
ALA=α-linolenic acid.
EPA=eicosapentaenoic acid.
DHA=docosahexaenoic acid.
Traditional Food Intake and Health Characteristics
Because the primary variable of interest was traditional food intake, the association between traditional food consumption and health indicators was examined. After adjusting for age, sex and BMI, participants in the highest quintile of traditional food intake (>31% energy) had a significantly higher HDL concentration (P=0.038) and lower triglyceride concentration than participants in the lowest quintile (<10% energy; P<0.001) (Table 4).
Table 4.
Health characteristics of the Center for Alaska Native Health Research study participants by extreme quintiles of traditional food intake
| Traditional Food Intake Quintile (% Energy) |
P value | ||
|---|---|---|---|
| 1 | 5 | ||
| <13% | ≥32% | ||
 |
|||
| Body mass indexb | 28.1±0.6 | 27.6±0.6 | 0.562 |
| Body fat (%) | 30.0±0.8 | 29.7±0.8 | 0.784 |
| Waist circumference (cm) | 92.9±1.5 | 89.1±1.6 | 0.121 |
| Triglyceride (mg/dL)c | 102.2±4.3 | 76.6±4.6 | <0.001 |
| High-density lipoprotein cholesterol (mg/dL)d | 60.7±1.4 | 65.4±1.5 | 0.038 |
| Low-density lipoprotein cholesterol (mg/dL)d | 122.5±3.7 | 129±4.0 | 0.279 |
| Cholesterol:high-density lipoprotein cholesterol | 3.5±0.1 | 3.3±0.1 | 0.164 |
| Glucose (mg/dL)e | 95.5±1.0 | 93.6±1.1 | 0.261 |
| Hemoglobin A1c (%) | 5.5±0 | 5.6±0 | 0.237 |
| Systolic blood pressure (mm Hg) | 123.5±1.2 | 120.8±1.3 | 0.164 |
| Diastolic blood pressure (mm Hg) | 71.6±0.9 | 70.3±1.0 | 0.339 |
All values are age, sex, and body mass index adjusted (except for body mass index and body fat).
Calculated as kg/m2.
To convert mg/dL triglyceride to mmol/L, multiply mg/dL by 0.0113. To convert mmol/L triglyceride to mg/dL, multiply mmol/L by 88.6. Triglyceride of 159 mg/dL=1.80 mmol/L.
To convert mg/dL cholesterol to mmol/L, multiply mg/dL by 0.0259. To convert mmol/L cholesterol to mg/dL, multiply mmol/L by 38.7. Cholesterol of 193 mg/dL=5.00 mmol/L.
To convert mg/dL glucose to mmol/L, multiply mg/dL by 0.0555. To convert mmol/L glucose to to mg/dL, multiply mmol/L by 18.0. Glucose of 108 mg/dL=6.0 mmol/L.
DISCUSSION
In the present study, a significant relationship between adherence to a traditional subsistence-based diet and dietary fatty acid composition was observed among Yup’ik Eskimos living in remote communities. Total fat intake in general, and specific types of PUFAs in particular, differed significantly between participants maintaining a more traditional diet and those adopting a more commercially based Western diet. These findings were reflected in the red blood cell membrane fatty acid composition. Importantly, diets emphasizing traditional Alaskan Native foods were associated with a fatty acid profile promoting greater cardiovascular health than diets emphasizing Western foods.
Although fat intake among participants consuming a more traditional Alaskan Native diet fell outside the acceptable macronutrient distribution range (mean=42% of energy), this did not appear to put them at greater risk for chronic diseases. This may be explained by examining the specific types of fatty acids supplied by the traditional diet.
Evidence suggests that the observed relationship between high-fat diets and cardiovascular disease may be mediated by high saturated fat intake (2,24,25). Numerous epidemiological and animal studies have demonstrated the effect of SFA on circulating low-density lipoprotein cholesterol and risk of cardiovascular disease (2,25–27). Data from the Continuing Survey of Food Intakes by Individuals, 1994–96 indicate that as percent of energy from carbohydrate decreases (and percent fat increases) saturated fat increases (5). The study results, however, indicate that saturated fat did not account for the excess fat found in the traditional Alaskan Native diet. Indeed, although total fat intake was higher among participants consuming more traditional foods, no significant difference was observed in total saturated fat intake. Moreover, when examining the specific types of fats, participants consuming a diet low in traditional foods had a significantly lower PUFA:SFA ratio than participants consuming a diet rich in traditional foods.
Several studies have shown that high-fat diets are associated with an increased prevalence of obesity (28–30); this finding was not corroborated in the present study. Fat provides more energy per gram than carbohydrates or protein; consequently high-fat diets tend to be hypercaloric. Although the traditional Alaskan Native diet was higher in fat, total energy intake was similar to that found in the lower fat Western diet. Furthermore, data from the present study did not show a relationship between the high-fat traditional diet and weight, body fat, or BMI when adjusted for age and sex.
Growing evidence suggest that the n-6:n-3 ratio plays an important role in the development of chronic diseases, given their opposing effects. Compared with a Western diet that emphasizes n-6 fatty acids (n-6 to n-3 ratio ~10-30:1) (23), the traditional Alaskan Native diet provided considerably more n-3 fatty acids, such that the ratio was closer to 1:1 in the diets of participants consuming ≥32% of their diet from traditional foods. Although there is debate as to the relative importance of the n-6 to n-3 ratio vs gram intake of the essential fatty acids, there is substantial evidence showing that a balance between the essential fatty acids has important lipidemic and cardiovascular effects (22,23,31).
Several studies among Arctic and sub-Arctic native populations have found an inverse relationship between glucose concentration and foods rich in long-chain n-3 fatty acids and plasma membrane n-3 fatty acid concentration (6–8,32). Results from the present study did not demonstrate a relationship between consumption of a more traditional diet, which was notably high in PUFAs and glucose concentration. The observed lack of association between traditional food intake and glucose concentration may be explained by the relatively small standard deviation observed in glucose concentration and the relatively healthy population. Only 24.8% and 1.7% of participants were characterized as having impaired glucose tolerance and diabetes based on a fasting plasma glucose test of ≥100 mg/dL (2.6 mmol/L) and ≥126 mg/dL (3.3 mmol/L), respectively.
Participants who derived a greater proportion of their diet from traditional foods had a significantly lower triglyceride concentration and a higher HDL concentration, both of which have been found to decrease the risk of chronic disease. These findings can likely be accounted for by the high intake of EPA and DHA among participants consuming a diet rich in traditional foods, and have been supported by previous studies (33,34).
A limitation of the present study includes using percent of energy from traditional foods as the only measure of Westernization; dietary patterns were not assessed in this study, which are likely to provide additional insight into the effects of Westernization on diet quality (35). The scope of the present study, however, was to describe and not attribute the differences in fat intake to specific foods. A strength of the study was using red blood cell membrane fatty acid composition to confirm the observed association between traditional food intake and fatty acid intake.
CONCLUSION
These findings suggest that replacement of a traditional Alaskan Native diet with a Western diet may increase the risk of cardiovascular disease. Although Alaskan Natives consuming a diet relatively high in Western foods met current recommendations for fat intake, it is plausible that if intake of traditional foods continues to decline, dietary fat composition may shift toward a more risky profile. Of particular concern would be a decrease in EPA and DHA and an increase in saturated fat intake.
That the effects of a Westernizing diet, specifically in relation to fat intake, are more apparent in the diets of youth than elders suggests that the future health of youth may be compromised. The majority of participants in the current study were healthy, based on the health characteristics measured. Interestingly, triglyceride concentration and cholesterol-to-HDL ratio did not worsen with age, as would be expected (data not shown). It is possible that some of the negative health consequences associated with aging may be prevented with promotion of traditional foods. Increased public awareness of the benefits of traditional foods along with strategies to select healthful Western foods is therefore recommended.
Future research should expand on the current study by identifying specific dietary patterns associated with a favorable health profile among Alaskan Natives living in rural communities. It is unlikely that a recommendation to consume a diet composed exclusively of traditional foods is feasible (nor is there research to suggest this is would be beneficial). Data from the Alaska Food Cost Survey indicates that food selection may be constrained by both economics and availability (36). Consequently, future research should focus on identifying and promoting accessible healthful diets that draw on local traditional foods and imported Western foods.
Acknowledgments
The project described was supported by grant no. P20-RR16430 from the National Center for Research Resources (NCRR), a component of the National Institute of Health (NIH). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of NCRR or NIH. The author was supported by Public Health Service Training Grant No. 5 T32 HL 07034 from the National Heart, Lung, and Blood Institute.
We thank our Yukon Kuskokwim research partners for their excellent assistance. We are also indebted to the participants and communities that welcomed us. The project described was supported by grant number P20-RR16430 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH).
Its contents are solely the responsibility of the authors and do not necessarily represent the official views of NCRR or NIH. The author was supported by Public Health Service Training Grant No. 5 T32 HL 07034 from the National Heart, Lung, and Blood Institute.
Contributor Information
ANDREA BERSAMIN, postdoctoral fellow, Stanford Prevention Research Center, Stanford University, Stanford, CA; at the time of the study, she was a graduate student researcher at the University of California, Davis.
BRET R. LUICK, cooperative extension specialist, University of Alaska Fairbanks.
IRENA B. KING, nutritional biochemist, Fred Hutchinson Cancer Research Center, Seattle, WA.
JUDITH S. STERN, distinguished professor, Departments of Nutrition and Internal Medicine, University of California, Davis..
SHERI ZIDENBERG-CHERR, cooperative extension specialist, Department of Nutrition, University of California, Davis.
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