Most adults don't eat enough fruits and vegetables. In fact, dietary intake of several nutrients found in fruits and vegetables — including potassium and dietary fibre — is low enough to be a public health concern for both adults and children in the US, and in Australia.

"The bottom line is that most Aussies are not eating enough vegetables each day," Alexandra Parker, accredited practising dietitian of The Biting Truth, told HuffPost Australia.

The health consequences can be serious. For example, there is compelling evidence that a diet rich in fruits and vegetables can lower the risk of heart disease and stroke.

A study of over 100,000 mean and women over 14 years found that, compared with those in the lowest category of fruit and vegetable intake (less than 1.5 servings a day), those who averaged 8 or more servings a day were 30% less likely to have had a heart attack or stroke.

Although all fruits and vegetables likely contributed to this benefit, green leafy vegetables, such as lettuce, spinach, Swiss chard, and mustard greens, were most strongly associated with decreased risk of cardiovascular disease.

What's perfect is to fill half your plate with vegetables at all main meals. That may not sound very scientific, but it is a whole lot better than worrying about the details.

Add in variety and a couple of pieces of fresh fruit, and you will start to feel the difference. That's all I do - I pay attention to mixing the colours, eating 5 or so serves daily, and eating some fruit.

How you do that starts with shopping! Typically, in this kind of article, we jump into the health benefits, and what should go onto the plate.

​Not in this case! Let's start at the shop.

Scientists in the UK are calling for ministers to add vitamin D to common foods such as bread and milk to help the fight against Covid-1.

However, the call is controversial.

Back in 2017, Professor Louis Levy, Public Health England's head of nutrition science, responded to calls for fortification by saying that there was not enough evidence that vitamin D would reduce the risk of respiratory infections.

Recently, researchers in Spain found that 82% of coronavirus patients out of 216 admitted to hospital had low vitamin D levels. The picture is mixed; some research shows that vitamin D levels have little or no effect on Covid-19, flu and other respiratory diseases.

​The benefits of omega-3 fats from fatty fish and likely from plant sources like flaxseeds and walnuts are well known. After all, the media frequently talk about the benefits of omega-3 fatty acids in fish oil, and sales of fish oil supplements are more than $1 billion per year in the United States.

Omega-3 is a polyunsaturated fatty acid, and our only source is from food. Omega-6 is omega-3's cousin, also derived from the food we eat. 

The only difference between omega-3 fatty acids and omega-6 fatty acids is in the structure of their molecules. Both are essential. Our body cannot produce them, so we need to obtain them from our diet.​

It is not a matter of one of them being "better" than the other. We need both, and generally, we all need to eat more of them, as long as we don't get the ratio out of balance.

An imbalance in our omega-3 to omega-6 ratio is associated with adverse health outcomes, potentially negating the overall benefits. For example, a high dietary intake of omega-6 induces a proinflammatory response (raising the level of chronic inflammation) whereas omega-3 has anti-inflammatory properties.