Don't like milk? How can you get enough calcium from food?

You can get enough calcium without drinking milk, as long as you know which Thai foods are rich in it. The Thai Reference Daily Intake (Thai RDI) for calcium is 1,000 mg per day. Foods that contribute a lot include small fish eaten whole, small dried shrimp with their shells, black sesame, cha plu leaves, Chinese kale, mustard greens, high-calcium firm tofu and yoghurt, spread across several meals in the day.

Calcium is needed for the maintenance of normal bones and teeth, and contributes to normal muscle function. The NIH ODS fact sheet from the US National Institutes of Health says about 99% of the calcium in the body is in bones and teeth, and that bone is constantly being broken down and rebuilt. Getting calcium from food every day therefore matters at every age, not only for people who drink milk.

If I don't drink milk, how much calcium do I need a day?

The Thai RDI for calcium is 1,000 mg per day. It is a single value for the general population aged 3 and over, and it is a useful yardstick for judging whether a food gives you a lot of calcium or a little.

How much calcium is in a carton of milk?

An infographic from Ramathibodi Hospital at Mahidol University puts 200 ml of cow's milk at about 250 mg of calcium, or roughly a quarter of the Thai RDI.

So skipping a single carton is not a huge gap. But if you used to drink two cartons a day and stopped, the roughly 500 mg that is missing needs to come from other foods.

Why do people who skip milk need to pay more attention?

The NIH ODS says people who get an upset stomach from milk, people who cannot have milk and people who avoid dairy (including vegans) are more likely not to get enough calcium, because dairy products are rich sources of it. Knowing the other sources in Thai food is what makes the difference.

Besides milk, which Thai foods are high in calcium?

The good news is that several foods used in Thai cooking contain more calcium than milk, weight for weight. The table uses values from USDA FoodData Central from the US Department of Agriculture, per 100 g.

Small fish and dried shrimp

Small fish and shrimp that you eat whole give you calcium because you eat the bones and shells. The UK's NHS lists fish where you eat the bones, such as sardines, as a source of calcium. A food table from Ramathibodi Hospital's Department of Family Medicine puts 2 tablespoons of small dried shrimp at about 460 mg of calcium, and 2 tablespoons of roasted black sesame at about 422 mg. Dried foods are eaten only a little at a time, so they work best sprinkled into dishes you already eat.

Thai-style green vegetables

Ramathibodi Hospital lists green leafy vegetables such as Chinese kale, broccoli, cha plu leaves and water mimosa among calcium-rich foods. Its family medicine table puts half a cup (70 g) of raw cha plu leaves at about 192 mg. These vegetables are easy to eat often in ordinary meals, such as stir-fried kale, clear soup with mustard greens or miang kham.

Tofu: check the type

Tofu varies a lot depending on how it is made. In USDA FoodData Central, firm tofu made with calcium sulfate has about 683 mg per 100 g, firm tofu made with calcium sulfate and nigari about 201 mg, and soft tofu made with calcium sulfate and nigari about 111 mg. The tofu values in the NIH ODS table are also for tofu made with a calcium salt. If you buy packaged tofu, check the calcium content on the nutrition label.

Soy milk: check the label

Soy milk without added calcium has about 25 mg of calcium per 100 g in USDA FoodData Central, much less than cow's milk, but calcium-fortified soy milk has more. The NIH ODS lists about 299 mg in one cup of calcium-fortified soy milk. If you use soy milk instead of milk, choose one labelled as calcium-fortified.

Why do you get less calcium from some vegetables?

The numbers in the table are the calcium in the food, but the body does not absorb the same share from every food.

Spinach compared with milk

The NIH ODS explains that some plants contain oxalic acid and phytic acid, which bind to calcium so the body absorbs less of it. Spinach is the example: only about 5% of its calcium is absorbed, compared with about 27% from milk. The NHS also notes that spinach contains a lot of calcium but the body cannot digest it all.

Vegetables that are absorbed well

According to the NIH ODS, vegetables without these compounds, such as broccoli, kale and cabbage, are absorbed about as well as milk, although they contain less calcium per serving. When you eat many different foods, these compounds probably make little difference. Eating a variety of vegetables is better than relying on one.

Other things that matter

The NIH ODS says caffeine and phosphorus reduce absorption a little, and low vitamin D status has a bigger effect. The share of calcium absorbed also falls as daily intake rises, and declines with age. Spreading calcium-rich foods across several meals is an easy everyday habit.

How can I plan a day of meals without milk?

Here is an example day with no milk at all, using the USDA FoodData Central and Ramathibodi Hospital values above.

That adds up to about 1,140 mg, around the Thai RDI. This is an illustration, not a personal meal plan. Vegetable weights are before cooking, and actual values depend on the ingredients and how they are prepared.

Small changes you can make today

• Sprinkle roasted black sesame on rice, salads or desserts.
• Add small dried shrimp to stir-fried vegetables, yam salads or som tam.
• Choose tofu made with a calcium salt, and check the calcium on the label.
• Keep canned fish that you eat with the bones at home for quick meals.
• Use cha plu leaves and dark leafy greens in curries and stir-fries more often.
• If you drink soy milk instead of milk, choose one labelled as calcium-fortified.

Who should pay extra attention, and who should I talk to?

If milk upsets your stomach

The NIH ODS says lactose-free and reduced-lactose dairy products contain the same amount of calcium as regular dairy, and people who avoid dairy altogether can get calcium from some vegetables, canned fish with bones and foods with added calcium.

Aim for the Thai RDI

Aim for close to the Thai RDI from a variety of foods. The NIH ODS says the share of calcium the body absorbs falls as daily intake rises: about 45% at intakes of 200 mg a day, but only about 15% at intakes above 2,000 mg a day.

When to get advice

If you have gone without milk, small fish and tofu for a long time, or you have several food restrictions, talk to a doctor or dietitian about planning meals that suit you.