Foods rich in vitamins C and D and omega-3

Three nutrients, three different logics

Vitamin C comes mainly from raw or lightly cooked fruits and vegetables. Vitamin D, on the other hand, is primarily produced by the skin thanks to the sun, with food playing only a supporting role. As for omega-3s, they are divided into two families: ALA from plants (walnuts, rapeseed, flax) and EPA and DHA from fatty fish. This article provides official benchmarks and contents from theCiqual 2020(ANSES) table, without individual advice: for supplementation, consulting a doctor or pharmacist remains the best starting point.

Vitamin C: role and benchmarks

Vitamin C (ascorbic acid) is involved in collagen synthesis and contributes to the defence against free radicals. A severe deficiency causes scurvy, a disease that is now rare. In its opinion on nutritional references, ANSES considers for adults apopulation reference of 110 mg per day(90 mg of average requirement), and notes that EFSA has proposed a lower value for women, 95 mg per day.

According to ANSES, the main sources are fruits (blackcurrants, citrus fruits) and vegetables, especially parsley and red pepper.

Where to find vitamin C: Ciqual contents

Contents in milligrams per 100 g of raw food, according to the Ciqual 2020 table:

• Fresh parsley: 177 mg
• Raw red pepper: 121 mg
• Raw broccoli: 106 mg
• Raw Brussels sprouts: 103 mg
• Kiwi (pulp and seeds): 81.9 mg
• Orange (pulp): 47.5 mg

A raw red pepper of about 100 g is therefore enough, roughly speaking, to reach the reference of 110 mg; it takes about two kiwis to get close to it. Citrus fruits, often cited first, are less concentrated than peppers or parsley. For current products, seeSeasonal fruits and vegetables, month by month.

Cooking and storage reduce the content

Vitamin C is soluble in water and sensitive to heat and oxygen. The Ciqual table shows this:broccoligoes from 106 mg per 100 g raw to 23.9 mg cooked, and to 20.7 mg steamed. Brussels sprouts go from 103 mg raw to 56.4 mg cooked. These values are averages, which vary depending on the duration and method of cooking.

A review published in the journal Foods in 2021 (Giannakourou and Taoukis) confirms that temperature and oxygen are the main factors in vitamin C loss in processed fruits and vegetables. Eating some vegetables raw and cooking briefly is therefore a simple solution.

Vitamin D: a vitamin mainly produced by the skin

Vitamin D helps to increase blood concentrations of calcium and phosphorus, and thus contributes to bone health. It also plays a role in hormonal regulation and immune cell activity, according to ANSES.

According to the High Council for Public Health (opinion of 21 June 2022), skin synthesis under the effect of UV rays provides80 to 90%of the body's vitamin D, with food providing 10 to 20%. In France, this synthesis is ineffective in winter. ANSES recommends exposing the skin to sunlight for 15 to 20 minutes in the late morning or afternoon, and HCSP recommends "moderate but sufficient" exposure that is compatible with the prevention of skin cancers.

In terms of benchmarks, ANSES (2021) sets asatisfactory intake of 15 µg per dayfor adults, and a safety limit of 100 µg per day. This benchmark only counts dietary vitamin D, not that produced by the sun.

Vitamin D: limited food sources

ANSES cites fatty fish (herring, sardines, salmon, anchovies, mackerel), liver and cod liver oil, fish eggs, egg yolks, fortified cereals, oils and dairy products, and certain mushrooms (chanterelles, cepes, morels). Ciqual 2020 contents, in µg per 100 g:

• Cod liver oil: 250 µg
• Raw sardine: 14 µg
• Farmed rainbow trout, baked: 15 µg
• Raw herring: 10.7 µg
• Raw mackerel: 6.44 µg
• Raw farmed salmon: 3.69 µg
• Raw egg yolk: 2 µg

A single meal of fatty fish can therefore approach or even exceed 15 µg. On the other hand, eggs, dairy products and butter provide little per portion. Vitamin D is also present in fortified products: the label then indicates the content.

Supplementation: the official position

For the general adult population, the HCSP does not recommend screening by blood test, notes the absence of a convincing randomised trial in favour of supplementation, and advisesavoiding self-medicationwith vitamin D-rich supplements. It identifies at-risk groups: people living in poverty, obese people, people with little exposure to sunlight, or people with very pigmented skin living at high latitudes. ANSES, for its part, states that any additional intake should only be made on dietary or medical advice, and that medicines are preferable to dietary supplements because their dosage is clearer.

These are general guidelines: only a doctor or pharmacist can assess your situation (pregnancy, age, treatment). The same applies to vitamin C or omega-3 supplements.

Omega-3: ALA, EPA and DHA

Omega-3s are essential fatty acids that are useful for the development and functioning of the brain, retina and nervous system, according to ANSES. The precursor isALA(alpha-linolenic acid), which must necessarily be found in food. The body can makeEPAandDHA, which fatty fish provide directly.

ANSES references (report of May 2011) for an adult consuming 2000 kcal are1% of energy intake as ALA(i.e. about 2 g per day),250 mg of DHAand250 mg of EPA, i.e. a total of 500 mg of EPA and DHA.

Where to find omega-3: Ciqual content levels

For ALA, in grams per 100 g:

• Linseed oil: 53.3 g
• Dried chia seeds: 17.8 g
• Flax seeds: 16.7 g
• Walnut oil: 11.9 g
• Dried walnuts: 7.5 g
• Rapeseed oil: 7.54 g

For EPA and DHA, total in grams per 100 g of raw fish (sum of the two Ciqual values):

• Sardine: about 2.7 g
• Mackerel: about 2.5 g
• Herring: about 1.75 g
• Farmed salmon: about 1.5 g
• Cod: about 0.18 g (lean fish)

A 100 g portion of fatty fish therefore largely covers the 500 mg reference level of EPA and DHA. Conversely, canned tuna in natural juices provides only about 0.11 g per 100 g, according to Ciqual: not all canned fish are equal.

Fatty fish: how much, and contaminants

ANSES recommends eating fishtwice a week, combining a fatty fish rich in omega-3 (salmon, sardine, mackerel, herring) with a lean fish (hake, whiting, cod, sole), and varying species and sources of supply.

Fatty fish also concentrate more dioxins and PCBs, and wild predatory fish concentrate methylmercury. For pregnant or breastfeeding women and children under 3 years of age, ANSES advises limiting wild predators such as tuna, sea bass, gilt-head bream or halibut, and avoiding swordfish, marlin, siki, shark and lamprey. Eel should only be consumed occasionally.

Without fish: plant-based alternatives and limitations

Nuts, rapeseed and linseed oils, flax and chia seeds provide ALA. Around 27 g of rapeseed oil contains 2 g of ALA, according to Ciqual content. But ALA is not a complete substitute. The 2011 ANSES report concludes that the conversion of ALA to EPA ismoderateandvery low in DHA, and the agency's page states that the rate of conversion of ALA to DHA is "too low to meet DHA needs", which must therefore also come from food.

For people who do not eat fish or seafood, or for pregnant women, a health professional can say whether a supplement is useful. See alsoFoods high in protein and fibreandFoods high in calcium, potassium and iodine, which complement this list.

Sources

• ANSES - Dietary reference values for vitamins and minerals (May 2021)
• ANSES - Updating the PNNS guidelines: development of nutritional references (vitamin C)
• ANSES - Vitamin D: why do I need an adequate intake and how can I make sure I get it?
• HCSP - Opinion on meeting the vitamin D and iron needs of the general population (21 June 2022)
• ANSES - Omega-3 fatty acids
• ANSES - Update of recommended dietary intakes for fatty acids (collective expert report, May 2011, PDF copy)
• ANSES - Eating fish: why? how?
• ANSES - Ciqual 2020 nutritional composition table
• Giannakourou and Taoukis - Vitamin C Stability in Fruit and Vegetable Products, Foods (2021)