More protein? How to eat for heart health

New research has found that proteins play a critical role in cutting the risk of hypertension. Variety matters more than quantity, experts say.

Oily fish such as salmon is one of the best sources of protein.

If you routinely slug a whey shake after a workout or eat yoghurt every day to meet your protein needs, take note. Researchers say that for prime health it is not just your fruit and veg intake that needs to be varied, but your protein consumption too.

The shredded-bodied stars of Instagram may hail pea, hemp and other fashionable plant proteins for their ability to accelerate the effects of weight training workouts, but the greater the variety of protein in your diet the better for all-round health.

In the latest paper to look at the subject, scientists at the Southern Medical University in China surveyed 12,200 adults about their diet over 18 years. The participants, who had been in their early forties when the study began, were given a regularly updated “protein variety score”, with points allotted for each type of protein they consumed regularly, from wholegrains to refined grains, processed red meat, unprocessed meat, poultry, fish, eggs and legumes.

During the research, more than one third (35 per cent) of them developed high blood pressure for the first time. However, findings published in the journal Hypertension showed that those eating protein from the widest variety of foods were least likely to develop it, and those with the most varied intake had a 66 per cent lower risk of hypertension.

Sea bream fish on a grill. Picture: Thinkstock

It wasn’t the amount of protein consumed that made the difference – people in the study who ate the most or least amount of protein foods had the highest risk of raised blood pressure – but the range. “The heart health message is that consuming a balanced diet with proteins from different sources, rather than focusing on a single source of dietary protein, may help to prevent the development of high blood pressure,” says Professor Xianhui Qin of Southern Medical University’s Nanfang Hospital, the paper’s lead author.

Alex Ruani, a researcher in nutrition science education at University College London and chief science educator at the Health Sciences Academy, says that in the case of blood pressure a good mix of different protein foods means you are adding beneficial nutrients that might otherwise be missing from your diet.

“Components such as plant fibre from protein-providing wholegrains and legumes, and omega-3 from oily fish and eggs, are also associated with lower blood pressure,” Ruani says. “So the more different types of protein foods you eat, the bigger the combined beneficial effect.”

People who depend on protein shakes may not be getting the best out of their diet.

It’s not just blood pressure that improves. Protein variety matters for other reasons, Ruani says. It is essential to body tissues, for mood regulation, skincare and is required for the growth and healthy maintenance of muscles and for the absorption of minerals that prevent deficiencies leading to weakened bones.

Protein is known to be the most satiating of all macronutrients and helps to assuage hunger pangs and cravings. But it is easy to become fixated with the latest trendy protein sources, restricting your intake to the detriment of your health.

“There are more than 140 amino acids found in nature and 20 of these amino acids are needed by human cells to produce biological proteins, while nine are considered essential in the diet because the body can’t manufacture them,” Ruani says. “The more types of protein we eat, the more we increase our intake of these essential and non-essential amino acids and experience the health benefits associated with them.” Here’s how to add to the protein mix:

How much protein do you need?

Government guidelines suggest that we need about 0.8g of protein per kilogram of body weight daily, or about 45g a day for an adult woman and 55.5g for a man, to remain in good health. To give an idea of what this looks like, there are about 21.5g in a serving of tofu, 10.6g in a small Greek yoghurt and 24.9g in a tuna steak.

While the Department of Health advises adults to avoid consuming more than twice the recommended daily intake, the scientific consensus is that, for many adults, the recommended targets are too low.

“We now believe that suggested levels of protein needed to support body and muscle health are currently underestimated,” says Dr Leigh Breen, a researcher in the field of skeletal muscle metabolism at the University of Birmingham. “Our need for protein increases as we age because our bodies become less efficient at using it and muscle mass starts to decline, but we also need more if we do endurance or strength exercise at any age as we have to put back what our muscles have used.”

Eggs are one of the best sources of protein.

Breen says a protein intake of about 1.2g protein a day from middle age onwards is probably needed to avoid deficiency and muscle loss, and about 1.6g of protein per kilogram of body weight a day (about 130g for someone weighing 12.5 stones), “if you are very active”. A study in the British Journal of Sports Medicine showed that, beyond that, more protein doesn’t produce more muscle enhancement. “There seems to be this sweet spot for protein benefits,” Breen says.

– Are animal proteins a premium source?

Milk, yoghurt, eggs, fish, meat and whey provide all nine essential amino acids our bodies need to function and that alone has led to a reputation that they are superior sources to plant proteins. But while you typically get more protein per 100g of animal foods – there’s 32g protein in a 100g chicken breast and 9g protein in 100g of lentils or haricot beans – it isn’t any better for you.

“Although many plants don’t contain all essential amino acids, it’s very easy to get them if you’re eating a mix of foods and a varied diet,” says Dr Megan Rossi, a research fellow in nutrition at King’s College London. “You just need a range of sources and variety is key.”

Can you get enough protein from plant sources alone?

Although there are some exceptions – including quinoa, hemp and soya – most plant foods aren’t “complete sources’‘ of the essential amino acids. But incomplete plant proteins – nuts, seeds, legumes, pulses, grains and many vegetables – are still important.

Incomplete plant proteins – nuts, seeds, legumes, pulses, grains and many vegetables – are still important. Picture: Thinkstock

“As long as you combine legumes with a grain or rice with beans, for example, you get a complete protein and it doesn’t all need to be eaten in the same meal as you can spread it through the day,” Rossi says. Ruani adds that a potential downside is that you need to eat a lot more plant foods.

“It’s definitely doable, but there’s a volume issue and that is why plant protein intake is sometimes linked to gastrointestinal discomfort,” she says. “Studies on athletes show that getting enough plant protein to support training can initially entail bloating and side effects that can also get in the way of sports performance, so it’s worth increasing amounts carefully.”

Rhiannon Lambert, a dietitian and the author of The Science of Nutrition, says she recommends her clients to get as many complete proteins every day or focus on complementary pairings of incomplete protein sources. “Baked beans on wholegrain toast, noodles in a peanut source and lentils or beans with pasta are all great pairings of incomplete plant proteins.”

Don’t overlook these foods

We might all think of tofu, lentils and beans as plant protein sources, but Rossi says the choices are much wider. “Most foods, including leafy greens such as cabbage and broccoli, contain some protein, but people are often surprised at some of the top plant protein providers,” she says.

A bowl of oats is an ideal source of protein. Picture: AAP.

One of her favourites is oats, with a 40g serving providing 7g of protein.

“Top that with a small handful of pistachios [6g of protein] or almonds [6.5g] and a tablespoon of pumpkin seeds [3.5g] and you are packing in protein at breakfast,” Rossi says. Unlikely protein sources include guava (2 fruits provides 3g of protein), artichoke (3.3g per 100g), mushrooms (3.1g per 100g), avocado (3g per 100g) and jackfruit (1.5g per 100g).

Spinach is another one with 2.5g of protein per cooked 90g serving – Ruani says frozen spinach has even higher amounts of the essential amino acids cysteine and methionine compared with the fresh variety – and potatoes, which have 1.9g per 100g and “significant amounts of the essential amino acids leucine, lysine, phenylalanine, valine and tyrosine”.

A side serving of green peas or 75g of cooked whole-wheat pasta will each give you 4.5g of protein. “Even a boring plate of lettuce leaves and cherry tomatoes supply a few grams of protein,” Rossi says. “But add couscous, chickpeas, almonds and a dollop of yoghurt for a super salad and it could easily be 30g protein per serving. The more sources the merrier.”

Vary when you eat your protein

Most of us consume more protein in our evening meal, but Breen says that balancing your intake throughout the day is increasingly important from middle age onwards.

In one of his studies, he and colleagues examined the dietary behaviour in 120 participants of different ages. They found that middle-aged and older people tended to eat lower quality and less variety of protein sources, often getting their only protein from bread at lunchtime.

“The body mechanisms responsible for producing new muscle need to be stimulated regularly if they are to function well. This stimulation happens when we eat protein foods, but from middle age onwards the mechanisms become less efficient and we found people really need to spread protein intake evenly across the day to maximise muscle benefits.”

– Are protein bars and shakes an option?

Unless you are an elite athlete, you can mostly do without them.

Rossi says her research team at King’s College London is investigating the role of such products on the microbiome. “Protein bars, products and shakes tend to be full of additives,” she says. “We are looking at the potential of these additives having a negative impact on our gut health.”

Cut back on processed meat

If most of your protein intake comes from processed meats, then not only will the “variety score” outlined in the recent study be shockingly low, but you will miss out on accompanying nutrients you would otherwise get from other protein-rich sources such fish, legumes and eggs, Ruani says.

“There’s the added factor that these processed meats tend to have a very high sodium content and that raises your hypertension risk even more. So these should really be avoided.”

The Times