SARAH DI LORENZO: Which are the best nuts to eat for health and how many do you actually need?

I have always loved nuts and not just for their flavour, but for the extraordinary amount of clinical evidence sitting behind what most people dismiss as a fattening snack.

Nuts are one of the most consistently health-protective foods and there is a lot of data on their benefits for longevity, cardiovascular health, metabolic health and brain function.

First I want to share a landmark meta-analysis published in the New England Journal of Medicine analysing data from more than 76,000 participants which found that people who ate nuts seven or more times per week had a 20 per cent lower risk of all-cause mortality compared to those who never ate nuts.

The largest reductions in mortality were seen for cardiovascular disease, cancer and respiratory disease.

Almonds are a metabolic powerhouse. They are usually my first recommendation for anyone focused on cardiovascular health, blood sugar management, and bone health, and the evidence base behind them is genuinely impressive.

A 30 gram serve of almonds — which is what you should be aiming for daily and is about 20 nuts — contains 6g of protein, 3.5g of fibre, 75mg of magnesium, 76mg of calcium, and 7.4mg of vitamin E which is one of the most potent fat-soluble antioxidants available in food.

The research on almonds and cardiovascular health is strong.

Regular almond consumption significantly reduces LDL cholesterol through the combined effects of their monounsaturated fat content, phytosterols and soluble fibre, all of which reduce intestinal cholesterol absorption.

For blood sugar management, the fibre and fat in almonds blunt post-meal glucose responses meaningfully when eaten alongside carbohydrates, making them an excellent strategic snack before a meal or alongside fruit.

Walnuts are amazing for our brain and heart and, as a bonus, they are anti-inflammatory. Walnuts are the only nut containing a significant amount of ALA which is the plant-based omega-3 fatty acid with about 2.5g per 30g serve.

This makes them the most directly brain and cardiovascular-protective nut available.

ALA is a precursor to EPA and DHA which are the long-chain omega-3s most associated with neurological health and while the conversion rate is limited, the absolute amount provided by walnuts daily is clinically meaningful and this is important for plant-based eaters who are not consuming oily fish.

The polyphenol content of walnuts is also the highest of any nut. Polyphenols are among the most potent anti-inflammatory and antioxidant compounds available in food.

For brain health, heart health, and inflammation management I always recommend walnuts first.

Brazil nuts are in a category of their own for one specific and clinically important reason and that is they are an amazing source of selenium.

A single Brazil nut delivers about 70–90 micrograms of selenium which is almost the entire recommended daily intake of 60–75 micrograms for adults.

It contains the organic form of selenomethionine, which is among the most bioavailable selenium compounds available in any food source.

Selenium is an antioxidant we need for thyroid hormone production, immune function, DNA repair, and the antioxidant enzyme glutathione peroxidase that protects cells from oxidative damage.

Selenium deficiency is more common than most Australians realise and is associated with impaired immunity and thyroid dysfunction.

There is an important clinical caution with Brazil nuts though — selenium toxicity, called selenosis, is possible with excessive intake. Symptoms include hair loss, nail brittleness, fatigue and neurological symptoms.

The tolerable upper intake level for selenium is about 400 micrograms per day so this means three to four Brazil nuts daily is the upper safe limit, and one to two Brazil nuts daily is the optimal target for most people.

Do not eat the whole bag. I always recommend only two daily.

So how many nuts do you really need?

The evidence-supported target across all nut research is a 30g daily serve which is about 20 almonds, seven walnuts, or two Brazil nuts.

This is the serving size consistently associated with the mortality and cardiovascular risk reductions in the large cohort studies.

One thing about nuts is it is very hard to stop at just this recommendation.

It is worth noting that significantly larger amounts do not appear to proportionally increase benefit and at very high intakes the caloric load becomes meaningful, a 30g serve of most nuts delivers about 170–200 calories.

When we eat nuts we don’t actually absorb all those calories.

We would absorb about two-thirds of those calories because we don’t fully break down the structure of nuts when we chew them.

My recommendation is to eat a mixture rather than choosing just one variety.

A small handful that includes almonds for cardiovascular and bone benefit, walnuts for omega-3 and brain health, and one or two Brazil nuts for selenium is the most complete and evidence-based nut strategy available.

Rotate between varieties across the week for maximum phytonutrient diversity and maximum benefit to the gut microbiome as different nuts feed different beneficial bacterial species, and diversity is always the goal.