Epidemiological studies have shown that consumption of green tea, coffee, and blueberries and dairy avoidance are associated with reduced likelihood of being diagnosed with Parkinson’s disease (PD) [
PD is a slowly progressing disease, so disease-modification trials require long follow-up periods. The heterogeneity of the disease requires enrollment of large populations, both of which increase the expense of clinical trials. Motor symptoms are now known to occur late in the disease and thus may not be an ideal outcome measure for protection, although biomarkers of early disease are lacking. Further complicating matters, results of efficacy (or lack thereof) seen in the controlled, ideal environment of a randomized controlled trial, may or may not translate to effectiveness in a real-life setting. To circumvent these issues, a study was designed to ask patients directly about their food choices and use of supplements. The positive deviance approach uses disease heterogeneity to our advantage, permitting the identification of individuals progressing at a substantially slower or faster rate of PD progression [
“Complementary and alternative medicine in PD (CAM Care in PD)” is a pragmatic, prospective observational study that was designed to accomplish the task. The questionnaire was designed by the PI (LKM) based on her experience as a nutritional neuroepidemiologist, clinical trialist, and physician specializing in PD. A study webpage, hosted by Bastyr University, provided automated access to participation. In addition to recruitment via social media, IRB-approved recruitment cards were distributed at PD support groups and to colleagues at neurology conferences.
The primary outcome measure was an assessment tool, patient-reported outcomes in PD (PRO-PD), designed to assess PD severity. The PRO-PD consists of 33 common PD symptoms, and the participant is asked to move the tab on a slider bar according to symptom severity. The left side of the bar always represents optimal health (lack of symptom), and the right side of the bar always represents maximum symptom severity. The PRO-PD score is the cumulative score of each of the symptoms, each of which is assigned a value 0–100, resulting in a continuous outcome measure that increases over time. In a cross-sectional analysis, PRO-PD scores correlated with disease duration (
The PRO-PD score is the sum of 33 motor, mood, and other nonmotor symptoms common in PD. Higher scores represent either more symptoms or greater symptom severity of a few symptoms. Lower PRO-PD scores correlate with better social, emotional, and physical quality of life [
Individuals with all forms of parkinsonism were invited to participate in the CAM Care in PD study. While the CAM Care in PD study is designed to be longitudinal, this initial analysis is cross-sectional, as more time is needed before there will be adequate sample size for a robust longitudinal analysis. In the meantime, a cross-sectional study adjusted for years since diagnosis can still offer insights into the association between PD severity and diet and lifestyle factors. For this cross-sectional analysis, only baseline data from individuals with a self-reported diagnosis of idiopathic PD were used. PD severity is defined by the cumulative PRO-PD score, and PD progression is defined by the PRO-PD score adjusted for years since diagnosis.
A food frequency questionnaire (FFQ) was developed to quantify dietary intake. The FFQ used in this study was created to be pragmatic and meet the needs of this study by drawing on limitations and successes of other nutritional intake questionnaires. Participants were asked to estimate their intake of foods, on average, over the prior six months. For all dietary variables, participants were given 10 options for rating consumption frequency, ranging from “never” to “5-6 times daily.” Other variables chosen were based on incidence data as well as on biological and clinical relevance. Participants were directed to “Please mark the box if you have taken any of the following consistently over the past 6 months” as well as to identify lifestyle choices that they had been engaged in consistently for the last 6 months. All supplement and behavior variables were recorded as binary variables as people either reported using specific supplements/lifestyles or did not.
Multiple linear and logistic regression models were used to examine the association between diet, lifestyle factors, and PD severity, with PRO-PD scores used as the outcome variable. Food frequency questionnaire data is ordinal; due to the relatively large number (10) of consumption frequencies that were offered as options, it was analyzed as a continuous variable. All models controlled for factors known to heavily influence PD severity including age, years since diagnosis, and gender. Additionally, a second model was created that also incorporated income, which may be associated with lifestyle and access factors that may affect PD severity. All statistical work was done using Stata Version 11 (College Station, TX) with alpha set to 0.05. No adjustments were made for multiple comparisons to avoid increasing the risk of type II errors, and the failure to detect an association that is present was a priority for this observational study [
Of the 1307 participants with parkinsonism, 1053 were identified as having a diagnosis of idiopathic PD and were thus available for analysis. The average age of participants was 63 years, with an average 5.2 years since diagnosis. Accordingly, the majority of the study participants were in HY stages 1–3 (93.5%). While gender and income were evenly distributed across the study population, there was very little ethnic diversity (Table
Demographics of the study participants.
|
|
---|---|
Age, years (SD) | 63.1 (9.2) |
Years since diagnosis (SD) | 5.2 (5.5) |
|
463 (44%) |
|
978 (92.9%) |
|
56 (5.3%) |
|
522 (49.6%) |
Using the food frequency questionnaire, the results of this analysis suggest that a plant- and fish-based diet is associated with the lowest PD severity score (Table
Multiple linear regression model of dietary intake and PD progression. Predicted PD severity score, as measured by the PRO-PD, per unit increase in food intake frequency, intake measured on a 10-point scale: never, <1/month, 1/month, 2-3×/month, 1/week, 2–4×/week, 5-6×/week, 1/day, 2–4×/day, 5-6×/day.
Association between dietary practices and Parkinson’s disease progression | ||||
---|---|---|---|---|
Food item (serving size) | Mean change in PRO-PD score (SE) |
|
Mean change in PRO-PD score (SE) |
|
Fresh vegetables (1/2 cup) | −53.2 (7.9) | <0.000 (−68.7 to −37.6) | −48.9 (8.3) | <0.000 (−64.7 to −33.1) |
Fresh fruit (1/2 cup) | −44.1 (8.5) | <0.000 (−60.7 to −27.5) | −40.7 (8.6) | <0.000 (−57.5 to −23.9) |
Nuts (1/4 cup or 2 tbsp spread) | −38.5 (7.5) | <0.000 (−53.2 to −23.7) | −33.2 (7.6) | <0.000 (−48.1 to −18.4) |
Fish (4 oz) | −37.1 (8.9) | <0.000 (−54.6 to −19.5) | −29.5 (9.1) | 0.001 (−47.3 to −11.6) |
Olive oil (1 tsp) | −34.1 (6.8) | <0.000 (−47.4 to −20.8) | −31.4 (6.8) | <0.000 (−44.7 to −18.1) |
Wine (6 oz) | −23.6 (5.3) | <0.000 (−34.1 to −13.1) | −14.6 (5.6) | 0.009 (−25.5 to −3.7) |
Turkey (4 oz) | −20.2 (18.7) | 0.281 (−57.1 to 16.7) | −10.8 (19.2) | 0.573 (−48.7 to 27) |
Coconut oil (1 tsp) | −18.6 (5.5) | 0.001 (−29.3 to −7.8) | −20.2 (5.5) | <0.000 (−31 to −9.4) |
Fresh herbs (1 tsp) | −14.9 (6.4) | 0.02 (−27.4 to −2.4) | −8.9 (6.5) | 0.169 (−21.7 to 3.8) |
Spices (1/4 tsp) | −14.2 (6.4) | 0.027 (−26.7 to −1.6) | −13.4 (6.4) | 0.037 (−26 to −0.8) |
Eggs (1 egg) | −9.5 (8.2) | 0.251 (−25.6 to 6.7) | −9.7 (8.3) | 0.241 (−26 to 6.5) |
Bread (1 slice) | −7.7 (6.8) | 0.26 (−21.2 to 5.7) | −6.9 (6.9) | 0.314 (−20.4 to 6.6) |
Beans (1/2 cup) | −6.3 (8.6) | 0.466 (−23.3 to 10.7) | −5.4 (8.8) | 0.54 (−22.6 to 11.8) |
Butter (1 tsp) | −4 (5.9) | 0.494 (−15.6 to 7.5) | −3.8 (6) | 0.522 (−15.5 to 7.9) |
Oatmeal (1 cup) | −3.2 (6.5) | 0.624 (−15.9 to 9.5) | −4.4 (6.6) | 0.501 (−17.3 to 8.5) |
Liquor (1 oz) | −2.8 (7.7) | 0.717 (−17.8 to 12.3) | 3.6 (7.7) | 0.47 (−11.5 to 18.7) |
Green tea (1 cup) | −2.3 (5.7) | 0.68 (−13.5 to 8.8) | 1.6 (5.7) | 0.779 (−9.6 to 12.7) |
Juice (8 oz) | −2.3 (5.8) | 0.687 (−13.8 to 9.1) | −1.4 (5.9) | 0.811 (−12.9 to 10.1) |
Frozen fruit (1/2 cup) | −1.9 (6.1) | 0.757 (−13.8 to 10) | −2.2 (6.1) | 0.714 (−14.1 to 9.7) |
Cream (1/4 cup) | −0.5 (7.4) | 0.942 (−15.2 to 14.1) | −0.3 (7.4) | 0.971 (−14.7 to 14.2) |
Coffee (8 oz) | −0.1 (4.4) | 0.983 (−8.8 to 8.6) | 4.3 (4.5) | 0.342 (−4.5 to 13.1) |
Soy (3 oz) | 0.4 (7.9) | 0.962 (−15.2 to 16) | 2.3 (8) | 0.77 (−13.4 to 18.1) |
Safflower oil (1 tsp) | 0.7 (6.9) | 0.922 (−12.8 to 14.2) | 6.8 (6.9) | 0.325 (−6.8 to 20.5) |
Beer (12 oz) | 1.1 (7.6) | 0.88 (−13.7 to 16) | 2 (7.5) | 0.789 (−12.8 to 16.8) |
Chicken (4 oz) | 3.3 (9.7) | 0.34 (−15.6 to 22.3) | 13.4 (9.8) | 0.171 (−5.8 to 32.5) |
Milk (1 cup) (mammalian, for example, cow) | 5.8 (4.8) | 0.226 (−3.6 to 15.2) | 5.1 (4.8) | 0.291 (−4.4 to 14.5) |
Pork (4 oz) | 6.1 (8.6) | 0.482 (−10.8 to 22.9) | 7 (8.7) | 0.42 (−10 to 24) |
Black tea (1 cup) | 8.6 (5.6) | 0.121 (−2.3 to 19.5) | 8.4 (5.6) | 0.131 (−2.5 to 19.3) |
Eat food from a can | 9.6 (8.1) | 0.234 (−6.2 to 25.4) | 6.1 (8.1) | 0.449 (−9.7 to 22) |
Pasta (1 cup) | 10.1 (9.3) | 0.28 (−8.2 to 28.4) | 9.2 (9.4) | 0.326 (−9.2 to 27.6) |
Frozen vegetables (1/2 cup) | 11 (6.9) | 0.11 (−2.5 to 24.4) | 10.3 (6.9) | 0.137 (−3.3 to 23.9) |
Cheese (1 slice, 1/2 oz, 1 tbsp) | 11.7 (6.9) | 0.091 (−1.9 to 25.3) | 15.5 (6.9) | 0.026 (1.9 to 29.1) |
Yogurt (3/4 cup) | 13.5 (7.5) | 0.073 (−1.3 to 28.3) | 15.2 (7.6) | 0.046 (0.2 to 30.1) |
Ice cream (1/2 cup) | 13.8 (7.4) | 0.064 (−0.8 to 28.3) | 18.3 (7.5) | 0.015 (3.6 to 32.9) |
Soda (12 oz) | 15.4 (7.8) | 0.049 (0.03 to 30.7) | 15.2 (7.9) | 0.054 (−0.3 to 30.6) |
Beef (4 oz) | 16.2 (8.3) | 0.051 (−0.1 to 32.4) | 21.8 (8.3) | 0.009 (5.5 to 38.1) |
Fried food (4 oz) | 19.5 (8.8) | 0.027 (2.2 to 36.8) | 23 (8.9) | 0.009 (5.6 to 40.4) |
Canned vegetables (1/2 cup) | 19.9 (7) | 0.005 (6.1 to 33.6) | 18.3 (7) | 0.009 (4.5 to 32.1) |
Diet soda (12 oz) | 20.7 (6.1) | 0.001 (8.7 to 32.8) | 23.6 (6.1) | <0.000 (11.6 to 35.6) |
Canned fruit (1/2 cup) | 36.1 (7.9) | <0.000 (20.5 to 51.6) | 32 (7.9) | <0.000 (16.5 to 47.6) |
These foods largely comprise the Mediterranean diet, which has been associated with reduced PD incidence and later age of diagnosis [
Ice cream, cheese, and yogurt intakes were associated with higher rates of PD progression (Table
There may be several mechanisms responsible to explain the association between PD progression and dairy consumption:
Dairy intake lowers uric acid [ Diary consumption is associated with insulin resistance [ Lactose intolerance, occurring when the enzyme, lactase, that digests the milk sugar decreases with age, is especially common in individuals of African, Asian, Hispanic, and Native American decent [ Presence of a neurotoxic component or contaminant, for example, pesticides, may be present in dairy [ Introduction of bovine microbiota, facilitating seeding of methanogenic organisms, leads to the development of methane-dominant small intestinal bacterial overgrowth (SIBO) and other forms of abnormal intestinal flora [
Consumption of canned fruits and vegetables was a strong predictor of PD progression. Initially thought to be associated with socioeconomic status, the association remained after adjusting for income. Bisphenol A (BPA) is used extensively worldwide in the inner coating of food cans, and there is evidence that BPA contaminates foods stored in the cans. BPA is a well-established endocrine conductor associated with obesity, and more recent evidence suggests that it is an energy balance disruptor [
The association with fried foods may be related to lipid peroxidation resulting from the well-established increase in reactive oxygen species (ROS) observed in PD. Lipid peroxidation results in the production of aldehydes, such as acrolein, that bind covalently with thiol groups of proteins, leading to protein aggregation and dysfunction [
Soda, specifically diet soda, was also associated with a faster rate of PD progression. Soda is a sugar-sweetened beverage associated with additional caloric intake and obesity [
Logistic regression model of nutritional supplements and PD progression. Predicted PD severity score, as measured by the PRO-PD, based on the positive report of consistently using of supplements over the previous 6 months.
Association between dietary supplements & risk of Parkinson’s disease progression | |||||
---|---|---|---|---|---|
Nutritional supplement |
|
Mean change in PRO-PD score (SE) |
|
Mean change in PRO-PD score (SE) |
|
Inosine | 13 | −181.1 (125.6) | 0.15 (−427.5 to 65.3) | −107.1 (122.9) | 0.384 (−348.4 to 134.2) |
Glutathione, oral | 43 | −126.1 (69) | 0.068 (−261.6 to 9.3) | −126.7 (70) | 0.07 (−263.9 to 10.5) |
DHEA | 47 | −87.6 (70.8) | 0.216 (−226.6 to 51.4) | −72.2 (70.9) | 0.309 (−211.3 to 67) |
Lithium, low dose | 21 | −84.9 (100.2) | 0.397 (−281.6 to 111.8) | −118.9 (100.4) | 0.237 (−315.9 to 78.1) |
Low-dose naltrexone | 14 | −76.1 (120.9) | 0.529 (−313.4 to 161.2) | −87.8 (118) | 0.457 (−319.3 to 143.8) |
CoQ10 | 286 | −70.4 (31.5) | 0.026 (−132.2 to −8.6) | −46.6 (31.6) | 0.141 (−108.7 to 15.4) |
Fish oil | 376 | −69.5 (29.5) | 0.019 (−127.4 to −11.6) | −57.7 (29.6) | 0.052 (−115.7 to 0.4) |
Quercetin | 21 | −50.7 (105.9) | 0.632 (−258.5 to 157.1) | −60.5 (106.4) | 0.569 (−269.3 to 148.2) |
Turmeric/curcumin | 197 | −47.3 (35.6) | 0.186 (−117.3 to 22.8) | −49.5 (35.9) | 0.168 (−120 to 20.9) |
|
30 | −47.2 (83.2) | 0.57 (−210.5 to 116) | −61.1 (81.2) | 0452 (−220.5 to 98.2) |
Coconut oil | 190 | −35.8 (36.4) | 0.324 (−107.2 to 35.5) | −52.7 (36.4) | 0.147 (−124.1 to 18.6) |
Resveratrol | 43 | −28.5 (70.7) | 0.687 (−167.3 to 110.3) | −18.7 (72.7) | 0.797 (−161.4 to 124) |
Vitamin D | 623 | −26.1 (29) | 0.368 (−83 to 30.8) | −3.6 (29.2) | 0.902 (−60.9 to 53.7) |
Alpha-lipoic acid | 79 | −19.1 (53.4) | 0.72 (−123.9 to 85.7) | 0.05 (54.4) | 0.999 (−106.7 to 106.7) |
5-Methyltetrahydrofolate (5-MTHF) | 27 | −17.1 (91.4) | 0.852 (−196.4 to 162.2) | −25.1 (95.6) | 0.793 (−212.7 to 162.5) |
Probiotics | 249 | −12.3 (32.7) | 0.708 (−76.5 to 52) | −12.4 (32.9) | 0.706 (−77 to 52) |
NADH | 14 | −9.7 (120.8) | 0.936 (−246.7 to 227.3) | −25.2 (122.6) | 0.837 (−265.7 to 215.4) |
Multivitamin/mineral | 342 | −7.8 (30.2) | 0.795 (−67.1 to 51.4) | 9.9 (30.3) | 0.744 (−49.6 to 69.5) |
Calcium | 324 | −6.2 (32.2) | 0.847 (−69.4 to 57) | 12.5 (32.6) | 0.701 (−51.4 to 76.4) |
B6, B12, folic acid, betaine combination | 88 | 3.4 (49.7) | 0.946 (−94.2 to 101) | 11.1 (48.9) | 0.82 (−84.9 to 107.1) |
Vitamin C | 327 | 4.2 (30.6) | 0.891 (−55.9 to 64.3) | −3.8 (31) | 0.902 (−64.6 to 56.9) |
N-Acetyl cysteine (NAC) | 59 | 12.8 (60.1) | 0.831 (−105 to 130.7) | 26.9 (60.8) | 0.658 (−92.4 to 146.1) |
Vitamin B12 (methyl-B12/cyano-B12) | 353 | 26.7 (29.8) | 0.37 (−31.8 to 85.3) | 43 (29.8) | 0.15 (−15.6 to 101.6) |
Rubidium | 2 | 34.2 (306) | 0.911 (−566.4 to 634.7) | 93.1 (298.5) | 0.755 (−492.7 to 678.8) |
Estrogen | 51 | 40 (67.4) | 0.553 (−92.2 to 172.3) | 15.2 (69.6) | 0.827 (−121.4 to 151.8) |
Glutathione, intranasal | 24 | 62.9 (95.5) | 0.51 (−124.5 to 250.4) | 55.6 (93.2) | 0.551 (−127.3 to 238.5) |
|
33 | 67 (81.7) | 0.412 (−93.3 to 227.2) | 21.8 (80) | 0.785 (−135.1 to 178.6) |
Fava beans | 17 | 122 (109) | 0.263 (−92 to 336) | 87.8 (110.1) | 0.425 (−128.2 to 303.8) |
Melatonin | 148 | 139.3 (40.5) | 0.001 (59.8 to 218.8) | 134.8 (40.2) | 0.001 (56 to 213.6) |
Iron (Fe) | 57 | 146.4 (63.9) | 0.022 (21 to 271.9) | 179.7 (64.3) | 0.005 (53.6 to 305.9) |
The association between beef and PD progression is congruent with traditional epidemiologic research demonstrating an association between beef consumption and PD incidence [
Of all the nutritional supplements studied, only coenzyme Q10 and fish oil were associated with statistically significant reduced rates of PD progression (Table
Fish oil is a rich source of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). There has been a tremendous amount of research conducted on the role of EPA and DHA in neuronal health. The neuroprotective effects of DHA, in particular, have been attributed to multiple mechanisms. In addition to acting as an antioxidant, DHA reduces inflammation by reducing arachidonic acid and its metabolites. As a precursor to neuroprotectin D1, it exerts antiapoptotic activity, enhances the synthesis of the neurotrophic factor, brain-derived neurotrophic factor (BDNF), and promotes neurogenesis via enhanced synaptogenesis and neurite outgrowth [
There is conflicting evidence regarding the use of melatonin, a hormone produced by the pineal gland, in PD. Melatonin regulates the body’s circadian rhythm: levels increase at night in response to the absence of light. The presence of this hormone induces the neurophysiological changes that occur during the brain restoration taking place during sleep. Sleep disorders are common in PD [
Correlation between insomnia and PD severity among individuals who do, and do not, report consistent use of melatonin over the previous six months.
Iron, prone to oxidation, has long been implicated in PD, and these results suggest that iron supplementation is associated with PD progression (Table
After adjusting for age, gender, years since diagnosis, and income, individuals who prepare their own meals, and meals for others, were afforded protection against PD progression (Table
Logistic regression model of dietary behaviors and PD progression. Predicted PD severity score, as measured by the PRO-PD. Participants were asked to select all of the statements that were true over the prior 6 months; plastic bottle utilization was evaluated on a 10-point scale, also over the prior 6 months.
Dietary behaviors associated with Parkinson’s disease progression | ||||
---|---|---|---|---|
Dietary behaviors | Mean change in PRO-PD score (SE) |
|
Mean change in PRO-PD score (SE) |
|
I routinely prepare meals for others. | −141.1 (29.3) | <0.000 (−198.7 to −83.6) | −112.8 (29.7) | <0.000 (−171.2 to −4.4) |
I cook most of my meals. | −115.1 (30.2) | <0.000 (−174.4 to −55.7) | −135.4 (30.3) | <0.000 (−194.9 to −5.8) |
I buy food from a local farmers (co-op, farmer’s markets) | −98 (28.3) | 0.001 (−153.5 to −42.5) | −97.2 (28.4) | 0.001 (−153 to −41.5) |
I try to eat organically grown foods when possible. | −61.3 (28.1) | 0.029 (−116.5 to −6.2) | −74.9 (28.1) | 0.008 (−130 to −19.8) |
I drink from a plastic bottle. | 11.2 (5.4) | 0.039 (0.6 to 21.8) | 11.9 (5.4) | 0.029 (1.2 to 22.6) |
I am overweight. | 169.4 (28.5) | <0.000 (113.5 to 225.3) | 165.8 (28.5) | <0.000 (109.8 to 221.8) |
It is difficult to afford groceries. | 443.5 (51.2) | <0.000 (343.1 to 543.9) | 348.7 (55.4) | <0.000 (240 to 457.3) |
I find it difficult to afford healthy food. | 473.6 (46.1) | <0.000 (383 to 564.1) | 389.3 (49.5) | <0.000 (292.2 to 486.5) |
Individuals who find it difficult to afford food, especially healthy food, were associated with a faster rate of PD progression. While type 2 diabetes increases risk of PD [
This pragmatic, natural history study offers the first evidence-base for prescribing lifestyle modification (beyond exercise) to patients with PD. The foods shown here to be associated with slower PD progression are common to the Mediterranean diet and support an existing body of literature. Whether iron, beef, dairy, fried foods, diet soda, or canned goods provide environmental insults that accelerate disease progression warrants immediate attention; until further research is conducted, minimizing exposure to these foods is justified.
Because weight loss commonly occurs as the disease progresses, any suggestion that patients avoid foods increases the risk of restricting calories and contributing to malnutrition. Patients should be counseled on alternative sources of protein (e.g., beans, nuts, and seeds) and calcium (e.g., almonds, green leafy vegetables, and tofu).
Fish oil supplementation is warranted in individuals with a diagnosis of PD and justified based on biological plausibility and the clinical epidemiological data. As fish oil supplements are sold over the counter, there is a tremendous amount of diversity in both content of EPA and DHA, as well as in quality (e.g., presence of contaminants), whereas providers should familiarize themselves with available products and recommend buying from companies that perform analysis on stability, purity, and potency. Consumption of nonfried oily fish, such as herring, sardines, mackerel, and salmon should be encouraged. Because the association between coenzyme Q10 and PD progression was no longer significant after adjusting for income, more research needs to be done before recommending patients to start supplementing coenzyme Q10.
Health care providers should routinely review patients’ supplement lists and ensure that the only patients taking iron are those with iron-deficiency anemia being treated under medical supervision. Because iron is commonly added to multivitamins, men and nonmenstruating women should not take a multivitamin containing iron, unless recommended by their physician.
The risk of bias should be considered in interpreting these data. Dietary intake is difficult to estimate (e.g., ingredients in casserole) and susceptible to recall bias (e.g., tasting food while cooking, food samples at the store, and other snacking are often under-reported). This is offset in this study because the questionnaire only asked about recent intake, the prior six months, and that all subjects in the study are affected equally by this limitation in recall. There is likely to be selection bias in this sample, as individuals using integrative medicine are expected to be more likely to enroll in a study called “Complementary and Alternative Medicine (CAM) in PD”. In an attempt to minimize this bias, the study home page explains that all individuals are invited to participate, regardless of disease duration, severity, or CAM use. Still, the degree to which these data are generalizable to the larger PD population has yet to be determined.
These data would be substantially improved with associated biomarkers of nutrient intake and physical examination of participants, both to screen for evidence of nutritional deficiencies and to confirm the diagnosis. This study is also limited by the homogeneity of the population, which was largely Caucasian and from the United States. Despite these limitations, these data suggest that the survey study design and PRO-PD are useful tools for deriving information about food, nutrition, and PD progression. As this is a longitudinal study that is still enrolling participants, it is likely that the foods and supplements associated with PD progression will change over time, as more people enroll, with evaluation of the longitudinal data. Clinicians now have data on which to base their recommendation for healthy eating in PD, and patients are likely to be empowered to know that their day-to-day choices may influence progression.
Dr. Laurie K. Mischley owns the PRO-PD rating scale. There are no other conflicts to disclose.
This work was supported by the NCCIH, National Institutes of Health/Bernard Osher K01 Career Transition Award (NIH K01 AT004404) and a donation from Sondra and Bill Fondren.