Health journalism is often filled with conflicting and confusing claims. And there may be no better example of this befuddlement than in the reporting around red wine. One day, a story emerges saying red wine is good for you. The next day, it's bad. The next day, it's good again.

The bottom line What we know: A small amount of alcohol — no more than one drink per day for women and two drinks per day for men — seems to be associated with a reduced risk of coronary heart disease and a higher life expectancy. However, red wine doesn't appear to bring any extra benefits here. What's more, too much alcohol can increase the risk of premature death and cause a host of other medical problems. What we don't know: None of the long-term research on alcohol involves randomized controlled trials, so it doesn't necessarily tell us that there's a causal link between alcohol and various health effects. Still, this isn't any different from the data we have on other big lifestyle activities, such as exercise or smoking. What this means for you: If you don't have other health issues or a history of alcoholism, a small amount of alcohol may have some benefit for your heart health and longevity. But that benefit needs to be weighed against alcohol's many risks and your individual health history. Welcome to Show Me the Evidence, where we go beyond the frenzy of daily headlines to take a deeper look at the state of science around the most pressing health questions of the day.

So what's the truth of the matter? To sort this out, I combed through more than 30 studies and spoke to five researchers who've studied the health benefits and risks of alcohol.

What I learned is that scientists did, in fact, once think red wine might carry some special health benefits. Back in the 1990s, researchers were puzzling over why the French had lower rates of heart disease than people in other countries, even though they smoked more and ate more saturated fat. Some suggested it might be due to their consumption of red wine, and that belief persisted for years.

Since then, however, science has progressed, and researchers have realized this isn't quite correct. Today, many experts will agree that drinking moderate amounts of any type of alcohol — up to one glass a day for women and up to two daily glasses for men — may have benefits for heart health specifically (though there are important caveats discussed further down). Red wine, however, isn't any more beneficial than beer or spirits in this regard.

What is the state of science around alcohol consumption?

It is decent, but far from perfect. Any claim made about the health effects of alcohol can never be considered definitive, since we don't have what scientists consider the highest-quality evidence on drinking.

The best way to study the effects of drinking would be to run a randomized controlled trial in which, say, one randomly selected group is told to drink two glasses of wine each day, for decades, and the other group is given a placebo. But scientists just haven't been able to conduct these studies, and likely never will. For one, it's considered unethical to force people to drink, since alcohol can be addictive. And as Stanford researcher John Ioannidis points out, it'd be tough to be sure that participants actually adhered to the regimen over a long time period.

Instead, alcohol researchers have to make use of two types of lower-quality evidence. First, they can conduct short-term trials that look at what wine does to people's physiology (say, lipid levels in their blood). The problem here is that these studies can't tell us much about long-term outcomes (like heart disease). At best, researchers can make inferences.

Second, researchers can conduct observational studies, where, say, they follow people who drink and people who don't drink and monitor their health over the long term. The trouble here is that these two groups may be different in other ways besides their alcohol consumption habits. That makes it much harder to tease out cause and effect. (If wine drinkers live longer than beer drinkers, is that due to the wine, or due to the fact that wine drinkers are likely to be wealthier and more health-conscious?)

That doesn't mean existing research is useless, however. After all, this is how scientists study all sorts of lifestyle choices, including exercise and smoking (you'd never conduct a randomized controlled trial for cigarettes). And generally, researchers feel fairly confident in drawing conclusions from these studies, which are the best evidence we have. So with those caveats in mind, here's what we know about red wine and alcohol.

1) Is drinking in moderation good for you?

It appears so. Researchers generally believe a small bit of alcohol — up to one serving a day for women, and up to two servings a day for men — can generally be good for your health, albeit with some caveats. (According to the National Institutes of Health, this intake of daily alcohol is considered "moderate drinking.")

This is what a serving looks like:

There are a few reasons alcohol researchers believe moderate drinking can be beneficial.

In short-term studies, where scientists measure physiological effects in people who drink moderately, alcohol seems to do the following: raise the amount of HDL (or good) cholesterol in the blood and decrease clotting, essentially acting as a blood thinner. "These mechanisms provide a biological basis for a causal relation between alcohol consumption and lower rates of coronary heart disease and death," explained Annlia Paganini Hill of the University of California Irvine.

Meanwhile, in long-term observational studies that compare drinkers to non-drinkers, these findings seem to translate pretty definitively to better health outcomes for the light to moderate drinkers. Overwhelmingly, they had lower rates of heart disease and heart attacks and longer lives. Moderate drinkers also had lower rates of diabetes, another important risk factor for heart disease (although this result is less definitive).

These findings are fairly significant, since heart disease is a major health issue that affects millions of people every year. Still, keep in mind that these studies are only observational. It's possible there could be some confounding factors here. (Paganini Hill notes that people with serious illnesses, including heart disease, tend to cut back on their consumption of alcohol, which could skew the results.)

The researchers I spoke to also emphasized that alcohol is by no means some magical health elixir. As Harvard's Kenneth Mukamal told me, moderate drinking really only appears to help with particular conditions. "To the degree we attribute benefit to moderate drinking, it's only with coronary heart disease and diabetes."

Moderate drinking can also carry risks for some people. For women, any amount of drinking appears to be associated with an increased breast cancer risk.

2) Does red wine have any special advantage over other types of alcohol?

Key studies: 1990: British Journal of Addition — "Correlates of alcoholic beverage preference: traits of persons who choose wine, liquor or beer" 1992: Lancet — "Wine, alcohol, platelets, and the French paradox for coronary heart disease" 1996: BMJ — "Review of moderate alcohol consumption and reduced risk of coronary heart disease: is the effect due to beer, wine, or spirits?" 2006: Nature — "Resveratrol improves health and survival of mice on a high-calorie diet" 2011: BMJ — "Effect of alcohol consumption on biological markers associated with risk of coronary heart disease: systematic review and meta-analysis of interventional studies" 2011: BMJ — "Association of alcohol consumption with selected cardiovascular disease outcomes: a systematic review and meta-analysis" 2014: JAMA — "Resveratrol Levels and All-Cause Mortality in Older Community-Dwelling Adults" 2015: Journal of Internal Medicine — "Alcohol and cardiovascular diseases: where do we stand today?"

It doesn't appear so. The researchers who have studied the effects of moderate drinking haven't really found any good evidence that the type of alcohol you drink matters very much.

"In our study, we found no difference in the effects of wine, beer, or hard liquor on mortality," said Paganini Hill. She notes that other studies have found little difference between the three; some studies have found a bit more benefit for red wine, others a bit more benefit for beer, and still others a bit more benefit for spirits.

Mukamal agrees. "It's not the red wine per se, but whatever they’re drinking moderately and frequently," he told me. "The pattern associated with the lowest risk is those who are consuming alcohol daily but never consuming a lot." (In one of his big studies, involving nearly 40,000 health professionals across the US, red wine was actually the least associated with cardiovascular benefits, while those who drank beer and spirits fared a bit better.)

The whole notion that red wine might somehow be better for you came from the observation that the French drank lots of it and had lower rates of cardiovascular disease. This was known as the "French paradox." Yet scientists no longer find this paradox quite so compelling. As New York University's Ira Goldberg told me, it doesn't explain why Canadians and Japanese have longer life expectancies despite lower levels of red wine consumption than France.

What's more, researchers have been analyzing red wine for years now to see if it has any unique properties that might confer special health benefits. And so far, they haven't found anything convincing.

Red wine is a combination of a few things: ethanol (alcohol), water, sugar, and coloring. The color comes from polyphenolic compounds, which are naturally occurring chemicals found in plants and other foods, including red wine. One of these polyphenols is an ingredient called resveratrol, found in the skins of grapes. Because red wine gets fermented with grape skins for longer than white wine, it has higher levels of resveratrol.

So if there were anything special about red wine, you'd expect it to be because of the resveratrol. But there's little evidence that resveratrol is anything magical. Yes, there are animal studies showing that resveratrol can slow down aging and improve the metabolism of mice on high-fat diets. But a human would need to consume 1,000 liters of red wine in one sitting to reach the levels these mice were injected with (which, suffice it to say, is not recommended). And when researchers studied resveratrol levels in the urine of a sample of older folks, they found no association with any positive health effects.

Ultimately, researchers tend to think that the benefits of red wine come from the alcohol itself, which is found in beer or liquor as well. "There’s some specific effects of alcohol on thinning our blood and raising good cholesterol, but that comes from all alcohol," said Mukamal. "Most of the benefit you’re getting out of red wine is in the alcohol component."

(He also notes that if polyphenols did have any unique health effects, you could just as easily get them from grape juice, tea, berries, olives, olive oil, or cocoa.)

3) How much alcohol is too much?

Mukamal's rule is simple: no more than two drinks per day for men, and one for women. "Not three, not four, not five."

And don't drink your week's allowance in one sitting, warns Arthur Klatsky of Kaiser Permanente. Getting too much alcohol in a single shot is harmful: It raises your blood pressure and stresses your liver, among other bad things.

Indeed, researchers tend to agree that once you start drinking heavily, the negative effects far outweigh the benefits. Heavy drinking has been linked with increased mortality, obesity, cirrhosis, pancreatitis, and a number of types of cancer — gastrointestinal, liver, head and neck, colorectal. Alcohol can also be addictive, with all the problems that can bring.

What's more, the benefits to heart health can disappear past a certain point. Drinking too much can also raise your blood pressure and actually weaken your heart muscles, leading to heart failure. This is why the major health associations in America, including the American Heart Association, don't suggest drinking to prevent heart disease.

These risks are also why some experts are wary of playing up the benefits of alcohol consumption too heavily. "The entire literature on wine benefits is overhyped," concludes Ioannidis. "Wine is pleasant to drink at low levels, and this should suffice to allow some temperate amount of wine in our lives. But I don’t think I would make a public health policy out of this, and I would not encourage people to focus on drinking wine of any color to get health benefits specifically. The risk of alcohol addiction is far greater."

Mukamal likewise points out that exercise might well be a better way to get heart benefits compared with moderate drinking. "On a per-minute basis, alcohol could be better than exercise, but it’s good for one or two things, while exercise is good for everything."

All the doctors also cautioned that the decision to drink any amount of booze has to be individualized. "Some people shouldn't drink because of their personal history. Pregnant women need to be careful," Klatsky said. Talk to your doctor about your own benefits and risks.