Essential fatty acids & Infant nutrition

Pankaj Garg / Hijam Rajendra Singha *

Essential fatty acids (EFA) are being discussed for their important role in brain development and functioning as well as their cardio protective role. There is also a growing evidence of their role in protection from infection and allergy disorders. It is important to understand the differences amongst the various EFA and also to understand role of one versus the other. In this article I will be discussing some basic facts about essential fatty acids and their role in infant nutrition.

Fats provide the main source of energy for infants and young children. It is not only important to provide flavor and texture to the food but is needed by all cell membranes including neuronal connections. It is also important for absorption of fat soluble vitamins and provides us with the EFA. EFA are so called because they can't be manufactured in the body and are essential for body's growth. Mammalian cells are unable to insert double bonds more proximal to methyl terminal of fatty acid than the 7th carbon.

The most abundant essential fatty acids are:  Linolenic acid (LA) 18 carbon: 2 n-6 (means it has 18 carbons ; two double bonds ; last double bond at 6th carbon from the methyl terminal of the fatty acid)  α Linolenic acid (ALA) 18 carbon: 3 n-3 By the process of desaturation and chain elongation, LA is converted to Arachidonic acid 20 carbon: 4 n-6 (AA) and ALA is converted to Eicosapetanenoic acid 20 carbon: 5 n-3 (EPA) and Docosahexaenoeic acid 22 carbon: 6 n-3(DHA). This conversion is affected by many factors like age, alcohol intake, smoking and certain drugs.

At extreme of ages and in pregnancy, this conversion is not sufficient enough to meet the increased needs for brain, retina development or to meet the fetal requirements. To summarize, Omega 3 fatty acids are ALA, EPA and DHA and Omega 6 fatty acids are LA and AA. Historical background: It has been seen documented as early as 1950 that infants given skimmed milk and hydrogenated coconut oil failed to gain wt and develop typical skin lesions c.f. those given small amounts of corn oil as well.

Similarly in 1960 it was shown that the use of parenteral nutrition with proteins and glucose alone led to poor growth and altered visual functions compared to PN+n-6 fatty acids emphasizing the importance of EFA. All EFA are not same There are important differences between Omega 6 and Omega 3 fatty acids and some of the differences are very important from clinical point of view. Omega 6 LCPUFA (Eicosanoids) are more potent, are proinflammatory and adipogenic Omegas 3 LCPUFA (Eicosanoids) on the other hand are anti inflammatory and decreases fat deposition. Fish oil (EPA & DHA) has been used in Rheumatoid arthritis emphasizing its anti inflammatory properties.

There are various differences between EPA and DHA as well. DHA has been shown to prevent CVS disease by reducing blood vessel inflammation and atherosclerosis1.There are less heart diseases in Eskimos and Japanese fisherman which has been attributed to higher blood DHA/EPA levels c.f. Omega 6 LCPUFA in them. Triglyceride levels fall more with 26% in DHA (26%) compared to EPA (21%). So evidence is in favor of DHA compared to EPA for the beneficial effects seen with Omega 3 fatty acids.

More over EPA concentration in mother's milk in negligible making its importance very doubtful in infant nutrition. Role of EFA in infant nutrition Recommendation for first 6 months of life: Understanding that "Mother's Milk Is the Best for the Baby" one need to look at the lipid composition in mother's milk first to draw some logical conclusions. 50% of energy as lipids 12% LA, 0.6% AA (12.6% Omega 6 FA), 0.5% ALA, 0.3% DHA (0.8%Omega 3 FA) Actual amount of LCPUFA depend on maternal diet. Baby should be given exclusive mother's milk for first six months of life and mother's diet should have sufficient amounts of EFA and especially DHA.

But Indian diet is very inadequate for Omega 3 FA content. Ratio of Omega 6: Omega 3 FA in various diets across the world: Ideal diet 5-10:1 Indian Diet 30-70:1 USA 12:1 Japan 2:1 The main reason for poor Omega 3 FA in Indian diet is lack of animal products especially fish and excess intake of animal milk and milk products. There are a number of vegetable sources of EFA and one must have knowledge so that the same can be advised to the mother.

Sources of Omega 3/6 fatty acids Omega 3 fatty acids Omega 6 fatty acids Flaxseed or linseed Sunflower Rapeseed or canola Safflower Peanut Sesame Olive Palmolive Perilla Corn Walnut Primrose Soya Borage Green leafy vegetables, dry fruits Invisible fats Fish / Fish oil Pregnancy & LCPUFA DHA accretion occurs in III rd trimester mainly and the transfer depends on the age of the mother (at elderly age transfer would be less), primi or second gravida (primi expected to have better transfer), interval between the pregnancies (less the interval, less is the transfer in the second baby), Maternal diet (Fish, Marine products) and alcohol intake (reduces DHA transfer).

Supplementation with DHA during pregnancy has shown to improve cord Omega 3 levels and neonatal short follow up 3- 6 mths has not shown any benefits (Malcom et al. Helland et al but long term follow up till 4 yrs has shown beneficial effects on mental ability2 Some studies also show less atopy and lower type I IDDM in supplemented infants. We must remember that these studies are done in west in mothers with better DHA content in their diet and if we reciprocate the results for Indian mother with poor DHA content in their diet, the beneficial effects are bound to be more.

Supplementation during Lactation has also shown to improve breast milk DHA content but clinical effects shown in different studies are not consistent. In Indian Context, DHA supplementation should help the neurodevelopment of the infants and children. WHO Guidelines recommend at least 2.6 gms of Omega 3 LCPUFA and 100-300 mg DHA/Day during pregnancy and lactation.

Infant Nutrition and EFA All infants should be fed on exclusive mother's milk for first six months and in case mother's milk is not sufficient, alternative milk with sufficient amounts of EFA should be provided. As unmodified bovine milk (cow or buffalo or goat) does not contain any EFA, the only option is a balanced infant formula with ratio of LA/ALA between 5:1 to 15:1. DHA supplementation in term formula: Cochrane (2001) reviews after analyzing 10 trials have concluded that there are contradictory results on beneficial effects on developmental indices.

Certain trials show better problem solving (finding a hidden toy)3 or higher scores on Bayley Mental Development Index until 17 weeks of age4 while others show no benefits5 / Transient benefit6 There is some effect seen in reduction of BP and Type I DM with no documented side effects. LCPUFA and preterm formula: there is no ambiguity as far as preterm milk formula and their supplementation is concerned. Meta analysis by San Giovanni show better visual acuity at 2&4 months. There is strong recommendation by AAP that preterm formulae should contain both AA and DHA.

Infant nutrition 6months to one year:
Recommendations for fat intake First 6 months  40-60% of total energy  Omega 6: omega 3 ratio 5-10:1  <1% trans fats After
2 yrs  Fat 30-35% calories  Omega 6: 4-10% energy  Omega 3: 1-2% energy  Transfats <2% energy
Infants must be continued breast milk or term baby follow-up formula along with addition of semisolid diet with emphasis on addition of vegetable oils with high Omega 3 FA (Soyabean oil, canola oil, mustard oil, fish oil, rapseed oil etc.)

Key Messages Essential fatty acids are important for brain, retina and growth
All essential fatty acids are not same Omega 3 LCPUFA have anti allergic properties, good for brain and heart
Maternal diet should contain enough DHA, otherwise supplementation is a good idea
Supplementation during lactation is less rewarding Breast feeds till 6 mths is best strategy If not Cow's milk is absolutely no
Term baby formulae is second best option
Preterm formulae should be supplemented with DHA For infants and bigger children: fat content should come down, DHA still important

References:
1. Grimble RF. Dietary lipids and the inflammatory response. Proceedings of the Nutrition Society 1998; 57:535-542.

2. Helland. Pediatrics 2003; 111(1): e 39-440.

3. Williatts P. Lancet 1998; 352:688-91)

4. Birch EE.Dev Med Child Neurol 2000; 42:174-81)

5. Makrides M. Pediatrics 2000; 105:32-38.

6. Carlson SE. J Pediatr 1992; 120:S159-67.