I got my first Fitbit in the spring of 2016 and almost immediately was hooked. The weekly step challenges brought out my competitive side, and the spiking heart rate the app showed after a night out drinking was illuminating. Scrolling through the app now, I can see my life told by the minute over the past four years.

All my personal health data, along with that of millions of other Americans, could soon be in the hands of Google once its $2.1 billion purchase of Fitbit is completed. Amazon, Apple, Google, and Microsoft are all rushing to disrupt the $3.6 trillion U.S. health care market. Jeff Bezos is even piloting a virtual medical clinic (Amazon Care) for his company's Seattle employees.

But are Americans ready to share their personal health data with Big Tech? And which tech giant is most likely to disrupt the industry?

To find out, Fortune and SurveyMonkey polled 1,276 U.S. adults between June 25 and 26.*

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The numbers to know

40%

40%

• …of U.S. adults trust Amazon and Apple with their personal data. That was 27% for Microsoft, 20% for Alphabet/Google, and 12% for Facebook.

31%

31%

• …of U.S. adults trust Apple with their personal health information. That is the highest level of trust for any Big Tech company.

18%

18%

• …of U.S. adults say they trust Alphabet/Google Health with their data, the lowest level of support among Big Tech companies.

30%

30%

• …of U.S. adults say Amazon is the Big Tech firm most likely to disrupt health care over the next five years.

27%

27%

• …of U.S. adults say none of the big tech firms are likely to disrupt health care over the next five years.

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The big picture

• The American public doesn't really trust tech giants. Amazon and Apple receive the highest levels of trust (40%)—pretty underwhelming for companies that interact with most of the country every week. And when asked specifically about health care information, 7 in 10 people are untrusting of all the tech giants. That could create a roadblock for them as they ramp up their health care businesses.

• Jeff Bezos is the public's bet on who is going to shake up the nation's health care system. Among the U.S. public, 85% view Amazon favorably. And when asked to pick who will be the top health care disrupter, the public sides with the Seattle-based e-commerce and data giant.

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A few deeper takeaways

1. The richest Americans trust Big Tech the least.

Just 31% of U.S. adults trust Apple with their personal health information. And that is actually the highest level of trust for Big Tech: 8 in 10 U.S. adults are untrusting of Amazon, Google, and Microsoft with their health data.

The customers of Apple and Amazon both lean more affluent. But Americans polled in the highest income bracket trust Amazon and Apple the least. Meanwhile, only 22% of Amazon Prime subscribers trust Amazon with their health data—that's barely higher than the response from non–Amazon Prime users (16%).

For health care to work, patients must have trust. This lack of trust could be a bigger challenge for Big Tech than they'd like to see.

2. The country is betting on Amazon.

The Apple Watch and Health app are helping their parent company make inroads into health care data. As are Azure and Microsoft Genomics for Microsoft, and Verily and Google Health for Alphabet/Google.

But it's Amazon that the public sees as the most likely to disrupt the health care industry, with 30% of respondents picking the Seattle-based firm. The least likely? Just 11% of U.S. adults say Microsoft is likely to be the top health care disrupter.

Why Amazon? "Reliable, fast, fewer scandals," says Danielle Abril, my Fortune colleague who covers tech.

However, 27% of U.S. don't see any of the Big Tech firms transforming health care.

*Methodology: The Fortune-SurveyMonkey poll was conducted among a national sample of 1,276 adults in the U.S. between June 25–26. This survey’s modeled error estimate is plus or minus 4 percentage points. The findings have been weighted for age, race, sex, education, and geography.