Here's some pretty simple health advice: Eat a handful of nuts every day.

This is the conclusion of a massive review of nearly 30 studies done around the world on nut consumption and the risk of disease. It found that eating 20 grams (about an ounce or the equivalent of a handful) of nuts a day cuts the risk of heart disease, cancer and premature death.

Just because nuts are so nutritious doesn’t mean more is better.

The studies in the review included men and women, people with varying risk factors, and those living in different areas; but across the board, nut consumption was associated with a reduced risk of disease — despite being high in calories and fat.

“We found a consistent reduction in risk across many different diseases, which is a strong indication that there is a real underlying relationship between nut consumption and different health outcomes. It's quite a substantial effect for such a small amount of food,” said Dagfinn Aune from Imperial College London, a co-author of the study, in a statement.

Eating nuts cut the risk of heart disease by about 30 percent, cancer by 15 percent and the risk of premature death by 22 percent when the results of all published studies were combined. Though less data were available in relation to death from respiratory disease and diabetes, daily nut consumption also reduced those risks.

All types of tree nuts were included in the study, as well as peanuts, which are really legumes, rather than nuts. It didn't matter whether total nut intake was analyzed or just tree nuts or only peanuts, the health benefits were similar.

Nuts are little powerhouses of nutrition. Their fiber, magnesium and polyunsaturated fats lower cholesterol levels in the blood and reduce the risk of cardiovascular disease. Some nuts, such as walnuts, contain beneficial antioxidants which may reduce the risk of cancer.

Pay Attention To Portion Sizes
Just because nuts are so nutritious doesn’t mean more is better. The study found that eating more than an ounce, or a handful, a day did not result in any further health benefits.

So, in a nutshell, here’s a guide to portion sizes. One ounce of nuts roughly equals:

  • 23 almonds
  • 14 walnut halves
  • 12 hazelnuts
  • 18 medium cashews
  • 8 Brazil nuts
  • 12 macadamia nuts
  • 35 peanuts
  • 15 pecan halves

    • The study is published in BMC Medicine.