The truth about calcium and milk

Decades of marketing campaigns designed to make you believe that only dairy milk can supply enough calcium for your bones have truly stuck in people’s minds. The truth is, dairy is neither the only nor the best source of this important mineral.

What is calcium and why do we need it?

Calcium is required for normal growth and development and it’s the most abundant mineral in the human body accounting for around two per cent of our total body weight.

Calcium plays an important role in building and maintaining your bones. Around 99 per cent of the calcium in your body is stored in your bones and teeth. The other one per cent is responsible for a range of important functions, such as regulating muscle contraction and heartbeat, blood clotting and functioning of the nervous system.

How much calcium do we need?

Official UK guidelines suggest that adults over 19 years of age need 700 milligrams per day.

Low calcium intake increases your risk of fracture but so does high intake – the risk from high intakes rises from about 2,000 milligrams per day. Your body cannot immediately use such high calcium doses and if you take in too much on a daily basis, your body may store it in the wrong places, such as blood vessel walls, making them harder and limiting their function. This has raised concerns that calcium supplements may increase the risk of cardiovascular disease. So, for most people, it’s better to obtain calcium from food than from supplements.

Best calcium sources

The best plant sources of calcium are:

• Kale
• Collard/spring/mustard greens
• Broccoli
• Chinese leaf/bok choy
• Cabbage
• Sesame seeds and tahini (sesame seed paste)
• Almonds
• Chia seeds
• Calcium-set tofu (made with calcium sulphate) and tempeh
• Beans
• Dried figs
• Plant-based milks and yoghurts fortified with calcium
• Fortified vegan breakfast cereal
• Wholemeal bread
• Butternut squash
• Oranges

How important is diet?

Your body can get the calcium it needs in two ways: from your diet or your bones. When the diet does not provide enough, calcium is ‘borrowed’ from the bones in order to restore blood levels and maintain essential calcium-dependent biological functions.

It’s nothing unusual, calcium in your bones is borrowed and replaced continuously as old bone cells break down and new ones form. If you supply enough calcium through your diet, balance is maintained but if the diet is lacking, calcium may be taken from the bones more than it is replaced. This may eventually lead to bone loss.

Eating calcium-rich foods is vital for healthy bones at any age – studies show that having a calcium intake at or slightly above the recommended intake produces stronger bones and reduces the risk of fracture.

The truth about milk

The idea that cow’s milk is the best source of calcium is drummed into us from early childhood and the narrative is sustained by the government-sponsored dairy industry and the Agriculture and Horticulture Development Board (AHDB) who work with schools and universities to encourage children and young people to drink dairy milk.

This is not only wrong, it’s also unethical given how many children suffer from lactose intolerance, and it’s dangerous since research suggests an association between hormones in cow’s milk and prostate cancer more and more.

When it comes to bone health, milk is no hero. A scientific review of 37 studies on dairy products and bone health concluded that there is no solid evidence that the consumption of dairy improves bone health in children and young adults.

In fact, many studies show that milk only improves bone health in people with low calcium intake but does nothing for those with sufficient calcium. So it’s not about milk but about a balanced diet!

Calcium absorption

Your body never absorbs 100 per cent of the calcium in your food. You may have heard of the term bioavailability, which means how much of a nutrient is actually available for absorption into the body.

The calcium in dark green leafy vegetables, such as kale, bok choy, Chinese leaf or broccoli, has the highest bioavailability of all calcium sources – you absorb between 35 and 40 per cent. However, there’s an exception – spinach and Swiss chard contain a substance called oxalate, which hinders calcium absorption, so they aren’t good calcium sources.

Interestingly, you also absorb around 40 per cent of calcium from wholemeal bread. Calcium-set tofu and fortified soya milk are next as they offer about 30 per cent of their calcium – same as dairy milk.

When it comes to beans, nuts and seeds, you absorb a little less calcium from them – around 20 per cent – but they are still valuable sources.

What hinders calcium absorption?

Too much caffeine (more than two or three cups of coffee per day), excessive alcohol intake (three drinks or more per day) and smoking have all been shown to reduce calcium absorption and may compromise bone health.

Indispensable buddy

Your body requires vitamin D to absorb and retain calcium in the bones. If you lack vitamin D, you can develop calcium deficiency even if your diet provides plenty.

In the summer, you can get enough vitamin D from sun exposure but you may need a supplement in winter.

Calcium-rich meals and snacks

Luckily, greens, such as broccoli, Chinese leaf and kale are superb calcium sources and go with almost any meal. If your meal also features beans, tofu or tahini, you’re onto a winning combination for both calcium and iron.

There are plenty of calcium-fortified plant milks and yoghurts, which make an easy option and you can conveniently top up your calcium intake with hummus, wholemeal bread, almonds, chia seeds, sesame seeds (tahini) and oranges.